An international team of earth scientists has linked the establishment of the Mekong River to a period of major intensification of the Asian monsoon during the middle Miocene, about 17 million years ago, findings that supplant the assumption that the river incised in response to tectonic causes. Their findings are the subject of a paper published in Nature Geoscience on Oct. 15.
Gregory Hoke, associate professor and associate chair of Earth sciences, and recent SU doctoral student Gregory Ruetenik, now a post-doctoral researcher at the University of Wisconsin, co-authored the article with colleagues from China, France, Sweden, Australia, and the United States. Hoke’s initial collaboration with first author Jungsheng Nie was co-editing a special volume on the growth of the Tibetan Plateau during the Cenozoic.
The Mekong River is the longest in Southeast Asia and the tenth largest worldwide in terms of water volume. Originating in the Tibetan Plateau, the Mekong runs through China, Myanmar, Laos, Thailand, Cambodia and Vietnam. The Chinese portion of the river (Lancang Jiang) occupies a spectacular canyon that is between 1-2 kilometers deep relative to the surrounding landscape.
“When the upper half of that river was established and at what point it incised the canyon it occupies today, as well as whether it was influenced by climate or by tectonics, has been debated by geologists for the last quarter century,” says Hoke. “Our work establishes when major canyon incision began and identifies the most likely mechanism responsible for that incision: an intensification of the Asian monsoon during the warmest period over the last 23 million years, the Middle Miocene climate optimum.”
River incision is the natural process by which a river cuts downward into its bed, deepening the active channel. “In most cases, you can attribute incision to some sort of some change in the overall relief of a landscape, which is typically interpreted to be in response to a tectonic influence,” says Hoke.
The standard interpretation for river incision of the Mekong and adjacent Yangtze basins had been a response to topographic growth of the Tibetan Plateau. However, a recent string of studies have determined that the southeastern margin of Tibet was already at or near modern elevations by 40 million years ago, throwing a monkey wrench into that hypothesis.
Using thermochronology of apatite minerals extracted from bedrock samples collected along the walls of the river canyon, the scientists were able to numerically model the cooling history of the rock as the river incised, which revealed synchronous downcutting at 15-17 million years along the entire river. Synchronous downcutting points towards a non-tectonic cause for incision. Ruetenik modeled whether or not a stronger monsoon was capable of achieving the magnitude of downcutting over the relatively short duration of the middle Miocene climate optimum using landscape models he developed during his SU doctoral study. According to Hoke, “This solves how river incision occurred in the absence of any clear pulse of plateau growth along the southeast margin of Tibet. In essence, an enhanced monsoon did a tremendous amount of work sawing through the landscape during the middle Miocene climate optimum.”
Previously, Hoke studied buried river sands in cave deposits to reconstruct the incision history of the Yangtze river, the next river to the east of the Mekong. “We found a sequence of ages that look similar to those from the thermochrometers in the Mekong,” he says of his findings, published in Geophysical Research Letters in 2016. He next hopes subsequent studies will be able to extend the results from this new Nature Geoscience paper to the three other big rivers that drain the southeastern margin of the Tibetan Plateau.
Reference:
Junsheng Nie, Gregory Ruetenik, Kerry Gallagher, Gregory Hoke, Carmala N. Garzione, Weitao Wang, Daniel Stockli, Xiaofei Hu, Zhao Wang, Ying Wang, Thomas Stevens, Martin Danišík, Shanpin Liu. Rapid incision of the Mekong River in the middle Miocene linked to monsoonal precipitation. Nature Geoscience, 2018; DOI: 10.1038/s41561-018-0244-z
Note: The above post is reprinted from materials provided by Syracuse University. Original written by Renee Levy.
Meltwater accumulation within 160 feet of the surface causes these bright, white reflections to dim to grey from June to early August before stabilizing in late August. Credit: Alexander Kendrick
Stanford scientists have revealed the presence of water stored within a glacier in Greenland, where the rapidly changing ice sheet is a major contributor to the sea-level rise North America will experience in the next 100 years. This observation — which came out of a new way of looking at existing data — has been a missing component for models aiming to predict how melting glaciers will impact the planet.
The group made the discovery looking at data intended to reveal the changing shape of Store Glacier in West Greenland. But graduate student Alexander Kendrick figured out that the same data could measure something much more difficult to observe: its capacity to store water. The resulting study, published in Geophysical Research Letters, presents evidence of glacier meltwater from the surface being stored within damaged, solid ice. While ice melting at the surface has been well documented, little is known about what happens below glacier surfaces, and this observation of liquid water stored within solid ice may explain the complex flow behavior of some Greenland glaciers.
“Things like this don’t always come along, but when they do, that is the real ‘joy of the discovery’ component of Earth science,” said co-author Dustin Schroeder, an assistant professor of geophysics at Stanford University’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “This paper not only highlights this component’s existence, but gives you a way to observe it in time.”
Surface meltwater plays an important role in Greenland by lubricating the bottoms of ice sheets and impacting how retreating glaciers are affected by the ocean. The process of how the glaciers melt and where the water flows contributes to their behavior in a changing climate, as these factors could alter glaciers’ response to melting or impact the timeline for sea-level rise. Knowing that some liquid is intercepted within glaciers after melting on the surface may help scientists more accurately predict oceanic changes and help people prepare for the future, Schroeder said.
“All of our predictions of sea-level rise are missing this meltwater component,” Schroeder said. “I think we’re only just realizing how important it is to understand at a fundamental physical scale what glacier meltwater does on its way from the surface to the bed.”
A different perspective
The researchers analyzed data from a high-resolution, low-power radio-echo sounder (ApRES) collected hourly from May to November 2014. Behaving like an ultrasound for ice, the radar sends an electronic wave that bounces off variations in ice density to create an image of ice structure that shows how quickly the ice melts or moves over time.
When the team plotted the radar data, it looked suspicious, said Kendrick, who was lead author on the paper. They tested ideas such as temperature variations and battery fluctuations to account for what they saw, then wondered if water within the ice was causing the peculiarity. By looking at a different aspect of the data, Kendrick noticed that the idiosyncrasies coming from deep within the glacier correlated with information from a nearby weather station indicating that the glacier had been melting at the time the data was collected. That finding backed up the idea that they were detecting water that had melted on the surface and then trickled down into the glacier, where it got trapped.
“This is a new way you could use these instruments to answer scientific questions — instead of just looking at changes in the ice thickness, we’re also looking at changes in the ice properties itself,” said co-author Winnie Chu, a postdoctoral researcher in Schroeder’s lab. “Alex set up the groundwork for trying to understand how this meltwater storage changes through time.”
The study reveals a significant amount of meltwater produced from the local area surrounding the radar is being intercepted and stored within the ice in a region extending between 15 to 148 feet below the surface during the summer, then released or refrozen during winter.
“The water system of Greenland is critical for understanding what’s happening on the planet,” said Schroeder, who is also a fellow at the Stanford Woods Institute for the Environment. “This component Alex has discovered shows that there is a piece of this glacier in particular — and maybe the entire Greenland hydrologic system in general — that we just were not modeling or thinking about in this way.”
The researchers hope this new geophysical method can be used to understand how meltwater impacts other glaciers and glacial systems, as well.
Reference:
A. K. Kendrick, D. M. Schroeder, W. Chu, T. J. Young, P. Christoffersen, J. Todd, S. H. Doyle, J. E. Box, A. Hubbard, B. Hubbard, P. V. Brennan, K. W. Nicholls, L. B. Lok. Surface Meltwater Impounded by Seasonal Englacial Storage in West Greenland. Geophysical Research Letters, 2018; DOI: 10.1029/2018GL079787
The University of California, San Diego’s outdoor shake table in Scripps Ranch will soon give engineers a truer sense of the fury released when big earthquakes erupt in places around the world,
The National Science Foundation gave the school $16.3 million to upgrade the center so it can more accurately simulate quakes, a complex phenomenon that in some years kills hundreds of thousands of people worldwide.
The table is the largest of its kind and has conducted experiments that have led to tougher building and design codes for bridges and housing. But it can move structures only backward and forward. Quakes can move the ground in many directions.
Engineers will modify the table so that it also can move up and down, right and left, and simulate the pitch, roll and yaw that can come with ground motion. Collectively, these movements are called the “six degrees of freedom.”
The upgrade involves adding pistons and power to a table that’s used by researchers from around nation to simulate quakes big enough to send seismic waves coursing through the earth for weeks.
“We will be able to reproduce earthquake motions with the most accuracy of any shake table in the world,” said Joel Conte, the structural engineer who is overseeing the project. “This will accelerate the discovery of the knowledge engineers need to build new bridges, power plants, dams, levees, telecommunication towers, wind turbines, retaining walls, tunnels, and to retrofit older structures. It will enhance the resiliency of our communities.”
The upgrade comes at a worrisome time in California.
In June, the U.S. Geological Survey said 38 high-rise buildings in San Francisco constructed between 1964 and 1994 could buckle if they were hit by the type of earthquake that devastated the city in 1906. The list includes the Transamerica Pyramid in the Financial District.
There’s also concern about a newer skyscraper, the 58-story Millennium Tower, which has been sinking and tilting, making it more vulnerable to big quakes.
San Diego is also on shaky ground.
In 2017, the Earthquake Engineering Research Institute released a report that says that 2,000 people could die in San Diego if a 6.9 magnitude quake erupts on the Rose Canyon fault, which runs through the heart of the city. Potential property damage: $40 billion.
The EERI emphasized that the figures are just estimates because modeling the complexities of earthquakes is hard to do with existing models and technology.
Even so, engineers have made progress.
Since it opened in the late 1980s, UC San Diego’s Powell Laboratories has been heavily involved in developing and testing key portions of roads and bridges, leading to changes in building codes.
The shake table was added in 2004 to give scientists and engineers better ability to test large structures, from wood-frame buildings to bridge columns to a 70-foot wind turbine.
The need for such a table had been apparent for decades.
The 6.7 magnitude Northridge quake in 1994 appears to have caused the ground to move vertically and horizontally. That vertical movement may be the reason that some bridge support columns rose and pierced the decks of bridges.
Such wild ground motion wasn’t unknown to engineers. The 1971 San Fernando earthquake, which measured 6.6, appears to have caused the soil to rotate in some areas. That, in turn, may have caused some buildings to turn like corkscrews.
The movement contributed to the billions of dollars in property damage inflicted by the quake.
The table has been used to simulate some of those jarring events, notably the Northridge quake.
That earthquake caused the collapse of a parking garage at Cal State Northridge. Engineers from the University of Arizona built a similar garage in 2008, and then shook it harder than the real quake.
The experiment revealed a great deal about how such structures absorb and distribute energy, leading to a strengthening of national building codes.
More recently, a team led by UC San Diego built and tested a five-story building that had many of the features of a hospital—such as an ICU and a surgery suite—and a working elevator and a sprinkler system. The goal was to understand what would happen inside a hospital during a catastrophic quake.
To ensure that they didn’t miss anything, engineers placed 500 sensors in and around the building, and installed 70 cameras.
Then they simulated several high-intensity earthquakes, and later set part of the building on fire to replicate a frequent aftereffect of quakes.
“What we are doing is the equivalent of giving a building an EKG,” lead engineer Tara Hutchinson said.
The experiment helped lead to the design of safer hospitals, and it was followed by a project that focused on a subject of great concern in California—four-story wood-frame residential buildings that have garages on the first floor.
The structures -built mostly in the 1920s, ’30s and ’40s—are now considered vulnerable to collapse in a huge quake.
In 2013, Colorado State University built one of the structures on the shake table and outfitted it with various types of retrofitting to see what would happen.
The result was good, and bad.
The building survived shake tests with the retrofitting in place. When it was taken out, calamity ensued.
“There was creaking and crunching, then a thunderous collapse, followed by dust and debris floating up,” said John W. van de Lindt, the Colorado State engineer who led the project.
Now, Lindt is drawing up plans for a 10-story building that will be built on the same spot. But this time, he’ll be able to move the building in any direction he wants.
“The U.S. and California have really been at the forefront of this kind of research,” Lindt said. “The upgrade will help us keep pace with the world. We really need this.”
One of the petrified remains of a victim of the eruption of Vesuvius volcano in 79 BC
A newly-discovered inscription at Pompeii proves the city was destroyed by Mount Vesuvius after October 17, 79 AD and not on August 24 as previously thought, archeologists said Tuesday.
Archeologists recently discovered that a worker had inscribed the date of “the 16th day before the calends of November”, meaning October 17, on a house at Pompeii, the head of archeology at the site, Massimo Osanna, told Italian media.
Pompeii and Herculaneum were previously thought to have been destroyed by the massive eruption of Mount Vesuvius on August 24, based on contemporary writings and archeological finds.
Nevertheless, evidence such as autumnal fruits on branches found in the ashen ruins had suggested a later date since the 19th century, Osanna said.
“Today, with much humility, perhaps we will rewrite the history books because we date the eruption to the second half of October,” said Italy’s Minister of Culture Alberto Bonisoli.
Pompeii is the second most visited tourist site in Italy, after the Colosseum in Rome, with more than three million visitors in the first eight months of this year.
Note: The above post is reprinted from materials provided by AFP.
Jaw with a durophagous dentition consisting of teeth with thick enamel of the gilthead sea bream (Sparus aurata): The large molariform tooth was used for oxygen isotope analysis and to estimate the size of the fish. Credit: Copyright Guy Sisma-Ventura
Some 3,500 years ago, there was already a brisk trade in fish on the shores of the southeastern Mediterranean Sea. This conclusion follows from the analysis of 100 fish teeth that were found at various archeological sites. The saltwater fish from which these teeth originated is the gilthead sea bream, which is also known as the dorade. It was caught in the Bardawil lagoon on the northern Sinai coast and then transported from Egypt to sites in the southern Levant. This fish transport persisted for about 2,000 years, beginning in the Late Bronze Age and continuing into the early Byzantine Period, roughly 300 to 600 AD. “Our examination of the teeth revealed that the sea bream must have come from a very saline waterbody, containing much more salt than the water in the Mediterranean Sea,” said Professor Thomas Tütken of Johannes Gutenberg University Mainz (JGU). The geoscientist participated in the study together with colleagues from Israel and Göttingen. The Bardawil lagoon formed 4,000 years ago, when the sea level finally stabilized after the end of the last Ice Age. The lagoon was fished intensively and was the point of origin of an extensive fish trade.
As demonstrated by archeological finds, fishing was an important economic factor for many ancient cultures. In the southern Levant, the gilthead sea bream with the scientific name of Sparus aurata was already being fished by local costal fishermen 50,000 years ago. More exotic fish, such as the Nile perch, were already being traded between Egypt and Canaan over 5,000 years ago. However, the current study shows the extent to which the trade between the neighbors increased in the Late Bronze Age and continued for 2,000 years into the Byzantine Period. “The Bardawil lagoon was apparently a major source of fish and the starting point for the fish deliveries to Canaan, today’s Israel, even though the sea bream could have been caught there locally,” stated co-author Professor Andreas Pack from the University of Göttingen.
Fish teeth document over 2,000 years of trade
Gilthead sea bream are a food fish that primarily feed on crabs and mussels. They have a durophagous dentition with button-shaped teeth that enable them to crush the shells to get at the flesh. For the purposes of the study, 100 large shell-cracking teeth of gilthead sea bream were examined. The teeth originate from 12 archeological sites in the southern Levant, some of which lie inland, some on the coast, and cover a time period from the Neolithic to the Byzantine Period. One approach of the researchers was to analyze the content of the oxygen isotopes ^18O and ^16O in the tooth enamel of the sea bream. The ratio of ^18O to ^16O provides information on the evaporation rate and thus on the salt content of the surrounding water in which the fish lived. In addition, the researchers were able to estimate the body size of the fish on the basis of the size of the shell-cracking teeth.
The analyses showed that some of the gilthead sea bream originated from the southeastern Mediterranean but that roughly three out of every four must have lived in a very saline body of water. The only water that comes into question in the locality is that of the Bardawil lagoon, the hypersaline water of which has a salt content of 3.9 to 7.4 percent, providing the perfect environment for the growth of sea bream. The Bardawil lagoon on the Sinai coast is approximately 30 kilometers long, 14 kilometers wide, and has a maximum depth of 3 meters. It is separated from the Mediterranean by a narrow sand bar.
“There was a mainland route from there to Canaan, but the fish were probably first dried and then transported by sea,” added Tütken. Even back then, sea bream were probably a very popular food fish, although it is impossible to estimate actual quantities consumed. However, it became apparent that the fish traded from the period of the Late Bronze Age were significantly smaller than in the previous era.
According to the researchers, this reduction in body size is a sign of an increase in the intensity of fishing that led to a depletion of stocks, which is to be witnessed also in modern times. “It would seem that fishing and the trade of fish expanded significantly, in fact to such a degree that the fish did not have the chance to grow as large,” continued Tütken, pointing out that this was an early form of the systematic commercial exploitation of fish, a type of proto-aquaculture, which persisted for some 2,000 years.
Reference:
Sisma-Ventura Guy, Tütken Thomas, Zohar Irit, Pack Andreas, Sivan Dorit, Lernau Omri, Gilboa Ayelet, Bar-Oz Guy. Tooth oxygen isotopes reveal Late Bronze Age origin of Mediterranean fish aquaculture and trade. Scientific Reports, 2018; 8 (1) DOI: 10.1038/s41598-018-32468-1
An artistic reconstruction of the extinct flying squirrel Miopetaurista neogrivensis. Credit: Oscar Sanisidro (CC BY-NC-SA 4.0)
The oldest flying squirrel fossil ever found has unearthed new insight on the origin and evolution of these airborne animals.
Writing in the open-access journal eLife, researchers from the Institut Català de Paleontologia Miquel Crusafont (ICP) in Barcelona, Spain, described the 11.6-million-year-old fossil, which was discovered in Can Mata landfill, approximately 40 kilometers outside the city.
“Due to the large size of the tail and thigh bones, we initially thought the remains belonged to a primate,” says first author Isaac Casanovas-Vilar, researcher at the ICP. In fact, and much to the disappointment of paleoprimatologists, further excavation revealed that it was a large rodent skeleton with minuscule specialised wrist bones, identifying it as Miopetaurista neogrivensis — an extinct flying squirrel.
Combining molecular and paleontological data to carry out evolutionary analyses of the fossil, Casanovas-Vilar and the team demonstrated that flying squirrels evolved from tree squirrels as far back as 31 to 25 million years ago, and possibly even earlier.
In addition, their results showed that Miopetaurista is closely related to an existing group of giant flying squirrels called Petaurista. Their skeletons are in fact so similar that the large species that currently inhabits the tropical and subtropical forests of Asia could be considered living fossils.
With 52 species scattered across the northern hemisphere, flying squirrels are the most successful group of mammals that adopted the ability to glide. To drift between trees in distances of up to 150 metres, these small animals pack their own ‘parachute’: a membrane draping between their lower limbs and the long cartilage rods that extend from their wrists. Their tiny, specialised wrist bones, which are unique to flying squirrels, help support the cartilaginous extensions.
But the origin of these animals is highly debated. While most genetic studies point towards the group splitting from tree squirrels about 23 million years ago, some 36-million-year-old remains that could belong to flying squirrels have previously been found. “The problem is that these ancient remains are mainly teeth,” Casanovas-Vilar explains. “As the dental features used to distinguish between gliding and non-gliding squirrels may actually be shared by the two groups, it is difficult to attribute the ancient teeth undoubtedly to a flying squirrel. In our study, we estimate that the split took place around 31 and 25 million years ago, earlier than previously thought, suggesting the oldest fossils may not belong to flying squirrels.
“Molecular and paleontological data are often at odds, but this fossil shows that they can be reconciled and combined to retrace history,” he adds. “Discovering even older fossils could help to retrace how flying squirrels diverged from the rest of their evolutionary tree.”
An exceptional site in a rubbish dump
The Can Mata landfill holds a set of more than 200 sites ranging in age between 12.6 and 11.4 Ma (middle to late Miocene). In the last 20 years, excavations carried out by the ICP in Can Mata have led to the identification of more than 80 species of mammals, birds, amphibians and reptiles. A remarkable number of primate remains from the site have revealed three new species of hominoids, nicknamed ‘Pau’ (Pierolapithecus catalaunicus), ‘Laia’ (Pliobates cataloniae) and ‘Lluc’ (Anoiapithecus brevirostris). Various studies of mammal remains recovered from the site, including the current work in eLife, indicate the existence of a dense subtropical forest.
Reference:
Isaac Casanovas-Vilar, Joan Garcia-Porta, Josep Fortuny, Óscar Sanisidro, Jérôme Prieto, Marina Querejeta, Sergio Llácer, Josep M Robles, Federico Bernardini, David M Alba. Oldest skeleton of a fossil flying squirrel casts new light on the phylogeny of the group. eLife, 2018; 7 DOI: 10.7554/eLife.39270
Note: The above post is reprinted from materials provided by eLife.
Mount Etna in Italy is a modern example of alkaline volcanism. Credit: Shawn Appel on Unsplash
As Europe’s most active volcano, Mount Etna is intensively monitored by scientists and Italian authorities. Satellite-based measurements have shown that the southeastern flank of the volcano is slowly sliding towards the sea, while the other slopes are largely stable. To date, it has been entirely unknown if and how movement continues under water, as satellite-based measurements are impossible below the ocean surface. With the new GeoSEA seafloor geodetic monitoring network, scientists from the GEOMAR Helmholtz Centre for Ocean Research Kiel, the Kiel University, priority research area Kiel Marine Science, and the Istituto Nazionale di Geofisica e Vulcanologia (INGV) have now been able to detect for the first time the horizontal and vertical movement of a submerged volcanic flank.
The results confirm that the entire southeastern flank is in motion. The driving force of flank movement is most likely gravity, and not the ascent of magma, as previously assumed. Catastrophic collapse involving the entire flank or large parts of it cannot be excluded and would trigger a major tsunami with extreme effects in the region. The results of the study have been published today in the international journal Science Advances.
“At Mount Etna we used a sound based underwater geodetic monitoring network, the so-called marine geodesy, on a volcano for the first time ,” says Dr. Morelia Urlaub, lead author of the study. She led the investigations as part of the “MAGOMET — Marine geodesy for offshore monitoring of Mount Etna” project. In April 2016, the GEOMAR team placed a total of five acoustic monitoring transponder stations across the fault line that represents the boundary between the sliding flank and the stable slope. “We placed three on the sliding sector and two on the presumably stable side of the fault line,” says Dr. Urlaub.
During their mission each transponder was sending an acoustic signal every 90 minutes. Since the speed of sound in water is known, the travel time of the signals between transponders gave information on the distances between transponders on the seafloor with a precision of less than one centimeter. “We noticed that in May 2017 the distances between transponders on different sides of the fault clearly changed. The flank slipped by four centimeters seawards and subsided by one centimeter within a period of eight days,” explains Dr. Urlaub. This movement can be compared to a very slow earthquake, a so-called “slow slip event.” It was the first time that the horizontal movement of such a slow slip event was recorded under water. In total, the system delivered data for about 15 months.
A comparison with ground deformation data obtained by satellite showed that the southeastern flank above sea level moved by a similar distance during the same observation period. “So the entire southeast flank changed its position,” says Dr. Urlaub.
“Overall, our results indicate that the slope is sliding due to gravity and not due to the rise of magma,” she continues. If magma dynamics in the centre of the volcano triggered flank deformation, displacement of the flank would be expected to be larger onshore than below water. This is crucial for hazard assessments. “The entire slope is in motion due to gravity. It is therefore quite possible that it could collapse catastrophically, which could trigger a tsunami in the entire Mediterranean,” explains Professor Heidrun Kopp, coordinator of the GeoSEA array and co-author of the study. However, the results of the study do not allow a prediction whether and when such an event might occur.
“Further basic research is needed to understand the geological processes at and around Etna and other coastal volcanoes. Our investigation shows that the sound-based geodetic monitoring network can be a tremendous help in this respect,” summarises Dr. Urlaub.
Reference:
Morelia Urlaub, Florian Petersen, Felix Gross, Alessandro Bonforte, Giuseppe Puglisi, Francesco Guglielmino, Sebastian Krastel, Dietrich Lange, Heidrun Kopp. Gravitational collapse of Mount Etna’s southeastern flank. Science Advances, 2018; 4 (10): eaat9700 DOI: 10.1126/sciadv.aat9700
Etna eruption, Catania, Sicily. Credit: Wead / Fotolia
To figure out where magma gathers in the earth’s crust and for how long, Vanderbilt University volcanologist Guilherme Gualda and his students traveled to their most active cluster: the Taupo Volcanic Zone of New Zealand, where some of the biggest eruptions of the last 2 million years occurred — seven in a period between 350,000 and 240,000 years ago.
After studying layers of pumice visible in road cuts and other outcrops, measuring the amount of crystals in the samples and using thermodynamic models, they determined that magma moved closer to the surface with each successive eruption.
The project fits into Gualda’s ongoing work studying supereruptions — how the magma systems that feed them are built and how the Earth reacts to repeated input of magma over short periods of time.
“As the system resets, the deposits become shallower,” said Gualda, associate professor of earth and environmental sciences. “The crust is getting warmer and weaker, so magma can lodge itself at shallower levels.”
What’s more, the dynamic nature of the Taupo Volcanic Zone’s crust made it more likely for the magma to erupt than be stored in the crust. The more frequent, smaller eruptions, which each produced 50 to 150 cubic kilometers of magma, likely prevented a supereruption. Supereruptions produce more than 450 cubic kilometers of magma and they affect the earth’s climate for years following the eruption.
“You have magma sitting there that’s crystal-poor, melt-rich for few decades, maybe 100 years, and then it erupts,” Gualda said. “Then another magma body is established, but we don’t know how gradually that body assembles. It’s a period in which you’re increasing the amount of melt in the crust.”
The question that remains is how long it look for these crystal-rich magma bodies to assemble between eruptions. It could be thousands of years, Gualda said, but he believes it’s shorter than that.
Reference:
Guilherme A. R. Gualda, Darren M. Gravley, Michelle Connor, Brooke Hollmann, Ayla S. Pamukcu, Florence Bégué, Mark S. Ghiorso, Chad D. Deering. Climbing the crustal ladder: Magma storage-depth evolution during a volcanic flare-up. Science Advances, 2018; 4 (10): eaap7567 DOI: 10.1126/sciadv.aap7567
This is a virtual rendering of the Visogliano and Fontana Ranuccio teeth. Credit: Zanolli et al., 2018 CC-BY – Redistribution allowed with credit.
Fossil teeth from Italy, among the oldest human remains on the Italian Peninsula, show that Neanderthal dental features had evolved by around 450,000 years ago, according to a study published October 3, 2018 in the open-access journal PLOS ONE by Clément Zanolli of the Université Toulouse III Paul Sabatier in France and colleagues. These teeth also add to a growing picture of a period of complex human evolution that we are only beginning to understand.
Zanolli and colleagues examined dental remains from the sites of Fontana Fanuccio, located 50km southeast of Rome, and Visogliano, located 18km northwest of Trieste. At around 450,000 years old, these teeth join a very short list of fossil human remains from Middle Pleistocene Europe. Using micro-CT scanning and detailed morphological analyses, the authors examined the shape and arrangement of tooth tissues and compared them with teeth of other human species. They found that the teeth of both sites share similarities with Neanderthals and are distinct from modern humans.
There has been much debate over the identities and relationships of Middle Pleistocene ancient humans in Eurasia. The discovery of Neanderthal-like teeth so early in the record adds support to the suggestion of an early divergence of the Neanderthal lineage from our own, around the Early-Middle Pleistocene transition. The teeth are also notably different from other teeth known from this time in Eurasia, suggesting that there may have been multiple human lineages populating the region at this time, adding to a growing list of evidence that the Middle Pleistocene was a time of more complex human evolution than previously recognized.
Zanolli adds: “The remains from Fontana Ranuccio and Visogliano represent among the oldest human fossil remains testifying to a peopling phase of the Italian Peninsula. Our analyses of the tooth internal structural organization reveal a Neanderthal-like signature, also resembling the condition shown by the contemporary assemblage from Atapuerca Sima de los Huesos, indicating that an overall Neanderthal morphological dental template was preconfigured in Western Europe at least 430 to 450 ka ago.”
Reference:
Clément Zanolli, María Martinón-Torres, Federico Bernardini, Giovanni Boschian, Alfredo Coppa, Diego Dreossi, Lucia Mancini, Marina Martínez de Pinillos, Laura Martín-Francés, José María Bermúdez de Castro, Carlo Tozzi, Claudio Tuniz, Roberto Macchiarelli. The Middle Pleistocene (MIS 12) human dental remains from Fontana Ranuccio (Latium) and Visogliano (Friuli-Venezia Giulia), Italy. A comparative high resolution endostructural assessment. PLOS ONE, 2018; 13 (10): e0189773 DOI: 10.1371/journal.pone.0189773
Note: The above post is reprinted from materials provided by PLOS.
Earth’s mantle (dark red) lies below the crust (brown layer near the surface) and above the outer core (bright red). Credit: CC image by Argonne National Laboratory via Flickr
Researchers at CU Boulder report that they may have solved a geophysical mystery, pinning down the likely cause of a phenomenon that resembles a wrench in the engine of the planet.
In a study published today in Nature Geoscience, the team explored the physics of “stagnant slabs.” These geophysical oddities form when huge chunks of Earth’s oceanic plates are forced deep underground at the edges of certain continental plates. The chunks sink down into the planet’s interior for hundreds of miles until they suddenly — and for reasons scientists can’t explain — stop like a stalled car.
CU Boulder’s Wei Mao and Shijie Zhong, however, may have found the reason for that halt. Using computer simulations, the researchers examined a series of stagnant slabs in the Pacific Ocean near Japan and the Philippines. They discovered that these cold rocks seem to be sliding on a thin layer of weak material lying at the boundary of the planet’s upper and lower mantle — roughly 660 kilometers, or 410 miles, below the surface.
And the stoppage is likely temporary: “Although we see these slabs stagnate, they are a fairly recent phenomena, probably happening in the last 20 million years,” said Zhong, a co-author of the new study and a professor in CU Boulder’s Department of Physics.
The findings matter for tectonics and volcanism on the Earth’s surface. Zhong explained that the planet’s mantle, which lies above the core, generates vast amounts of heat. To cool the globe down, hotter rocks rise up through the mantle and colder rocks sink.
“You can think of this mantle convection as a big engine that drives all of what we see on Earth’s surface: earthquakes, mountain building, plate tectonics, volcanos and even Earth’s magnetic field,” Zhong said.
The existence of stagnant slabs, which geophysicists first located about a decade ago, however, complicates that metaphor, suggesting that Earth’s engine may grind to a halt in some areas. That, in turn, may change how scientists think diverse features, such as East Asia’s roiling volcanos, form over geologic time.
Scientists have mostly located such slabs in the western Pacific Ocean, specifically off the east coast of Japan and deep below the Mariana Trench. They occur at the sites of subduction zones, or areas where oceanic plates at the surface of the planet plunge hundreds of miles below ground.
Slabs seen at similar sites near North and South America behave in ways that geophysicists might expect: They dive through Earth’s upper mantle and into the lower mantle where they heat up near the core.
But around Asia, “they simply don’t go down,” Zhong said. Instead, the slabs spread out horizontally near the boundary between the upper and lower mantle, a point at which heat and pressure inside Earth cause minerals to change from one phase to another.
To find out why slabs go stagnant, Zhong and Mao, a graduate student in physics, developed realistic simulations of how energy and rock cycle around the entire planet.
They found that the only way they could explain the behavior of the stagnant slabs was if a thin layer of less-viscous rock was wedged in between the two halves of the mantle. While no one has directly observed such a layer, researchers have predicted that it exists by studying the effects of heat and pressure on rock.
If it does, such a layer would act like a greasy puddle in the middle of the planet. “If you introduce a weak layer at that depth, somehow the reduced viscosity helps lubricate the region,” Zhong said. “The slabs get deflected and can keep going for a long distance horizontally.”
Stagnant slabs seem to occur off the coast of Asia, but not the Americas, because the movement of the continents above gives those chunks of rock more room to slide. Zhong, however, said that he doesn’t think the slabs will stay stuck. With enough time, he suspects that they will break through the slick part of the mantle and continue their plunge toward the planet’s core.
The planet, in other words, would still behave like an engine — just with a few sticky spots. “New research suggests that the story may be more complicated than we previously thought,” Zhong said.
Reference:
Wei Mao, Shijie Zhong. Slab stagnation due to a reduced viscosity layer beneath the mantle transition zone. Nature Geoscience, 2018; DOI: 10.1038/s41561-018-0225-2
New research led by Victoria University of Wellington geophysicist Associate Professor Simon Lamb and published in Nature Geoscience has revealed how understanding the events leading up to the 2016 Kaikōura Earthquake may lead to a different approach to forecasting earthquakes.
“It has been commonly thought that the best way to predict future earthquakes is to analyse the earthquake histories of individual faults,” says Associate Professor Lamb. “Data about past earthquakes are entered into modelling software and used to predict future earthquakes on each fault. This method assumes that each fault has its own in-built pacemaker or driving mechanism, giving rise to semi-regular earthquakes on the fault.”
Associate Professor Lamb thinks there are a number of issues with this method.
“It is impractical to characterise every fault—there are just too many and some are not visible at the surface,” he says.
But a more fundamental issue with this method was revealed by analysis done in conjunction with Associate Professor Richard Arnold of Victoria University of Wellington and Dr. James Moore at the Nanyang Technical University, Singapore. Associate Professor Lamb says the team’s work showed that, in most cases, the earthquakes that happen on faults are triggered by earthquakes on faults elsewhere.
To come to this conclusion, the team looked at the slow movements of the landscape in the two decades prior to the 2016 Kaikōura earthquake, measured very precisely with satellite mapping of ground motions.
“We found that the measured ground motions were caused by slippage only on the single major fault separating the two tectonic plates that lie under New Zealand. This large fault, called the megathrust, underlies much of New Zealand, and only reaches the surface offshore.”
The megathrust moves freely at depths of 30 kilometres or more, but at shallower depths it is locked in place. This combination of steady movement in some places and no movement in others slowly forces the southern North Island and northern South Island to bend like a piece of elastic. Associate Professor Lamb says that this movement puts extreme stress on the landscape, and that this was the cause of the 2016 Kaikōura quake.
“The Kaikōura earthquake initiated a complex pattern of fault movement, essentially shattering the landscape, and causing a cascade of earthquakes on 20 or more faults,” Associate Professor Lamb says. “The data we studied show a strong link between the pattern of shattering and locking of the underlying megathrust prior to the earthquake and the movement during the earthquake itself. The damage caused by the Kaikōura earthquake runs parallel to this locking of the megathrust, but cuts across many of the big surface faults in the area, indicating a strong link to the movement of the megathrust rather than any of the individual faults.”
These findings may be significant for the way we predict future earthquakes, Associate Professor Lamb says.
“While we may not be able to predict the movement of individual faults, we can track the underlying cause of an earthquake and give an indication of where future shaking might occur by understanding and modelling the megathrust.”
Reference:
Simon Lamb et al. Locking on a megathrust as a cause of distributed faulting and fault-jumping earthquakes, Nature Geoscience (2018). DOI: 10.1038/s41561-018-0230-5
The Hunga Island Tonga Hunga Ha’apai or HTHH emerged in 2015 after the eruption of a submarine volcano in the Pacific Ocean. Credit: Pixabay
Mountains are among the most biodiverse places on Earth, but scientists have struggled to fully understand why they are so important in creating high species richness. An international research team, including four scientists from the University of Amsterdam, has now shed new light on answering this long-standing question.
The team found that mountain building, through a process of uplift and erosion, continuously reshapes the landscape and is responsible for creating habitat heterogeneity in an elevational gradient. “The complex interplay between growing mountains and climate generates plenty of opportunities for the creation of new species,” says Carina Hoorn, senior author of the paper. “Although climate and ruggedness of the terrain were previously thought to be the principal cause for mountain biodiversity, our global synthesis now makes clear that geological history plays a paramount role in this process,” explains Hoorn.
The team reached this conclusion by applying statistical models to biological, geological and climatological datasets from across the globe. “In our models, we related the species richness of birds, mammals and amphibians to global datasets of temperature, precipitation, erosion rates, relief and soil composition,” says Daniel Kissling who conducted the statistical analyses of the paper. “I was surprised to find not only the usual correlations with climate, but a significant relation between biodiversity, erosion history, relief and number of soil types,” continues Kissling. While the study shows that this is evident globally, it also revealed that the relationship can vary depending on which mountain system is considered. “This regional variation in the importance of geological drivers was really unexpected,” says Kissling.
The study further showed that geographic position (e.g. whether a mountain intercepts atmospheric currents or not) and the duration of mountain building process (young or old) are also important processes influencing biodiversity in mountains. On shorter geological time scales, Quaternary climatic fluctuations can also promote the creation of new species in mountains. “We suggests that the waxing and waning of glaciers, which has strongly reshaped the landscape and repeatedly connected and disconnected animal and plant populations, has played an important role for the creation of new mountain species,” says Suzette Flantua who studied the effects of Quaternary climate change on mountain biodiversity in Latin America for her Ph.D. at the University of Amsterdam.
The advances in geological methods and the increasingly complete global data sets on climate, soils, erosion history, and species richness only now have made it possible to gain such comprehensive insights into the relation between mountain building and biodiversity. The scientists are optimistic that with the new methods and datasets, further insights into the complex relationship between biodiversity, climate and mountain building can be expected in the near future.
Reference:
Alexandre Antonelli et al. Geological and climatic influences on mountain biodiversity, Nature Geoscience (2018). DOI: 10.1038/s41561-018-0236-z
The genus Vibrio is one of the best model marine heterotrophic bacterial groups, and many Vibrio species grow very quickly with short generation times. In addition, many Vibrio spp. are well-known bacterial pathogens, causing disease in humans or marine animals. For example, Vibrio cholerae is the causative agent of cholera. Over the past 40 years, many nonpathogenic species of Vibrio have also been described.
Vibrios are ubiquitous in estuarine and marine environments on a global scale, especially in coastal areas. They are easily cultured on standard or selective media and are capable of a diverse array of metabolic activities. Also, vibrios are capable of responding rapidly to nutrient pulses with explosive growth responses in amended microcosms, such as during phytoplankton blooms and dust storms, suggesting that the short period of Vibrio blooms should be considered when attempting to determine their overall contribution to the recycling of organic macromolecules. Currently, the role of Vibrio spp. in marine organic carbon cycling, particularly in coastal environments, is underestimated.
In an article coauthored by Xiao-Hua Zhang, Heyu Lin, Xiaolei Wang and Brian Austin, scholars at College of Marine Life Sciences, Ocean University of China, and the Institute of Aquaculture, University of Stirling, U.K., provided an overview of distribution and environmental drivers of Vibrio populations in the marine environment, and discussed their potential role in marine organic carbon cycling.
These four scholars proposed in the study, which was published in Science China, that “Vibrio spp. may exert large impacts on marine organic carbon cycling especially in marginal seas.” In addition, they proposed a potential action mode of Vibrio species in marine organic carbon cycling (Figure 1).
“All currently described Vibrio spp. are obligate heterotrophs and, as such, rely on organic matter for their carbon sources. Generally, vibrios consume a wide array of organic carbon compounds as carbon and energy sources, with most species being able to utilize over 40 compounds. Many of the polysaccharides are derived from macroalgal cell walls (i.e., alginic acid, agar, fucoidan and laminarin) or zooplankton exoskeletons (i.e., chitin). In our previous work, 56.8 percent of Vibrio cultures (330 out of 581 isolates) isolated from Chinese marginal seas possessed chitin, while 11.2 percent of Vibrio cultures (65 out of 581 isolates) could degrade alginic acid (data not shown). Vibrios are able to engage in both respiratory and fermentative metabolism and transform organic carbon into cell material and the waste products of energy metabolism. During aerobic or anaerobic respiration, large amounts of metabolic end products are excreted. Hence, Vibrio spp. are undoubtedly key players in marine organic carbon cycles, especially in marginal seas,” the authors write.
Reference:
Xiaohua Zhang et al, Significance of Vibrio species in the marine organic carbon cycle—A review, Science China Earth Sciences (2018). DOI: 10.1007/s11430-017-9229-x
Note: The above post is reprinted from materials provided by Science China Press.
The calcium carbonate skeleton of this living brain coral (Diploria labyrinthiformis) was evaluated for this study. From the coral, which is about one meter in diameter, the researchers extracted a small section of the skeleton without harming the coral. Credit: Photo courtesy of the researchers.
When nitrogen-based fertilizers flow into water bodies, the result can be deadly for marine life near shore, but what is the effect of nitrogen pollution far out in the open ocean?
A 130-year-old brain coral has provided the answer, at least for the North Atlantic Ocean off the East Coast of the United States. By measuring the nitrogen in the coral’s skeleton, a team of researchers led by Princeton University found significantly less nitrogen pollution than previously estimated. The study was published online in the Proceedings of the National Academy of Sciences.
“To our surprise, we did not see evidence of increased nitrogen pollution in the North Atlantic Ocean over the past several decades,” said Xingchen (Tony) Wang, who conducted the work as part of his doctorate in geosciences at Princeton and is now a postdoctoral scholar at the California Institute of Technology.
Earlier work by the Princeton-based team, however, did find elevated nitrogen pollution in another open ocean site in the South China Sea, coinciding with the dramatic increase in coal production and fertilizer usage in China over the past two decades.
In the new study, the researchers looked at coral skeleton samples collected in the open ocean about 620 miles east of the North American continent near the island of Bermuda, a region thought to be strongly influenced by airborne nitrogen released from U.S. mainland sources such as vehicle exhaust and power plants.
Although the team found no evidence that human-made nitrogen was on the rise, the researchers noted variations in nitrogen that corresponded to levels expected from a natural climate phenomenon called the North Atlantic Oscillation, Wang said.
The result is in contrast to previously published computer models that predicted a significant increase in human-made nitrogen pollution in the North Atlantic.
The work may indicate that U.S. pollution control measures are successfully limiting the amount of human-generated nitrogen emissions that enter the ocean.
“Our finding has important implications for the future of human nitrogen impact on the North Atlantic Ocean,” said Wang. “Largely due to advances in pollution technology, human nitrogen emissions from the U.S. have held steady or even declined in recent decades,” he said. “If emissions continue at this level, our results imply that the open North Atlantic will remain minimally affected by nitrogen pollution in coming decades.”
Nitrogen, when in its biologically available form and supplied in excess, can cause overgrowth of plants and algae and lead to severe ecosystem harm, including marine “dead zones” that form when microorganisms consume all the oxygen in the water, leaving none for fish. Fertilizer production and fossil fuel burning have greatly increased the production of biologically available, or “fixed,” nitrogen since the early 20th century.
When emitted to the atmosphere, fixed nitrogen can influence the ocean far from land. However, the impacts on the ocean are difficult to study because of the challenges involved in making long-term observations in the open ocean.
Corals can help. Stony or “Scleractinian” corals are long-lived organisms that build a calcium carbonate skeleton as they grow. The corals soak up nitrogen from the surrounding water and deposit a small portion in their skeletons. The skeletons provide a natural record of nitrogen emissions.
To distinguish human-made, or anthropogenic, nitrogen from the naturally occurring kind, the researchers take advantage of the fact that nitrogen comes in two weights. The heavier version, known as 15N, contains one more neutron than the lighter 14N. Anthropogenic nitrogen has a lower ratio of 15N to 14N than does the nitrogen in the ocean.
“It has long been my dream to use the nitrogen in coral skeletons to reconstruct past environmental changes; thanks to Tony, we are now doing it,” said Daniel Sigman, the Dusenbury Professor of Geological and Geophysical Sciences at Princeton.
While a graduate student at Princeton, Wang developed a sensitive and precise method to measure the 15N-to-14N ratio using a mass spectrometer, which is like a bathroom scale for weighing molecules.
To collect coral samples in the North Atlantic Ocean, Wang and Anne Cohen, an associate scientist in geology and geophysics at Woods Hole Oceanographic Institution, led a team in 2014 to Bermuda. The investigators removed a 23-inch-long core from a living brain coral (Diploria labyrinthiformis) about 10 feet below the surface on Hog Reef, about six miles from the main island. The researchers confirmed that Bermuda’s nitrogen run-off was not a factor at the site by measuring nitrogen levels in plankton floating nearby.
In addition to Wang, Cohen and Sigman, the research featured contributions from Princeton graduate student in geosciences Victoria Luu, Haojia Ren of National Taiwan University, Zhan Su of Caltech, and Gerald Haug of the Max Planck Institute for Chemistry.
This work was supported by the National Science Foundation and Princeton University’s Grand Challenges Program.
The study, “Natural forcing of the North Atlantic nitrogen cycle in the Anthropocene,” by Xingchen Tony Wang, Anne Cohen, Victoria Luu, Haojia Ren, Zhan Su, Gerald Haug and Daniel Sigman, was published online the week of October 1, 2018 in the Proceedings of the National Academy of Sciences.
Note: The above post is reprinted from materials provided by Princeton University. Original written by Catherine Zandonella.
Seismogram being recorded by a seismograph at the Weston Observatory in Massachusetts, USA. Credit: Wikipedia
Accurate monitoring of the ground beneath our feet for signs of seismic activity to identify natural phenomena such as earthquakes, volcanic eruptions and the leakage of fluids stored deep underground remains challenging.
Time-lapse 4-dimensional seismic monitoring surveys that employ an active seismic source can accurately map the subsurface, and comparing results from different surveys can show how fluids (such as carbon dioxide, CO2) move in deep geological reservoirs. However, the expense of such surveys limits how often data can be gathered meaning that subsequent analysis often has poor temporal resolution. An alternative that provides a continuous dataset is the passive monitoring of ambient seismic noise, but the accuracy of this approach depends on the ambient sources, which can change over time.
In an article recently published in Geophysics, a team of researchers from Kyushu University and industrial and governmental representatives from Japan and Canada report a new method for accurately monitoring the shallow subsurface at a high spatiotemporal resolution. The method was developed using data from 2014 to 2016 that was collected from the Accurately Controlled Routinely Operated Signal System (ACROSS) located at the Aquistore CO2 storage site in Saskatchewan, Canada.
Obtaining a high-resolution characterization of the shallow subsurface has previously been held back by the limited number of ACROSS units, however the researchers were able to overcome this obstacle. As the lead author Tatsunori Ikeda explains: “applying spatially windowed surface-wave analysis allowed us to study the spatial variation of surface wave velocities using data from a single ACROSS unit.”
The research team validated their method against data gathered from hundreds of geophone measuring devices located around the ACROSS unit and a computational model of the site. Their analysis of the surface waves shows spatial variation in the surface wave velocities, and the impact of seasonal weather on these velocities. Confirmation of the method’s accuracy highlights its potential to identify changes in the shallow subsurface that may be caused by natural phenomena or fluids leaking from storage sites much deeper underground.
As well as drawing together experts from a variety of organizations in Japan and Canada, the publication represents another step forward for researchers in Kyushu University’s International Institute for Carbon-Neutral Energy Research (I2CNER). As co-author Takeshi Tsuji notes: “The approach contributes to our ongoing work in Kyushu University to develop a downsized, continuous and controlled seismic monitoring system.” The researchers have been operating the downsized monitoring system at the Kuju geothermal and volcanological research station on Japan’s Kyushu Island.
Reference:
Tatsunori Ikeda, Takeshi Tsuji, Masashi Nakatsukasa, Hideaki Ban, Ayato Kato, Kyle Worth, Don White, Brian Roberts. Imaging and monitoring of the shallow subsurface using spatially windowed surface-wave analysis with a single permanent seismic source. Geophysics, 2018; DOI: 10.1190/GEO2018-0084.1
Diamond is a solid form of carbon with a diamond cubic crystal structure. At room temperature and pressure it is metastable and graphite is the stable form, but diamond almost never converts to graphite. Diamond is renowned for its superlative physical qualities, most of which originate from the strong covalent bonding between its atoms. In particular, it has the highest hardness and thermal conductivity of any bulk material. Those properties determine the major industrial applications of diamond in cutting and polishing tools and the scientific applications in diamond knives and diamond anvil cells.
Because of its extremely rigid lattice, diamond can be contaminated by very few types of impurities, such as boron and nitrogen. Small amounts of defects or impurities (about one per million of lattice atoms) color diamond blue (boron), yellow (nitrogen), brown (lattice defects), green (radiation exposure), purple, pink, orange or red. Diamond also has relatively high optical dispersion (ability to disperse light of different colors).
Chemical Formula: C Locality: Kimberly, republic of South Africa. India. Brazil. Ural Mountains, Russia. Murfreesboro, Arkansas, USA. Name Origin: From the Greek, adamas, meaning “invincible” or “hardest.”
In mineralogy, diamond is a metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice.
Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5–8 on the Mohs scale. Most emeralds are highly included, so their toughness (resistance to breakage) is classified as generally poor.
The word “Emerald” is derived (via Old French: Esmeraude and Middle English: Emeraude), from Vulgar Latin: Esmaralda/Esmaraldus, a variant of Latin Smaragdus, which originated in Greek: σμάραγδος (smaragdos; “green gem”).
Sapphire gemstones, up to 2.59 carats, from Kimmirut. Photo courtesy of True North Gems Inc.
Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, chromium, copper, or magnesium. It is typically blue, but natural “fancy” sapphires also occur in yellow, purple, orange, and green colors; “parti sapphires” show two or more colors. The only color that sapphire cannot be is red – as red colored corundum is called ruby, another corundum variety.
Pink colored corundum may be either classified as ruby or sapphire depending on locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of very special-purpose solid-state electronics (especially integrated circuits and GaN-based LEDs).
Ruby
Corundum ruby, 17.30 g, crystal in calcite, from Kyauksaung, Myanmar. Gift of William F. Larson.
A ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide). Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, together with amethyst, sapphire, emerald, and diamond. The word ruby comes from ruber, Latin for red. The color of a ruby is due to the element chromium.
The quality of a ruby is determined by its color, cut, and clarity, which, along with carat weight, affect its value. The brightest and most valuable shade of red called blood-red or pigeon blood, commands a large premium over other rubies of similar quality. After color follows clarity: similar to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions may indicate that the stone has been treated. Ruby is the traditional birthstone for July and is usually more pink than garnet, although some rhodolite garnets have a similar pinkish hue to most rubies. The world’s most valuable ruby is the Sunrise Ruby.
Rubies have a hardness of 9.0 on the Mohs scale of mineral hardness. Among the natural gems only moissanite and diamond are harder, with diamond having a Mohs hardness of 10.0 and moissanite falling somewhere in between corundum (ruby) and diamond in hardness. Sapphire, ruby, and pure corundum are α-alumina, the most stable form of Al2O3, in which 3 electrons leave each aluminum ion to join the regular octahedral group of six nearby O2− ions; in pure corundum this leaves all of the aluminum ions with a very stable configuration of no unpaired electrons or unfilled energy levels, and the crystal is perfectly colorless.
Taaffeite
Taaffeite
Taaffeite is a mineral, named after its discoverer Richard Taaffe (1898–1967) who found the first sample, a cut and polished gem, in October 1945 in a jeweler’s shop in Dublin, Ireland. As such, it is the only gemstone to have been initially identified from a faceted stone. Most pieces of the gem, prior to Taaffe, had been misidentified as spinel. For many years afterwards, it was known only in a few samples, and it is still one of the rarest gemstone minerals in the world.
Since 2002, the International Mineralogical Association-approved name for taaffeite as a mineral is magnesiotaaffeite-2N’2S.
Taaffe bought a number of precious stones from a jeweller in October 1945. Upon noticing inconsistencies between the taaffeite and spinels, Taaffe sent some examples to B. W. Anderson of the Laboratory of the London Chamber of Commerce for identification on 1 November 1945. When Anderson replied on 5 November 1945, he told Taaffe that they were unsure of whether it was a spinel or something new; he also offered to write it up in Gemologist.
In 1951, chemical and X-ray analysis confirmed the principal constituents of taaffeite as beryllium, magnesium and aluminium, making taaffeite the first mineral to contain both beryllium and magnesium as essential components.
The confusion between spinel and taaffeite is understandable as certain structural features are identical in both. Anderson et al., classified taaffeite as an intermediate mineral between spinel and chrysoberyl. Unlike spinel, taaffeite displays the property of double refraction that allows distinction between these two minerals.
Because of its rarity, taaffeite is used only as a gemstone.
Poudretteite
Poudretteite
Poudretteite is an extremely rare mineral and gemstone that was first discovered as minute crystals in Mont St. Hilaire, Quebec, Canada, during the 1960s. The mineral was named for the Poudrette family because they operated a quarry in the Mont St. Hilaire area where poudretteite was originally found.
Chemical Formula: KNa2B3Si12O30 Locality: From Mont Saint-Hilaire, Quebec, Canada. Name Origin: Named for the Poudrette family, operators of the quarry where type material was discovered.
This 0.86 ct gray musgravite displays an unusual iridescent phenomenon that is clearly visible in the table facet. Photo by Kevin Schumacher.
Musgravite or magnesiotaaffeite-6N’3S (chemical formula of Be(Mg, Fe, Zn)2Al6O12)
, is a rare oxide mineral. It is used as a gemstone. Its type locality is the Ernabella Mission, Musgrave Ranges, South Australia for which it was named. It is a member of the taaffeite family of minerals. Its hardness is 8 to 8.5 on the Mohs scale.
The alexandrite variety displays a color change (alexandrite effect) dependent upon the nature of ambient lighting. Alexandrite effect is the phenomenon of an observed color change from greenish to reddish with a change in source illumination. Alexandrite results from small scale replacement of aluminium by chromium ions in the crystal structure, which causes intense absorption of light over a narrow range of wavelengths in the yellow region (580 nm) of the visible light spectrum. Because human vision is more sensitive to light in the green spectrum and the red spectrum, alexandrite appears greenish in daylight where a full spectrum of visible light is present and reddish in incandescent light which emits less green and blue spectrum. This color change is independent of any change of hue with viewing direction through the crystal that would arise from pleochroism.
Alexandrite from the Ural Mountains in Russia can be green by daylight and red by incandescent light. Other varieties of alexandrite may be yellowish or pink in daylight and a columbine or raspberry red by incandescent light.
Stones that show a dramatic color change and strong colors (e.g. red-to-green) are rare and sought-after, but stones that show less distinct colors (e.g. yellowish green changing to brownish yellow) may also be considered alexandrite by gem labs such as the Gemological Institute of America.
According to a popular but controversial story, alexandrite was discovered by the Finnish mineralogist Nils Gustaf Nordenskiöld (1792–1866), and named alexandrite in honor of the future Tsar Alexander II of Russia. Nordenskiöld’s initial discovery occurred as a result of an examination of a newly found mineral sample he had received from Perovskii, which he identified as emerald at first. The first emerald mine had been opened in 1831.
Alexandrite 5 carats (1,000 mg) and larger were traditionally thought to be found only in the Ural Mountains, but have since been found in larger sizes in Brazil. Other deposits are located in India (Andhra Pradesh), Madagascar, Tanzania and Sri Lanka. Alexandrite in sizes over three carats are very rare.
5.4Ct World Rare Grandidierite High Quality Gems for Collection IGCRGD05. Credit: Gem Rock Auctions
Grandidierite is an extremely rare mineral and gem that was first discovered in 1902 in southern Madagascar. The mineral was named in honor of French explorer Alfred Grandidier (1836–1912) who studied the natural history of Madagascar.
A fossil Leggadina webbi jaw from the cavers’ explorations. Credit: Image courtesy of University of Queensland
The fossils of two extinct mice species have been discovered in caves in tropical Queensland by University of Queensland scientists tracking environment changes.
Fossils of Webb’s short-tailed mouse (Leggadina webbi) were found at Mount Etna near Rockhampton, while Irvin’s short-tailed mouse (Leggadina irvini), was discovered near Chillagoe at the base of Cape York Peninsula.
Dr Jonathan Cramb from UQ’s School of Earth and Environmental Sciences said the finds show that analysing fossils found in caves could help determine how the local environment had changed over time.
“Caves are great places for the preservation of fossils, partially because they’re natural traps that animals fall into, but also because they’re roosting sites for owls and other flying predators,” he said.
“Owls are exceptionally good at catching small mammals in particular, so the cave floor beneath their roosts is littered with the bones of rodents and small marsupials.
“The accumulation of bones build up over time, providing us with a record of what species were living in the local area, which can stretch back hundreds of thousands of years.
“Many species are only found in certain habitats — for example, hopping mice (Notomys spp.) generally live in deserts, while tree mice (Pogonomys spp.) only live in rainforests — so changes in the fauna tell us about changes in the environment.”
Dr Cramb said the team, including UQ’s Dr Gilbert Price and alumnus Scott Hocknull from the Queensland Museum, was able to confirm a number of environmental changes thanks to the fossils.
“Our findings show that the caves around Mount Etna had gone through a period of local extinction of rainforests, which were replaced by dry to arid habitats less than 280,000 years ago,” Dr Cramb said.
“My colleagues and I wondered if the same environmental change happened elsewhere in Queensland, which is why we were searching the caves near Chillagoe.
“Our analysis of fossils from the caves in north-east Queensland has shown that rainforest extinction was widespread.
“This research shows that, at least in these instances, rainforest extinction is correlated with a sudden shift in climate — a warning that rainforests are particularly vulnerable to climate change.”
The new species of mice were named after UQ palaeontologist Professor Gregory Webb and citizen scientist and caving guide Douglas Irvin.
Reference:
Jonathan Cramb, Gilbert J. Price, Scott A. Hocknull. Short-tailed mice with a long fossil record: the genus Leggadina (Rodentia: Muridae) from the Quaternary of Queensland, Australia. PeerJ, 2018; 6: e5639 DOI: 10.7717/peerj.5639
The inclusion of euconodonts in the vertebrates, or even craniates, is still controversial. Admittedly, the tissue structure of the “conodonts” (i.e; the denticles situated in their mouth; left) is at odds with conventional vertebrate hard tissues. Nevertheless, the eyes, body shape, and tail stucture of the euconodonta are strikingly vertebrate-like. After Purnell et al. 1995. Credit: Tree of Life Web Project/Wikimedia Commons.
The earliest predators appeared on Earth 480 million years ago—and they even had teeth capable of repairing themselves. A team of palaeontologists led by Bryan Shirley and Madleen Grohganz from the Chair for Palaeoenviromental Research at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have discovered more about how these organisms were able to grow and regenerate their teeth. The results have now been published in Proceedings of the Royal Society B.
Millions of years ago: A fast-moving predator with sharp teeth goes hunting in the prehistoric sea. It spies prey and advances stealthily. It goes in for the kill and devours its prey. Some of the predator’s teeth break, but they will grow back.
This is a description of a conodont. Although these eel-like vertebrates were only a few centimetres long, they are considered the Earth’s first predators. Their small teeth, which are among the most important microfossils, could repair themselves after being damaged. How, exactly, this happened is difficult to ascertain—although the fossilised teeth are often found in marine rock, their soft tissue is only rarely preserved. Since only a few examples of soft tissue from conodonts have survived, it is very difficult to determine how they grew.
Analyses carried out by FAU researchers are now shedding more light on the subject. By using electron microscopes, the scientists examined the layers of conodont teeth to learn more about how they grew. During this scanning process, a material is bombarded with electrons. Different materials reflect a different number of electrons back to the microscope. For example, heavy elements reflect electrons more strongly than lighter ones, which is why they are shown in a lighter colour on the image. This method enabled researchers to reproduce the individual layers and investigate them at a much higher resolution than before.
By using X-ray spectroscopy, in which elements are detected by means of the the radiation they emit, the scientists were also able to analyse the chemical composition of each layer.
The teeth grew in an alternating cycle between wear and the growth of new layers. Furthermore, the shape of the teeth varied greatly depending on the animals’ stage of growth. Using the chemical composition and the shape of the teeth, the researchers were able to identify three stages of growth during the development of an animal that were influenced (amongst others) by feeding habits. After the first stage, a type of larval state, in which food was not digested mechanically (by chewing), conodonts evolved into the first hunters during the second and third stages of growth. During this time, their teeth underwent a metamorphosis as they evolved into predators.
Up to now, there have been two models to explain how conodont teeth were able to regenerate themselves. In contrast to human teeth, for example, which grow from the inside out, conodonts’ teeth repaired themselves from the outside, continuously adding new layers. One theory developed by scientists is that conodonts retracted their teeth during periods of rest, and the apposition of new layers in epidermal pockets induced growth. This could be compared to the mechanism of retractable teeth used for injecting venom by some species of snake. On the other hand, another theory suggests that the teeth were permanently enveloped by tissue and a type of horn cap, allowing new layers to build up over time. The research carried out by FAU scientists has now confirmed the first theory.
The results of the research have been published under the title “Wear, tear and systematic repair: testing models of growth dynamics in conodonts with high-resolution imaging” in the journal Proceedings of the Royal Society B.
Reference:
Bryan Shirley et al, Wear, tear and systematic repair: testing models of growth dynamics in conodonts with high-resolution imaging, Proceedings of the Royal Society B: Biological Sciences (2018). DOI: 10.1098/rspb.2018.1614
A 127-million-year-old fossil bird, Jinguofortis perplexus (reconstruction on the right, artwork by Chung-Tat Cheung), second earliest member of the short-tailed birds Pygostylia. Credit: WANG Min
A newly identified extinct bird species from a 127 million-year-old fossil deposit in northeastern China provides new information about avian development during the early evolution of flight.
Drs. Wang Min, Thomas Stidham, and Zhou Zhonghe from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences reported their study of the well-preserved complete skeleton and feathers of this early bird in the Proceedings of the National Academy of Sciences (PNAS).
The analysis of this early Cretaceous fossil shows it is from a pivotal point in the evolution of flight—after birds lost their long bony tail, but before they evolved a fan of flight feathers on their shortened tail.
The scientists named this extinct species Jinguofortis perplexus. The genus name “Jinguofortis” honors women scientists around the world. It derives from the Chinese word “jinguo,” meaning female warrior, and the Latin word “fortis” meaning brave.
Jinguofortis perplexus has a unique combination of traits, including a jaw with small teeth like its theropod dinosaur relatives; a short bony tail ending in a compound bone called a pygostyle; gizzard stones showing that it mostly ate plants; and a third finger with only two bones, unlike other early birds.
The fossil’s shoulder joint also gives clues about its flight capacity. In flying birds, the shoulder, which experiences high stress during flight, is a tight joint between unfused bones. In contrast, Jinguofortis perplexus preserves a shoulder girdle where the major bones of the shoulder, the shoulder blade (scapula) and the coracoid, are fused to one another, forming a scapulocoracoid.
The existence of a fused shoulder girdle in this short-tailed fossil suggests evolutionary variety during this stage of evolution, which probably resulted in different styles of flight.Based on its skeleton and feathers, Jinguofortis perplexus probably flew a bit differently than birds do today.
Measurement of the fossil’s wing size and estimation of its body mass show that the extinct species had a wing shape and wing loading (wing area divided by body mass) similar to living
Reference:
Min Wang el al., “A new clade of basal Early Cretaceous pygostylian birds and developmental plasticity of the avian shoulder girdle,” PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1812176115
The Highland Giant: Artist Viktor Radermacher’s reconstuction of what Ledumahadi mafube may have looked like. Another South African dinosaur, Heterodontosaurus tucki, watches in the foreground. Credit: Viktor Radermacher
A new species of a giant dinosaur has been found in South Africa’s Free State Province. The plant-eating dinosaur, named Ledumahadi mafube, weighed 12 tonnes and stood about four metres high at the hips. Ledumahadi mafube was the largest land animal alive on Earth when it lived, nearly 200 million years ago. It was roughly double the size of a large African elephant.
A team of international scientists, led by University of the Witwatersrand (Wits) palaeontologist Professor Jonah Choiniere, described the new species in the journal Current Biology today.
The dinosaur’s name is Sesotho for “a giant thunderclap at dawn” (Sesotho is one of South Africa’s 11 official languages and an indigenous language in the area where the dinosaur was found).
“The name reflects the great size of the animal as well as the fact that its lineage appeared at the origins of sauropod dinosaurs,” said Choiniere. “It honours both the recent and ancient heritage of southern Africa.”
Ledumahadi mafube is one of the closest relatives of sauropod dinosaurs. Sauropods, weighing up to 60 tonnes, include well-known species like Brontosaurus. All sauropods ate plants and stood on four legs, with a posture like modern elephants. Ledumahadi evolved its giant size independently from sauropods, and although it stood on four legs, its forelimbs would have been more crouched. This caused the scientific team to consider Ledumahadi an evolutionary “experiment” with giant body size.
Ledumahadi’s fossil tells a fascinating story not only of its individual life history, but also the geographic history of where it lived, and of the evolutionary history of sauropod dinosaurs.
“The first thing that struck me about this animal is the incredible robustness of the limb bones,” says lead author, Dr Blair McPhee. “It was of similar size to the gigantic sauropod dinosaurs, but whereas the arms and legs of those animals are typically quite slender, Ledumahadi’s are incredibly thick. To me this indicated that the path towards gigantism in sauropodomorphs was far from straightforward, and that the way that these animals solved the usual problems of life, such as eating and moving, was much more dynamic within the group than previously thought.”
The research team developed a new method, using measurements from the “arms” and “legs” to show that Ledumahadi walked on all fours, like the later sauropod dinosaurs, but unlike many other members of its own group alive at its time such as Massospondylus. The team also showed that many earlier relatives of sauropods stood on all fours, that this body posture evolved more than once, and that it appeared earlier than scientists previously thought.
“Many giant dinosaurs walked on four legs but had ancestors that walked on two legs. Scientists want to know about this evolutionary change, but amazingly, no-one came up with a simple method to tell how each dinosaur walked, until now,” says Dr Roger Benson.
By analysing the fossil’s bone tissue through osteohistological analysis, Dr Jennifer Botha-Brink from the South African National Museum in Bloemfontein established the animal’s age.
“We can tell by looking at the fossilised bone microstructure that the animal grew rapidly to adulthood. Closely-spaced, annually deposited growth rings at the periphery show that the growth rate had decreased substantially by the time it died,” says Botha-Brink. This indicates that the animal had reached adulthood.
“It was also interesting to see that the bone tissues display aspects of both basal sauropodomorphs and the more derived sauropods, showing that Ledumahadi represents a transitional stage between these two major groups of dinosaurs.”
Ledumahadi lived in the area around Clarens in South Africa’s Free State Province. This is currently a scenic mountainous area, but looked much different at that time, with a flat, semi-arid landscape and shallow, intermittently dry streambeds.
“We can tell from the properties of the sedimentary rock layers in which the bone fossils are preserved that 200 million years ago most of South Africa looked a lot more like the current region around Musina in the Limpopo Province of South Africa, or South Africa’s central Karoo,” says Dr Emese Bordy.
Ledumahadi is closely related to other gigantic dinosaurs from Argentina that lived at a similar time, which reinforces that the supercontinent of Pangaea was still assembled in the Early Jurassic. “It shows how easily dinosaurs could have walked from Johannesburg to Buenos Aires at that time,” says Choiniere.
South Africa’s Minister of Science and Technology Mmamoloko Kubayi-Ngubane says the discovery of this dinosaur underscores just how important South African palaeontology is to the world.
“Not only does our country hold the Cradle of Humankind, but we also have fossils that help us understand the rise of the gigantic dinosaurs. This is another example of South Africa taking the high road and making scientific breakthroughs of international significance on the basis of its geographic advantage, as it does in astronomy, marine and polar research, indigenous knowledge, and biodiversity,” says Kubayi-Ngubane.
The research team behind Ledumahadi includes South African-based palaeoscientists, Dr Emese Bordy and Dr Jennifer Botha-Brink, from the University of Cape Town and the South African National Museum in Bloemfontein, respectively.
The project also had a strong international component with the collaboration of Professor Roger BJ Benson of Oxford University and Dr Blair McPhee, currently residing in Brazil.
“South Africa employs some of the world’s top palaeontologists and it was a privilege to be able to build a working group with them and leading researchers in the UK,” says Choiniere, who recently emigrated from the USA to South Africa. “Dinosaurs didn’t observe international boundaries and it’s important that our research groups don’t either.”
Reference:
Blair W. McPhee, Roger B.J. Benson, Jennifer Botha-Brink, Emese M. Bordy, Jonah N. Choiniere. A Giant Dinosaur from the Earliest Jurassic of South Africa and the Transition to Quadrupedality in Early Sauropodomorphs. Current Biology, 2018; DOI: 10.1016/j.cub.2018.07.063
