Wolf Volcano, Isabela Island, Galapagos Credit: NASA Landsat 7
A volcano perched atop one of Ecuador’s Galapagos Islands erupted in the early hours of Monday, the local authorities said, potentially threatening a unique species of pink iguanas.
The roughly 1.7-kilometer (1.1-mile) high Wolf volcano is located on Isabela Island, home to a rich variety of flora and fauna typical of the archipelago that helped inspire Charles Darwin’s theory of evolution following his 1835 visit.
“The Wolf volcano is not located near a populated area. There is not risk for the human population. This is the only population of pink iguanas in the world,” Galapagos National Park said in a posting on Twitter.
The park posted pictures showing lava pouring down the sides of the Wolf volcano, the Galapagos’ highest point, while a dark plume estimated to be 10 km (6.4 miles) high, billowed overhead.
Wolf had been inactive 33 years, according to the park.
The lava is flowing down the volcano’s southern face while the iguanas, officially an endangered species, inhabit the opposite side, the Environment Ministry said in a statement, adding it expected the animals to escape harm.
The flow is likely to reach the sea, however, where it could harm marine life, the Geophysics Institute said separately. While populated areas of the island are safe from the eruption, the institute said some of the ash cloud could descend upon them.
In April, unusual seismic activity was also reported at the Sierra volcano on the same Isabela Island, the archipelago’s biggest, where yellow iguanas and giant turtles also live.
The eruption in Ecuador comes on the heels of eruptions in Chile, another South American country located on the so-called Pacific Ring of Fire.
Note : The above story is based on materials Reporting by Alexandra Valencia, writing by Alexandra Ulmer and Peter Murphy; editing by Marguerita Choy and G Crosse. “Reuters“
This May 10, 2015, view from Curiosity’s Mastcam shows terrain judged difficult for traversing between the rover and an outcrop in the middle distance where a pale rock unit meets a darker rock unit above it. The rover team decided not to approach this outcrop and identified an alternative. Credit: NASA/JPL-Caltech/MSSS
NASA’s Curiosity Mars rover climbed a hill Thursday to approach an alternative site for investigating a geological boundary, after a comparable site proved hard to reach.
The drive of about 72 feet (22 meters) up slopes as steep as 21 degrees brought Curiosity close to a target area where two distinctive types of bedrock meet. The rover science team wants to examine an outcrop that contains the contact between the pale rock unit the mission analyzed lower on Mount Sharp and a darker, bedded rock unit that the mission has not yet examined up close.
Two weeks ago, Curiosity was headed for a comparable geological contact farther south. Foiled by slippery slopes on the way there, the team rerouted the vehicle and chose a westward path.The mission’s strategic planning keeps multiple route options open to deal with such situations.
“Mars can be very deceptive,” said Chris Roumeliotis, Curiosity’s lead rover driver at NASA’s Jet Propulsion Laboratory, Pasadena, California. “We knew that polygonal sand ripples have caused Curiosity a lot of drive slip in the past, but there appeared to be terrain with rockier, more consolidated characteristics directly adjacent to these ripples. So we drove around the sand ripples onto what we expected to be firmer terrain that would give Curiosity better traction. Unfortunately, this terrain turned out to be unconsolidated material too, which definitely surprised us and Curiosity.”
In three out of four drives between May 7 and May 13, Curiosity experienced wheel slippage in excess of the limit set for the drive, and it stopped mid-drive for safety. The rover’s onboard software determines the amount of slippage occurring by comparing the wheel-rotation tally to actual drive distance calculated from analysis of images taken during the drive.
The rover was heading generally southward from near the base of a feature called “Jocko Butte” toward a geological contact in the eastern part of the “Logan Pass” area.
Routes to this contact site would have required driving across steeper slopes than Curiosity has yet experienced on Mars, and the rover had already experienced some sideways slipping on one slope in this area.
“We decided to go back to Jocko Butte, and, in parallel, work with the scientists to identify alternate routes,” Roumeliotis said.
The team spent a few days analyzing images from the rover and from NASA’s Mars Reconnaissance Orbiter to choose the best route for short-term and long-term objectives.
“One factor the science team considers is how much time to spend reaching a particular target, when there are many others ahead,” said Curiosity Project Scientist Ashwin Vasavada of JPL. “We used observations from NASA’s Mars Reconnaissance Orbiter to identify an alternative site for investigating the geological contact in the Logan Pass area. It’s a little mind-blowing to drive up a hill to a site we saw only in satellite images and then find it in front of us.”
Curiosity has been exploring on Mars since 2012. It reached the base of Mount Sharp last year after fruitfully investigating outcrops closer to its landing site and then trekking to the mountain. The main mission objective now is to examine successively higher layers of Mount Sharp.
This is a coverage map of the the seismic wave sensors in Long Beach that the researchers drew upon for their study. Credit: Courtesy of Nori Nakata.
A new technique developed at Stanford University harnesses the buzz of everyday human activity to map the interior of the Earth. “We think we can use it to image the subsurface of the entire continental United States,” said Stanford geophysics postdoctoral researcher Nori Nakata.
Using tiny ground tremors generated by the rumble of cars and trucks across highways, the activities within offices and homes, pedestrians crossing the street and even airplanes flying overhead, a team led by Nakata created detailed three-dimensional subsurface maps of the California port city of Long Beach.
The maps, detailed in a recent issue of the Journal of Geophysical Research, marks the first successful demonstration of an elusive Earth-imaging technique, called ambient noise body wave tomography. “It’s a technique that scientists have been trying to develop for more than 15 years,” said Nakata, who is the Thompson Postdoctoral Fellow at the School of Earth, Energy & Environmental Sciences.
The subsurface maps were created by applying a new signal processing technique to a particular type of seismic waves — energy waves that travel across the Earth’s surface and through its interior. Seismic waves can be generated naturally, during earthquakes and volcanic eruptions, for example, or by artificial means such as explosions.
There are two major types of seismic waves: surface waves and body waves. As their name suggests, surface waves travel along the surface of the Earth. Scientists have long been able to harness surface waves to study the upper layers of the planet’s crust, and recently they have even been able to extract surface waves from the so-called ambient seismic field. Also known as ambient noise, these are very weak but continuous seismic waves that are generated by colliding ocean waves, among other things.
Body waves, in contrast, travel through the Earth, and as a result can provide much better spatial resolution of the planet’s interior than surface waves. “Scientists have been performing body-wave tomography with signals from earthquakes and explosives for decades,” said study coauthor Jesse Lawrence, an assistant professor of geophysics at Stanford. “But you can’t control when and where an earthquake happens, and explosives are expensive and often damaging.”
For this reason, geophysicists have long sought to develop a way to perform body wave tomography without relying on earthquakes or resorting to explosives. This has proven challenging, however, because body waves have lower amplitudes than surface waves, and are therefore harder to observe.
“Usually you need to combine and average lots and lots of data to even see them,” Lawrence said.
In the new study, the Stanford team applied a new software processing technique, called a body-wave extraction filter. Nakata developed the filter to analyze ambient noise data gathered from a network of thousands of sensors that had been installed across Long Beach to monitor existing oil reservoirs beneath the city.
While experimenting with different types of filters for parsing and analyzing ambient noise, Nakata came up with an idea for a filter of his own that focused specifically on body waves. “When I saw the Long Beach data, I realized I had all of the pieces in my hand to isolate body- wave energy from ambient noise,” Nakata said. “I was excited, but at the same time I was skeptical my idea would work.”
The filter Nakata developed and then refined with help from his Stanford colleagues represents a new way of processing the ambient noise by comparing each observation to every other observation, which boosts the body-wave signal while reducing the noise.
Using its filter, the team was able to create maps that revealed details about the subsurface of Long Beach down to a depth of more than half a mile (1.1. kilometers). The body-wave maps were comparable to, and in some cases better than, existing imaging techniques.
One map, for example, clearly revealed the Newport-Inglewood fault, an active geological fault that cuts through Long Beach. This fault also shows up in surface-wave maps, but the spatial resolution of the body-wave velocity map was much higher, and revealed new information about the velocity of seismic waves traveling through the fault’s surrounding rocks, which in turn provides valuable clues about their composition and organization.
“This has been something of a holy grail in Earth imaging, and Nori’s work is a first-of-its-kind study,” said geophysicist Greg Beroza, the Wayne Loel Professor at Stanford, who was not involved in the study. “His groundbreaking achievement is sure to be widely emulated.”
Lawrence says the real power of the new technique will come when it is combined with surface wave tomography. “Primary waves, which are a type of body wave, are sensitive to compressional forces, whereas surface waves are more sensitive to shear, or sliding, forces,” Lawrence said. “To characterize the subsurface properly, one must measure both shear and compressional properties. Using one wave type and not the other is like trying to study a painting by looking at it through a frosted window.”
Now that ambient-noise body wave tomography has been shown to work, Nakata says he plans to apply his technique to much larger test areas.
Reference:
Nori Nakata, Jason P. Chang, Jesse F. Lawrence, Pierre Bou�. Body wave extraction and tomography at Long Beach, California, with ambient-noise interferometry. Journal of Geophysical Research: Solid Earth, 2015; 120 (2): 1159 DOI: 10.1002/2015JB011870
This map shows the California Borderland and its major tectonic features, as well as the locations of earthquakes greater than Magnitude 5.5. The dashed box shows the area of the new study. Large arrows show relative plate motion for the Pacific-North America fault boundary. The abbreviations stand for the following: BP = Banning Pass, CH = Chino Hills, CP = Cajon Pass, LA = Los Angeles, PS = Palm Springs, V = Ventura; ESC = Santa Cruz Basin; ESCBZ = East Santa Cruz Basin Fault Zone; SCI = Santa Catalina Island; SCL = San Clemente Island; SMB = Santa Monica Basin; SNI = San Nicolas Island. Credit: Mark Legg
While their attention may be inland on the San Andreas Fault, residents of coastal Southern California could be surprised by very large earthquakes — and even tsunamis — from several major faults that lie offshore, a new study finds.
The latest research into the little known, fault-riddled, undersea landscape off of Southern California and northern Baja California has revealed more worrisome details about a tectonic train wreck in the Earth’s crust with the potential for magnitude 7.9 to 8.0 earthquakes. The new study supports the likelihood that these vertical fault zones have displaced the seafloor in the past, which means they could send out tsunami-generating pulses towards the nearby coastal mega-city of Los Angeles and neighboring San Diego.
“We’re dealing with continental collision,” said geologist Mark Legg of Legg Geophysical in Huntington Beach, California, regarding the cause of the offshore danger. “That’s fundamental. That’s why we have this mess of a complicated logjam.”
Legg is the lead author of the new analysis accepted for publication in the Journal of Geophysical Research: Earth Surface, a journal of the American Geophysical Union. He is also one of a handful of geologists who have been trying for decades to piece together the complicated picture of what lies beyond Southern California’s famous beaches.
The logjam Legg referred to is composed of blocks of the Earth’s crust caught in the ongoing tectonic battle between the North American tectonic plate and the Pacific plate. The blocks are wedged together all the way from the San Andreas Fault on the east, to the edge of the continental shelf on the west, from 150 to 200 kilometers (90 to 125 miles) offshore. These chunks of crust get squeezed and rotated as the Pacific plate slides northwest, away from California, relative to the North American plate. The mostly underwater part of this region is called the California Continental Borderland, and includes the Channel Islands.
By combining older seafloor data and digital seismic data from earthquakes along with 4,500 kilometers (2,796 miles) of new seafloor depth measurements, or bathymetry, collected in 2010, Legg and his colleagues were able to take a closer look at the structure of two of the larger seafloor faults in the Borderland: the Santa Cruz-Catalina Ridge Fault and the Ferrelo Fault. What they were searching for are signs, like those seen along the San Andreas, that indicate how much the faults have slipped over time and whether some of that slippage caused some of the seafloor to thrust upwards.
What they found along the Santa Cruz-Catalina Ridge Fault are ridges, valleys and other clear signs that the fragmented, blocky crust has been lifted upward, while also slipping sideways like the plates along the San Andreas Fault do. Further out to sea, the Ferrelo Fault zone showed thrust faulting — which is an upwards movement of one side of the fault. The vertical movement means that blocks of crust are being compressed as well as sliding horizontally relative to each other-what Legg describes as “transpression.”
Compression comes from the blocks of the Borderland being dragged northwest, but then slamming into the roots of the Transverse Ranges — which are east-west running mountains north and west of Los Angeles. In fact, the logjam has helped build the Transverse Ranges, Legg explained.
“The Transverse Ranges rose quickly, like a mini Himalaya,” Legg said.
The real Himalaya arose from a tectonic-plate collision in which the crumpled crust on both sides piled up into fast-growing, steep mountains rather than getting pushed down into Earth’s mantle as happens at some plate boundaries.
As Southern California’s pile-up continues, the plate movements that build up seismic stress on the San Andreas are also putting stress on the long Santa Cruz-Catalina Ridge and Ferrelo Faults. And there is no reason to believe that those faults and others in the Borderlands can’t rupture in the same manner as the San Andreas, said Legg.
“Such large faults could even have the potential of a magnitude 8 quake,” said geologist Christopher Sorlien of the University of California at Santa Barbara, who is not a co-author on the new paper.
“This continental shelf off California is not like other continental shelves — like in the Eastern U.S.,” said Sorlien.
Whereas most continental shelves are about twice as wide and inactive, like that off the U.S. Atlantic coast, the California continental shelf is very narrow and is dominated by active faults and tectonics. In fact, it’s unlike most continental shelves in the world, he said. It’s also one of the least well mapped and understood. “It’s essentially terra incognita.”
“This is one of the only parts of the continental shelf of the 48 contiguous states that didn’t have complete … high-resolution bathymetry years ago,” Sorlien said.
And that’s why getting a better handle on the hazards posed by the Borderland’s undersea faults has been long in coming and slow to catch on, even among earth scientists, he said.
NOAA was working on complete high-resolution bathymetry of the U.S. Exclusive Economic Zone — the waters within 200 miles of shore — until the budget was cut, said Legg. That left out Southern California and left researchers like himself using whatever bits and pieces of smaller surveys to assemble a picture of what’s going on in the Borderland, he explained.
“We’ve got high resolution maps of the surface of Mars,” Legg said, “yet we still don’t have decent bathymetry for our own backyard.”
Reference:
Mark Legg, Monica D. Kohler, Natsumi Shintaku, Dayanthie Weeraratne. High-resolution mapping of two large-scale transpressional fault zones in the California Continental Borderland: Santa Cruz-Catalina Ridge and Ferrelo faults. Journal of Geophysical Research: Earth Surface, 2015; DOI: 10.1002/2014JF003322
Professor John Long with the Gogo shark (Gogoselachus) fossil in 2005
Most people know that sharks have a distinctive, all-cartilage skeleton, but now a fossil from Western Australia has revealed a surprise ‘missing link’ to an earlier, more bony form of the fish.
Published today in the scientific journal PLOS One, research by Flinders University palaeontologist Professor John Long substantially strengthens the theory that the modern shark is less primitive than previously believed.
In testing fossil remains discovered by Professor Long in July 2005 at Gogo in the Kimberley in Western Australia, detailed CT scanning analysis has shown that the three-dimensional remnant skeleton contains a small proportion of bone as well as cartilage.
Professor Long said the fossil, which dates from the Devonian Period (380 million years old), reveals an ancient shark caught in evolutionary transition.
Because sharks and rays have entirely cartilaginous skeletons, Professor Long said it was traditionally thought that they were part of a primitive evolutionary pathway, and that bone in other fish was the more advanced condition.
But a series of discoveries in recent years has suggested that sharks are “more evolutionarily derived”, and are likely to be descended from bony ancestors.
“Our shark more or less nails that theory, because here we have a heavily mineralised type of cartilage in the skeleton, which contains remnant bone cells,” Professor Long said.
“It’s almost a missing link condition showing that early sharks had a lot more bone in their skeleton, and that just before modern sharks evolved they lost the bone, with only the soft cartilage remaining.”
Professor Long said the research indicates a direction in their evolution that shows that sharks to be much more specialised than previously thought.
The Gogo formation, which is the remains of a tropical reef now located far inland, has proved to be one of the most important sources of Devonian fossil fish in the world.
Professor Long said sharks are poorly known from the Devonian period, with research heavily reliant on fossil teeth. The rarity makes the Gogo shark all the more remarkable, Professor Long said.
“This is a partial articulated skeleton, with the jaws and shoulder and all the teeth and scales, but best of all, we have acid-etched the fossils out of the rock, so they are three-dimensional, uncrushed and perfect,” he said. “It’s the first time a shark of that age has been prepared in that manner.”
“This is a really interesting discovery,” said Professor Per Ahlberg, a palaeontologist at Uppsala University in Sweden, which was not involved in the study.
“The new Gogo shark shows what seems to be an early version of prismatic calcified cartilage: unlike the modern kind, the gaps between the prisms contain cells that resemble bone cells. This may help to explain the relationship between prismatic calcified cartilage and bone.”
The find also represented a breakthrough in that it was the first specimen of a shark discovered at the Gogo site in 60 years of investigation.
“It means that we can go back and find more sharks with continued collecting,” said Professor Long, who will head back to the site later this year.
Reference:
“First Shark from the Late Devonian (Frasnian) Gogo Formation, Western Australia Sheds New Light on the Development of Tessellated Calcified Cartilage.” PLoS ONE 10(5): e0126066. DOI: 10.1371/journal.pone.0126066
Skeleton of Columbian mammoth, Mammuthus columbi, in the George C. Page Museum at the La Brea Tar Pits, Los Angeles, California Credit: WolfmanSF, Wikipedia
Recently, U.S. Geological Survey researchers and partners working in California’s Channel Islands National Park discovered mammoth remains in uplifted marine deposits that date to about 80,000 years ago, confirming a long-held but never proven hypothesis that mammoths may have been on the Channel Islands long before the last glacial period 25,000 to 12,000 years ago.
“These are the first confidently dated fossils from the California Channel Islands showing that mammoths had been on the islands a long time, not just during the last glacial period,” said lead author and USGS research geologist Dan Muhs. “It supports an older hypothesis that mammoths could have swum from the mainland to the islands any time that conditions were favorable for such a journey, when sea level was low.”
This discovery on Santa Rosa Island, detailed in the online and print journal editions of Quaternary Research, shows that mammoths likely ventured to the islands during at least one earlier glacial period, when sea level was lower than present and the swimming distance from the mainland to the islands was minimal.
The older age of mammoths also challenges the hypothesis that climate change and sea level rise at the close of the last glacial period (about 12,000 years ago) were the causes of mammoth extinction on the Channel Islands. Earlier mammoth populations also would have had to contend with climate change and sea level rise, but apparently survived.
The newly discovered fossil mammoth remains are likely Mammuthus exilis, the pygmy mammoth. The Columbian mammoth immigrated to the islands from the California mainland by swimming and the pygmy mammoth evolved on the islands from this ancestral stock. Most mammoth remains previously reported on the Channel Islands date to the last glacial period, about 25,000 to 12,000 years ago.
Mammoths are iconic animals of the Pleistocene Ice Ages, both in North America and Eurasia. Fossil mammoths and other proboscideans (elephants and their relatives) have also been found on many islands of the Mediterranean.
Reference:
Daniel R. Muhsa, Kathleen R. Simmonsa, Lindsey T. Grovesb, John P. McGeehinc, R. Randall Schumanna, Larry D. Agenbroadd. Late Quaternary sea-level history and the antiquity of mammoths (Mammuthus exilis and Mammuthus columbi), Channel Islands National Park, California, USA. DOI:10.1016/j.yqres.2015.03.001
A microscopic image of the thigh bone (femur) of a dinosaur shows concentric rings. Like tree rings, they formed each year in the dinosaur’s bones during the season when resources were scarce. The rings represent unrecorded time, so an annual growth rate (dashed line in graph) is an underestimate relative to the true growth rate during the favorable growing season. Credit: Scott Hartman
Dinosaurs grew as fast as your average living mammal, according to a research paper published by Stony Brook University paleontologist Michael D’Emic, PhD. The paper, to published in Science on May 29, is a re-analysis of a widely publicized 2014 Science paper on dinosaur metabolism and growth that concluded dinosaurs were neither ectothermic nor endothermic — terms popularly simplified as ‘cold-blooded’ and ‘warm-blooded’ — but instead occupied an intermediate category.
“The study that I re-analyzed was remarkable for its breadth — the authors compiled an unprecedented dataset on growth and metabolism from studies of hundreds of living animals,” said Dr. D’Emic, a Research Instructor in the Department of Anatomical Sciences as Stony Brook, when referring to “Evidence for mesothermy in dinosaurs.”
“Upon re-analysis, it was apparent that dinosaurs weren’t just somewhat like living mammals in their physiology — they fit right within our understanding of what it means to be a ‘warm-blooded’ mammal,” he said.
Dr. D’Emic specializes in bone microanatomy, or the study of the structure of bone on scales that are just a fraction of the width of a human hair. Based on his knowledge of how dinosaurs grew, Dr. D’Emic re-analyzed that study, which led him to the strikingly different conclusion that dinosaurs were more like mammals than reptiles in their growth and metabolism.
Dr. D’Emic re-analyzed the study from two aspects. First, the original study had scaled yearly growth rates to daily ones in order to standardize comparisons.
“This is problematic,” Dr. D’Emic explains, “because many animals do not grow continuously throughout the year, generally slowing or pausing growth during colder, drier, or otherwise more stressful seasons.
“Therefore, the previous study underestimated dinosaur growth rates by failing to account for their uneven growth. Like most animals, dinosaurs slowed or paused their growth annually, as shown by rings in their bones analogous to tree rings,” he explained.
He added that the growth rates were especially underestimated for larger animals and animals that live in very stressful or seasonal environments — both of which characterize dinosaurs.
The second aspect of the re-analysis with the original study takes into account that dinosaurs should be statistically analyzed within the same group as living birds, which are also warm-blooded, because birds are descendants of Mesozoic dinosaurs.
“Separating what we commonly think of as ‘dinosaurs’ from birds in a statistical analysis is generally inappropriate, because birds are dinosaurs — they’re just the dinosaurs that haven’t gone extinct.”
He explained that re-analyzing the data with birds as dinosaurs lends more support that dinosaurs were ‘warm-blooded,’ not occupants of a special, intermediate metabolic category.
According to Holly Woodward, Assistant Professor in the Center for Health Sciences at Oklahoma State University, Dr. D’Emic’s re-analysis is crucial to building research on the metabolism and development of dinosaurs.
“D’Emic’s study reveals how important access to the data behind published results is for hypothesis testing and advancing our understanding of dinosaur growth dynamics,” said Woodward.
Dr. D’Emic hopes that his study will also spur new research into when, why, and how pauses or slowdowns in growth are recorded in bones, which may have implications in the development of other species and in the study of bone diseases such as osteoporosis.
J. M. Grady, B. J. Enquist, E. Dettweiler-Robinson, N. A. Wright, F. A. Smith. Evidence for mesothermy in dinosaurs. Science, 2014; 344 (6189): 1268 DOI: 10.1126/science.1253143
Scientists at the Goethe University Frankfurt and at the Senckenberg Biodiversity and Climate Research Centre working together with their Canadian counterparts, have reconstructed the climatic development of the Arctic Ocean during the Cretaceous period, 145 to 66 million years ago. The research team comes to the conclusion that there was a severe cold snap during the geological age known for its extreme greenhouse climate. The study published in the professional journal Geology is also intended to help improve prognoses of future climate and environmental development and the assessment of human influence on climate change.
The Cretaceous, which occurred approximately 145 million to 66 million years ago, was one of the warmest periods in the history of Earth. The poles were devoid of ice and average temperatures of up to 35 degrees Celsius prevailed in the oceans. “A typical greenhouse climate; some even refer to it as a ‘super greenhouse’ ,” explains Professor Dr. Jens Herrle of the Goethe University and Senckenberg Biodiversity and Climate Research Centre, and adds: “We have now found indications in the Arctic that this warm era 112 to 118 million years ago was interrupted for a period of about 6 million years.”
In cooperation with his Canadian colleague Professor Claudia Schröder-Adams of the Carleton University in Ottawa, the Frankfurt palaeontologist sampled the Arctic Fjord Glacier and the Lost Hammer diapir locality on Axel Heiberg Island in 5 to 10 metre intervals. “In so doing, we also found so-called glendonites,” Herrle recounts. Glendonite refers to star-shaped calcite minerals, which have taken on the crystal shape of the mineral ikaite. “These so-called pseudomorphs from calcite to ikaite are formed because ikaite is stable only below 8 degrees Celsius and metamorphoses into calcite at warmer temperatures,” explains Herrle and adds: “Thus, our sedimentological analyses and age dating provide a concrete indication for the environmental conditions in the cretaceous Arctic and substantiate the assumption that there was an extended interruption of the interglacial period in the Arctic Ocean at that time.”
In two research expeditions to the Arctic undertaken in 2011 and 2014, Herrle brought 1700 rock samples back to Frankfurt, where he and his working group analysed them using geochemical and paleontological methods. But can the Cretaceous rocks from the polar region also help to get a better understanding of the current climate change? “Yes,” Herrle thinks, elaborating: “The polar regions are particularly sensitive to global climatic fluctuations. Looking into the geological past allows us to gain fundamental knowledge regarding the dynamics of climate change and oceanic circulation under extreme greenhouse conditions. To be capable of better assessing the current human-made climate change, we must, for example, understand what processes in an extreme greenhouse climate contribute significantly to climate change.” In the case of the Cretaceous cold snap, Herrle assumes that due to the opening of the Atlantic in conjunction with changes in oceanic circulation and marine productivity, more carbon was incorporated into the sediments. This resulted in a decrease in the carbon dioxide content in the atmosphere, which in turn produced global cooling.
The Frankfurt scientist’s newly acquired data from the Cretaceous period will now be correlated with results for this era derived from the Atlantic, “in order to achieve a more accurate stratigraphic classification of the Cretaceous period and to better understand the interrelationships between the polar regions and the subtropics,” is the outlook Herrle provides.
Reference:
J. O. Herrle, C. J. Schroder-Adams, W. Davis, A. T. Pugh, J. M. Galloway, J. Fath. Mid-Cretaceous High Arctic stratigraphy, climate, and Oceanic Anoxic Events. Geology, 2015; 43 (5): 403 DOI: 10.1130/G36439.1
Antarctica. Credit: Andrew Thurber, Oregon State University
A new study shows how huge influxes of fresh water into the North Atlantic Ocean from icebergs calving off North America during the last ice age had an unexpected effect – they increased the production of methane in the tropical wetlands.
Usually increases in methane levels are linked to warming in the Northern Hemisphere, but scientists who are publishing their findings this week in the journal Science have identified rapid increases in methane during particularly cold intervals during the last ice age.
These findings are important, researchers say, because they identify a critical piece of evidence for how the Earth responds to changes in climate.
“Essentially what happened was that the cold water influx altered the rainfall patterns at the middle of the globe,” said Rachael Rhodes, a research associate in the College of Earth, Ocean, and Atmospheric Sciences at Oregon State University and lead author on the study, which was funded by the National Science Foundation. “The band of tropical rainfall, which includes the monsoons, shifts to the north and south through the year.
“Our data suggest that when the icebergs entered the North Atlantic causing exceptional cooling, the rainfall belt was condensed into the Southern Hemisphere, causing tropical wetland expansion and abrupt spikes in atmospheric methane,” she added.
During the last ice age, much of North America was covered by a giant ice sheet that many scientists believe underwent several catastrophic collapses, causing huge icebergs to enter the North Atlantic – phenomena known as Heinrich events. And though they have known about them for some time, it hasn’t been clear just when they took place and how long they lasted.
Rhodes and her colleagues examined evidence from the highly detailed West Antarctic Ice Sheet Divide ice core (http://www.waisdivide.unh.edu). They used a new analytical method perfected in collaboration with Joe McConnell at the Desert Research Institute in Reno, Nevada, to make extremely detailed measurements of the air trapped in the ice.
“Using this new method, we were able to develop a nearly 60,000-year, ultra-high-resolution record of methane much more efficiently and inexpensively than in past ice core studies, while simultaneously measuring a broad range of other chemical parameters on the same small sample of ice,” McConnell noted.
Utilizing the high resolution of the measurements, the team was able to detect methane fingerprints from the Southern Hemisphere that don’t match temperature records from Greenland ice cores.
“The cooling caused by the iceberg influx was regional but the impact on climate was much broader,” said Edward Brook, an internationally recognized paleoclimatologist from Oregon State University and co-author on the study. “The iceberg surges push the rain belts, or the tropical climate system, to the south and the impact on climate can be rather significant.”
Concentrating monsoon seasons into a smaller geographic area “intensifies the rainfall and lengthens the wet season,” Rhodes said.
“It is a great example of how inter-connected things are when it comes to climate,” she pointed out. “This shows the link between polar areas and the tropics, and these changes can happen very rapidly. Climate models suggest only a decade passed between the iceberg intrusion and a resulting impact in the tropics.”
Reference:
Enhanced tropical methane production in response to iceberg discharge in the North Atlantic, DOI: 10.1126/science.1262005
Southern part of the Barberton Greenstone Belt, South Africa, shows mafic/ultramafic volcanics and cherts of the Kromberg Formation, Onverwacht Group, in the foreground and to the right, looking SSW toward the reddish-colored sediments of the Fig Tree and Moodies Groups at the Swaziland border. See the open-access article by Frances Westall et al. Credit: Westall et al., Geology, 2015.
The modern sedimentary environment contains a diversity of microbes that interact very closely with the sediments, sometimes to such an extent that they form “biosediments.” But can such a phenomenon be fossilized? How far back in time can “biosedimentation” be traced? In this study for Geology, Frances Westall and colleagues examine some of the oldest rocks on Earth — in the Barberton Greenstone Belt, South Africa (older than 3.3 billion years), to answer this question.
Westall and colleagues use multi-scale methods to document the simultaneous presence of diverse types of microorganisms, including phototrophs and chemotrophs, directly interacting with coastal volcanic sediments that were bathed by hydrothermal fluids. They note that the hydrothermal fluids acted as a major nutrient source for the chemotrophic microbial communities and thus strongly controlled their development and distribution, while distribution of the photosynthetic biofilms was, of course, controlled by access to sunlight.
The silica-rich hydrothermal fluids also contributed to the rapid fossilization of the microbes and lithification of the sediments, fixing the diversity of microbial life and their interactions with the sediments for posterity. Westall and colleagues thus show that intricate microbe-sediment systems are deep-rooted in time and that at least some early life may indeed have been thermophilic.
Reference:
Archean (3.33 Ga) microbe-sediment systems were diverse and flourished in a hydrothermal context
Frances Westall et al., Centre de Biophysique Moléculaire (CBM), Centre National de la Recherche Scientifique (CNRS), Orléans, France. Published online ahead of print on 26 May 2015; DOI: 10.1130/G36646.1. This article is OPEN ACCESS online.
Earthquakes kill, but their aftershocks can cause the rapid collapse of buildings left standing in the aftermath of the initial quake. Research published in the International Journal of Reliability and Safety offers a new approach to predicting which buildings might be most susceptible to potentially devastating collapse due to the ground-shaking aftershock tremors.
Negar Nazari and John W. van de Lindt of the Department of Civil and Environmental Engineering, at Colorado State University in Fort Collins and Yue Li of Michigan Technological University, in Houghton, USA, point out that it is relatively obvious that buildings that survive a main shock will be at varying degrees of risk of collapse as aftershocks travel through the earthquake zone. Aftershocks are usually several orders of magnitude less intense than the primary earthquake, but can nevertheless have high ground motion intensity, last longer and occur at different vibration frequencies. In addition, changes in the structure of a building and its foundations, whether crippling or not, mean that the different energy content of the ground acceleration can during an aftershock further complicates any analysis. This adds up to a very difficult risk assessment for surviving buildings.
In order to compute the risk of collapse, the probability, for building damaged by a main shock, the team has introduced a logical method based on two key earthquake variables: magnitude and site-to-source distance. They have carried out tests using different site-to-source distances with an incremental dynamic analysis based on simulated ground motions caused by the main shock and aftershocks and applied this to a computer modeled, two-storey, timber-frame building in a hypothetical town in California relatively close to a geological fault line, as a proof of principle. Full-scale structural data was available from an actual building.
The team found that collapse probability increased if there were a sequence of aftershocks following a main shock just 10 kilometers distant from the building. Stronger aftershocks mean greater risk that correlates with the actual magnitude of the shock. As one might also expect if the site-to-source distance is greater, risk is lower. Overall, however, the analysis allows the team to quantify this risk based on the two variables, distance and aftershock magnitude.
Reference:
Nazari, N., van de Lindt, J.W. and Li, Y. (2014) ‘Effect of aftershock intensity on seismic collapse fragilities’, Int. J. Reliability and Safety, Vol. 8, Nos. 2/3/4, pp.174-195. DOI: 10.1504/IJRS.2014.069526
Set-up as part of the Syracuse University Lava Project, this cook-off was a collaboration with experimental UK chef Sam Bompas and the Syracuse University earth sciences team, who have created a car-sized, man-made volcano that melts rock down into lava in around 70 hours.
The researchers use these synthetic lava flows to learn more about the morphology and behaviour of molten rock, but in July last year they decided to team up with Bompas to see if they could create the hottest barbeque in the world. The result? A grill that reached just over 1,000 degrees Celsius (2,000 Fahrenheit) – more than double the maximum temperature of average ovens.
This is a feather under reflected and matrix fluoresced illumination. (A) Reflected light microscopy, with only barbs visible. (B) Polarized light, some traces of barbules. (C) A laser-stimulated fluorescence of matrix behind carbon film backlights the feather and renders the barbules visible across the entire field of view. Credit: KU News Service/University of Kansas
A team of scientists based largely at the University of Kansas and the Burke Museum of Natural History and Culture in Washington has developed methods of using commercial-grade laser equipment to find and analyze fossils of dinosaurs. Their techniques are introduced via a paper in the journal PLOS ONE today.
The new laser method causes fossil samples to fluoresce, revealing complex details unseen with traditional visual enhancers like ultraviolet light.
“Nobody else is doing this, as far as I know,” said David Burnham, preparator at KU’s Biodiversity Institute & Natural History Museum and a co-author on the paper. “Basically you want to excite electrons in the object so it emits photons you can see. This requires a camera filter of some kind, and that’s where an orange or yellow long-pass filter is used — it takes away everything else so we can see the photons.”
The authors first used lasers a few years ago during examination of a Microraptor specimen from China, when they noticed a second fossil in the surrounding material.
“We had a mystery fossil on the same piece,” Burnham said.
The KU researchers contacted Thomas Kaye of the Burke Museum for help identifying it. “We sent him the specimen, and he came up with this laser technique,” Burnham said.
Since then, the researchers have worked to fine-tune the laser-identification process, often using lasers on samples from Jehol Biota, a “mother lode” of 27-million-year-old fossils unearthed in the Chinese province of Liaoning.
“There have been many dinosaurs with feathers and scales that nobody has seen before because of this locality in China, where volcanic ash has preserved fossils much like in Pompeii,” Burnham said. “Tissues are preserved — not just the bones. With things like feathers, we can see details really well using lasers. If the fossils themselves won’t fluoresce, the background will. We can see if a primitive feather looks like a modern feather.”
Because high-end technology has become less expensive, the researchers have been able to buy medium-power short wavelength lasers on websites like eBay and experiment with digital photographic equipment and filters. Thus, they’ve developed novel uses for lasers, such as backlighting opaque specimens to reveal detail and even finding new fossils hidden within rocks or dirt.
“We’re finding that a blue hand-held laser is easiest to use — it’s sold by a company called Dragon Laser,” Burnham said. “You can buy them at different wavelengths and energy levels — you just have to be really careful to wear protective glasses.”
In the PLOS ONE paper, the researchers give examples of using lasers in various ways: silhouette illumination of carbon fibers, such as the feathers of a primitive bird; microscopic imaging of specimens fluorescing beneath the specimen surface to capture details; and in-situ analysis with minimal invasiveness, where the team analyzed the arm bracelet on the skeleton of a small girl from the mid-Holocene without removing or disturbing it, finding it was fashioned from a hippopotamus tooth.
Indeed, the researchers have even developed a proof-of-concept automated fossil sorter that employs a laser beam to pick microfossils from surrounding rocks and dirt.
“The reason we collect microfossils is to find tiny little teeth and they preserve well because they’re enamel — the hardest substance body produces,” Burnham said. “You walk around, find fossils, take burlap sack and fill it with dirt, or matrix. Before, we’d bring it back to museum and go through it with a magnifying glass, separating things by hand, one by one — mostly getting rocks. To speed this up, now we have a machine that emits laser light and pops out the teeth.”
Beyond these applications, the KU researcher said that lasers would allow paleontologists to spot phony fossils, or specimens cobbled together from many fossils and passed off as whole. This is because bones from different places or times would emit dissimilar fluorescence once exposed to laser light.
“It allows us to detect fakes,” Burnham said. “It’s been going on ever since man has been around. People are trying to make the specimen look better or more intact. Museums want pretty things, so people doctor these up to make them look better. People do it fraudulently because they’re easier to sell when you make something more complete. Some artists are so good you can’t tell where the real thing stops and the fake thing begins. With lasers, now we’ll know.”
Reference:
Thomas G. Kaye, Amanda R. Falk, Michael Pittman, Paul C. Sereno, Larry D. Martin, David A. Burnham, Enpu Gong, Xing Xu, Yinan Wang. Laser-Stimulated Fluorescence in Paleontology. PLOS ONE, 27 May 2015 DOI: 10.1371/journal.pone.0125923
Casts of the jaws of Australopithecus deyiremeda, a new human ancestor species from Ethiopia, held by principal investigator and lead author Dr. Yohannes Haile-Selassie of The Cleveland Museum of Natural History. Photo credit: Laura Dempsey Credit: Cleveland Museum of Natural History
A new relative joins “Lucy” on the human family tree. An international team of scientists, led by Dr. Yohannes Haile-Selassie of The Cleveland Museum of Natural History, has discovered a 3.3 to 3.5 million-year-old new human ancestor species. Upper and lower jaw fossils recovered from the Woranso-Mille area of the Afar region of Ethiopia have been assigned to the new species Australopithecus deyiremeda. This hominin lived alongside the famous “Lucy’s” species, Australopithecus afarensis. The species will be described in the May 28, 2015 issue of the international scientific journal Nature.
Lucy’s species lived from 2.9 million years ago to 3.8 million years ago, overlapping in time with the new species Australopithecus deyiremeda. The new species is the most conclusive evidence for the contemporaneous presence of more than one closely related early human ancestor species prior to 3 million years ago. The species name “deyiremeda” (day-ihreme-dah) means “close relative” in the language spoken by the Afar people.
Australopithecus deyiremeda differs from Lucy’s species in terms of the shape and size of its thick-enameled teeth and the robust architecture of its lower jaws. The anterior teeth are also relatively small indicating that it probably had a different diet.
“The new species is yet another confirmation that Lucy’s species, Australopithecus afarensis, was not the only potential human ancestor species that roamed in what is now the Afar region of Ethiopia during the middle Pliocene,” said lead author and Woranso-Mille project team leader Dr. Yohannes Haile-Selassie, curator of physical anthropology at The Cleveland Museum of Natural History. “Current fossil evidence from the Woranso-Mille study area clearly shows that there were at least two, if not three, early human species living at the same time and in close geographic proximity.”
“The age of the new fossils is very well constrained by the regional geology, radiometric dating, and new paleomagnetic data,” said co-author Dr. Beverly Saylor of Case Western Reserve University. The combined evidence from radiometric, paleomagnetic, and depositional rate analyses yields estimated minimum and maximum ages of 3.3 and 3.5 million years.
“This new species from Ethiopia takes the ongoing debate on early hominin diversity to another level,” said Haile-Selassie. “Some of our colleagues are going to be skeptical about this new species, which is not unusual. However, I think it is time that we look into the earlier phases of our evolution with an open mind and carefully examine the currently available fossil evidence rather than immediately dismissing the fossils that do not fit our long-held hypotheses,” said Haile-Selassie.
Scientists have long argued that there was only one pre-human species at any given time between 3 and 4 million years ago, subsequently giving rise to another new species through time. This was what the fossil record appeared to indicate until the end of the 20th century. However, the naming of Australopithecus bahrelghazali from Chad and Kenyanthropus platyops from Kenya, both from the same time period as Lucy’s species, challenged this long-held idea. Although a number of researchers were skeptical about the validity of these species, the announcement by Haile-Selassie of the 3.4 million-year-old Burtele partial foot in 2012 cleared some of the skepticism on the likelihood of multiple early hominin species in the 3 to 4 million-year range.
The Burtele partial fossil foot did not belong to a member of Lucy’s species. However, despite the similarity in geological age and close geographic proximity, the researchers have not assigned the partial foot to the new species due to lack of clear association. Regardless, the new species Australopithecus deyiremeda incontrovertibly confirms that multiple species did indeed co-exist during this time period.
This discovery has important implications for our understanding of early hominin ecology. It also raises significant questions, such as how multiple early hominins living at the same time and geographic area might have used the shared landscape and available resources.
The holotype (type specimen) of Australopithecus deyiremeda is an upper jaw with teeth discovered on March 4, 2011, on top of a silty clay surface at one of the Burtele localities. The paratype lower jaws were also surface discoveries found on March 4 and 5, 2011, at the same locality as the holotype and another nearby locality called Waytaleyta. The holotype upper jaw was found in one piece (except for one of the teeth which was found nearby), whereas the mandible was recovered in two halves that were found about two meters apart from each other. The other mandible was found about 2 kilometers east of where the Burtele specimens were found.
Location of the Discovery
The fossil specimens were found in the Woranso-Mille Paleontological Project study area located in the central Afar region of Ethiopia about 325 miles (520 kilometers) northeast of the capital Addis Ababa and 22 miles (35 kilometers) north of Hadar (“Lucy’s” site). Burtele and Waytaleyta are local names for the areas where the holotype and paratypes were found and they are located in the Mille district, Zone 1 of the Afar Regional State.
The Woranso-Mille Project
The Woranso-Mille Paleontological project conducts field and laboratory work in Ethiopia every year. This multidisciplinary project is led by Dr. Yohannes Haile-Selassie of The Cleveland Museum of Natural History. Additional co-authors of this research include: Dr. Luis Gibert of University of Barcelona (Spain), Dr. Stephanie Melillo of the Max Planck Institute (Leipzig, Germany), Dr. Timothy M. Ryan of Pennsylvania State University, Dr. Mulugeta Alene of Addis Ababa University (Ethiopia), Drs. Alan Deino and Gary Scott of the Berkeley Geochronology Center, Dr. Naomi E. Levin of Johns Hopkins University, and Dr. Beverly Z. Saylor of Case Western Reserve University. Graduate and undergraduate students from Ethiopia and the United States of America also participated in the field and laboratory activities of the project.
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Reference:
Yohannes Haile-Selassie, Luis Gibert, Stephanie M. Melillo, Timothy M. Ryan, Mulugeta Alene, Alan Deino, Naomi E. Levin, Gary Scott, Beverly Z. Saylor. New species from Ethiopia further expands Middle Pliocene hominin diversity. Nature, 2015; 521 (7553): 483 DOI: 10.1038/nature14448
Lip reading normally involves deciphering speech patterns, movements, gestures and expressions just by watching a person speak. Planet Earth has LIPS, too – they are an acronym for Large Igneous Provinces, huge accumulations of igneous rocks that form when hot magma extrudes from inside the Earth and flows onto the surface of the seafloor under several kilometres of water.
An international team of scientists including University of Sydney geophysicists Professor Dietmar Müller, Dr Simon Williams and Dr Maria Seton from the School of Geosciences have found a novel way to ‘read the Earth’s LIPS’. Their findings are reported in a Nature Geoscience article in which they show for the first time that LIPS have a close working relationship with underwater mountain ranges called mid-ocean ridges.
LIPS are known to form at hotspots where hot cylindrical upwellings called plumes are rising from the deep Earth’s interior, intersecting the surface.
Professor Müller explains: “Conventional wisdom has it that these plumes, and their associated catastrophic LIPS, have no relationship to mid-ocean ridges where the slow divergence between tectonic plates gives rise to volcanism that steadily and continuously generates new ocean crust.”
Now the research team has uncovered a previously missed connection between LIPS and mid-ocean ridges. They found that mantle plumes can anchor mid-ocean ridges over long periods of time, leading to a connection of mid-ocean ridges and hotspots that cannot easily be broken up.
This attraction of mid-ocean ridges to plumes promotes successive eruptions of LIPS near mid-ocean ridges over long time periods, resulting in a myriad of igneous extrusions on top of and next to each other.
“It is important in our understanding of LIPS in the ocean basins, as it means that not all LIPS form as giant eruptions over very short times, as was originally thought,” said Dr Williams.
Unlike massive eruptions on continents, the undersea eruptions are not catastrophic and are unlikely to have caused mass extinctions and climate change. However, they are just as impressive in terms of volume.
Dr Seton adds: “It means that LIPS in the oceans are less dangerous to life on Earth, as they trickle out in many successive eruptions, not just one giant outpouring of lava, as LIPS on continents.”
“The findings change our understanding of massive volcanism deep in the ocean basins”, said Professor Müller. “For example, the Kerguelen Plateau in the southern Indian Ocean, is over twice as big as New South Wales, and has acquired its massive size over tens of millions of years, whereas the similarly large Siberian Flood Basalts wiped out the majority of marine and land species on Earth within just 60,000 years.”
Reference:
Long-term interaction between mid-ocean ridges and mantle plumes, Nature Geoscience 8, 479–483 (2015) DOI: 10.1038/ngeo2437
Tons of volcanic ash entered the atmosphere in 2010 when the Icelandic volcano erupted. Researchers want to understand the ash particle properties and how well these particles can provide a nucleus for cloud ice crystals.
When tons of ash spewed into the atmosphere from a 2010 Icelandic volcano it caused havoc for vacationers across Europe. But did it also dramatically change clouds? Researchers at Pacific Northwest National Laboratory found that volcanic ash is not as efficient as common dust in birthing clouds’ ice particles. Using a novel laboratory testing chamber they formed cloud ice, a process called ice nucleation, around particles of dust and volcanic ash. Their results revealed the importance of optimal particle structure to efficiently attract super cold water vapor to nucleate ice.
“We described the detailed particle properties of ash, not currently included in atmospheric models,” said Dr. Gourihar Kulkarni, atmospheric scientist at PNNL and lead author of the study. “By including the missing information, we can increase model confidence in simulating the deposition mode of ice nucleation.”
Volcanic eruptions occur almost every day somewhere around the globe. These eruptions provide a constant source of fine ash injected into the part of the atmosphere where clouds are born. These particles can alter clouds but the process is not yet well understood. Researchers at PNNL are using novel techniques to simulate how ash particles compete with already existing natural particles such as dust to birth cloud ice. Because more than half the Earth’s precipitation comes from cloud ice particles, scientists are working to understand all the ways ice crystals are formed during ice nucleation. Including these fundamental discoveries about cloud formation in climate and weather forecast models will support new insight for precipitation and prediction of climate change.
PNNL scientists and a collaborator from the Qatar Environment and Energy Research Institute investigated the ice nucleating properties of ash particles from the 2010 Iceland volcanic eruption at Eyjafjallajökull (see sidebar, Cloud Ice Birthing, and the Icelandic Volcano with the Hard-to-Say Name). They used the ice nucleation chamber at PNNL’s Atmospheric Measurement Laboratory (AML) to test and compare how ash and dust particles nucleate ice in a super cold atmosphere.
At the same time, they applied bulk and single-particle techniques to analyze the surface elemental composition, morphology structural, and shape factor properties of volcanic ash particles at the U.S. Department of Energy’s Environmental Molecular Sciences Laboratory (EMSL) user facility. Researchers also examined the relative importance of ice nucleation behavior of these particles to proxy natural dust particles. These techniques provide detailed information at a molecular level to compare and understand the ice formation ability of ash and dust particles.
Detailed quantification of structural properties is necessary to develop the simplified equations, called parameterizations, used to describe heterogeneous (water to non-water particle) ice nucleation in climate models. Determining ice nucleation efficiencies of volcanic ash particles from different eruption periods will further explain the impact of volcanic particles on clouds. Understanding cloud condensation nucleation properties of these volcanic particles will advance the long-term goal to provide a fundamental theory basis representing the ice nucleation process in climate models.
Reference:
“Effects of Crystallographic Properties on the Ice Nucleation Properties of Volcanic Ash Particles.” Geophysical Research Letters 42. DOI: 10.1002/2015GL063270.
Figure 2A from Jackson et al.: Regional map showing the main basement-involved structures and salt-related structural domains of Santos Basin, offshore Brazil. Click on the figure for a larger image. This paper is open access online.
Salt rock behaves as a fluid and can play a pivotal role in the large-scale, long-term collapse of the world’s continental margins. However, the precise way in which this occurs is laced in controversy; nowhere is this controversy more apparent than along the Brazilian continental margin, where the origin of a feature called “the Albian Gap” has generated much heated debate over several decades.
In this new, open-access GSA Bulletin article, Christopher A-L. Jackson and colleagues enter this debate, critiquing the geological and geophysical evidence forwarded in support of the two main competing genetic models. Their study suggests that much of this evidence is not diagnostic of either model and that a revised model is required. Although their results are unlikely to be universally accepted, they at least will stimulate ongoing debate regarding the origin of this enigmatic structure.
Reference:
Understanding passive margin kinematics: A critical test of competing hypotheses for the origin of the Albian Gap, Santos Basin, offshore Brazil C. A-L. Jackson et al., Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, University Station, Austin, Texas, USA. Published online ahead of print on 19 May 2015; DOI: 10.1130/B31290.1. This paper is OPEN ACCESS online.
The birth of Sholan island. First image in 2010, last image in 2012. Credit: Jónsson et al., Nature Communications
The birth of a volcanic island is a potent and beautiful reminder of our dynamic planet’s ability to make new land. Given the destruction we’ve seen following natural events like earthquakes and tsunamis in the past few years, stunning images of two islands forming in the southern Red Sea are most welcome.
The images have been published as part of a study in Nature Communications. It describes how the two new islands formed during volcanic eruptions in 2011 and 2013 respectively, are now being steadily eroded back into the depths. And they erode quickly: one of the islands has lost 30% of its area in just two years. Superb images document the birth and growth of these new islands and also document their changing shape as the Red Sea washes over them.
Magma from an undersea eruption has a difficult journey to travel from the sea floor to the surface to form a new volcanic island, as it becomes continually quenched by an endless supply of water. But that’s what happened when the two volcanic islands, dubbed Sholan and Jadid, formed in the remote Zubair archipelago, part of Yemen.
The southern Red Sea is not a part of the world that many people would recognise as being volcanically active, but it is part of an immense African rift system – a chain of cracks in the Earth’s crust more than 3,000km long. The southern Red Sea is a place where a new ocean is forming as the tectonic plates spread apart at about 6mm per year. Underneath the Red Sea is an embryonic mid-ocean ridge, an undersea range of mountains created by volcanic eruptions.
Mid-ocean ridge spreading is mimicked in the system that feeds the eruptions – long and linear magma-filled cracks called dykes. The researchers used satellite images and knowledge of ground deformation to understand the eruptions and their feeder systems. They discovered that the dykes were at least 10km in length whereas the islands are both less than 1km in diameter.
This is similar to what happens in other volcanic areas where spreading takes place such as Iceland, where a long fissure may be active at the very start of an eruption, but as the eruption progresses the activity becomes focused around just a few vents. These features support the claim by the researchers that active spreading is taking part.
Growing archipelago?
Another key finding of the research is that the seismic swarms that occurred during the formation of these volcanic islands have been observed in the past, but without eruptions being witnessed (this is a remote area). The authors argue that these older seismic swarms were caused by dyke intrusions or submarine eruptions – either of which would suggest that this area is more volcanically active than previously thought.
This is corroborated by observations that the islands in the Zubair archipelago are all constructed of a type of fragmental volcanic rock that characterises the magma-water interactions which occur when volcanic islands are formed.
The value of this research is that by combining high-resolution optical imagery, satellite (InSAR) observations, and seismicity, the researchers have characterised the birth and development of two volcanic islands along a mid-ocean ridge system with unprecedented detail.
Perhaps the most exciting finding of the new research is that the birth of these islands suggests that the Zubair archipelago is undergoing active spreading and that further submarine and island-building eruptions are to be expected.
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Note : The above story is based on materials provided by The Conversation. This story is published courtesy of The Conversation (under Creative Commons-Attribution/No derivatives).
This Landsat 8 image, acquired on September 6, 2014, is a false-color view of the Holuhraun lava field north of Vatnajökull glacier in Iceland. The image combines shortwave infrared, near infrared, and green light to distinguish between cooler ice and steam and hot extruded lava. The Bárðarbunga caldera, visible in the lower left of the image under the ice cap, experienced a large-scale collapse starting in mid-August. Credit: USGS
On August 16 of last year, Mark Simons, a professor of geophysics at Caltech, landed in Reykjavik with 15 students and two other faculty members to begin leading a tour of the volcanic, tectonic, and glaciological highlights of Iceland. That same day, a swarm of earthquakes began shaking the island nation—seismicity that was related to one of Iceland’s many volcanoes, Bárðarbunga caldera, which lies beneath Vatnajökull ice cap.
As the trip proceeded, it became clear to scientists studying the event that magma beneath the caldera was feeding a dyke, a vertical sheet of magma slicing through the crust in a northeasterly direction. On August 29, as the Caltech group departed Iceland, the dike triggered an eruption in a lava field called Holuhraun, about 40 kilometers (roughly 25 miles) from the caldera just beyond the northern limit of the ice cap.
Although the timing of the volcanic activity necessitated some shuffling of the trip’s activities, such as canceling planned overnight visits near what was soon to become the eruption zone, it was also scientifically fortuitous. Simons is one of the leaders of a Caltech/JPL project known as the Advanced Rapid Imaging and Analysis (ARIA) program, which aims to use a growing constellation of international imaging radar satellites that will improve situational awareness, and thus response, following natural disasters. Under the ARIA umbrella, Caltech and JPL/NASA had already formed a collaboration with the Italian Space Agency (ASI) to use its COSMO-SkyMed (CSK) constellation (consisting of four orbiting X-Band radar satellites) following such events.
Through the ASI/ARIA collaboration, the managers of CSK agreed to target the activity at Bárðarbunga for imaging using a technique called interferometric synthetic aperture radar (InSAR). As two CSK satellites flew over, separated by just one day, they bounced signals off the ground to create images of the surface of the glacier above the caldera. By comparing those two images in what is called an interferogram, the scientists could see how the glacier surface had moved during that intervening day. By the evening of August 28, Simons was able to pull up that first interferogram on his cell phone. It showed that the ice above the caldera was subsiding at a rate of 50 centimeters (more than a foot and a half) a day—a clear indication that the magma chamber below Bárðarbunga caldera was deflating.
The next morning, before his return flight to the United States, Simons took the data to researchers at the University of Iceland who were tracking Bárðarbunga’s activity.
“At that point, there had been no recognition that the caldera was collapsing. Naturally, they were focused on the dyke and all the earthquakes to the north,” says Simons. “Our goal was just to let them know about the activity at the caldera because we were really worried about the possibility of triggering a subglacial melt event that would generate a catastrophic flood.”
Luckily, that flood never happened, but the researchers at the University of Iceland did ramp up observations of the caldera with radar altimetry flights and installed a continuous GPS station on the ice overlying the center of the caldera.
Last December, Icelandic researchers published a paper in Nature about the Bárðarbunga event, largely focusing on the dyke and eruption. Now, completing the picture, Simons and his colleagues have developed a model to describe the collapsing caldera and the earthquakes produced by that action. The new findings appear in the journal Geophysical Journal International.
“Over a span of two months, there were more than 50 magnitude-5 earthquakes in this area. But they didn’t look like regular faulting—like shearing a crack,” says Simons. “Instead, the earthquakes looked like they resulted from movement inward along a vertical axis and horizontally outward in a radial direction—like an aluminum can when it’s being crushed.”
To try to determine what was actually generating the unusual earthquakes, Bryan Riel, a graduate student in Simons’s group and lead author on the paper, used the original one-day interferogram of the Bárðarbunga area along with four others collected by CSK in September and October. Most of those one-day pairs spanned at least one of the earthquakes, but in a couple of cases, they did not. That allowed Riel to isolate the effect of the earthquakes and determine that most of the subsidence of the ice was due to what is called aseismic activity—the kind that does not produce big earthquakes. Thus, Riel was able to show that the earthquakes were not the primary cause of the surface deformation inferred from the satellite radar data.
“What we know for sure is that the magma chamber was deflating as the magma was feeding the dyke going northward,” says Riel. “We have come up with two different models to explain what was actually generating the earthquakes.”
In the first scenario, because the magma chamber deflated, pressure from the overlying rock and ice caused the caldera to collapse, producing the unusual earthquakes. This mechanism has been observed in cases of collapsing mines (e.g., the Crandall Canyon Mine in Utah).
The second model hypothesizes that there is a ring fault arcing around a significant portion of the caldera. As the magma chamber deflated, the large block of rock above it dropped but periodically got stuck on portions of the ring fault. As the block became unstuck, it caused rapid slip on the curved fault, producing the unusual earthquakes.
“Because we had access to these satellite images as well as GPS data, we have been able to produce two potential interpretations for the collapse of a caldera—a rare event that occurs maybe once every 50 to 100 years,” says Simons. “To be able to see this documented as it’s happening is truly phenomenal.”
Reference:
“The collapse of Bárðarbunga caldera, Iceland.” Geophys. J. Int. (July, 2015) 202 (1): 446-453 DOI: 10.1093/gji/ggv157
This mixture of multicellular organisms, small zooplanktonic animals, larvae, and single cell protists was collected from the Pacific Ocean. Credit: Christian Sardet/CNRS/Tara Expeditions
Plankton are vital to life on Earth — they absorb carbon dioxide, generate nearly half of the oxygen we breathe, break down waste, and are a cornerstone of the marine food chain. Now, new research indicates the diminutive creatures are not only more diverse than previously thought, but also profoundly affected by their environment.
Tara Oceans, an international consortium of researchers from MIT and elsewhere that has been exploring the world’s oceans in hopes of learning more about one of its smallest inhabitants, reported their initial findings this week in a special issue of Science. From 2009 to 2012, a small crew sailed on a 110-foot schooner collecting 35,000 samples of marine microbes and viruses from 200 locations around the globe — facing pirates, high winds, and ice storms in the process. But the effort was worth it. Among the studies’ findings: millions of new genes, thousands of new viruses, insights into microbial interactions, and ocean temperature’s impact on species diversity.
The researchers identified 40 million genes in the upper ocean, most of which are new to science. In comparison, the human gut microbiome only has 10 million genes. Additionally, researchers identified more than 5,000 viruses, only 39 of which were known previously.
Underneath the ocean surface, viruses, plankton, and other microbes battle one another for survival. These interactions — which are mainly parasitic in nature — are vital for maintaining diversity, as they prevent one species from dominating the environment, the study’s authors found. The expedition also revealed that species diversity is shaped by ocean temperature, which is on the rise. The new plethora of data should allow researchers to build predictive models that show how microbial communities will change in a warming world and its resulting impacts on oxygen production, carbon dioxide absorption, and ecosystem dynamics.
“The finding that temperature shapes which species are present, for instance, is especially relevant in the context of climate change, but to some extent this is just the beginning,” says Chris Bowler, a plant biologist from the French National Centre for Scientific Research. “The resources we’ve generated will allow us and others to delve even deeper, and finally begin to really understand the workings of this invisible world.”
Mick Follows, an MIT oceanographer and a co-author of one of the studies did just that, providing a new understanding of how ocean physics and chemistry affect microbial diversity. Agulhas rings are eddies that mediate the transport of waters from the Indian Ocean to the South Atlantic, bringing with them populations of plankton. As currents travel from the Indian Ocean around the tip of South Africa, sweeping up plankton along the way, large swirls (or rings) form that drastically mix and cool the microscopic hitchhikers. Only a fraction of the species survive the journey. What’s more, the unique environment inside the rings — characterized by a complex nitrogen cycle — may act as the filter.
“Oceanography is controlling the communication of these different organisms through the channel,” Follows says. “Our contribution has been to help untangle the complex nitrogen cycle inside the rings.”
Crew members on the Tara expedition collected samples from some of these rings and examined how the water’s biological markers changed over time. They found a large spike in the nitrite levels of younger rings, but had no clue as to its cause. That’s where Follows and colleagues Oliver Jahn and Chris Hill come in.
Using MIT’s General Circulation Model, they found that a combination of energy provided by storms and a weak temperature gradient in the water contribute to strong mixing in the rings, which set in motion a unique nitrogen cycle. Strong mixing dredges up nitrate and other nutrients, sparking an explosion of plankton populations. As the plankton feast they convert the nitrate into ammonium, which is then devoured by other microbes and converted into nitrite.
“Nitrification is a globally important process,” Follows says. “What happens in one ring isn’t necessarily a globally significant amount, but what’s beautiful is that it’s so exaggerated there that we can clearly interpret some of the environmental factors driving it.”
Other co-authors examined the abundance of nitrogen cycle-related genes in the rings, which revealed a very complex set of interactions. “That’s one thing that surprised me,” he said. “A whole suite of genes have been upregulated for all kinds of nitrogen cycle processes. It’s not a one way street. There is a complex enhancement of local nitrogen cycling, which will take some time to fully disentangle.”
Follows’ research is a small part of a larger effort to understand this ecosystem’s intricacies. The five studies released this week provided major insights from just 579 of 35,000 samples. Members of the more than 200-person research team composed of experts from 18 institutions are continuing to analyze the mountain of data, which is now publicly available.
Reference:
P. Bork, C. Bowler, C. de Vargas, G. Gorsky, E. Karsenti, P. Wincker. Tara Oceans studies plankton at planetary scale . DOI: 10.1126/science.aac5605
Note : The above story is based on materials provided by Massachusetts Institute of Technology. The original article was written by Cassie Martin. This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.
