Artist’s impression of the Chicxulub asteroid impacting the Yucatan Peninsula as pterodactyls fly in the sky above. Painting by Donald E. Davis. Credit: NASA
An international research team is formalizing plans to drill nearly 5,000 feet below the seabed to take core samples from the crater of the asteroid that wiped out the dinosaurs.
The group met last week in Merida, Mexico, a city within the nearly 125-mile-wide impact site, to explain the research plans and put out a call for scientists to join the expedition planned for spring 2016. The roughly $10 million in funding for the expedition has been approved and scheduled by the European Consortium for Ocean Research Drilling (ECORD)—part of the International Ocean Discovery Program (IODP)—and the International Continental Scientific Drilling Program (ICDP).
Dinosaurs and other reptiles ruled the planet for 135 million years. That all changed 65.5 million years ago when a 9-mile-wide asteroid slammed into the Earth, triggering a series of apocalyptic events that killed most large animals and plants, and wiped out the dinosaurs and large marine reptiles. The event set the stage for mammals—and eventually humans—to take over. Yet, we have few geologic samples of the now buried impact crater.
Sean Gulick, a researcher at The University of Texas at Austin Institute for Geophysics (UTIG), and a team of scientists from the U.K. and Mexico are working to change that. The team is planning to take the first offshore core samples from near the center of the impact crater, which is called Chicxulub after the seaside village on the Yucatán Peninsula near the crater’s center.
The team, led by Gulick and Joanna Morgan of Imperial College London, will be sampling the crater’s “peak ring”—an enigmatic ring of topographically elevated rocks that surrounds the crater’s center, rises above its floor and has been buried during the past 65.5 million years by sediments.
A peak ring is a feature that is present in all craters caused by large impacts on rocky planetoids. By sampling the Chicxulub peak ring and analyzing its key features, researchers hope to uncover the impact details that set in motion one of the planet’s most profound extinctions, while also shedding light on the mechanisms of large impacts on Earth and on other rocky planets.
“What are the peaks made of? And what can they tell us about the fundamental processes of impacts, which is this dominant planetary resurfacing phenomena?” said Gulick, who is also a research associate professor at the UT Jackson School of Geosciences. UTIG is a research unit of the Jackson School.
The researchers are also interested in examining traces of life that may have lived inside the peak ring’s rocks. Density readings of the rocks indicate that they probably are heavily broken and porous—features that may have served as protected microenvironments for exotic life that could have thrived in the hot, chemically enriched environment of the crater site after impact. Additionally, the earliest recovery of marine life should be recorded within the sediments that filled in the crater in the millions of years after the impact.
“The sediments that filled in the [crater] should have the record for organisms living on the sea floor and in the water that were there for the first recovery after the mass extinction event,” Gulick said. “The hope is we can watch life come back.”
The expedition will last for two months and involve penetrating nearly 5,000 feet beneath the seabed from an offshore platform. The core will be the first complete sample of the rock layers from near the crater’s center.
Once extracted, the core will be shipped to Germany and split in two. Half will be immediately analyzed by an international team of scientists from the U.S., U.K., Mexico and other nations, and half will be saved at a core repository at Texas A&M University for future research needs by the international community.
The team also includes researchers from the National Autonomous University of Mexico (UNAM) and Centro de Investigación Científica de Yucatán (CICY). Scientists interested in joining the mission must apply by May 8, 2015. For more information on the mission and the application process, see the European Consortium for Ocean Research Drilling’s call for applications.
New research sheds light on the evolutionary relationships of living and extinct reptiles. This skeleton belonged to a mosasaur, a carnivorous marine lizard that died out with the dinosaurs 65 million years ago. Credit: Wikimedia Commons
A new study has helped settle the controversial relationships among the major groups of lizards and snakes, and it sheds light on the origins of a group of giant fossil lizards.
Squamate reptiles—lizards and snakes—are among the most diverse groups of vertebrates, with more than 9,000 living species. They are important for humans because venomous snakes cause tens of thousands of deaths every year. At the same time, their toxins are a critical resource for many medicines, including those for heart disease and diabetes. Lizards and snakes also are important model systems for biological research, especially in ecology and evolutionary biology.
Unfortunately, studies of squamate biology have been hampered by controversy over their evolutionary relationships, and some researchers consider their family tree to be unresolved. The problem is that studies based on traditional, anatomical characters and those based on molecular data from DNA sequences have strongly disagreed, especially on how the iguanas and their relatives (called iguanians) are related to snakes and to other groups of lizards. Iguanians include horned lizards, flying dragons and basilisks.
A new study by scientists from the University of Arizona, San Diego State University, the Smithsonian Institution, Brigham Young University and the University of Mississippi has now helped to resolve this controversy, and it also offers new insights on the evolution of fossil lizards. The results are published online in the journal PLoS One.
“Anatomical data put iguanians at the base of the tree, whereas molecular data suggest that the iguanians evolved more recently and are closely related to snakes and a group including the monitor and alligator lizards, called the anguimorphs,” said John J. Wiens, a professor in the Department of Ecology and Evolutionary Biology in the UA College of Science. “The results of our study overwhelmingly support the molecular hypothesis.”
The team assembled the largest-yet datasets of both anatomical and molecular characters for the major groups of lizards and snakes. The researchers showed that when the anatomical and molecular data are combined, the results conclusively support the molecular hypothesis, placing iguanas and relatives with snakes and anguimorphs.
One possible explanation for these results is the greater number of molecular characters relative to morphological characters (35,673 molecular versus 691 morphological). This larger number might favor the molecular hypothesis, regardless of which hypothesis is actually true. To test this idea, the researchers trimmed the molecular dataset to only 63 characters. When they analyzed this reduced molecular dataset with all 691 anatomical characters, the results still supported the molecular hypothesis, placing iguanians with snakes and anguimorphs instead of at the base of the tree.
Wiens’ team also found that there was support for the molecular hypothesis hidden in the morphological dataset. When the researchers combined the molecular and morphological data, they found that the number of morphological characters that supported the branch uniting iguanians, snakes and anguimorphs (the molecular hypothesis) was almost equal to the number placing iguanians near the base of the tree (the morphological hypothesis).
In addition, the researchers found that when they divided up the anatomical characters and analyzed each set separately, only one of the six sets clearly supported the morphological hypothesis.
“In fact, the morphological data are really ambiguous,” Wiens said. “Or in some cases, even worse than ambiguous.”
He explained that the morphological data give very strange, non-traditional relationships in which all burrowing species are placed together, including those classified in different families.
“Basically, burrowing lizards tend to evolve elongate bodies, reduced limbs and a whole suite of other anatomical traits, even if they are only distantly related to each other,” Wiens said. “Placing all burrowing species together disagrees strongly with the molecular data, and also with traditional taxonomy. In summary, the anatomical data can be widely misleading in squamate reptiles.”
Wiens and co-authors suggest a similar explanation for why the anatomical data are misleading about the placement of iguanians in particular.
According to Wiens, iguanian lizards typically capture prey using their tongue, whereas snakes and other lizards use their jaws. Scientists have documented many differences in diet, behavior and anatomy that seem to be associated with capturing prey with the tongue versus the jaw. It turns out that the closest living relative to lizards and snakes, the tuatara of New Zealand, also uses its tongue to capture prey. Therefore, the anatomical characters that place iguanians at the base of the tree may reflect parallel evolution associated with these different feedings modes.
The study also has implications for understanding the evolution of fossil lizards, such as mosasaurs, as well. These carnivorous marine lizards, which died out with the dinosaurs around 65 million years ago, have traditionally been thought to either be close relatives of monitor lizards, or close to the base of the squamate family tree. The new study combined data from both living and fossil species and revealed mosasaurs to be close relatives of snakes, and only distantly related to monitor lizards and species at the base of the tree.
“What is really interesting about this is that we have no molecular data for mosasaurs at all,” Wiens said. “Our results show how combining molecular and anatomical data can reveal evolutionary relationships of fossil species that one might not predict from the anatomical data alone.”
Reference:
“Integrated Analyses Resolve Conflicts over Squamate Reptile Phylogeny and Reveal Unexpected Placements for Fossil Taxa.” PLoS ONE 10(3): e0118199. DOI: 10.1371/journal.pone.0118199
Zircon from East Antarctica with nanospheres of metallic lead under GFZ’s transmissionelectron-microscope TEM. The rock sample is more than 3,4 billion years old. Photo Credit: GFZ
Rocks do not loose their memory during Earth history but their true ages might be distorted: even under ultra high-temperature metamorphic conditions exceeding 1200°C zircon maintains its lead content accumulated during radioactive decay of uranium and thorium.
Giga year old zircon crystals still contain lead in form of nanometre size spheres of pure lead. However, the inhomogeneous spatial distribution of the lead spheres might falsify ages determined from high-resolution Pb isotope measurement with ion probe.
Zircon is an ideal mineral for age determination of very old rocks because it is believed to be a closed system during Earth history. Zircon geochronology thus is a standard method of geological age determination. Recently, an international group of earth scientists studied zircon from 3,4 billion years old high-temperature metamorphic rocks from Antarctica with transmission electron microscopy TEM at the GFZ German Research Centre for Geosciences. TEM investigations revealed that the lead from radioactive decay was not homogeneously distributed in zircon but was accumulated withinin inhomogeneously distributed Pb nano-spheres in zircon with only 5 to 30 nm in diameter. The inhomogeneous distribution of lead in zircon might adulterate the ages measured with high-spatial resolution ion probe technique.
Reference:
Monika A. Kusiak et al.: “Metallic lead nanospheres discovered in ancient zircons”, Proceedings of the National Academy of Sciences, PNAS Early Edition, 06.04.2015, DOI: doi/10.1073/pnas.1415264112
Landslides occur in all 50 states and U.S. territories, and cause $1-2 billion in damages and more than 25 fatalities on average each year. USGS scientists aim to improve our understanding of landslide hazards to help protect communities and reduce associated losses.
Video Sections:
Types of Landslides
USGS Science
Did You See It?
Debris Flow Early Warning System (NOAA Partnership)
The city of Philadelphia is shown inside a theoretical lunar lava tube. A Purdue University team of researchers explored whether lava tubes more than 1 kilometer wide could remain structurally stable on the moon. Credit: Purdue University/courtesy of David Blair
Lava tubes large enough to house cities could be structurally stable on the moon, according to a theoretical study presented at the Lunar and Planetary Science Conference on March 17.
The volcanic features are an important target for future human space exploration because they could provide shelter from cosmic radiation, meteorite impacts and temperature extremes.
Lava tubes are tunnels formed from the lava flow of volcanic eruptions. The edges of the lava cool as it flows to form a pipe-like crust around the flowing river of lava. When the eruption ends and the lava flow stops, the pipe drains leave behind a hollow tunnel, said Jay Melosh, a Purdue University distinguished professor of earth, atmospheric and planetary sciences who is involved in the research.
“There has been some discussion of whether lava tubes might exist on the moon,” he said. “Some evidence, like the sinuous rilles observed on the surface, suggest that if lunar lava tubes exist they might be really big.”
Sinuous rilles are large channels visible on the lunar surface thought to be formed by lava flows. The sinuous rilles range in size up to 10 kilometers wide, and the Purdue team explored whether lava tubes of the same scale could exist.
David Blair, a graduate student in Purdue’s Department of Earth, Atmospheric and Planetary Sciences, led the study that examined whether empty lava tubes more than 1 kilometer wide could remain structurally stable on the moon.
“We found that if lunar lava tubes existed with a strong arched shape like those on Earth, they would be stable at sizes up to 5,000 meters, or several miles wide, on the moon,” Blair said. “This wouldn’t be possible on Earth, but gravity is much lower on the moon and lunar rock doesn’t have to withstand the same weathering and erosion. In theory, huge lava tubes — big enough to easily house a city — could be structurally sound on the moon.”
Blair worked with Antonio Bobet, a Purdue professor of civil engineering, and applied known information about lunar rock and the moon’s environment to civil engineering technology used to design tunnels on Earth.
The team found that a lava tube’s stability depended on the width, roof thickness and the stress state of the cooled lava, and the team modeled a range of these variables. The researchers also modeled lava tubes with walls created by lava placed in one thick layer and with lava placed in many thin layers, Blair said.
Only one other study, published in 1969, has attempted to model lunar lava tubes, he said.
In addition to Melosh, Blair and Bobet, team members include Loic Chappaz and Rohan Sood, graduate students in the School of Aeronautics and Astronautics; Kathleen Howell, Purdue’s Hsu Lo Professor of Aeronautical and Astronautical Engineering; Andy M. Freed, an associate professor of earth, atmospheric and planetary sciences; and Colleen Milbury, a postdoctoral research associate in the Department of Earth, Atmospheric and Planetary Sciences.
Note: The above story is based on materials provided by Purdue University. The original article was written by Elizabeth K. Gardner.
Photograph from aerial survey showing the upper parts of the landslide that occurred in northwest Washington on March 22, 2014. This photo was taken on March 27, 2014. Credit: Jonathan Godt, USGS
A landslide, also known as a landslip, is a geological phenomenon that includes a wide range of ground movements, such as rockfalls, deep failure of slopes and shallow debris flows. Landslides can occur in offshore, coastal and onshore environments. Although the action of gravity is the primary driving force for a landslide to occur, there are other contributing factors affecting the original slope stability. Typically, pre-conditional factors build up specific sub-surface conditions that make the area/slope prone to failure, whereas the actual landslide often requires a trigger before being released.
The causes of landslides are usually related to instabilities in slopes. It is usually possible to identify one or more landslide causes and one landslide trigger. The difference between these two concepts is subtle but important. The landslide causes are the reasons that a landslide occurred in that location and at that time. Landslide causes are listed in the following table, and include geological factors, morphological factors, physical factors and factors associated with human activity.
Causes may be considered to be factors that made the slope vulnerable to failure, that
Intense rain triggered widespread landslides in southern Thailand during the last week of March 2011. Credit: NASA Earth Observatory
predispose the slope to becoming unstable. The trigger is the single event that finally initiated the landslide. Thus, causes combine to make a slope vulnerable to failure, and the trigger finally initiates the movement. Landslides can have many causes but can only have one trigger as shown in the next figure. Usually, it is relatively easy to determine the trigger after the landslide has occurred (although it is generally very difficult to determine the exact nature of landslide triggers ahead of a movement event).
Geological causes
Weathered Materials e.g. heavy rainfall
Sheared materials
Jointed or fissured materials
Adversely orientated discontinuities
Permeability contrasts
Material contrasts
Rainfall and snow fall
Earthquakes
Morphological causes
Slope angle
Uplift
Rebound
Fluvial erosion
Wave erosion
Glacial erosion
Erosion of lateral margins
Subterranean erosion
Slope loading
Vegetation change
Erosion
Physical causes
Intense rainfall
Rapid snow melt
Prolonged precipitation
Rapid drawdown
Earthquake
Volcanic eruption
Thawing
Freeze-thaw
Ground water changes
Soil pore water pressure
Surface runoff
Seismic activity
Soil erosion
Human causes
Excavation
Loading
Draw-down
Land use (e.g. construction of roads, houses etc.)
Water management
Mining
Quarrying
Vibration
Water leakage
Deforestation
Land use pattern
Pollution
Although there are multiple types of causes of landslides, the three that cause most of the damaging landslides around the world are these:
Landslides and Water
Slope saturation by water is a primary cause of landslides. This effect can occur in the form of intense rainfall, snowmelt, changes in ground-water levels, and water-level changes along coastlines, earth dams, and the banks of lakes, reservoirs, canals, and rivers.
Landsliding and flooding are closely allied because both are related to precipitation, runoff, and the saturation of ground by water. In addition, debris flows and mudflows usually occur in small, steep stream channels and often are mistaken for floods; in fact, these two events often occur simultaneously in the same area.
Landslides can cause flooding by forming landslide dams that block valleys and stream channels, allowing large amounts of water to back up. This causes backwater flooding and, if the dam fails, subsequent downstream flooding. Also, solid landslide debris can “bulk” or add volume and density to otherwise normal streamflow or cause channel blockages and diversions creating flood conditions or localized erosion. Landslides can also cause overtopping of reservoirs and/or reduced capacity of reservoirs to store water.
Landslides and Seismic Activity
Many mountainous areas that are vulnerable to landslides have also experienced at least moderate rates of earthquake occurrence in recorded times. The occurrence of earthquakes in steep landslide-prone areas greatly increases the likelihood that landslides will occur, due to ground shaking alone or shaking-caused dilation of soil materials, which allows rapid infiltration of water. The 1964 Great Alaska Earthquake caused widespread landsliding and other ground failure, which caused most of the monetary loss due to the earthquake. Other areas of the United States, such as California and the Puget Sound region in Washington, have experienced slides, lateral spreading, and other types of ground failure due to moderate to large earthquakes. Widespread rockfalls also are caused by loosening of rocks as a result of ground shaking. Worldwide, landslides caused by earthquakes kill people and damage structures at higher rates than in the United States.
Landslides and Volcanic Activity
Landslides due to volcanic activity are some of the most devastating types. Volcanic lava may melt snow at a rapid rate, causing a deluge of rock, soil, ash, and water that accelerates rapidly on the steep slopes of volcanoes, devastating anything in its path. These volcanic debris flows (also known as lahars) reach great distances, once they leave the flanks of the volcano, and can damage structures in flat areas surrounding the volcanoes. The 1980 eruption of Mount St. Helens, in Washington triggered a massive landslide on the north flank of the volcano, the largest landslide in recorded times.
Types
Debris flow
Debris flow channel with deposits left after 2010 storms in Ladakh,NW Indian Himalaya.
Slope material that becomes saturated with water may develop into a debris flow or mud flow. The resulting slurry of rock and mud may pick up trees, houses and cars, thus blocking bridges and tributaries causing flooding along its path.
Debris flow is often mistaken for flash flood, but they are entirely different processes.
Muddy-debris flows in alpine areas cause severe damage to structures and infrastructure and often claim human lives. Muddy-debris flows can start as a result of slope-related factors and shallow landslides can dam stream beds, resulting in temporary water blockage. As the impoundments fail, a “domino effect” may be created, with a remarkable growth in the volume of the flowing mass, which takes up the debris in the stream channel. The solid-liquid mixture can reach densities of up to 2 tons/m³ and velocities of up to 14 m/s (Chiarle and Luino, 1998; Arattano, 2003). These processes normally cause the first severe road interruptions, due not only to deposits accumulated on the road (from several cubic metres to hundreds of cubic metres), but in some cases to the complete removal of bridges or roadways or railways crossing the stream channel. Damage usually derives from a common underestimation of mud-debris flows: in the alpine valleys, for example, bridges are frequently destroyed by the impact force of the flow because their span is usually calculated only for a water discharge. For a small basin in the Italian Alps (area = 1.76 km²) affected by a debris flow, Chiarle and Luino (1998) estimated a peak discharge of 750 m3/s for a section located in the middle stretch of the main channel. At the same cross section, the maximum foreseeable water discharge (by HEC-1), was 19 m³/s, a value about 40 times lower than that calculated for the debris flow that occurred.
Earthflows
Earthflows are downslope, viscous flows of saturated, fine-grained materials, which move at any speed from slow to fast. Typically, they can move at speeds from 0.17 to 20 km/h (0.1 to 12.4 mph). Though these are a lot like mudflows, overall they are more slow moving and are covered with solid material carried along by flow from within. They are different from fluid flows because they are more rapid. Clay, fine sand and silt, and fine-grained, pyroclastic material are all susceptible to earthflows. The velocity of the earthflow is all dependent on how much water content is in the flow itself: if there is more water content in the flow, the higher the velocity will be.
These flows usually begin when the pore pressures in a fine-grained mass increase until enough of the weight of the material is supported by pore water to significantly decrease the internal shearing strength of the material. This thereby creates a bulging lobe which advances with a slow, rolling motion. As these lobes spread out, drainage of the mass increases and the margins dry out, thereby lowering the overall velocity of the flow. This process causes the flow to thicken. The bulbous variety of earthflows are not that spectacular, but they are much more common than their rapid counterparts. They develop a sag at their heads and are usually derived from the slumping at the source.
Earthflows occur much more during periods of high precipitation, which saturates the ground and adds water to the slope content. Fissures develop during the movement of clay-like material which creates the intrusion of water into the earthflows. Water then increases the pore-water pressure and reduces the shearing strength of the material.
Debris landslide
A debris slide is a type of slide characterized by the chaotic movement of rocks soil and debris mixed with water or ice (or both). They are usually triggered by the saturation of thickly vegetated slopes which results in an incoherent mixture of broken timber, smaller vegetation and other debris. Debris avalanches differ from debris slides because their movement is much more rapid. This is usually a result of lower cohesion or higher water content and commonly steeper slopes.
Steep coastal cliffs can be caused by catastrophic debris avalanches. These have been common on the submerged flanks of ocean island volcanos such as the Hawaiian Islands and the Cape Verde Islands. Another slip of this type was Storegga landslide.
Movement: Debris slides generally start with big rocks that start at the top of the slide and begin to break apart as they slide towards the bottom. This is much slower than a debris avalanche. Debris avalanches are very fast and the entire mass seems to liquefy as it slides down the slope. This is caused by a combination of saturated material, and steep slopes. As the debris moves down the slope it generally follows stream channels leaving a v-shaped scar as it moves down the hill. This differs from the more U-shaped scar of a slump. Debris avalanches can also travel well past the foot of the slope due to their tremendous speed.
Sturzstrom
A sturzstrom is a rare, poorly understood type of landslide, typically with a long run-out. Often very large, these slides are unusually mobile, flowing very far over a low angle, flat, or even slightly uphill terrain.
Shallow landslide
Lateral Spreads
Landslide in which the sliding surface is located within the soil mantle or weathered bedrock (typically to a depth from few decimetres to some metres)is called a shallow landslide. They usually include debris slides, debris flow, and failures of road cut-slopes. Landslides occurring as single large blocks of rock moving slowly down slope are sometimes called block glides.
Shallow landslides can often happen in areas that have slopes with high permeable soils on top of low permeable bottom soils. The low permeable, bottom soils trap the water in the shallower, high permeable soils creating high water pressure in the top soils. As the top soils are filled with water and become heavy, slopes can become very unstable and slide over the low permeable bottom soils. Say there is a slope with silt and sand as its top soil and bedrock as its bottom soil. During an intense rainstorm, the bedrock will keep the rain trapped in the top soils of silt and sand. As the topsoil becomes saturated and heavy, it can start to slide over the bedrock and become a shallow landslide. R. H. Campbell did a study on shallow landslides on Santa Cruz Island California. He notes that if permeability decreases with depth, a perched water table may develop in soils at intense precipitation. When pore water pressures are sufficient to reduce effective normal stress to a critical level, failure occurs.
Deep-seated landslide
Deep-seated landslide on a mountain in Sehara, Kihō, Japan caused by torrential rain of Tropical Storm Talas
Landslides in which the sliding surface is mostly deeply located below the maximum rooting depth of trees (typically to depths greater than ten meters). Deep-seated landslides usually involve deep regolith, weathered rock, and/or bedrock and include large slope failure associated with translational, rotational, or complex movement. This type of landslides are potentially occur in an tectonic active region like Zagros Mountain in Iran. These typically move slowly, only several meters per year, but occasionally move faster. They tend to be larger than shallow landslides and form along a plane of weakness such as a fault or bedding plane. They can be visually identified by concave scarps at the top and steep areas at the toe.
Types and classification
In the following table shows a schematic landslide classification adopting the classification of Varnes 1978 and taking into account the modifications made by Cruden and Varnes, in 1996. Some integration has been made by using the definitions of Hutchinson (1988) and Hungr et al. 2001.
Type of movementType of materialBedrockEngineering soils Predominantly finePredominantly coarseFallsRockfallEarth fallDebris fallTopplesRock toppleEarth toppleDebris toppleSlidesRotational Rock slumpEarth slumpDebris slumpTranslationalFew unitsRock block slideEarth block slideDebris block slideMany unitsRock slideEarth slideDebris slideLateral spreadsRock spreadEarth spreadDebris spreadFlowsRock flowEarth flowDebris flowRock avalanche Debris avalanche(Deep creep)(Soil creep)Complex and compoundCombination in time and/or space of two or more principal types of movement
Factors Influencing Landslide Risk
Bluff Characteristics
Height: The height of a bluff can generally indicate landslide risk. While sediment strength depends on several factors, the thicker the sediment deposit, the more likely its weight will cause subsurface movement or slippage that leads to a landslide. The risk of a landslide increases when mud bluffs have a height of twenty feet or more. In general, the higher the exposed bluff face the greater the risk of a landslide.
Sediment type: Earth material that makes up a coastal bluff influences the risk of a landslide occurring. Clay and silt (muddy) sediment is the most unstable material that can make up a bluff. These fine-grained sediments are weak and prone to moving in the form of slow-motion creep, moderate-sized slumping, or large landslides. Sand and gravel deposits tend to be stronger and better drained than muddy sediment. Landslides can occur in coarse-grained bluffs although they are less frequent than muddy landslides along the Maine coast.
Slope: Coastal bluffs have a relatively steep ocean-facing slope. The angle of a bluff face varies due to factors such as the sediment type and rate of erosion at the base of the bluff. Slope is also affected by the history of slumps and landslides at the site. Some slopes are uniformly straight while others are terraced or uneven due to earth movements. In general, the steeper the slope, the easier it is for gravity to initiate a landslide.
Vegetation: Types, shapes, and distribution of vegetation above and on a bluff face can be used as an indication of site stability. In areas where the soil has shifted, either due to previous landslides or to gradual surface creep, many tree trunks can become tilted or twisted in the same direction. Curved tree trunks near the roots often indicate land movement down the face of a bluff. Large trees on the bluff face may be moved by wind and resulting root motion may loosen bluff sediment. Natural vegetation that consists only of small shrubs and trees may indicate recent bluff erosion or a landslide.
Bedrock: Crystalline rock or ledge is much more stable than any sediment bluff and not likely to erode or slide. The elevation of bedrock at the shore and inland beneath a bluff is important in determining landslide risk. Bedrock exposures along the shoreline may slow erosion and make sediment less susceptible to landsliding. Beneath a sediment bluff, bedrock may rise toward the surface and reduce the overall thickness of sediment and thus reduce the risk of deep-seated movement below the ground surface.
Natural Conditions
Waves, tides, and sea level: Several marine processes affect the risk of landslides along a coastal bluff. A gradual, but ongoing rise in sea level at a rate of about an inch per decade is causing chronic erosion along the base of many bluffs. As sea level rises, wave action and coastal flooding can reach higher and farther inland and scour more sediment from a bluff. Sea ice erodes tidal flats and the base of bluffs by abrasion and freezing sediment in ice blocks. Erosion can increase a bluff slope and make it more susceptible to landsliding. Tides are also important in washing away eroded bluff sediment which helps wave action move inland. Storms that create wind, waves, and flooding can cause more extreme erosion at the base of a bluff, increase the bluff slope, and make a landslide more likely.
Surface water: The amount, type, and location of surface water can influence bluff slope stability and may contribute to some landslides. Wetlands, ponds, and streams above the bluff can supply water to the bluff face and also to the ground water. The elevation or topography of the land surface determines which way surface water will flow. Water that runs over the face of a bluff can wash sediment to sea, increase the bluff face slope, and weaken the remaining sediment holding up the bluff. Removal of sediment from the bluff face can increase the risk of a landslide.
Ground water: Ground water inland of a bluff comes from surface sources, such as rain or a stream, uphill in the local watershed. Ground water tends to flow horizontally beneath the surface and may seep out the face of a bluff. Seeps and springs on the bluff face contribute to surface water flow and destabilize the bluff face. In addition, a high water table can saturate and weaken muddy sediment and make the ground more prone to slope failure.
Weathering: Weathering in clay and silt can change the strength of bluff sediment and stability of the bluff face. Drying of clay can increase resistance to sliding. The seasonal cycle of freezing and thawing of the bluff face can lead to slumping after a thaw.
Earthquakes: Landslides can be triggered by earthquakes. Ground vibration loosens sediment enough to reduce the strength of material supporting a bluff and a landslide results. Most landslides triggered by earthquakes in sediment like that found in Maine have been of Richter magnitude 5 or more. These are relatively rare events, but a few have occurred in historical time.
Human Activity
Land use: Human activity and land use may contribute to or reduce the risk of a landslide. Actions that increase surface water flow to a bluff face, watering lawns or grading slopes, add to natural processes destabilizing the bluff face. Surface water, collected by roofs, driveways, paths, and lawns flows toward and down the bluff face. Walkways down the face of a bluff can lead to greater erosion from foot traffic or the concentration of surface water flow. Both surface and ground water above a bluff can be supplied by pipes, culverts, surface drains, and septic systems. Increased water below ground can weaken a bluff and contribute to internal weakness that leads to a landslide. Greater seepage of water out of the bluff face can also increase the risk.
Clearing of vegetation from the bluff face can lead to greater bluff erosion and a steeper bluff that is more prone to landslide. Vegetation tends to remove ground water, strengthen soil with roots, and lessen the impact of heavy rain on the bluff face.
Adding weight to the top of a bluff can increase the risk of a landslide. Buildings, landscaping, or fill on the top of the bluff can increase the forces that result in a landslide. Saturating the ground with water that raises the water table also adds weight. Even ground vibration, such as well drilling or deep excavation, may locally increase the risk of a landslide.
Shoreline engineering in the form of seawalls, rip rap, or other solid structures is sometimes used to reduce wave erosion at the toe of a bluff. In some settings, engineering can increase the rate of beach or tidal flat erosion and lower the shore profile over time. This intertidal erosion can undermine engineering and result in less physical support of the base of the bluff by natural sediment. Where engineering ends along a shore, erosion can become worse on adjacent properties. Engineering alone cannot prevent some large landslides.
In general, human activities that increase the amount or rate of natural processes may, in various ways, contribute to landslide risk.
The Bay Area fault system and the spot (red star) where the Hayward Fault branches off from the Calaveras Fault. The white lines indicate faults recognized by the USGS. The red line is the newly discovered surface trace connecting the southern end of the Hayward Fault to the Calaveras Fault, once thought to be an independent system. The surface trace is offset by several kilometers from the deep portion of the fault 3-5 km below ground (blue line). Credit: Estelle Chaussard, UC Berkeley
University of California, Berkeley seismologists have proven that the Hayward Fault is essentially a branch of the Calaveras Fault that runs east of San Jose, which means that both could rupture together, resulting in a significantly more destructive earthquake than previously thought.
“The maximum earthquake on a fault is proportional to its length, so by having the two directly connected, we can have a rupture propagating across from one to the other, making a larger quake,” said lead researcher Estelle Chaussard, a postdoctoral fellow in the Berkeley Seismological Laboratory. “People have been looking for evidence of this for a long time, but only now do we have the data to prove it.”
The 70-kilometer-long Hayward Fault is already known as one of the most dangerous in the country because it runs through large population areas from its northern limit on San Pablo Bay at Richmond to its southern end south of Fremont.
In an update of seismic hazards last month, the U.S. Geological Survey estimated a 14.3 percent likelihood of a magnitude 6.7 or greater earthquake on the Hayward Fault in the next 30 years, and a 7.4 percent chance on the Calaveras Fault.
These are based on the assumption that the two faults are independent systems, and that the maximum quake on the Hayward Fault would be between magnitudes 6.9 and 7.0. Given that the Hayward and Calaveras faults are connected, the energy released in a simultaneous rupture could be 2.5 times greater, or a magnitude 7.3 quake.
“A rupture from Richmond to Gilroy would produce about a 7.3 magnitude quake, but it would be even greater if the rupture extended south to Hollister, where the Calaveras Fault meets the San Andreas Fault,” Chaussard said.
Chaussard and her colleagues, including Roland Bürgmann, a UC Berkeley professor of earth and planetary science, reported their findings in the journal Geophysical Research Letters.
Chaussard said there has always been ambiguity about whether the two faults are connected. The Hayward Fault ends just short of the Calaveras Fault, which runs about 123 kilometers from north of Danville south to Hollister in the Salinas Valley.
The UC Berkeley team used 19 years of satellite data to map ground deformation using interferometric synthetic aperture radar (InSAR) and measure creep along the southern end of the Hayward Fault, and found, surprisingly, that the creep didn’t stop south of Fremont, the presumed southern end of the fault, but continued as far as the Calaveras Fault.
“We found that it continued on another 15 kilometers and that the trace merged with the trace of the Calaveras Fault,” she said. In addition, seismic data show that micro-earthquakes on these faults 3-5 kilometers underground also merge. “With this evidence from surface creep and seismicity, we can argue for a direct junction on the surface and at depth for the two faults.”
Both are strike-slip faults — the western side moves northward relative to the eastern side. The researchers found that the underground portion of the Hayward Fault meets the Calaveras Fault 10 kilometers farther north than where the creeping surface traces of both faults meet. This geometry implies that the Hayward Fault dips at an angle where it meets the Calaveras Fault.
InSAR revolutionizes mapping
Chaussard said that the many years of InSAR data, in particular from the European Space Agency’s ERS and Envisat satellites from 1992 to 2011, were critical to connecting the two faults.
Creep, or the surface movement along a fault, is evidenced by offset curbs, streets and home foundations. It is normally determined by measuring points on opposite sides of a fault every few years, but that is hard to do along an entire fault or in difficult terrain. InSAR provides data over large areas even in vegetated terrains and outside of urban areas, and with the repeated measurements over many years InSAR can detect deformation with a precision of 2 millimeters per year.
“With InSAR, we have access to much larger spatial coverage,” said Chaussard, who has been expanding the use of InSAR to measure water resources and now ground deformation that occurs between earthquakes. “Instead of having a few points, we have over 200,000 points in the Bay Area. And we have access to areas we couldn’t go to on the ground.”
She noted that while creep relieves stress on a fault gradually, eventually the surface movement must catch up with the long-term underground fault movement. The Hayward Fault moves at about 10 millimeters per year underground, but it creeps at only 3 to 8 millimeters per year. Earthquakes occur when the surface suddenly catches up with a fault’s underground long-term movement.
“Creep is delaying the accumulation of stress needed to get to an earthquake, but it does not cancel the earthquake,” Chaussard said.
Reference:
E. Chaussard, R. Bürgmann, H. Fattahi, R. M. Nadeau, T. Taira, C. W. Johnson, I. Johanson. Potential for larger earthquakes in the East San Francisco Bay Area due to the direct connection between the Hayward and Calaveras Faults. Geophysical Research Letters, 2015; DOI: 10.1002/2015GL063575
Simulation of the Deepwater Horizon blowout based on oil-in-water experimental data: distribution of oil mass in the water column? at day 60, assuming no injection of dispersant at the wellhead. We note that the highest oil concentration (red) remain at depth. Diluted oil by 5-25 folds, reaches the surface as far as 200 km downstream from the response zone of the accident. Credit: C-IMAGE
A first-of-its-kind study observed how oil droplets are formed and measured their size under high pressure. They further simulated how the atomized oil spewing from the Macondo well reached the ocean’s surface during the Deepwater Horizon accident. The findings from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science and University of Western Australia research team suggest that the physical properties in deep water create a natural dispersion mechanism for oil droplets that generates a similar effect to the application of chemical dispersants at oil spill source.
“These results support our initial modeling work that the use of toxic dispersants at depth should not be a systematic oil spill response,” said Claire Paris, Associate Professor of Ocean Sciences at the UM Rosenstiel School. “It could very well be unnecessary in some cases.”
The research team from C-IMAGE (Center for the Integrated Modeling and Analysis of the Gulf Ecosystem) conducted eight experiments to simulate different pressures of oil from a blowout at depth. The oil was placed in a high-pressure chamber, called a sapphire autoclave, and monitored using a high-speed, high-resolution camera to evaluate how droplets form at varying turbulent conditions.
“This is the first time that we’ve been able to visually monitor how droplets break up and coalesce at up to 120 times atmospheric pressure,” said Zachary Aman, associate professor of mechanical and chemical engineering at the University of Western Australia. “When paired with the high pressures and flow rates of Macondo, the results suggest a natural mechanism by which oil is dispersed into small droplets.”
The results of the laboratory experiment were applied in a field-scale simulation under the same physical conditions that existed during the Macondo well blowout. In the computer simulation, the team tracked the oil released at a constant rate of 1000 oil droplets every two hours at a depth of 300 meters above the Macondo well, corresponding to the depth of the observed deep plume, from April 20 to July 15, 2010, when the Macondo well was capped; droplets were tracked for an additional 24 days after the cap was in place.
Based on the experimental data and modelling, the researchers suggest that the use of chemical dispersants may have reduced the mean oil droplet diameter from about 80 to 45 µm, which would have reduced the amount of oil reaching the surface only by up to 3%. The model simulations showed that if the blowout occurred in shallow water conditions, or at a smaller rate of hydrocarbon release, dispersant may have had a more significant impact on the oil flowing from the well.
The research paper, entitled “High-pressure visual experimental studies of oil-in-water dispersion droplet size,” will be published in the May 4 edition of the journal Chemical Engineering Science and is currently available in the online edition. The study’s co-author’s include Claire B. Paris and David Lindo-Atichati of the UM Rosenstiel School and Zachary Aman, Eric F. May and Michael L. Johns of the University of Western Australia.
Reference:
Zachary M. Aman, Claire B. Paris, Eric F. May, Michael L. Johns, David Lindo-Atichati. High-pressure visual experimental studies of oil-in-water dispersion droplet size. Chemical Engineering Science, 2015; 127: 392 DOI: 10.1016/j.ces.2015.01.058
Backscattered electron image of Hyperammina deformis. Credit: Courtesy Merlynd and Galina Nestell
A new study led by scientists with The University of Texas at Arlington demonstrates for the first time how elemental carbon became an important construction material of some forms of ocean life after one of the greatest mass extinctions in the history of Earth more than 252 million years ago.
As the Permian Period of the Paleozoic Era ended and the Triassic Period of the Mesozoic Era began, more than 90 percent of terrestrial and marine species became extinct. Various proposals have been suggested for this extinction event, including extensive volcanic activity, global heating, or even one or more extraterrestrial impacts.
The work is explained in the paper, “High influx of carbon in walls of agglutinated foraminifers during the Permian-Triassic transition in global oceans,” which is published in the March edition of International Geology Review.
Researchers focused on a section of the latest Permian aged rocks in Vietnam, just south of the Chinese border, where closely spaced samples were collected and studied from about a four-meter interval in the boundary strata.
Merlynd Nestell, professor of earth and environmental sciences in the UT Arlington College of Science and a co-author of the paper, said there was extensive volcanic activity in both the Northern and the Southern Hemispheres during the Permian-Triassic transition.
“Much of the volcanic activity was connected with the extensive Siberian flood basalt known as the Siberian Traps that emerged through Permian aged coal deposits and, of course, the burning of coal created CO2,” Nestell said.
He noted that there was also synchronous volcanic activity in what is now Australia and southern China that could have burned Permian vegetation. The carbon from ash accumulated in the atmosphere and marine environment and was used by some marine microorganisms in the construction of their shells, something they had not done before.
This new discovery documents elemental carbon as being a major construction component of the tiny shells of single-celled agglutinated foraminifers, ostracodes, and worm tubes that made up part of the very limited population of bottom-dwelling marine organisms surviving the extinction event.
“Specimens of the boundary interval foraminifers seen in slices of rock that were ground thin and studied from other places in the world revealed black layers,” said Galina P. Nestell, study co-author and adjunct research professor of earth and environmental sciences at UT Arlington. “But nobody really checked the composition of the black material.”
Nestell said this phenomenon has never been reported although sequences of rocks that cross this important Permian-Triassic boundary have been studied in Iran, Hungary, China, Turkey, Slovenia and many other parts of the world.
For the study, Asish Basu, chair of earth and environmental sciences at UT Arlington, analyzed clusters of iron pyrite attached to the walls of the foraminifer shells for lead isotopes. Data from these pyrite clusters support the presence of products of coal combustion that contributed to the high input of carbon into the marine environment immediately after the extinction event.
Brooks Ellwood, emeritus professor of Earth and Environmental Sciences at UT Arlington and a professor in the Louisiana State University Department of Geology and Geophysics, collected the samples to study the Permian-Triassic boundary interval using magnetic and geochemical properties. He and his colleague Luu Thi Phuong Lan of the Vietnamese Academy of Science and Technology in Hanoi, Vietnam, also collected the samples used in the biostratigraphic work by the Nestells and Bruce Wardlaw of the Eastern Geology and Paleoclimate Science Center at the U.S. Geological Survey and adjunct professor at UT Arlington.
By using time-series analysis of magnetic measurements, Ellwood discovered the extinction event to have lasted about 28,000 years. It ended about 91,000 years before the actual Permian-Triassic boundary level — as defined worldwide by the first appearance of the fossil conodont species Hindeodus parvus — identification done by Wardlaw.
Galina Nestell said the high carbon levels began after the extinction event about 82,000 years before the official boundary horizon and continued until about 3,000 years after the Permian-Triassic boundary horizon. The boundary horizon is calculated to be 252.2 million years before present.
Other co-authors who contributed to parts of the study include Andrew Hunt, EES associate professor at UT Arlington, Nilotpal Ghosh of the University of Rochester; Harry Rowe of the Bureau of Economic Geology at the University of Texas at Austin; Jonathan Tomkin of the University of Illinois, Urbana; and Kenneth Ratcliffe of Chemostrat Inc. in Houston.
Reference:
Galina P. Nestell, Merlynd K. Nestell, Brooks B. Ellwood, Bruce R. Wardlaw, Asish R. Basu, Nilotpal Ghosh, Luu Thi Phuong Lan, Harry D. Rowe, Andrew Hunt, Jonathan H. Tomkin, Kenneth T. Ratcliffe. High influx of carbon in walls of agglutinated foraminifers during the Permian–Triassic transition in global oceans. International Geology Review, 2015; 57 (4): 411 DOI: 10.1080/00206814.2015.1010610
Artist’s conception of an oviraptor using its tail feathers in a mating display. Credit: Sydney Mohr
Paleontologists at the University of Alberta have discovered evidence of a prehistoric romance and the secret to sexing some dinosaurs.
“Determining a dinosaur’s gender is really hard,” says graduate student Scott Persons, lead author of the research. “Because soft anatomy seldom fossilizes, a dinosaur fossil usually provides no direct evidence of whether it was a male or a female.”
Instead, the new research focuses on indirect evidence. Modern birds, the living descendants of dinosaurs, frequently show sexually dimorphic display structures. Such structures—like the fans of peacocks, the tall crests of roosters or the long tail feathers of some birds of paradise—are used to attract and court mates, and are almost always much larger in males (who do the courting) than in females (who do the choosing).
Back in 2011, Persons and his colleagues published research on the tails of a group of birdlike dinosaurs called oviraptors. Oviraptors were strictly land-bound animals, but according to the study, they possessed fans of long feathers on the ends of their tails. If these dinosaurs weren’t able to fly, what good were their tail feathers?
“Our theory,” explains Persons, “was that these large feather fans were used for the same purpose as the feather fans of many modern ground birds, like turkeys, peacocks and prairie chickens: they were used to enhance courtship displays. My analysis of the tail skeletons supported this theory, because the skeletons showed adaptations for both high tail flexibility and enlarged tail musculature—both traits that would have helped an oviraptor to flaunt its tail fan in a mating dance.”
The U of A researchers took the idea a step further. “The greatest test of any scientific theory is its predictive power,” says Persons. “If we were right, and oviraptors really were using their tail fans to court mates, then, just as in modern birds, the display structures ought to be sexually dimorphic. We published the prediction that careful analysis of more oviraptor tails would reveal male and female differences within the same species.”
That prediction has come home to roost. In the new study, published this week in the journal Scientific Reports, Persons and his team have confirmed sexual dimorphism, after meticulous observation of two oviraptor specimens. The two raptors were discovered in the Gobi Desert of Mongolia. Both died and were buried next to each other when a large sand dune collapsed on top of them.
When they were first unearthed, the two oviraptors were given the nicknames “Romeo and Juliet,” because they seemed reminiscent of Shakespeare’s famously doomed lovers. It turns out that the nickname may have been entirely appropriate.
“We discovered that, although both oviraptors were roughly the same size, the same age and otherwise identical in all anatomical regards, ‘Romeo’ had larger and specially shaped tail bones,” says Persons. “This indicates that it had a greater capacity for courtship displays and was likely a male.” By comparison, the second specimen, “Juliet,” had shorter and simpler tail bones, suggesting a lesser capacity for peacocking, and has been interpreted as a female.
According to Persons, the two may very well have been a mated pair, making for an altogether romantic story, as the dinosaur couple was preserved side by side for more than 75 million years.
Reference:
“A possible instance of sexual dimorphism in the tails of two oviraptorosaur dinosaurs.” Scientific Reports 5, Article number: 9472 DOI: 10.1038/srep09472
Rhawn Denniston (right), professor of geology at Cornell College, with Dan Cleary ’13, a member of his student research team, examining stalagmites in an Australian cave. Credit: Image courtesy of Cornell College
Stalagmites, which crystallize from water dropping onto the floors of caves, millimeter by millimeter, over thousands of years, leave behind a record of climate change encased in stone. Newly published research by Rhawn Denniston, professor of geology at Cornell College, and his research team, applied a novel technique to stalagmites from the Australian tropics to create a 2,200-year-long record of flood events that might also help predict future climate change.
A paper by Denniston and 10 others, including a 2014 Cornell College graduate, is published this week in the journal Proceedings of the National Academy of Sciences. The article, “Extreme rainfall activity in the Australian tropics reflects changes in the El Niño/Southern Oscillation over the last two millennia,” presents a precisely dated stalagmite record of cave flooding events that are tied to tropical cyclones, which include storms such as hurricanes and typhoons.
Denniston is one of few researchers worldwide using stalagmites to reconstruct past tropical cyclone activity, a field of research called paleotempestology. His work in Australia began in 2009 and was originally intended to focus on the chemical composition of the stalagmites as a means of reconstructing past changes in the intensity of Australian summer monsoon rains. But Denniston and his research team found more than just variations in the chemical composition of the stalagmites they examined; they discovered that the interiors of the stalagmites also contained prominent layers of mud.
“Seeing mud accumulations like these was really unusual,” Denniston said. “There was no doubt that the mud layers came from the cave having flooded. The water stirred up the sediment and when the water receded, the mud coated everything in the cave — the floor, the walls, and the stalagmites. Then the stalagmites started forming again and the mud got trapped inside.”
The stalagmites were precisely dated by Denniston, Cornell College geology majors, and Denniston’s colleagues at the University of New Mexico. Once the ages of the stalagmites were known, the mud layers were measured. Angelique Gonzales ’14, who worked with Denniston on the research and is third author on the paper, examined nearly 11 meters of stalagmites, measuring them in half millimeter increments and recording the location and thickness of mud layers. This work gave the team more than 2,000 years of data about the frequency of cave flooding.
But the origins of the floods were still unclear. Given the area’s climatology, Denniston found that these rains could have come from the Australian monsoon or from tropical cyclones.
“We were sort of stuck,” Denniston said, “but then I started working with Gabriele.” Gabriele Villarini, an assistant professor of engineering at the University of Iowa and the second author of the paper, studies extreme meteorological events, what drives the frequency and magnitude of those events, and their impact on policy and economics. With Denniston and Gonzales, Villarini examined historical rainfall records from a weather station near the cave.
“The largest rainfall events, almost regardless of duration, are tied to tropical cyclones,” Villarini said.
Next, they compared flood events recorded in a stalagmite that grew over the past several decades to historical records of tropical cyclones. This analysis revealed that timing of flood events in the cave was consistent with the passing of tropical cyclones through the area. Thus, the researchers interpreted the flood layers in their stalagmites largely as recording tropical cyclone activity.
The resulting data tell scientists about more than just the frequencies of tropical cyclones in one part of Australia over the past 2,200 years. A major driver of year-to-year changes in tropical cyclones around the world is the El Niño/Southern Oscillation, which influences weather patterns across the globe. During El Niño events, for example, Australia and the Atlantic generally experience fewer tropical cyclones, while during La Niña events, the climatological opposite of El Niño, the regions see more tropical cyclones.
“Our work, and that of several other researchers, reveals that the frequency of storms has changed over the past hundreds and thousands of years,” Denniston said. “But why? Could it have been due to El Niño? Direct observations only go back about a hundred years, and there hasn’t been much variation in the nature of El Niño/Southern Oscillation over that time. Further back there was more, and so our goal was to test the link between storms and El Niño in prehistory.”
Denniston noted that the variations over time in the numbers of flood events recorded by his stalagmites matched reconstructed numbers of hurricanes in the Atlantic, Gulf of Mexico, and Caribbean.
“Tropical cyclone activity in these regions responds similarly to El Niño, and previous studies had also suggested that some periods, such as those when we had lots of flood layers in our stalagmites, were likely characterized by more frequent La Niñas. Similarly, times with fewer storms were characterized by more frequent El Niños.” The results of this study mark an important step towards understanding how future climate change may be expressed.
“It is difficult to use climate models to study hurricane activity, and so studies such as ours, which produced a record of storms under different climate conditions, are important for our understanding of future storm activity,” Denniston said.
Gonzales, who is planning to pursue a Ph.D. in geology, said that her experience with Denniston and his research, including two senior seminars and an honors thesis, was valuable because she got both field and lab experience as she helped determine not just what had happened in the past, but what that meant.
“There were a lot of different aspects to put this together — dating, measuring, literature review, and modeling,” she said. “It was really exciting.”
Denniston is now gearing up to establish a detailed cave monitoring program in this and other regional caves. “We want to extend this study,” he said, “to examine what conditions trigger cave flooding.”
In addition to Denniston, Villarini, and Gonzales, the other authors on the paper were Karl-Heinz Wyrwoll from the University of Western Australia, Victor J. Polyak from the University of New Mexico, Caroline C. Ummenhofer from the Woods Hole Oceanographic Institution, Matthew S. Lachniet from the University of Nevada Las Vegas, Alan D. Wanamaker Jr. from Iowa State University, William F. Humphreys from the Western Australian Museum, David Woods from the Australian Department of Parks and Wildlife, and John Cugley from the Australian Speleological Federation.
Reference:
Rhawn F. Denniston, Gabriele Villarini, Angelique N. Gonzales, Karl-Heinz Wyrwoll, Victor J. Polyak, Caroline C. Ummenhofer, Matthew S. Lachniet, Alan D. Wanamaker, Jr., William F. Humphreys, David Woods, and John Cugley. Extreme rainfall activity in the Australian tropics reflects changes in the El Niño/Southern Oscillation over the last two millennia. PNAS, 2015 DOI: 10.1073/pnas.1422270112
A plume of the active Hawaiian shield volcano Kilauea exposes residents to a highly acidic atmospheric pollutant mix. Photo: Jesse Kroll
Since 1983, the 180,000 residents of the Big Island of Hawaii have lived in the wake of the pollution caused by the active shield volcano Kilauea. The destructive nature of the volcanic smog (“vog”) has imprinted a significant ecological footprint on the surrounding infrastructure, vegetation, and human health.
With the volcano’s eruption now in its 33rd year, research from the Department of Civil and Environmental Engineering (CEE) provides an improved understanding of the atmospheric pollutant mix that island residents are exposed to on a daily basis.
In particular, a new study uncovers two fundamental features of Kilauea’s volcanic plume: a strong dependence of sulfur partitioning on meteorology and time of day, and the presence of particles that are exceedingly high in acidity. The findings were published March 18 in the journal Environmental Science and Technology, and were carried out by 28 CEE undergraduate students; lead authors Jesse Kroll, associate professor in CEE, and CEE research scientist Eben Cross; and nine other MIT researchers and collaborators.
The study was conducted in coordination with CEE’s Traveling Research Environmental eXperience (TREX) in 2012 and 2013, a program that is offered to Course 1 undergraduates during the Independent Activities Period and which involves an annual trip to carry out environmental fieldwork.
“As a sophomore, TREX was an excellent chance for me to develop my research skills so I could apply them to other projects in the future,” says Theresa Oehmke, now a fourth-year Course 1 undergraduate. “It is a program that not many other universities offer.” The support system she gained in CEE and the opportunity to participate in published research were two invaluable benefits earned from the program, she adds.
According to Sidhant Pai ’14, a Course 1 undergraduate participant in the 2013 trip, TREX was one of the “most enjoyable and memorable MIT experiences” and “really got [him] excited about environmental science.” After TREX, Pai continued to study Kilauea with Kroll and Cross as part of the Course 1 Undergraduate Research Opportunities Program (UROP).
“Given that millions of people live close to volcanoes globally, it is important to understand plume chemistry before we can characterize the impact that the emissions have on human health and the environment,” Pai says. “The work done by TREX is an important step in that direction.” The team’s unique approach to studying the sulfur emissions allowed them to better understand the intensity of the vog and the acidity of the particles.
Connecting with locals
During their time on the island, the CEE team spoke with a wide range of residents regarding the volcano’s influence on the locals’ daily lives. One Pahala rancher, Lani Petrie, recently had to replace her fences for the second time, attributing her property’s rotted infrastructure to the volcanic emissions. Originally constructed from steel, Petrie’s fences corroded when Kilauea’s vent opened in 2008 and spewed higher amounts of sulfuric acid into the air. She then attempted to replace the material with stainless steel, only to result in similar deterioration. Petrie is now testing fences constructed from fiberglass—a resilient, but more expensive material.
“The whole island is impacted from the volcano, and we’re just exposed to it constantly—Pahala especially,” says Lisa Wallace, a chemist from the Hawaii State Department of Health. “Residents, mostly downwind, complain of respiratory complications, eye, and throat irritation. A couple of my coworkers even experience chronic bronchitis that just will not go away, and this isn’t unheard of.” Wallace herself experienced the firsthand effects of the vog, when the roof on her home completely corroded after only five years.
To have similar, in-depth studies such as this conducted on the chemical nature of Kilauea, she said, would “certainly help to improve the way construction processes, construction materials and even plumbing are handled” on the island.
“The majority of the data was collected by the students in 2013,” says Kroll. “The 2012 group, however, set the precedent for how to collect the data. They gave us all of the information we needed on how to make the 2013 TREX mission work.”
In 2013, the students carried out real-time measurements of the key chemical components from Kilauea’s volcanic plume, and produced a detailed characterization of sulfur partitioning with unprecedented time resolution.
“Sulfur dioxide (SO2) oxidizes in the air to form sulfuric acid particles, and these can then neutralize to create ammonium sulfate,” says Kroll. “Our intention with this project was to understand the extent and the rate at which these chemical processes happen and what the people are exposed to on the island: SO2 versus sulfuric acid versus more neutralized particles.”
Breaking through the vog
Vog, a type of pollution formed from acidic gases and particles, is released by active volcanoes. These gases are primarily composed of sulfur dioxide gas and its oxidation products, such as sulfate aerosol.
Over the course of the study, the students analyzed the emissions from the vent of Kilauea’s crater at two different locations—seven days at Kilauea Military Camp located on the north rim of the crater and 12 days directly downwind of the vent in the town of Pahala. The team used a sulfur dioxide monitor and an aerosol chemical speciation monitor to measure the relative amounts of gas-phase SO2 and particulate sulfate every five minutes.
According to Cross, the particles within the plume were measured to have a pH value of as low as -0.8.
“It’s rare that you would see such a highly acidic aerosol plume persisting over space and time,” he says. “In most environments, there’s going to be a sufficient amount of ammonia present in the gas phase, both from natural and anthropogenic sources. This would normally turn that sulfate from sulfuric acid to more neutralized forms.” However, the team found that the amount of sulfuric acid was much too high to be neutralized by the available ammonia, giving it an acidity level lower than that of battery acid.
SO2 is highly toxic to both humans and plants; since it is emitted directly from the volcano, it is known as a “primary pollutant.” In the atmosphere, SO2 will oxidize to form sulfuric acid (H2SO4), a “secondary pollutant,” that can contribute to harmful particulate matter and acid deposition. As secondary pollutants are formed by chemistry and not simple emissions, they can be exceedingly problematic to isolate. In this case, the TREX team knew that the vast majority of the measured SO2 and H2SO4 came from the volcano, allowing them to monitor out the conversion of one pollutant to the other.
Further studies
Today, the team’s goal is to employ measurements from this study in upcoming TREX expeditions to the Big Island.
“The next important step in this exploration is to make robust measurements with lower-cost equipment,” says Cross. This objective drove the most recent TREX expedition, during which the students increased the instruments used at the Pahala site and built and deployed homemade SO2 sensors in various locations.
“In 2013, we got a clear snapshot of one place,” Kroll says. “We need to perform this experiment all around the island and attempt to truly understand where the SO2 is going and how fast its chemistry is occurring.” Future findings will lend themselves to the development and implementation of solutions for the island’s infrastructural challenges.
Course 1’s TREX subject for undergraduates will continue its exploration of the influence of Kilauea’s plume on the environment, enabling communities to understand the vog’s ongoing impact on local air quality and ecological health.
“Since TREX, I have gotten more exposure to the field and intend to eventually apply to grad school to pursue it further,” says Pai. “To be credited in the publication alongside my instructors is an honor, and I’m really glad I could be a part of the process.”
Video
Reference:
“Atmospheric Evolution of Sulfur Emissions from Kı̅lauea: Real-Time Measurements of Oxidation, Dilution, and Neutralization within a Volcanic Plume” Environ. Sci. Technol., Article ASAP DOI: 10.1021/es506119x
Hong Kong’s first dinosaur-era fish – a specimen of the Chinese osteoglossoid osteoglossomorph fish Paralycoptera. Credit: Copyright IVPP
A ~147 million-year-old Jurassic-aged osteoglossoid osteoglossomorph fish Paralycoptera from outcrops at Lai Chi Chong has been described. This fossil represents the first dinosaur-era fish — as well as vertebrate — from Hong Kong to be identified.
The fossil was rediscovered in the collections of the Stephen Hui Geological Museum by Mr. Edison Tse Tze-kei, graduate of the Class of 2014, Department of Earth Sciences, Faculty of Science, the University of Hong Kong (HKU). Mr. Tse studied the specimen during his HKU Faculty of Science Summer Research Fellowship and Earth Sciences Major final-year project, under the supervision of Dr. Michael Pittman who leads the University’s Vertebrate Palaeontology Laboratory and is an expert on dinosaur evolution, as well as Professor Chang Mee-mann, an Academician of the Chinese Academy of Sciences from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing. A paper on this study has recently been published in the open-access journal PeerJ, demonstrating international recognition of the outstanding ability of HKU undergraduate students in conducting scientific research.
The fossil consists of the posterior portion of a small, about 4cm long osteoglossoid osteoglossomorph fish from the genus Paralycoptera, and was collected at Lai Chi Chong, Tolo Channel, from rocks that have been previously radiometrically dated to 146.6 ± 0.2 million years old (Tithonian stage of the Late Jurassic). Paralycoptera is a typical member of the Mesoclupea fish fauna of Southeast China. Its discovery in Hong Kong extends the geographic range of the genus — and potentially of the Mesoclupea fish fauna — by about 700 km further south. The Jurassic-age of the Hong Kong specimen extends the temporal range of the genus about 40 million years back in time because all mainland specimens are currently known from the Early Cretaceous.
Hong Kong’s last major vertebrate fossil identification was the discovery of a ~370 million-year-old early fish (Devonian-aged placoderm fish) by Mr. Lee Cho-min 35 years ago on the north shore of Tolo Channel, Hong Kong, almost directly opposite to Lai Chi Chong.
When asked about the impact of the new specimen towards our broader knowledge of osteoglossomorph fish, Research Assistant Professor Dr. Pittman replied, ‘The fossil’s Late Jurassic age also adds support to the hypothesis that osteoglossomorph fish originated on the portion of the ancient supercontinent of Pangaea (which broke apart about 200 million years ago) that is now East Asia.’
This study improves our understanding of the habitat of Paralycoptera, based on the geological information preserved at Lai Chi Chong, a beautiful tidal rock outcrop within the Hong Kong Global Geopark of China. Elaborating on this, Mr. Tse said, ‘Our Paralycoptera specimen appears to have lived in a tropical-subtropical freshwater lake that was periodically subjected to catastrophic volcanic eruptions and earthquakes.’
Dr Pittman said that undergraduate students worldwide typically do not publish peer-reviewed research, so Edison’s valuable contribution towards Hong Kong palaeontology is a credit to him and the research ability of HKU students. The detailed identification and description of the specimen was also aided by Professor Mee-mann Chang, a global expert on Chinese fossil fish.
Reference:
Tze-Kei Tse, Michael Pittman, Mee-mann Chang. A specimen ofParalycopteraChang & Chou 1977 (Teleostei: Osteoglossoidei) from Hong Kong (China) with a potential Late Jurassic age that extends the temporal and geographical range of the genus. PeerJ, 2015; 3: e865 DOI: 10.7717/peerj.865
This image shows the Little Foot skull (STW 573). Credit: Photo courtesy of the University of the Witwatersrand
A skeleton named Little Foot is among the oldest hominid skeletons ever dated at 3.67 million years old, according to an advanced dating method.
Little Foot is a rare, nearly complete skeleton of Australopithecus first discovered 21 years ago in a cave at Sterkfontein, in central South Africa. The new date places Little Foot as an older relative of Lucy, a famous Australopithecus skeleton dated at 3.2 million years old that was found in Ethiopia. It is thought that Australopithecus is an evolutionary ancestor to humans that lived between 2 million and 4 million years ago.
Stone tools found at a different level of the Sterkfontein cave also were dated at 2.18 million years old, making them among the oldest known stone tools in South Africa.
A team of scientists from Purdue University; the University of the Witwatersrand, in South Africa; the University of New Brunswick, in Canada; and the University of Toulouse, in France, performed the research, which will be featured in the journal Nature.
Ronald Clarke, a professor in the Evolutionary Studies Institute at the University of the Witwatersrand who discovered the Little Foot skeleton, said the fossil represents Australopithecus prometheus, a species very different from its contemporary, Australopithecus afarensis, and with more similarities to the Paranthropus lineage.
“It demonstrates that the later hominids, for example, Australopithecus africanus and Paranthropus did not all have to have derived from Australopithecus afarensis,” he said. “We have only a small number of sites and we tend to base our evolutionary scenarios on the few fossils we have from those sites. This new date is a reminder that there could well have been many species of Australopithecus extending over a much wider area of Africa.”
There had not been a consensus on the age of the Little Foot skeleton, named for four small foot bones found in a box of animal fossils that led to the skeleton’s discovery. Previous dates ranged from 2 million to 4 million years old, with an estimate of 3 million years old preferred by paleontologists familiar with the site, said Darryl Granger, a professor of earth, atmospheric and planetary sciences at Purdue, who in collaboration with Ryan Gibbon, a former postdoctoral researcher, led the team and performed the dating.
The dating relied on a radioisotopic dating technique pioneered by Granger coupled with a powerful detector originally intended to analyze solar wind samples from NASA’s Genesis mission. The result was a a relatively small margin of error of 160,000 years for Little Foot and 210,000 years for the stone tools.
The technique, called isochron burial dating, uses radioisotopes within several rock samples surrounding a fossil to date when the rocks and the fossil were first buried underground.
The burial dating relies on measuring radioactive isotopes aluminum-26 and beryllium-10 in quartz within the rock. These isotopes are only created when the rock is exposed to cosmic rays. When a rock is on the surface, it builds up these isotopes. When it is buried or deposited in a cave, the isotopes decay at known rates. The ratio of the remaining aluminum-26 and beryllium-10 can be used to determine how long the rock has been underground, Granger said.
A graph of the isotope ratios, called an isochron, is created for the rock samples. If a strong isochron line forms, it increases the confidence that the samples on the line meet the criteria to be good candidates for accurate dating. Samples that have been compromised, due to reburial or natural movement of sediment within a site, fall above or below the line can be tossed out of the analysis, Granger said.
“If we had only one sample and that rock happened to have been buried, then re-exposed and buried again, the date would be off because the amount of radioisotopes would have increased during its second exposure,” he said. “With this method we can tell if that has happened or if the sample has remained undisturbed since burial with the fossil. It is expensive and a lot of work to take and run multiple samples, but I think this is the future of burial dating because of the confidence one can have in the results.”
Out of 11 samples collected from the site over the past decade, nine fell into a single isochron line, which is a very robust result, he said.
This was Granger’s second attempt at dating the fossil through the burial dating technique and a chance to prove its abilities. In 2003 he estimated the fossil to be around 4 million years old, give or take a few hundred thousand years. The dates were questioned because this earlier work could not show whether the burial dates were compromised by earlier burial elsewhere in the cave, he said.
“The original date we published was considered to be too old, and it wasn’t well received,” Granger said. “However, dating the Little Foot fossil as 3.67 million years old actually falls within the margin of error we had for our original work. It turns out it was a good idea after all.”
Granger’s original attempt was the first time aluminum-26 and beryllium-10 radioisotopic dating had been used to determine the age of a fossil. He developed the method in 1997 and first used it to study changes in mountains, rivers and other geological formations. Because of their very slow rate of decay, these particular radioisotopes allow dating to reach back millions of years, much further in history than the more commonly known carbon-14 dating that can only stretch back about 50,000 years, he said.
Only a small amount of the radioisotopes remain in the quartz after millions of years, and it can only be measured by the ultrasensitive analysis of accelerator mass spectrometry. Purdue’s Rare Isotope Measurement Laboratory, or PRIME Lab, is one of only two laboratories in the nation with equipment capable of performing this kind of dating, said Marc Caffee, a Purdue professor of physics and director of the PRIME Lab who was involved in the research.
Gibbon joined Granger in his work on the Sterkfontein samples in 2010 and was a key player in the research. Granger and Gibbon decided to use the new isochron technique to test whether the quartz was reworked and if the dates could be trusted.
To measure the radioisotopes the quartz is separated from the rocks and then pulverized and dissolved into a solution that can be analyzed by the accelerator and detector. A common difficulty in measuring the presence of trace amounts of specific radioisotopes is the presence of other radioisotopes. In past measurement attempts of the Sterkfontein samples using a different detector, aluminum-26 was especially difficult to measure because of magnesium-26.
“We had given up and nearly walked away from the project thinking we had failed,” he said. “Then the new detector was completed, and we thought we would give it one last try.”
This time the team used the PRIME Lab’s powerful accelerator mass spectrometer and a new detector, called a gas-filled magnet detector, to measure the radioisotopes.
“We succeeded in our measurement, but we were surprised the dates were so old,” Granger said. “We double-and triple-checked our results, running the measurement again and again.”
The gas-filled magnet creates a different charge on the two radioisotopes and throws the magnesium-26 on a different path with a curvature that misses the detector. This lowers the magnesium ratio and increases the aluminum-26 count in the sample that makes it to the detector, which results in a much smaller margin of error in the measurement, Caffee said.
The gas-filled magnet detector was originally to be used to analyze samples of solar wind collected by the Genesis spacecraft. Unfortunately, the space capsule carrying the samples crashed in 2004 on its return to Earth. The crash delayed analysis of the Genesis samples, but Caffee continued to build the detector and it was completed the summer of 2014. Caffee has since used it to perform analysis for other projects, including those from the Sterkfontein site.
“Only a few detectors of this kind exist in the world,” Caffee said. “One of the reasons I came to Purdue was to be a part of the revolutionary science that can be done when such resources are applied to challenging problems. These results highlight what can be accomplished through a collaboration that spans multiple disciplines. It couldn’t have happened without the unique skills and resources each person brought to the table.”
In addition to Granger, Clarke, Gibbon and Caffee, co-authors of the paper include Kathleen Kuman, a professor in earlier and middle stone age archaeology in the School of Geography, Archaeology and Environmentla Studies at the University of the Witwatersrand in Johannesburg, South Africa; and Laurent Bruxelles, a researcher in geomorphology and karstology at the French National Institute for Preventive Archaeological Research in Nimes, France.
The tools from the site had earlier been determined to be Oldowan, a simple flaked stone tool technology considered the earliest stone tool industry in prehistory.
The new Sterkfontein date for the Oldowan artifacts shows that this industry is consistently present in South Africa by 2 million years ago, a much earlier age for tool-bearing hominids than previously anticipated in this part of Africa, Kuman said.
“It is now clear that the small number of Oldowan sites in southern Africa is due only to limited research and not to the absence of these hominids,” she said.
Granger looks forward to applying the technique to more fossils at Sterkfontein and elsewhere.
Video
Reference:
Darryl E. Granger, Ryan J. Gibbon, Kathleen Kuman, Ronald J. Clarke, Laurent Bruxelles, Marc W. Caffee. New cosmogenic burial ages for Sterkfontein Member 2 Australopithecus and Member 5 Oldowan. Nature, 2015; DOI: 10.1038/nature14268
Note: The above story is based on materials provided by Purdue University. The original article was written by Elizabeth K. Gardner.
Mofettes close to the Czech river Plesná. These small openings in the ground are leaking carbon dioxide, which originates in the magma chambers of the earth’s mantel or the earth’s crust. Credit: Felix Beulig/FSU
Researchers of the University Jena analyze the microbial community in volcanically active soils. In a mofette close to the Czech river Plesná in north-western Bohemia, the team working with Prof. Dr. Kirsten Küsel found numerous organisms that were thriving in this environment which seems to be so hostile to life.
The “Villa trans lacum” at the eastern shore of the Laacher See (lake) in the volcanic part of the Eifel — a rural landscape in Germany — was a highly dangerous place. In the 19th century the Jesuit order bought the abbey Maria Laach and built a villa at the shore of the lake. This is where the friars congregated to pray far away from everyday life. But numerous Jesuits paid with their lives for the religious beliefs in the villa. Between 1864 and 1888 17 of them died in the building — literally in their sleep.
“The monks possibly died of carbon dioxide emssions, coming up from the ground at the eastern shore of the lake in large quantities, which could, over time accumulate in the building,” as Prof. Dr. Kirsten Küsel of the Friedrich-Schiller Universiy Jena, explains the mysterious series of deaths. The lake is the crater of a volcano which last erupted about 12,000 years ago, reports the chair of Aquatic Geomicrobiology, “and up to now there are traces of volcanicity, which we regularly analyze on a yearly basis in an outdoor seminar in the degree course Biogeosciences.” Hints of volcanism are given by so-called mofettes. These are small openings in the ground, leaking carbon dioxide, which originates in the magma chambers of the earth’s mantel or the earth’s crust.
Small wonder then, that mofettes were places that are supposed to be very hostile to life. However, as the team of researchers working with Prof. Küsel was able to demonstrate in a new study: there is life even there, although hidden underground. In a mofette close to the Czech river Plesná in north-western Bohemia the researchers followed the path of the carbon dioxide along its last few meters through the ground up to the surface and found numerous organisms that were thriving in this environment which seems to be so hostile to life.
“Our investigation was aiming at examining microbial communities of a mofette and to find out if organisms profit from carbon dioxide emissions, and if so, which.” Felix Beulig from Küsels team says. “We could show, that the carbon dioxide degassing from the interior of the earth is being absorbed by a number of groups of microorganisms and is being transformed into biomass and in chemical bonds like methane and acetic acid. These in turn offer the basic food resource for other organisms in the mofette, and that is why the emitting carbon dioxide plays an important role in the carbon cycle of the soil,” the postgraduate student and first author of the study points out.
However, the new study shows that the biodiversity in a mofette is far less than that found in comparable soils. “But we are not dealing with a environment that is so hostile to life as seems to be the case above ground,” Kirsten Küsel sums up and reports, that there are habitually dead birds, mice and other small animals around mofettes, and only a few plants defy the “poisonous breath of the sleeping volcanos.”
Apart from these elementary findings about the carbon cycle in the soil, the research results of the Uni Jena can be useful in the long run to forecast the potential impact of unwanted degassing from underground carbon dioxide storage (“Carbon Capture and Storage”-technology) and to estimate possible future risks.
Reference:
Felix Beulig, Verena B Heuer, Denise M Akob, Bernhard Viehweger, Marcus Elvert, Martina Herrmann, Kai-Uwe Hinrichs, Kirsten Küsel. Carbon flow from volcanic CO2 into soil microbial communities of a wetland mofette. The ISME Journal, 2014; 9 (3): 746 DOI: 10.1038/ismej.2014.148
Three of the newly described species, Conus carlottae (left column), Conus garrisoni (middle column), and Conus bellacoensis (right column) photographed under regular light (top row) and ultraviolet light (middle row). The brightly fluorescing regions revealed under ultraviolet light would have been darkly pigmented in life (bottom row). Credit: Jonathan Hendricks; CC-BY
Nearly 30 ancient seashell species coloration patterns were revealed using ultraviolet (UV) light, according to a study published April 1, 2015 in the open-access journal PLOS ONE by Jonathan Hendricks from San Jose State University, CA.
Unlike their modern relatives, the 4.8-6.6 million-year-old fossil cone shells often appear white and without a pattern when viewed in regular visible light. By placing these fossils under ultraviolet (UV) light, the organic matter remaining in the shells fluoresces, revealing the original coloration patterns of the once living animals. However, it remains unclear which compounds in the shell matrix are emitting light when exposed to UV rays.
Using this technique, the author of this study was able to view and document the coloration patterns of 28 different cone shell species from the northern Dominican Republic, 13 of which appear to be new species. Determining the coloration patterns of the ancient shells may be important for understanding their relationships to modern species.
Hendricks compared the preserved patterns with those of modern Caribbean cone snail shells and found that many of the fossils showed similar patterns, indicating that some modern species belong to lineages that survived in the Caribbean for millions of years. According to the author, a striking exception in this study was the newly described species Conus carlottae, which has a shell covered by large polka dots, a pattern that is apparently extinct among modern cone snails.
Reference:
Hendricks JR. Glowing Seashells: Diversity of Fossilized Coloration Patterns on Coral Reef-Associated Cone Snail (Gastropoda: Conidae) Shells from the Neogene of the Dominican Republic. PLoS ONE, 2015 DOI: 10.1371/journal.pone.0120924
Note: The above story is based on materials provided by PLOS.
The female ensign scale (Ortheziidae) carries an egg sac formed out of wax plated on the the ventral side. Credit Photo: Dr. Bo Wang
Scientists at the University of Bonn, together with colleagues from China, UK and Poland, have described the oldest evidence of brood care in insects: it is in a female scale insect with her young that is encased in amber as a fossil. The approximately100-million-year-old “snapshot” from the Earth’s history shows the six millimetre long tiny insect with a wax cocoon, which protected the eggs from predators and drying out plus associated young nymphs. The researchers are now presenting their results in the respected journal eLIFE.
The small female insect with the waxy cocoon or reticulum is clearly visible in the brownish translucent amber. The wax cover protected both the scale insect and her approximately 60 eggs from predators and from drying out. In contrast to male scale insects, the female has no wings and is specialized to suck on leaves and provide for her offspring.
“Fossils of fragile female scale insects are extremely rare”, says Chinese paleontologist Dr. Bo Wang, who as a fellow at the Alexander von Humboldt Foundation researching at the Steinmann Institute of the University of Bonn. “What is unique here is the age of the discovery: 100-million-year-old evidence of brood care among insects has not been found until now.” The age of the site of the discovery was determined using the radiometric uranium-lead dating method. In addition to the insect, its eggs and the waxy cover, six young insects are also preserved in this “snapshot” of the Earth’s history captured in amber.
Dr. Wang used his good contact with collectors in northern Myanmar to find this extraordinarily rare amber inclusion. The international team of scientists gave the 100-million-year-old scale insect the name “Wathondara kotejai” – after the Buddhist earth goddess Wathondara and the Polish entomologist Jan Koteja.
That the female scale insect was preserved in amber was a very rare occurrence, explains Associate Professor and co-author Dr. Torsten Wappler of the Steinmann Institute at the University of Bonn. Usually, it is the male scale insects that are encased by the resin when they stop on the trunks or branches of trees. In this case, resin probably dripped from a branch onto a leaf which enclosed the female scale insect with her cocoon, eggs and nymphs.
Then the resin fossilized. The scientists cut and polish the amber until only a thin layer remained over the enclosed insect. Like looking through a window, the researchers were then able to take three-dimensional, high-resolution photographs of this witness of the past under the microscope.
Brood care increases the survival chances of the offspring
“With brood care, the scale insect increases the survival chances of its offspring”, says Dr. Wappler. Once the young scale insect is far enough along in its development, it slips out of the protective wax coating and looks for a new plant where to suck its high-sugar and high-energy sap. Even today, common scale insects have a wax cocoon. Their wax gland is found on the hind end. While turning in circles, they discharge the secretion. The result is a round structure with grooves. “The wax case then looks sort of like a record album from the top”, says the paleontologist with a grin. If the animal grows, it moults and discharges wax again. Skin and wax layers therefore alternate in the cocoon.
Amber as a window to the past
From comparing modern scale insects with the amber discovery, the paleontologists concludes that the lifestyle and reproductive behaviour of these insects around 100 million years ago was already quite similar to the current forms. “Inclusions in amber are a unique opportunity to look at life in the past”, explains Dr. Wappler. Insects in fossilized resin are usually very well preserved, whereas articulated animals embedded in sediment either do not remain intact at all or are often crushed or crimped by the pressure of the weight of the overlying layers. “That is why the amber discovery of Wathondara kotejai is unique”, the scientists at the University of Bonn are convinced.
Reference:
Publication: Brood Care in a 100-million-year-old scale insect, Journal eLIFE; DOI: 10.7554/eLife.05447.001
Note : The above story is based on materials provided by University of Bonn.
Life of the Triassic met a choking end in a runaway greenhouse climate, heating the seas into warm stagnation. Credit: Victor Leshyk
Changes in the biochemical balance of the ocean were a crucial factor in the end-Triassic mass extinction, during which half of all plant, animal and marine life on Earth perished, according to new research involving the University of Southampton.
The study, published in the upcoming edition of Geology, reveals that a condition called ‘marine photic zone euxinia’ took place in the Panathalassic Ocean- the larger of the two oceans surrounding the supercontinent of Pangaea.
Photic zone euxinia occurs when the sun-lit surface waters of the ocean become devoid of oxygen and are poisoned by hydrogen sulphide — a by-product of microorganisms that live without oxygen that is extremely toxic to most other lifeforms.
The international team of researchers studied fossilised organic molecules extracted from sedimentary rocks that originally accumulated on the bottom of the north-eastern Panthalassic Ocean, but are now exposed on the Queen Charlotte Islands, off the coast of British Columbia, Canada.
The team found molecules derived from photosynthesising brown-pigmented green sulphur bacteria — microorganisms that only exist under severely anoxic conditions — proving severe oxygen depletion and hydrogen sulphide poisoning of the upper ocean at the end of Triassic, 201 million years ago.
The researchers also documented marked changes in the nitrogen composition of organic matter, indicating that disruptions in marine nutrient cycles coincided with the development of low oxygen conditions.
Previous studies have reported evidence of photic zone euxinia from terrestrial and shallow, near-shore environments during the latest Triassic, but the new research is the first to provide such evidence from an open ocean setting, indicating these changes may have occurred on a global scale.
The University of Southampton’s Professor Jessica Whiteside, who co-authored the study, explains: “As tectonic plates shifted to break up Pangaea, huge volcanic rifts would have spewed carbon dioxide into the atmosphere, leading to rising temperatures from the greenhouse effect. The rapid rises in CO2 would have triggered changes in ocean circulation, acidification and deoxygenation.”
“These changes have the potential to disrupt nutrient cycles and alter food chains essential for the survival of marine ecosystems. Our data now provides direct evidence that anoxic, and ultimately euxinic, conditions severely affected food chains.”
“The same CO2 rise that led to the oxygen depleted oceans also led to a mass extinction on land, and ultimately to the ecological take-over by dinosaurs, although the mechanisms are still under study.”
Although the Earth was very different during the Triassic Period compared to today, the rate of carbon dioxide release from volcanic rifts are similar to those that we are experiencing now through the burning of fossil fuels.
Professor Whiteside comments: “The release of CO2 was probably at least as rapid as that caused by the burning of fossil fuels today, although the initial concentrations were much higher in the Triassic. The consequences of rapidly rising CO2 in ancient times inform us of the possible consequences of our own carbon dioxide crisis.”
Reference:
A. H. Kasprak, J. Sepulveda, R. Price-Waldman, K. H. Williford, S. D. Schoepfer, J. W. Haggart, P. D. Ward, R. E. Summons, J. H. Whiteside. Episodic photic zone euxinia in the northeastern Panthalassic Ocean during the end-Triassic extinction. Geology, 2015; 43 (4): 307 DOI: 10.1130/G36371.1
An outcrop of Peach Spring Tuff is a remnant of a supereruption that occurred in the American Southwest about 19 million years ago. Credit: Ayla Pamukcu
To understand when and why volcanoes erupt, scientists study the rocks left behind by eruptions past. A method called geobarometry uses the composition of volcanic rocks to estimate the pressure and depth at which molten magma was stored just before it erupted.
A research team led by a Brown University geologist has tested a new type of geobarometer that is well-suited to study the kind of magma often produced in explosive and destructive volcanic eruptions, particularly supereruptions—volcanic events hundreds of times larger than any eruption that has occurred during human history. The research, published in Contributions to Mineralogy and Petrology, shows that the new method is able to calculate depths and pressures of these magma bodies more precisely than other methods.
That makes this new geobarometer—the rhyolite-MELTS geobarometer—a useful tool in understanding how supereruptive systems work, according to Ayla Pamukcu, a postdoctoral researcher at Brown and the new paper’s lead author. There haven’t been any supereruptions during human history, but there are several sites around the world where such eruptions could happen in the future. “Understanding supereruptive systems is something that we care about,” Pamukcu said. “The Yellowstone hotspot, for example, has been the source of multiple supereruptions in the past and is an active system that could create one again.”
The underlying principle of geobarometry is the fact that different minerals crystalize in magma at different pressures. Many geobarometers are mathematical models that calculate pressure based on assemblages of certain minerals present in magmatic rock. That pressure estimate is used to calculate the depth in the crust where the magma was stored.
The rhyolite-MELTS geobarometer looks specifically for the pressure where quartz and feldspar minerals are crystallizing simultaneously. The geobarometer was developed by researchers at Vanderbilt University, where Pamukcu received her Ph.D. and conducted this work, and OFM Research. Some other commonly used barometers use crystals of amphibole along with a suite of five or six other minerals to determine pressure. Because the rhyolite-MELTS geobarometer uses a smaller assemblage of minerals, it could be more broadly applicable than other barometers.
To test the rhyolite-MELTS geobarometer, the researchers looked at a supereruption that happened around 19 million years ago in the southwestern United States. The eruption spewed magma across a large swath of Arizona, Nevada, and California. It’s a rare system that happens to have the right minerals for both the rhyolite-MELTS barometer and amphibole barometers, enabling researchers to compare the performance of each.
They found that the rhyolite-MELTS geobarometer returned much more consistent pressure measurements compared to other barometers. As such, the new technique was able to put tighter constraints on magma depths.
“Some of the amphibole geobarometers are useful for establishing broad crustal locations of magmas—whether they were in the upper, middle, lower crust,” Pamukcu said. “But they are not so good for getting at variations within a crustal horizon. Understanding these small variations is of critical importance, though, and we find that the new geobarometer is effective at garnering such information.”
The research also showed that the new system is good at weeding out rocks that have had their composition altered after they erupted. Interactions with water and a number of other weathering processes can all change the composition of a rock. That can cause geobarometers to return inaccurate pressures. But when the rhyolite-MELTS geobarometer encounters an altered composition, it doesn’t return a pressure.
“So instead of putting bad data in and getting a result out that is wrong, if you put bad data into the rhyolite-MELTS geobarometer, you don’t get anything out at all.”
Now that they have this new validation of the rhyolite-MELTS geobarometer, the researchers are looking forward to using it on other volcanic systems. And because the minerals it uses are widespread, it can be used on many other systems.
“We’re always striving to get new and better barometers,” Pamukcu said. “The fact that this one is more widely applicable is exciting.”
Reference:
“Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS—Part 3: Application to the Peach Spring Tuff (Arizona–California–Nevada, USA).” Contributions to Mineralogy and Petrology. DOI: 10.1007/s00410-015-1122-y
Note : The above story is based on materials provided by Brown University.
Dickinsonia fossil from Nilpena, South Australia. Black arrow points to lifted portion of the specimen and is pointed in the direction the waves would have moved during the Ediacaran. Photo credit: Droser Lab, UC Riverside.
Certain specimens of the fossil Dickinsonia are incomplete because ancient currents lifted them from the sea floor, a team of researchers led by paleontologists at the University of California, Riverside has found. Sand then got deposited beneath the lifted portion, the researchers report, strongly suggesting that Dickinsonia was mobile, easily separated from the sea floor and not attached to the substrate on which it lived.
Resembling a symmetrical ribbed oval, Dickinsonia is a fossil of the Ediacaran biota that could reach several feet in size (the Ediacaran Period extended from about 635 million years ago to about 542 million years ago).
“Basically the fossils we studied are exceptionally well preserved, but some samples appear to be missing a part of their body,” said Scott D. Evans, a graduate student in the UC Riverside Department of Earth Sciences. “We believed this to be the result of wave action. So we measured the direction of this missing part and showed that this feature was actually aligned, that is, all of the missing parts ‘pointed’ in the same direction. The alignment of this feature matched the alignment of other features that formed under wave action found with these fossils, indicating that it did, in fact, form from moving water currents in the ancient ocean. This idea shows us that these Dickinsonia weren’t ‘missing’ parts of their body but instead that those parts were not preserved.
“These aren’t just organisms frozen in time but show evidence of what the environment they lived in looked like and how that environment affected them,” he added. “By looking at these fossils we can see that they were altered by a current that flowed over them more than 550 million years ago.”
Study results appeared online last month in Palaeogeography, Palaeoclimatology, Palaeoecology.
“When we look at a fossil, we aren’t just looking at an animal frozen in time but an animal that has gone through many process in the more than 550 million years since it was living on the seafloor,” Evans explained. “There are also questions about whether Dickinsonia was capable of movement and this research shows that it was able to be lifted off the seafloor, indicating that it wasn’t attached to the bottom of the ocean. This doesn’t prove that it could move but it does support the hypothesis that it was a free-living organism.”
Dickinsonia are of interest to paleontologists because these animals are the first to become big and complex and the first also to form communities. Much remains unknown about what exactly they are. Scientists such as UCR’s Mary L. Droser, in whose lab Evans works, have been trying to better understand these animals — how they got nutrients, how they reproduced, what interactions, if any, they had with each other and what the environment in which they lived looked like.
“These questions may seem simple to a modern biologist but these fossils are so different from the animals we see today,” said Droser, a professor of paleontology. “Since we can’t observe them in real life these questions become very difficult to answer. This project adds a small piece to our knowledge of these animals.”
To do the research Droser and Evans spent several months over the last two summers in South Australia, where Dickinsonia fossils are abundantly found. They also spent more than two months in Australia’s desert outback (in an old sheep shearing shed with beds, electricity and running water, and not much else) to study the fossils.
“We spent pretty much every available hour of sunlight looking at the fossils that occur in the Outback,” Evans said. “The fossils we report on in the research paper are actually on rock beds that have been previously excavated and laid out as individual layers. These beds that are about the size of a small classroom allow us to see what the seafloor would have actually looked like. We were able to measure the angles of the missing pieces and orient them with respect to each other.”
Evans is surprised that despite decades of paleontological research scientists know very little about Dickinsonia.
“I want to add to our knowledge of what they were, how they existed, and what they tell us about how the complex animals we are familiar with today evolved from very primitive organisms,” he said. “I am currently working on a research paper that looks at the size distributions of different populations of Dickinsonia which will tell us a little bit about how they lived and reproduced. I then want to investigate how they grew and possibly how they moved and what material they might have been made of.”
Reference:
Scott D. Evans, Mary L. Droser, James G. Gehling. Dickinsonia liftoff: Evidence of current derived morphologies. Palaeogeography, Palaeoclimatology, Palaeoecology, 16 February 2015 “Dickinsonia liftoff: Evidence of current derived morphologies”
