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Newly discovered Minerals in Volcanic Rock that May Offer new insights into earth’s evolution

fresh olivine (large green, blue and pink crystals) and glass inclusion (lower left inset)
Photomicrographs of fresh olivine (large green, blue and pink crystals) and glass inclusion (lower left inset). Komatiite volcanic rocks from the 3.3 billion-year-old Weltevreden Formation are the freshest yet discovered in from Earth’s early Archean. Trace elements, radiogenic and stable isotopes from these rocks and olivine separates provide key evidence for evolution of Earth’s mantle. Credit: Keena Kareem, LSU

The first 1.5 billion years of Earth’s evolution is subject to considerable uncertainty due to the lack of any significant rock record prior to four billion years ago and a very limited record until about three billion years ago. Rocks of this age are usually extensively altered making comparisons to modern rock quite difficult. In new research conducted at LSU, scientists have found evidence showing that komatiites, three-billion-year old volcanic rock found within the Earth’s mantle, had a different composition than modern ones. Their discovery may offer new information about the first one billion years of Earth’s development and early origins of life. Results of the team’s work has been published in the October 2017 edition of NATURE Geoscience.

The basic research came from more than three decades of LSU scientists studying and mapping the Barberton Mountains of South Africa. The research team, including LSU geology professors Gary Byerly and Huiming Bao, geology PhD graduate Keena Kareem, and LSU researcher Benjamin Byerly, conducted chemical analyses of hundreds of komatiite rocks sampled from about 10 lava flows.

“Early workers had mapped large areas incorrectly by assuming they were correlatives to the much more famous Komati Formation in the southern part of the mountains. We recognized this error and began a detailed study of the rocks to prove our mapping-based interpretations,” said Gary Byerly.

Within the rocks, they discovered original minerals called fresh olivine, which had been preserved in remarkable detail. Though the mineral is rarely found in rocks subjected to metamorphism and surface weathering, olivine is the major constituent of Earth’s upper mantle and controls the nature of volcanism and tectonism of the planet. Using compositions of these fresh minerals, the researchers had previously concluded that these were the hottest lavas to ever erupt on Earth’s surface with temperatures near 1600 degrees centigrade, which is roughly 400 degrees hotter than modern eruptions in Hawaii.

“Discovering fresh unaltered olivine in these ancient lavas was a remarkable find. The field work was wonderfully productive and we were eager to return to the lab to use the chemistry of these preserved olivine crystals to reveal clues of the Archean Mantle,” said Kareem

The researchers suggest that maybe a chunk of early-Earth magma ocean is preserved in the approximately 3.2 billion year-old minerals.

“The modern Earth shows little or no evidence of this early magma ocean because convection of the mantle has largely homogenized the layering produced in the magma ocean. Oxygen isotopes in these fresh olivines support the existence of ancient chunks of the frozen magma ocean. Rocks like this are very rare and scientifically valuable. An obvious next step was to do oxygen isotopes,” said Byerly.

This study grew out of work taking place in LSU’s laboratory for the study of oxygen isotopes, a world-class facility that attracts scientists from the U.S. and international institutions for collaborative work. The results of the study were so unusual that it required extra care to be certain of the results. Huiming Bao, who is also the head of LSU’s oxygen isotopes lab, said that the team triple and quadruple checked the data by running with different reference minerals and by calibrating with other independent labs.

“We attempted to reconcile the findings with some of the conventional explanations for lavas with oxygen isotope compositions like these, but nothing could fully explain all of the observations. It became apparent that these rocks preserve signatures of processes that occurred over four billion years ago and that are still not completely understood,” said Benjamin Byerly.

Oxygen isotopes are measured by the conversion of rock or minerals into a gas and measuring the ratios of oxygen with the different masses of 16, 17, and 18. A variety of processes fractionate oxygen on Earth and in the Solar System, including atmospheric, hydrospheric, biological, and high temperature and pressure.

“Different planets in our solar system have different oxygen isotope ratios. On Earth this is modified by surface atmosphere and hydrosphere, so variations could be due either to heterogeneous mantle (original accumulation of planetary debris or remnants of magma ocean) or surface processes,” said Byerly. “Either might be interesting to study. The latter because it would also provide information about the early surface temperature of Earth and early origins of life.”

This work was supported by a National Science Foundation grant awarded to Byerly, a NASA grant awarded to Bao, and general support from LSU.

Reference:
Benjamin L. Byerly, Keena Kareem, Huiming Bao, Gary R. Byerly. Early Earth mantle heterogeneity revealed by light oxygen isotopes of Archaean komatiites. Nature Geoscience, 2017; 10 (11): 871 DOI: 10.1038/ngeo3054

Note: The above post is reprinted from materials provided by Louisiana State University.

Male mammoths more often fell into ‘natural traps’ and died, DNA evidence suggests

A mammoth tusk
A mammoth tusk on Wrangel Island. Credit: Patrícia Pe?nerová

Researchers who have sexed 98 woolly mammoth specimens collected from various parts of Siberia have discovered that the fossilized remains more often came from males of the species than females. They speculate that this skewed sex ratio — seven out of every ten specimens examined belonged to males — exists in the fossil record because inexperienced male mammoths more often travelled alone and got themselves killed by falling into natural traps that made their preservation more likely. The findings are reported in Current Biology on November 2.

“Most bones, tusks, and teeth from mammoths and other Ice Age animals haven’t survived,” said Love Dalen of the Swedish Museum of Natural History. “It is highly likely that the remains that are found in Siberia these days have been preserved because they have been buried, and thus protected from weathering. The new findings imply that male mammoths more often died in a way that meant their remains were buried, perhaps by falling through lake ice in winter or getting stuck in bogs.”

“We were very surprised because there was no reason to expect a sex bias in the fossil record,” added Patrícia Pecnerova, the study’s first author, also at the Swedish Museum of Natural History. “Since the ratio of females to males was likely balanced at birth, we had to consider explanations that involved better preservation of male remains.”

The researchers made the discovery in the midst of a larger, long-term effort to examine the genomes of woolly mammoth populations. For some of the analyses, they needed to know the sex of individuals. They initially set out to determine the sex of a small number of mammoths. “It became apparent that we were finding an excess of male samples, which we found very interesting,” Dalen said.

They decided to sex more samples and to examine the sex ratio of individuals collected from the Siberian mainland and from Wrangel Island, off the coast. Overall, they found, males consistently outnumbered females among their samples.

The researchers say the findings suggest that woolly mammoths lived similarly to modern elephants, with herds of females and young elephants led by an experienced adult female. In contrast, they suspect that male mammoths, like elephants, more often lived in bachelor groups or alone and engaged in more risk-taking behavior.

“Without the benefit of living in a herd led by an experienced female, male mammoths may have had a higher risk of dying in natural traps such as bogs, crevices, and lakes,” Dalen said.

The findings highlight the utility of fossil remains for making inferences about the socioecology and behavior of extinct animals, the researchers say. At the same time, they are a reminder to researchers that fossil assemblages don’t necessarily represent a random sample of a population.

The researchers say they’ll continue to study woolly mammoth genomes and those of several other extinct Ice Age mammals. They’re curious to see whether they observe the same skewed sex ratio in other species.

Reference:
Pecnerova et al. Genome-Based Sexing Provides Clues about Behavior and Social Structure in the Woolly Mammoth. Current Biology, 2017 DOI: 10.1016/j.cub.2017.09.064

Note: The above post is reprinted from materials provided by Cell Press.

New study of plankton shells overturns decades-old understanding of their formation and chemistry

Foraminifera Orbulina Universa eating a small copepod
Foraminifera Orbulina Universa eating a small copepod. Credit: Oscar Branson/ANU

The results of new international research into tiny marine plankton will allow scientists to more precisely estimate past ocean conditions and predict future changes, and suggests global warming may have a bigger impact on shell-bearing plankton than previously thought.

Tiny marine plankton, foraminifers, record information about the environment in which they grew in the chemical composition of their carbonate shells. Foraminifer shells are one of our most important climate archives. Reading these archives correctly is key to understand past and to predict future climate.

Researchers from Macquarie University, the GFZ German Research Centre for Geosciences in Potsdam and The Australian National University have used transmission electron microscopy to examine ultra-thin slices of these shells, to understand how the shells record ocean conditions.

“Magnesium found in the plankton shells, for example, is used to calculate seawater temperatures going back tens of millions of years,” said lead researcher Professor Dorrit Jacob, of Macquarie University’s Department of Earth and Planetary Sciences.

“Understanding how the shells develop is key to understanding how magnesium and other elements get into the shells, and therefore how we read the shells’ climate records.”

As published in Nature Communications, the team found these plankton shells first form as the unstable carbonate vaterite, which eventually transforms into stable calcite.

“This was a big surprise. Since the 1950s, we’ve thought the shells were made directly of calcite – and this is what we have been teaching students to this day,” stated Dr. Jacob.

“Which type of carbonate forms first, vaterite or calcite, determines how much magnesium is incorporated into the shell. This finding about how foraminifer shells form will now enable us to estimate past ocean temperatures more precisely, and more accurately predict future climate change.”

The presence of unstable vaterite in these abundant organisms also means foraminifer shells may be far more susceptible to ocean acidification than previously thought. This could have drastic ramifications for carbon dioxide transfer to the deep ocean and seafloor in the marine carbon cycle, as foraminifer shells are dense and assist rapid sinking of organic matter.

Reference:
D. E. Jacob et al, Planktic foraminifera form their shells via metastable carbonate phases, Nature Communications (2017). DOI: 10.1038/s41467-017-00955-0

Note: The above post is reprinted from materials provided by Macquarie University.

Time to rewrite the dinosaur textbooks? Not quite yet!

Two possible branches of the dinosaur family tree (left and middle). Credit: Max Langer

The classification of the dinosaurs might seem to be too obscure to excite anyone but the specialists.

However, this is not at all the case. Recently, Matthew Baron and colleagues from the University of Cambridge proposed a radical revision to our understanding of the major branches of dinosaurs, but in a critique published today some caution is proposed before we rewrite the textbooks.

Every child learns that dinosaurs fall into two major groups, the Ornithischia (bird-hipped dinosaurs; Stegosaurus, Triceratops, Iguanodon and their kin) and the Saurischia (lizard-hipped dinosaurs; the predatory theropods, such as Tyrannosaurus, and the long-necked sauropodomorphs, including such well-known forms as Diplodocus).

Baron and colleagues proposed a very different split, pairing the Ornithischia with the Theropoda, terming the new group the Ornithoscelida, and leaving the Sauropodomorpha on its own.

Their evidence seemed overwhelming, since they identified at least 18 unique characters shared by ornithischians and theropods, and used these as evidence that the two groups had shared a common ancestor.

An international consortium of specialists in early dinosaurs, led by Max Langer from the Universidade de São Paulo, Brazil, and including experts from Argentina, Brazil, Germany, Great Britain, and Spain has now re-evaluated the data provided by Baron et al. in support of their claim.

Their results, presented today in the journal Nature, show that it might still be too early to re-write the textbooks for dinosaurs.

In this new evaluation, the authors found support for the traditional model of an Ornithischia-Saurischia split of Dinosauria, but also noted that this support was very weak, and the alternative idea of Ornithoscelida is only slightly less likely.

Max Langer said: “This took a great deal of work by our consortium, checking many dinosaurs on all continents first-hand to make sure we coded their characters correctly.

“We thought at the start we might only cast some doubt on the idea of Ornithoscelida, but I’d say the whole question now has to be looked at again very carefully.”

Baron and colleagues believed their data suggested that dinosaurs might have originated in the northern hemisphere, but the re-analysis confirms the long-held view that the most likely site of origin is the southern hemisphere, and probably South America.

Professor Mike Benton from the University of Bristol’s School of Earth Sciences, a member of the revising consortium, added: “In science, if you wish to overthrow the standard viewpoint, you need strong evidence.

“We found the evidence to be pretty balanced in favour of two possible arrangements at the base of the dinosaurian tree. Baron and colleagues might be correct, but we would argue that we should stick to the orthodox Saurischia-Ornithischia split for the moment until more convincing evidence emerges.”

Steve Brusatte of the University of Edinburgh, a member of the consortium, said: “Up until this year, we thought we had the dinosaur family tree figured out.

“But right now, we just can’t be certain how the three major groups of dinosaurs are related to each other. In one sense it’s frustrating, but in another, it’s exciting because it means that we need to keep finding new fossils to solve this mystery.”

Reference:
Max C. Langer, Martín D. Ezcurra, Oliver W. M. Rauhut, Michael J. Benton, Fabien Knoll, Blair W. McPhee, Fernando E. Novas, Diego Pol, Stephen L. Brusatte. Untangling the dinosaur family tree. Nature, 2017; 551 (7678): E1 DOI: 10.1038/nature24011

Note: The above post is reprinted from materials provided by University of Bristol.

Dinosaur-killing asteroid impact cooled Earth’s climate more than previously thought

A simulation of the crater and impact plume formed eight seconds after the Chicxulub impact at 45 degrees.
A simulation of the crater and impact plume formed eight seconds after the Chicxulub impact at 45 degrees. Chart A shows the density of different materials created in the impact. The colors show the atmosphere (blue), sediment (yellow), asteroid (gray) and basement (red), with darker colors reflecting higher densities. SW is the shock wave formed by the impact. Chart B shows the temperature in Kelvin at different locations in the impact. Credit: Pierazzo and Artemieva (2012).

The Chicxulub asteroid impact that wiped out the dinosaurs likely released far more climate-altering sulfur gas into the atmosphere than originally thought, according to new research.

A new study makes a more refined estimate of how much sulfur and carbon dioxide gas were ejected into Earth’s atmosphere from vaporized rocks immediately after the Chicxulub event. The study’s authors estimate more than three times as much sulfur may have entered the air compared to what previous models assumed, implying the ensuing period of cool weather may have been colder than previously thought.

The new study lends support to the hypothesis that the impact played a significant role in the Cretaceous–Paleogene extinction event that eradicated nearly three-quarters of Earth’s plant and animal species, according to Joanna Morgan, a geophysicist at Imperial College London in the United Kingdom and co-author of the new study published in Geophysical Research Letters, a journal of the American Geophysical Union.

“Many climate models can’t currently capture all of the consequences of the Chicxulub impact due to uncertainty in how much gas was initially released,” Morgan said. “We wanted to revisit this significant event and refine our collision model to better capture its immediate effects on the atmosphere.”

The new findings could ultimately help scientists better understand how Earth’s climate radically changed in the aftermath of the asteroid collision, according to Georg Feulner, a climate scientist at the Potsdam Institute for Climate Impact Research in Potsdam, Germany who was not involved with the new research. The research could help give new insights into how Earth’s climate and ecosystem can significantly change due to impact events, he said.

“The key finding of the study is that they get a larger amount of sulfur and a smaller amount of carbon dioxide ejected than in other studies,” he said. “These improved estimates have big implications for the climactic consequences of the impact, which could have been even more dramatic than what previous studies have found.”

A titanic collision

The Chicxulub impact occurred 66 million years ago when an asteroid approximately 12 kilometers (7 miles) wide slammed into Earth. The collision took place near what is now the Yucatán peninsula in the Gulf of Mexico. The asteroid is often cited as a potential cause of the Cretaceous-Paleogene extinction event, a mass extinction that erased up to 75 percent of all plant and animal species, including the dinosaurs.

The asteroid collision had global consequences because it threw massive amounts of dust, sulfur and carbon dioxide into the atmosphere. The dust and sulfur formed a cloud that reflected sunlight and dramatically reduced Earth’s temperature. Based on earlier estimates of the amount of sulfur and carbon dioxide released by the impact, a recent study published in Geophysical Research Letters showed Earth’s average surface air temperature may have dropped by as much as 26 degrees Celsius (47 degrees Fahrenheit) and that sub-freezing temperatures persisted for at least three years after the impact.

In the new research, the authors used a computer code that simulates the pressure of the shock waves created by the impact to estimate the amounts of gases released in different impact scenarios. They changed variables such as the angle of the impact and the composition of the vaporized rocks to reduce the uncertainty of their calculations.

The new results show the impact likely released approximately 325 gigatons of sulfur and 425 gigatons of carbon dioxide into the atmosphere, more than 10 times global human emissions of carbon dioxide in 2014. In contrast, the previous study in Geophysical Research Letters that modeled Earth’s climate after the collision had assumed 100 gigatons of sulfur and 1,400 gigatons of carbon dioxide were ejected as a result of the impact.

Improving the impact model

The new study’s methods stand out because they ensured only gases that were ejected upwards with a minimum velocity of 1 kilometer per second (2,200 miles per hour) were included in the calculations. Gases ejected at slower speeds didn’t reach a high enough altitude to stay in the atmosphere and influence the climate, according to Natalia Artemieva, a senior scientist at the Planetary Science Institute in Tucson, Arizona and co-author of the new study.

Older models of the impact didn’t have as much computing power and were forced to assume all the ejected gas entered the atmosphere, limiting their accuracy, Artemieva said.

The study authors also based their model on updated estimates of the impact’s angle. An older study assumed the asteroid hit the surface at an angle of 90 degrees, but newer research shows the asteroid hit at an angle of approximately 60 degrees. Using this revised angle of impact led to a larger amount of sulfur being ejected into the atmosphere, Morgan said.

The study’s authors did not model how much cooler Earth would have been as a result of their revised estimates of how much gas was ejected. Judging from the cooling seen in the previous study, which assumed a smaller amount of sulfur was released by the impact, the release of so much sulfur gas likely played a key role in the extinction event. The sulfur gas would have blocked out a significant amount of sunlight, likely leading to years of extremely cold weather potentially colder than the previous study found. The lack of sunlight and changes in ocean circulation would have devastated Earth’s plant life and marine biosphere, according to Feulner.

The release of carbon dioxide likely led to some long-term climate warming, but its influence was minor compared to the cooling effect of the sulfur cloud, Feulner said.

Along with gaining a better understand of the Chicxulub impact, researchers can also use the new study’s methods to estimate the amount of gas released during other large impacts in Earth’s history. For example, the authors calculated the Ries crater located in Bavaria, Germany was formed by an impact that ejected 1.3 gigatons of carbon dioxide into the atmosphere. This amount of gas likely had little effect on Earth’s climate, but the idea could be applied to help understand the climactic effects of larger impacts.

Reference:
Natalia Artemieva, Joanna Morgan. Quantifying the Release of Climate-Active Gases by Large Meteorite Impacts With a Case Study of Chicxulub. Geophysical Research Letters, 2017; DOI: 10.1002/2017GL074879

Note: The above post is reprinted from materials provided by American Geophysical Union.

Research provides unique insight into extinction dynamics in late Triassic

Petrified Forest National Park
URI junior Amanda Bednarick (background) and research assistant Sam Hemmendinger use a Jacob’s staff to measure the thickness of rocks at Petrified Forest National Park. Credit: Reilly Hayes

One of the most exciting discoveries that paleontologists can make is finding the causal relationship between the extinction of ancient creatures and the environmental conditions that led to that extinction. A team of scientists and students at the University of Rhode Island is inching closer to revealing how a group of animals from the Late Triassic went extinct, thanks to the precise dating of fossils at Petrified Forest National Park in Arizona.

URI Professor David Fastovsky, who made important discoveries about the extinction of the dinosaurs between the Cretaceous and Tertiary periods 66 million years ago, is leading a team of researchers working to understand what caused the extinction of the near-relatives of North America’s earliest dinosaurs around 215 million years ago.

“Reconstructing extinctions is extremely difficult,” he said, “but at Petrified Forest we have the best-dated ancient river deposits in the world, which allow us to ask very precise questions about this extinction — in particular, whether it was gradual or catastrophic. This could be one of the extremely rare instances in the ancient record when this could actually be determined quantitatively using direct evidence.”

If the researchers determine that all of the animals went extinct at about the same time — rather than gradually over a long period — they may be able to link the animals’ extinction to the catastrophic impact of an asteroid that left a 50-mile-wide crater in Quebec, an impact that some scientists believe was responsible for the extinctions at that time.

Fastovsky has been studying the fossils at Petrified Forest since 1991. He said the rocks there indicate a distinct “faunal turnover” when one set of organisms disappeared and another set of organisms appeared.

“The question is, can we date that faunal turnover, and how precisely,” he said.

Using what he called “high-precision uranium-lead dating” developed by researchers at the Massachusetts Institute of Technology and applied by URI geoscientists in Petrified Forest National Park, Fastovsky is hopeful that his team will have some answers by the end of next year.

To meet that goal, Fastovsky engaged Gavino Puggioni, URI assistant professor of statistics, who is using sophisticated statistical analyses to determine whether the ancient animals all went extinct simultaneously, which would be expected from a catastrophic event.

“The processes that we’re studying took place over thousands of years,” said Puggioni. “We’re trying to extract a very weak signal from this small data set. But there are statistical techniques that can help us identify what we’re observing. We are trying to extend and push the boundaries.”

“This is an unheard-of level of quantitative precision being applied to an extinction event,” added Fastovsky.

To fill in gaps in the existing data, URI graduate student Reilly Hayes and junior Amanda Bednarick spent three months last summer finding the precise locations where more than 100 fossils had been collected from Petrified Forest over the last century. It wasn’t easy.

“River systems like at Petrified Forest tear themselves up when the sediments build up,” explained Hayes. “So you find a lot of discontinuities between the beds of rock. But we already had dates in the model of how certain beds fit together into the larger sequence at the park. We just didn’t know where all the fossils occurred relative to those.”

The dates in the model were first collected by a previous generation of URI researchers, and they run through the full thickness of the rock sequence exposed in the Park, which Fastovsky and his MIT colleagues nicknamed the “backbone.”

Hayes and Bednarick hiked many miles each week last summer and found 51 sites around the park where they could link previously collected fossils with rocks of known age.

“We relocated all these fossil localities, some of which didn’t have exact information for where they were originally found, and then we established a game plan for how to correlate this spot on the ground to a place where the backbone was exposed,” said Bednarick.

Over the next year, additional field work will be required to relocate about 20 more fossil sites, and the statistical analyses will continue. And then the researchers hope to be able to draw conclusions about the cause of the extinction.

“We’re looking forward to testing whether the extinctions occurred at the same time and whether this particular extinction would be concordant with what you would expect if an asteroid did the deed,” concluded Fastovsky. “That would be pretty special.”

Note: The above post is reprinted from materials provided by University of Rhode Island.

Future volcanic eruptions could cause more climate disruption

An aerial view of Mount Tambora's caldera
An aerial view of Mount Tambora’s caldera, formed during the 1815 eruption. Credit: Wikipedia

Major volcanic eruptions in the future have the potential to affect global temperatures and precipitation more dramatically than in the past because of climate change, according to a new study led by the National Center for Atmospheric Research (NCAR).

The study authors focused on the cataclysmic eruption of Indonesia’s Mount Tambora in April 1815, which is thought to have triggered the so-called “year without a summer” in 1816. They found that if a similar eruption occurred in the year 2085, temperatures would plunge more deeply, although not enough to offset the future warming associated with climate change. The increased cooling after a future eruption would also disrupt the water cycle more severely, decreasing the amount of precipitation that falls globally.

The reason for the difference in climate response between 1815 and 2085 is tied to the oceans, which are expected to become more stratified as the planet warms, and therefore less able to moderate the climate impacts caused by volcanic eruptions.

“We discovered that the oceans play a very large role in moderating, while also lengthening, the surface cooling induced by the 1815 eruption,” said NCAR scientist John Fasullo, lead author of the new study. “The volcanic kick is just that — it’s a cooling kick that lasts for a year or so. But the oceans change the timescale. They act to not only dampen the initial cooling but also to spread it out over several years.”

The research will be published Oct. 31 in the journal Nature Communications. The work was funded in part by the National Science Foundation, NCAR’s sponsor. Other funders include NASA and the U.S. Department of Energy. The study co-authors are Robert Tomas, Samantha Stevenson, Bette Otto-Bliesner, and Esther Brady, all of NCAR, as well as Eugene Wahl, of the National Oceanic and Atmospheric Administration.

A detailed look at a deadly past

Mount Tambora’s eruption, the largest in the past several centuries, spewed a huge amount of sulfur dioxide into the upper atmosphere, where it turned into sulfate particles called aerosols. The layer of light-reflecting aerosols cooled Earth, setting in motion a chain of reactions that led to an extremely cold summer in 1816, especially across Europe and the northeast of North America. The “year without a summer” is blamed for widespread crop failure and disease, causing more than 100,000 deaths globally.

To better understand and quantify the climate effects of Mount Tambora’s eruption, and to explore how those effects might differ for a future eruption if climate change continues on its current trajectory, the research team turned to a sophisticated computer model developed by scientists from NCAR and the broader community.

The scientists looked at two sets of simulations from the Community Earth System Model. The first was taken from the CESM Last Millennium Ensemble Project, which simulates Earth’s climate from the year 850 through 2005, including volcanic eruptions in the historic record. The second set, which assumes that greenhouse gas emission continue unabated, was created by running CESM forward and repeating a hypothetical Mount Tambora eruption in 2085.

The historical model simulations revealed that two countervailing processes helped regulate Earth’s temperature after Tambora’s eruption. As aerosols in the stratosphere began blocking some of the Sun’s heat, this cooling was intensified by an increase in the amount of land covered by snow and ice, which reflected heat back to space. At the same time, the oceans served as an important counterbalance. As the surface of the oceans cooled, the colder water sank, allowing warmer water to rise and release more heat into the atmosphere.

By the time the oceans themselves had cooled substantially, the aerosol layer had begun to dissipate, allowing more of the Sun’s heat to again reach Earth’s surface. At that point, the ocean took on the opposite role, keeping the atmosphere cooler, since the oceans take much longer to warm back up than land.

“In our model runs, we found that Earth actually reached its minimum temperature the following year, when the aerosols were almost gone,” Fasullo said. “It turns out the aerosols did not need to stick around for an entire year to still have a year without a summer in 1816, since by then the oceans had cooled substantially.”

The oceans in a changed climate

When the scientists studied how the climate in 2085 would respond to a hypothetical eruption that mimicked Mount Tambora’s, they found that Earth would experience a similar increase in land area covered by snow and ice.

However, the ocean’s ability to moderate the cooling would be diminished substantially in 2085. As a result, the magnitude of Earth’s surface cooling could be as much as 40 percent greater in the future. The scientists caution, however, that the exact magnitude is difficult to quantify, since they had only a relatively small number of simulations of the future eruption.

The reason for the change has to do with a more stratified ocean. As the climate warms, sea surface temperatures increase. The warmer water at the ocean’s surface is then less able to mix with the colder, denser water below.

In the model runs, this increase in ocean stratification meant that the water that was cooled after the volcanic eruption became trapped at the surface instead of mixing deeper into the ocean, reducing the heat released into the atmosphere.

The scientists also found that the future eruption would have a larger effect on rainfall than the historical eruption of Mount Tambora. Cooler sea surface temperatures decrease the amount of water that evaporates into the atmosphere and, therefore, also decrease global average precipitation.

Though the study found that Earth’s response to a Tambora-like eruption would be more acute in the future than in the past, the scientists note that the average surface cooling caused by the 2085 eruption (about 1.1 degrees Celsius) would not be nearly enough to offset the warming caused by human-induced climate change (about 4.2 degrees Celsius by 2085).

Study co-author Otto-Bliesner said, “The response of the climate system to the 1815 eruption of Indonesia’s Mount Tambora gives us a perspective on potential surprises for the future, but with the twist that our climate system may respond much differently.”

Reference:
J. T. Fasullo, R. Tomas, S. Stevenson, B. Otto-Bliesner, E. Brady, E. Wahl. The amplifying influence of increased ocean stratification on a future year without a summer. Nature Communications, 2017; 8 (1) DOI: 10.1038/s41467-017-01302-z

Note: The above post is reprinted from materials provided by National Center for Atmospheric Research/University Corporation for Atmospheric Research.

Formation of magma oceans on exoplanet

Development of a magma ocean through induction heating in the mantle of exoplanet Trappist-1c.
Development of a magma ocean through induction heating in the mantle of exoplanet Trappist-1c. Credit: IWF/ÖAW

Induction heating can completely change the energy budget of an exoplanet and even melt its interior. In a study published by Nature Astronomy an international team led by the Space Research Institute of the Austrian Academy of Sciences with participation of the University of Vienna explains how magma oceans can form under the surface of exoplanets as a result of induction heating.

When a conductive material is embedded in a changing magnetic field, an electrical current is produced inside the body by a process called electromagnetic induction. If the electrical current is strong enough, it can heat the material in which it flows because of electrical resistance. This process called induction heating is widely used in industry to melt materials and at home to cook using induction stoves.

Fast rotation causes heating

An international team led by the Space Research Institute (IWF) of the Austrian Academy of Sciences (OeAW) with participation of the Department of Astrophysics of the University of Vienna was inspired by these examples. “We wanted to investigate if induction heating can play a role on a much bigger scale,” explains first author Kristina Kislyakova. “We were particularly interested in planets orbiting stars that have strong magnetic fields.” These stars can rotate very rapidly, which causes the magnetic field at the planet’s orbit to change rapidly as well. In such cases, induction heating can take place inside the planet.

Impacts on planetary habitability

The team studied low mass stars that exhibit some exotic characteristics in comparison to our Sun. They are much smaller and dimmer. Some of them rotate very fast and possess magnetic fields hundreds of times stronger than the solar one. A good example of such a low-mass star is Trappist-1, which hosts a big family of seven close-in rocky planets, three of which may have liquid water on their surface. This planetary system is a top candidate for the search of Earth-like planets.

Kislyakova and her team have calculated the energy release inside the Trappist-1 planets due to induction heating. “We have shown that for some of the planets, the heating is strong enough to drive enormous volcanic activity or even lead to the formation of a magma ocean beneath the planetary surface.”

As we know from Earth, strong volcanic activity can have a severe influence on a planet’s atmosphere. “Therefore, induction heating can strongly influence the habitability of an exoplanet,” adds IWF co-author Luca Fossati. This new study shows that this effect has to be taken into account when studying the habitability and evolution of planets orbiting low-mass stars.

Reference:
K. G. Kislyakova et al. Magma oceans and enhanced volcanism on TRAPPIST-1 planets due to induction heating, Nature Astronomy (2017). DOI: 10.1038/s41550-017-0284-0

Note: The above post is reprinted from materials provided by University of Vienna.

‘Bandit-masked’ feathered dinosaur hid from predators using multiple types of camouflage

preserved fossil specimen of Sinosauropteryx from the Early Cretaceous Jehol Biota of China
The best-preserved fossil specimen of Sinosauropteryx from the Early Cretaceous Jehol Biota of China and an interpretive drawing of the bones, stomach contents and darkly pigmented feathers. Scale bar represents 50 mm. Credit: University of Bristol

Researchers from the University of Bristol have revealed how a small feathered dinosaur used its colour patterning, including a bandit mask-like stripe across its eyes, to avoid being detected by its predators and prey.

By reconstructing the likely colour patterning of the Chinese dinosaur Sinosauropteryx, researchers have shown that it had multiple types of camouflage which likely helped it to avoid being eaten in a world full of larger meat-eating dinosaurs, including relatives of the infamous Tyrannosaurus Rex, as well as potentially allowing it to sneak up more easily on its own prey.

Fiann Smithwick from the University’s School of Earth Sciences led the work, which has been published today in the journal Current Biology. He said: “Far from all being the lumbering prehistoric grey beasts of past children’s books, at least some dinosaurs showed sophisticated colour patterns to hide from and confuse predators, just like today’s animals.

“Vision was likely very important in dinosaurs, just like today’s birds, and so it is not surprising that they evolved elaborate colour patterns.” The colour patterns also allowed the team to identify the likely habitat in which the dinosaur lived 130 million years ago.

The work involved mapping out how dark pigmented feathers were distributed across the body and revealed some distinctive colour patterns.

These colour patterns can also be seen in modern animals where they serve as different types of camouflage.

The patterns include a dark stripe around the eye, or ‘bandit mask’, which in modern birds helps to hide the eye from would-be predators, and a striped tail that may have been used to confuse both predators and prey.

Senior author, Dr Jakob Vinther, added: “Dinosaurs might be weird in our eyes, but their colour patterns very much resemble modern counterparts.

“They had excellent vision, were fierce predators and would have evolved camouflage patterns like we see in living mammals and birds.”

The small dinosaur also showed a ‘counter-shaded’ pattern with a dark back and light belly; a pattern used by many modern animals to make the body look flatter and less 3D.

This stops animals standing out from their background, making them harder to spot, avoiding detection from would-be predators and potential prey.

Previous work on modern animals, carried out by one of the authors, Bristol’s Professor Innes Cuthill, has shown that the precise pattern of countershading relates to the specific environments in which animals live.

Animals living in open habitats, such as savannahs, often have a counter-shaded pattern that goes from dark to light sharply and high on the side of the body, while those living in more closed habitats, like forests, usually change from dark to light much lower and more gradually.

This principal was applied to Sinosauropteryx, and allowed for the reconstruction of its habitat 130 million years ago. The countershading on Sinosauropteryx went from dark to light high on the body, suggesting that it would be more likely to live in open habitats with minimal vegetation.

Behavioural ecologist Professor Cuthill, who was also a co-author of this study, said: “We’ve shown before that countershading can act as effective camouflage against living predators. It’s exciting that we can now use the colours of extinct animals to predict the sort of environment they lived in.”

Fiann Smithwick added: “By reconstructing the colour of these long-extinct dinosaurs, we have gained a better understanding of not only how they behaved and possible predator-prey dynamics, but also the environments in which they lived.

“This highlights how palaeocolour reconstructions can tell us things not possible from looking at just the bones of these animals.”

Reference:
Fiann M. Smithwick, Robert Nicholls, Innes C. Cuthill, Jakob Vinther. Countershading and Stripes in the Theropod Dinosaur Sinosauropteryx Reveal Heterogeneous Habitats in the Early Cretaceous Jehol Biota. Current Biology, 2017; DOI: 10.1016/j.cub.2017.09.032

Note: The above post is reprinted from materials provided by University of Bristol.

Late Triassic terrestrial ecosystem changes

Strata of the Chinle Formation below the prominent silcrete horizon exposed in the Petrified Forest National Park.
Strata of the Chinle Formation below the prominent silcrete horizon exposed in the Petrified Forest National Park. Photo courtesy of Andrew V. Kearns, 2012.

The Norian Chinle Formation in the Southwestern United States provides a snapshot into an ancient terrestrial ecosystem with its famous petrified tree trunks and various plant and vertebrate remains. The fossil plant assemblages, including spores and pollen grains, provide useful information on past vegetation and the response of the vegetation to climate changes.

New pollen and spore data from the Chinle Formation at the Petrified Forest National Park, Arizona, suggest that a extinction of plants occurred between 213 and 217 million years ago in tandem with an extinction of several reptile groups.

The predominance of plants adapted to drier conditions after the extinction event is consistent with the gradual aridification of the North American continent due to the uplift of the Cordilleran volcanic mountain range and the probable northward shift of North America through plate tectonics. Plant community analysis reveals that the floral turnover was followed by the colonization of new plant groups such as the varieties of conifer trees and the decrease in the contribution of seed ferns in the vegetation along waterways.

In their study published in The Geological Society of America Bulletin, Viktoria Baranyi and colleagues propose that the floral reorganization of the riparian communities can be attributed to the gradual climate change and changes in river styles, possibly linked to changes in the mountain chain distributions.

Marked increases in the pollen species e.g., Klausipollenites gouldii, Patinasporites spp. and Froelichsporites traversei are probable indicators of further environmental stress, such as changes of atmospheric pCO2, acid rain, and atmospheric aerosol accumulation due to volcanism in connection with the Pangean rifting and uplift of the Cordilleran mountain chain.

Comparison of the vegetation turnover with younger assemblages from the Chinle Formation in New Mexico reveals similar floral turnover patterns, suggesting their regional significance.

The floral turnover may have affected terrestrial vertebrate communities as the loss of wetland habitat space and an increase in arid climate adapted plants may have dwindled the supply of palatable vegetation for herbivores. The Manicouagan impact event might have contributed to the vegetation change at the Petrified Forest National Park in Arizona but the existing data are unable to prove a direct cause.

Reference:
Viktória Baranyi, Tammo Reichgelt, Paul E. Olsen, William G. Parker, Wolfram M. Kürschner. Norian vegetation history and related environmental changes: New data from the Chinle Formation, Petrified Forest National Park (Arizona, SW USA). GSA Bulletin, 2017; DOI: 10.1130/B31673.1

Note: The above post is reprinted from materials provided by Geological Society of America.

Determining when humans started impacting the planet on a large scale

An illustration of an asteroid impacting Earth. Credit: Image courtesy NASA

Humans have so profoundly altered Earth that, some scientists argue, our current geologic epoch requires a new name: the Anthropocene. But defining the precise start of the era is tricky. Would it begin with the spread of domesticated farm animals or the appearance of radioactive elements from nuclear bomb tests? Scientists report in ACS’ Environmental Science & Technology a method to measure levels of human-made contaminants in sediments that could help pinpoint the Anthropocene’s onset.

The geologic record can sometimes provide clear-cut evidence of epoch changes. For example, when a meteorite collided with Earth 66 million years ago, levels of the metal iridium from the space rock spiked in sediments around the world. This clearly marked the end of the Cretaceous period. However, trying to define the start of the proposed — and much debated — Anthropocene could be more complicated. Human influence over the climate and environment began with the Industrial Revolution in the 1800s, and accelerated dramatically in the second half of the 20th century.

Many markers of human impact on the planet from agriculture, waste disposal and other activities have been archived in the planet’s sedimentary records. The rise in industrial chemicals, such as pesticides and pharmaceuticals, is another example of a human-driven activity that has been captured in sediment layers. To explore the record of synthetic compounds as a possible marker to help define the Anthropocene, Aurea C. Chiaia-Hernández, Juliane Hollender and colleagues turned to a new analytical technique combined with sophisticated data analysis to characterize patterns of contamination over time.

The researchers applied high-resolution mass spectrometry to investigate synthetic chemical contamination in two lakes in Central Europe. They examined 1-meter long cores from each lake bottom, capturing the past 100 years of sediment layers. According to the analysis, the lakes’ sediments contained few synthetic contaminants before the 1950s. But during the 1950s, concentrations of industrial chemicals started to appear in the samples, which is consistent with the boom in industrial activities post-World War II. The researchers say this record clearly demonstrates the beginning of large-scale human impact on the environment. It also shows a decline in contamination following the installation of wastewater treatment plants in the 1970s, providing evidence for successful mitigation measures. Additionally, the introduction of new pollutants that are now finding their way into surface waters can be discovered.

Reference:
Aurea C. Chiaia-Hernández, Barbara F. Günthardt, Martin P. Frey, Juliane Hollender. Unravelling Contaminants in the Anthropocene Using Statistical Analysis of Liquid Chromatography–High-Resolution Mass Spectrometry Nontarget Screening Data Recorded in Lake Sediments. Environmental Science & Technology, 2017; DOI: 10.1021/acs.est.7b03357

Note: The above post is reprinted from materials provided by American Chemical Society.

The oceans were colder than we thought

Dr. Itay Halevy of the Weizmann Institute of Science has looked to the distant past — all the way back to Earth’s earliest oceans. The model he developed, together with Dr. Aviv Bachan of Stanford University, suggests that the early oceans, right around the time that life originated, were somewhat acidic, and that they gradually became alkaline. Credit: Weizmann Institute of Science

A team of researchers has discovered a flaw in the way past ocean temperatures have been estimated up to now. Their findings could mean that the current period of climate change is unparalleled over the last 100 million years.

According to the methodology widely used by the scientific community, the temperature of the ocean depths and that of the surface of the polar ocean 100 million years ago were around 15 degrees higher than current readings. This approach, however, is now being challenged: ocean temperatures may in fact have remained relatively stable throughout this period, which raises serious concerns about current levels of climate change. These are the conclusions of a study conducted by a team of French researchers from the French National Center for Scientific Research (CNRS), Sorbonne University and the University of Strasbourg, and Swiss researchers from the Swiss Federal Institute of Technology in Lausanne (EPFL) and the University of Lausanne. The study has just been published in Nature Communications.

“If we are right, our study challenges decades of paleoclimate research,” says Anders Meibom, the head of EPFL’s Laboratory for Biological Geochemistry and a professor at the University of Lausanne. Meibom is categorical: “Oceans cover 70% of our planet. They play a key role in Earth’s climate. Knowing the extent to which their temperatures have varied over geological time is crucial if we are to gain a fuller understanding of how they behave and to predict the consequences of current climate change more accurately.”

How could the existing methodology be so flawed? The study’s authors believe that the influence of certain processes was overlooked. For over 50 years, the scientific community based its estimates on what they learned from foraminifera, which are the fossils of tiny marine organisms found in sediment cores taken from the ocean floor. The foraminifera form calcareous shells called tests in which the content of oxygen-18 depends on the temperature of the water in which they live. Changes in the ocean’s temperature over time were therefore calculated on the basis of the oxygen-18 content of the fossil foraminifera tests found in the sediment. According to these measurements, the ocean’s temperature has fallen by 15 degrees over the past 100 million years.

Yet all these estimates are based on the principle that the oxygen-18 content of the foraminifera tests remained constant while the fossils were lodged in the sediment. Indeed, until now, nothing indicated otherwise: no change is visible to the naked eye or under the microscope. To test their hypothesis, the authors of this latest study exposed these tiny organisms to high temperatures in artificial sea water that contained only oxygen-18. Using a NanoSIMS (nanoscale secondary ion mass spectrometer), an instrument used to run very small-scale chemical analyses, they then observed the incorporation of oxygen-18 in the calcareous shells. The results show that the level of oxygen-18 present in the foraminifera tests can in fact change without leaving a visible trace, thereby challenging the reliability of their use as a thermometer: “What appeared to be perfectly preserved fossils are in fact not. This means that the paleotemperature estimates made up to now are incorrect,” says Sylvain Bernard, a CNRS researcher at the Paris-based Institute of Mineralogy, Materials Physics and Cosmochemistry and the study’s lead author.

For the French and Swiss team of researchers, rather than showing a gradual decline in ocean temperatures over the past 100 million years, these measurements simply reflect the change in oxygen-18 content in the fossil foraminifera tests. And this change appears to be the result of a process called re-equilibration: during sedimentation, temperatures rise by 20 to 30°C, causing the foraminifera tests to re-equilibrate with the surrounding water. Over the course of some ten million years, this process has a significant impact on paleotemperature estimates, especially those based on foraminifera that lived in cold water. Computer simulations run by the researchers suggest that paleotemperatures in the ocean depths and at the surface of the polar ocean have been overestimated.

For Meibom, the next steps are clear: “To revisit the ocean’s paleotemperatures now, we need to carefully quantify this re-equilibration, which has been overlooked for too long. For that, we have to work on other types of marine organisms so that we clearly understand what took place in the sediment over geological time.” The article’s authors are already hard at work.

Reference:
S. Bernard, D. Daval, P. Ackerer, S. Pont, A. Meibom. Burial-induced oxygen-isotope re-equilibration of fossil foraminifera explains ocean paleotemperature paradoxes. Nature Communications, 2017; 8 (1) DOI: 10.1038/s41467-017-01225-9

Note: The above post is reprinted from materials provided by Ecole Polytechnique Fédérale de Lausanne.

Japanese earthquake zone strongly influenced by the effects of friction

This is a location map showing fault planes of the 2016 earthquake
(a) This is a location map showing fault planes of the 2016 earthquake (red) and the 1944 Tonankai earthquake (blue). Yellow and blue stars indicate the hypocenters of the 2016 earthquake and 1944 Tonankai earthquake, respectively. Orange-shaded area indicates ancient accretionary prism. (b) Schematic sections of the accretionary prism in the study area. Fully coupled and partially coupled plate interfaces are shown in red and orange, respectively. Credit: Kyushu University

The islands of the Japanese archipelago are affected both by frequent, low-magnitude earthquakes and tremors and by larger, highly destructive events. One of the largest quakes to strike Japan occurred in 1944, leading to the loss of more than 1,200 lives on the main and most populated island of Honshu. Its strength resulted from the abrupt release of plate tectonic forces, a process known as subduction, centered on an area beneath Honshu where it slides over the top of oceanic crust.

Highly destructive earthquakes caused by subduction occur because of excessive friction that develops during the sliding process, resulting in a build-up of stress. Sudden release of this stress, a condition called rupturing, leads to the violent shaking felt during an earthquake. A recent study led by the International Institute for Carbon-Neutral Energy Research (I2CNER) at Kyushu University in Japan, and published in Earth and Planetary Science Letters, now sheds new light on this stress build-up in tectonic plates. The focus was on the Nankai Trough, one of three major subduction zones offshore of Japan.

“Our understanding of the dynamic behavior of plate boundary faults has advanced,” the study’s lead author Takeshi Tsuji says. “Yet the factors that control the build-up of friction and stress along plate interfaces and in co-seismic zones are less established.”

The researchers used advanced 2D and 3D seismic profiles to reveal the detailed structure of the Nankai Trough, particularly of an ancient accretionary prism — a large mass of rock and sediment accumulated in the trough.

The added mass of this rock and sediment has impeded subduction, ultimately causing stress to build up over time. This stress build-up, and rupturing, was the root cause of the massive 1944 Tonankai earthquake and the smaller Off-Mie earthquake that struck almost the same area on April 1, 2016.

“Along with evidence of frictional obstruction to subduction,” Tsuji says, “the fault structure appears to have also impacted earthquake location and behavior. We found that aftershocks of the 2016 quake only occurred in front of the accretionary prism, where stress accumulation is greatest.”

The long-term implications of the study hinge on evidence that the pre-existing faults from the 1944 earthquake have strongly influenced the orientation and location of rupturing during the 2016 event, suggesting that large earthquakes in Japan are most likely to occur in this very same region of the Nankai Trough in the future.

Reference:
Takeshi Tsuji, Shohei Minato, Rie Kamei, Tetsuro Tsuru, Gaku Kimura. 3D geometry of a plate boundary fault related to the 2016 Off-Mie earthquake in the Nankai subduction zone, Japan. Earth and Planetary Science Letters, 2017; 478: 234 DOI: 10.1016/j.epsl.2017.08.041

Note: The above post is reprinted from materials provided by Kyushu University, I2CNER.

A new Late Cretaceous Rhabdodontid dinosaur from Southern France

Extreme tooth enlargement in a new Late Cretaceous rhabdodontid dinosaur from Southern France
Right maxilla of Matheronodon provincialis gen. et sp. nov. (MMS/VBN-02–102; holotype) in dorsal (a), lateral (b), medial (c), and ventral (d) views. (e) Close-up of the second and third maxillary crowns.

Rhabdodontidae is a successful clade of ornithopod dinosaurs, characteristic of Late Cretaceous continental faunas in Europe.

A new rhabdodontid from the late Campanian, of southern France, Matheronodon provincialis gen. et sp. nov., is characterized by the extreme enlargement of both its maxillary and dentary teeth, correlated to a drastic reduction in the number of maxillary teeth (4 per generation in MMS/VBN-02-102).

The interalveolar septa on the maxilla are alternately present or resorbed ventrally so as to be able to lodge such enlarged teeth. The rhabdodontid dentition and masticatory apparatus were adapted for producing a strict and powerful shearing action, resembling a pair of scissors. With their relatively simple dentition, contrasting with the sophisticated dental batteries in contemporary hadrosaurids, Matheronodon and other rhabdodontids are tentatively interpreted as specialized consumers of tough plant parts rich in sclerenchyma fibers, such as Sabalites and Pandanites.

Rhabdodontids are basal iguanodontian dinosaurs and characteristic elements of Late Cretaceous dinosaur faunas in Europe. They have also been described in Early Cretaceous deposits of Spain. Rhabdodontids are commonly represented, in late Campanian-early Maastrichtian dinosaur faunas of southern France, by two species of the genus Rhabdodon: R. priscus and R. septimanicus.

Rhabdodontid disarticulated elements have recently been discovered at Velaux-La Bastide Neuve, Bouches-du-Rhône Department, southern France. This locality has yielded an abundant and diversified vertebrate fauna, including the titanosaurid sauropod Atsinganosaurus velauciensis, ankylosaurian remains, theropod teeth, an ontogenetic series of cranial and postcranial elements of the basal eusuchian crocodile Allodaposuchus precedens, pleurodiran and cryptodiran turtles, pterosaurs, hybodont shark teeth, and mawsoniid bones. Here we describe a new rhabdodontid dinosaur, Matheronodon provincialis, from Velaux-La Bastide Neuve, with a quite unusual dentition.

Reference:
Extreme tooth enlargement in a new Late Cretaceous rhabdodontid dinosaur from Southern France. DOI:10.1038/s41598-017-13160-2

Earthquake risk elevated with detection of spontaneous tectonic tremor in Anza Gap

Locations of tectonic tremor
Locations of tectonic tremor (colored circles and squares) detected under the San Jacinto Fault by researchers at UCR. Credit: University of California – Riverside

Scientists at the University of California, Riverside have detected spontaneous tectonic tremor—a signature of slow earthquakes deep below the earth’s surface—in the Anza Gap region of the San Jacinto Fault. Tectonic tremors are believed to increase the likelihood of a moderate to large, damaging earthquake occurring close to the earth’s surface by altering the stress along the fault.

Abhijit Ghosh, an assistant professor of earth sciences in UCR’s College of Natural and Agricultural Sciences, and Alexandra Hutchinson, an earth sciences graduate student, published the research in the Bulletin of the Seismologic Society of America.

The paper is titled “Ambient Tectonic Tremor in the San Jacinto Fault, Near the Anza Gap, Detected by Multiple Mini Seismic Arrays.”

The San Jacinto Fault zone, which is part of the San Andreas Fault system, runs underneath densely populated areas of Inland Southern California, including San Bernardino, Redlands, and Moreno Valley. It is the most active fault in Southern California and sits five miles from the UCR campus. While it is technically not a plate boundary, the San Jacinto Fault accommodates some of the movement that occurs as the North American Plate and the Pacific Plate grind together at the San Andreas Fault.

Over the past 200 years, the 20-km region known as the Anza Gap is the only stretch along the 200-km fault line that has not experienced an earthquake of magnitude 5.5 or greater.

“While other regions of the San Jacinto fault give rise to small and moderate earthquakes on a regular basis, the Anza Gap is surprisingly quiet, which raises questions about how it is releasing the stress it accumulates,” Ghosh said. “For that reason, many experts suspect that this area is ripe to produce a damaging earthquake.”

Using data from 2011 and a new, highly sensitive detection method developed by Ghosh called “multibeam backprojection,” the researchers uncovered the first evidence of a spontaneous tectonic tremor in the Anza Gap. Relatively little is known about tectonic tremors, which were first identified in Japan in 2001. Researchers now know they are associated with a phenomenon called “slow slip,” a slow and transient movement of plates deep below the earth’s surface that can last from several minutes to several years and may occur daily, annually, or anywhere between, depending on the fault.

“While relatively little is known about tectonic tremors, in part because they have historically been difficult to detect, we know that these tremors are being caused by slow slip deep in the fault, and that when the deep part of the fault slips it adds stress to the shallow part. This may ultimately help to cause a damaging earthquake,” Ghosh said.

Ghosh said seismologists should further study tremor activity in the area to learn how the deep roots of fault zones impact activity closer to the earth’s surface and affect earthquake hazard.

“Tectonic tremors and slow slip will change the way we view faults. For example, our research on the Anza gap shows that the fault is spontaneously slipping at a greater depth than we previously thought, with slow earthquakes occurring between 13 and 24 km deep.”

“Since there is a connection between deep slow slip and damaging earthquakes closer to the surface, it may be possible that tectonic tremors will enable us to forecast major earthquakes in the future. Much more research is needed before that can happen, though.”

Reference:
Ambient Tectonic Tremor in the San Jacinto Fault, near the Anza Gap, Detected by Multiple Mini Seismic Arrays. Bulletin of the Seismological Society of America. DOI: doi.org/10.1785/0120160385

Note: The above post is reprinted from materials provided by University of California – Riverside.

‘Mega-carnivore’ dinosaur roamed southern Africa 200 million years ago

New exceptionally large carnivorous dinosaur footprints found in Lesotho.
Fabien Knoll, Honorary Senior Research Fellow at the University of Manchester, lies next to the new exceptionally large carnivorous dinosaur footprints found in Lesotho. Credit: Fabien Knoll

An international team of scientists has discovered the first evidence that a huge carnivorous dinosaur roamed southern Africa 200 million year ago.

The team, which includes researchers from The University of Manchester, University of Cape Town, South Africa, and Universidade de São Paulo, Brazil, have found several three-toed footprints measuring 57cm long and 50cm wide.

This means the dinosaur would have an estimated body length of around nine metres (30 feet) and be a little less than three metres tall at the hip. That’s four times the size of a lion, which is currently the largest carnivore in southern Africa.

The footprints belong to a new species, named Kayentapus ambrokholohali, which is part of the group of dinosaurs called “megatheropod.” The term “Megatheropods” describes the giant two-legged carnivorous dinosaurs, such as the iconic Tyrannosaurus rex (T. rex) which fossil evidence shows was around 12 metres long.

This study, which is published in PLOS ONE, also reveals that these footprints make up the largest theropod tracks in Africa.

The tracks were found on an ancient land surface, known as a palaeosurface, in the Maseru District of Lesotho, a small country in southern Africa. The surface is covered in 200 million years old ‘current-ripple marks’ and ‘desiccation cracks’ which are signs of a prehistoric watering hole or river bank.

Dr Fabien Knoll, Senior Research Fellow at The University of Manchester, said: ‘The latest discovery is very exciting and sheds new light on the kind of carnivore that roamed what is now southern Africa.

‘That’s because it is the first evidence of an extremely large meat-eating animal roaming a landscape otherwise dominated by a variety of herbivorous, omnivorous and much smaller carnivorous dinosaurs. It really would have been top of the food chain.’

What makes the discovery even more important is that these footprints date back to the Early Jurassic epoch, when it was thought the size of most theropod dinosaurs was considerably smaller. On average they were previously thought to be around three to five metres in body length, with some records showing they may have reached seven metres at the very most. It is only much later in the Jurassic and during the Cretaceous, which starts 145 million years ago, that truly large forms of theropods, such as T. rex, appear in body and trace fossil records.

Dr Lara Sciscio, postdoctoral Research Fellow at the University of Cape Town, said: ‘This discovery marks the first occurrence of very large carnivorous dinosaurs in the Early Jurassic of southern Gondwana — the prehistoric continent which would later break up and become Africa and other landmasses. This makes it a significant find. Globally, these large tracks are very rare. There is only one other known site similar in age and sized tracks, which is in Poland.’

The ancient surface where these footprints were found is also covered with the tracks of much smaller theropod dinosaurs.

Dr Knoll added: ‘In South Africa, Lesotho, Zimbabwe and Namibia, there is good record of theropod footprints from the Late Triassic and Early Jurassic epochs. In fact, there are numerous palaeosurfaces where footprints and even tail and body impressions of these, and other animals, can be found. But now we have evidence this region of Africa was also home to a mega-carnivore.’

Reference:
L. Sciscio, E. M. Bordy, M. Abrahams, F. Knoll, B. W. McPhee. The first megatheropod tracks from the Lower Jurassic upper Elliot Formation, Karoo Basin, Lesotho. PLOS ONE, 2017; 12 (10): e0185941 DOI: 10.1371/journal.pone.0185941

Note: The above post is reprinted from materials provided by University of Manchester.

First Jurassic ichthyosaur fossil found in India

Articulated skeleton of Ophthalmosaurid ichthyosaur at the excavation site south of Lodai village
Articulated skeleton of Ophthalmosaurid ichthyosaur at the excavation site south of Lodai village, situated 30 km northeast of Bhuj town, the headquarters of Ka-chchh District in Gujarat state, western India. Credit: Guntupalli V.R. Prasad CC-BY

A new near-complete fossilized skeleton is thought to represent the first Jurassic ichthyosaur found in India, according to a study published October 25, 2017 in the open-access journal PLOS ONE by Guntupalli Prasad from the University of Delhi, India, and colleagues.

Ichthyosaurs, literally ‘fish lizards’ in Greek, were large marine reptiles which lived alongside dinosaurs in the Mesozoic Era. While many ichthyosaur fossils have been found in North American and Europe, in the Southern Hemisphere, their fossil record has mostly been limited to South America and Australia.

Now, the authors of the present study report what they believe to be the first Jurassic ichthyosaur found in India, from the Kachchh area in Gujarat. The near-complete skeleton, nearly 5.5m long, is thought to belong to the Ophthalmosauridae family, which likely lived between around 165 and 90 million years ago. It was found among fossils of ammonites and squid-like belemnites, and its tooth wear patterns suggest it predated such hard, abrasive animals.

While the authors have not yet been able to pinpoint the ichthyosaur’s species, they believe that a full identification could inform on possible ophthalmosaurid dispersal between India and South America. They hope that unearthing more Jurassic vertebrates in this region could provide further insights into the evolution of marine reptiles in this part of the globe.

Lead author Guntupalli Prasad notes: “This is a remarkable discovery not only because it is the first Jurassic ichthyosaur record from India, but also it throws light on the evolution and diversity of ichthyosaurs in the Indo-Madagascan region of the former Gondwanaland and India’s biological connectivity with other continents in the Jurassic.”

Reference:
Guntupalli V. R. Prasad, Dhirendra K. Pandey, Matthias Alberti, Franz T. Fürsich, Mahesh G. Thakkar, Gaurav D. Chauhan. Discovery of the first ichthyosaur from the Jurassic of India: Implications for Gondwanan palaeobiogeography. PLOS ONE, 2017; 12 (10): e0185851 DOI: 10.1371/journal.pone.0185851

Note: The above post is reprinted from materials provided by PLOS.

Alvarezsaurid dinosaur from the late Cretaceous found in Uzbekistan

This is an image of alvarezsauridae gen. et sp. indet., posterior caudal vertebrae.
This is an image of alvarezsauridae gen. et sp. indet., posterior caudal vertebrae. Credit: Averianov et al (2017); CCAL

Bones from an Alvarezsaurid dinosaur were discovered in Uzbekistan and could shed light on the evolution and origin of the species, according to a study published October 25, 2017 in the open-access journal PLOS ONE by Alexander Averianov of Zoological Institute of the Russian Academy of Sciences, Russia and Hans-Dieter Sues of the Smithsonian Institution, USA.

Previous studies have described Alvarezsauridae as small, long-legged, bipedal dinosaurs with short forelimbs that featured bird-like hands. Since Alvarezsaurid remains are extremely rare, there is plenty to learn about the evolution of this species.

The authors of this study analyzed previously excavated Alvarezsaurid remains from the Turonian Bissekty Formation of Uzbekistan. They examined the vertebrae, the bird-like bone that fuses the wrist and knuckle known as the carpometacarpus, and pieces of what would be the fingers or toes, known as the phalanx. They then measured and compared the shapes and sizes of these bones with those from similar species from the literature.

The authors state that the characteristics for the Alvarezsaurid bones are so distinctive that it could be identified just from the seven bones collected at the Bissekty Formation. These distinctive features included rounded vertebrae located close to the tail, a large and depressed second metacarpal, and a robust second digit with a claw-like end.

While there are competing theories about where the Alvarezsaurid originated, the authors suggest that the discovery of an Alvarezsaurid at this site in Uzbekistan indicates that this group had an evolutionary history in Asia and provides evidence that this continent could have been where the clade originated.

Lead author Hans Sues says: “Our paper reports the discovery of the earliest known alvarezsaurid dinosaur from the Northern Hemisphere, based on 90-million-year-old fossils from Central Asia. Alvarezsaurids were unusual small predatory dinosaurs that had very short but powerfuly built arms that ended in a single large digit.”

Reference:
Alexander Averianov, Hans-Dieter Sues. The oldest record of Alvarezsauridae (Dinosauria: Theropoda) in the Northern Hemisphere. PLOS ONE, 2017; 12 (10): e0186254 DOI: 10.1371/journal.pone.0186254

Note: The above post is reprinted from materials provided by PLOS.

Marine species threatened by deep-sea mining

These are polymetallic nodules with Plenaster craigi. White line is 1 cm.
These are polymetallic nodules with Plenaster craigi. White line is 1 cm. Credit: The University of Gothenburg

Less than half of our planet’s surface is covered by land. The rest is water, and this environment is home to an enormous range of animal species, most of which remain undiscovered and thus have not yet been named.

Threatened by Mining Activities

A newly discovered species, Plenaster craigi, has turned out to be the most abundant species on the ocean floors. Its habitat is dominated by nodules, which are metal balls the size of grapefruits that have been formed over millions of years and that are found in most big oceans at depths of over 4 000 metres. A new study involving researchers from the University of Gothenburg finds that, as deep-sea mining companies remove the nodules in order to extract the metals inside them, Plenaster craigi will probably disappear entirely from the affected areas.

‘Modern society, with its power lines and advanced batteries, has a great need for cobalt, nickel and copper, metals found in high concentrations in so-called polymetallic nodules on the Pacific seafloor in the Clarion-Clipperton Zone,’ says Thomas Dahlgren from the Department of Marine Sciences, University of Gothenburg.

Needs an Undisturbed Environment to Survive

The sponge Plenaster craigi must filter the water to find small particles with nutrients and energy that after being formed at surface level several kilometres above have slowly fallen down to the bottom.

‘There is not a whole lot of material that makes it all the way to the bottom. Most of it gets eaten by zooplankton and small fish on its way down and is returned to the food web in the ocean’s upper sunlit layer. Consequently, Plenaster craigi must filter large amounts of water to survive. This makes it vulnerable to the sand and mud stirred up when the nodules are harvested and pumped the 4 000 metres to the collection barges waiting at the surface,’ says Dahlgren.

New Species Can Reveal Effects of Deep-Sea Mining

Since 2013 when the sponge was first discovered, the species has temporarily been referred to as Porifera sp. A. Following the recent species description (see link to the article below), the sponge has now been assigned a permanent name, Plenaster craigi.

Plenaster craigi is the only known species of the newly defined genus Plenaster, which means ‘many stars’. Craigi was included in the name to honour Professor Craig Smith at the University of Hawaii, who led the two expeditions during which the animal was first discovered and collected.

The new species can now be used to explore how deep-see mining of minerals affects an environment that has not been touched for billions of years.

Reference:
A new genus and species of abyssal sponge commonly encrusting polymetallic nodules in the Clarion-Clipperton Zone, East Pacific Ocean. DOI: 10.1080/14772000.2017.1358218

Note: The above post is reprinted from materials provided by University of Gothenburg.

Scientists use seismic waves to measure tornado intensity

Tornado with dust and debris cloud forming at surface.
Tornado with dust and debris cloud forming at surface. Credit: NOAA Photo Library/Flickr

Seismic waves generated by tornadoes when they touch down could be used to measure a twister’s intensity, according to a new study.

The new research examined a catastrophic tornado that struck Joplin, Missouri in May 2011 and revealed the size of seismic waves produced by the tornado on the ground correlated with its strength.

The results suggest researchers can estimate a large tornado’s strength by measuring the seismic waves it creates, a finding that could open the door to devising more accurate methods to study tornadoes from the ground, according to the authors of the new study published in Geophysical Research Letters, a journal of the American Geophysical Union.

Weather authorities currently forecast the locations of tornadoes using surface weather stations and Doppler radar. But they still rely on storm chasers and spotters to find out when a tornado touches down. There is also no way to directly measure a tornado’s wind speed, so authorities rely on damage reports to indirectly judge its intensity.

“Our results have applications for developing a more quantitative measure of a tornado’s strength,” said Anne Valovcin, a graduate student in the Earth science department at the University of California in Santa Barbara and lead author of the new study. “Also, we only see the seismic signals when it touches the ground, so that could provide a new way to directly determine when a tornado has touched down.”

A new way to monitor twisters

Seismic waves are vibrations in the Earth created when the ground shakes, usually felt during earthquakes, volcanic eruptions or large explosions. Tornadoes also generate small seismic waves when they travel over the ground, but scientists know little about how these waves vary with storm strength.

In the new study, Valovcin and her colleagues analyzed seismic waves generated by the May 22, 2011 Joplin tornado to characterize the relationship between the size of these waves and the tornado’s strength. The Joplin twister clocked in as a powerful EF5 on the Enhanced Fujita Scale, a scale that rates the intensity of tornadoes by how much damage they cause. It killed 158 people and resulted in $2.8 billion in damage, making it the costliest single tornado in U.S. history.

The study’s authors hypothesized that if the tornado touched the ground close enough to a seismic station, the instruments could pick up those signals. “We wanted to see if we could detect these ground signals, then work backwards and create a model for the seismic waves generated by the tornado along its entire path,” Valovcin said.

The researchers collected data from a network of stations built to detect small earthquakes and map Earth’s interior under North America. These stations are equipped with seismometers and barometers that measure seismic signals and changes in air pressure. The measurements for the new study came from one station close enough to the Joplin tornado to detect its seismic signals.

The authors divided the tornado’s path on land into hundreds of individual points and calculated the size of the seismic wave generated at each point. They then correlated the size of the seismic waves at each stage in the tornado’s lifetime with the tornado’s intensity at that time.

The results show the size of the seismic waves correlated well with the tornado’s EF rating. EF ratings range from EF0 to EF5, with EF5 being the most destructive category. The Joplin tornado went from an EF1-2 to an EF4-5 in fewer than 10 minutes, and stayed at that intensity for approximately 15 minutes before beginning to lose its strength. As the twister got stronger and then weaker, the size of the seismic waves it generated increased and decreased accordingly.

Measuring a tornado’s seismic signals could provide a better way for researchers to measure a tornado’s strength and could help determine exactly when a twister touches down, according to the study’s authors. But they cautioned the new method is largely preliminary and has several limitations.

For example, the technique requires measuring the air pressure at the time of the tornado to eliminate seismic interference from the turbulent air surrounding the twister. Seismic stations therefore need to be located next to functioning barometers to provide usable data.

Additionally, seismic waves generated by tornadoes are very small, and can’t be felt by a person without equipment. They don’t propagate far from their source, unlike seismic waves generated by earthquakes, which are often larger and can travel long distances. Detecting tornadoes in real-time with this method would require building a much denser network of seismic stations and barometers than currently exists, Valovcin said.

Reference:
Anne Valovcin et al. Modeling the Excitation of Seismic Waves by the Joplin Tornado, Geophysical Research Letters (2017). DOI: 10.1002/2017GL074185

Note: The above post is reprinted from materials provided by American Geophysical Union.

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