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Large meteorite impacts drove plate-tectonic processes on the early Earth

Figure: Geodynamic simulation of the early Earth, showing a global subduction event driven by a giant (1700km diameter) impactor 4 million years into the simulation’s evolution. Dark colours indicate subducting crust and lithosphere, hot colours indicate upwelling mantle which drives volcanic activity at the surface. Credit: Macquarie University

An international study led by researchers at Macquarie University has uncovered the ways in which giant meteorite impacts may have helped to kick-start our planet’s global tectonic processes and magnetic field. The study, being published in the premier journal Nature Geoscience, explores the effect of meteorite bombardment, in geodynamic simulations of the early Earth.

“Our results indicate that giant meteorite impacts in the past could have triggered events where the solid outer section of the Earth sinks into the deeper mantle at ocean trenches – a process known as subduction. This would have effectively recycled large portions of the Earth’s surface, drastically changing the geography of the planet,” explained lead author Associate Professor Craig O’Neill from Macquarie University.

“Large impact events may have also kick-started the Earth’s magnetic field by triggering the planet’s cold outer crust to suddenly move downward and interact with the Earth’s outer core. This affects convection in the core, and thus the geodynamo – the process that creates the Earth’s magnetic field,” he added.

To date, there is still not clear evidence to show whether plate tectonics operated in Earth’s early history, with the first 500 million years of our planet’s life, called the Hadean, often being dubbed as Earth’s geological dark ages. The little crust that has been preserved from this elusive period – mostly single grains of a mineral called zircon – has been used to argue for early tectonic activity. However, this is at odds with geochemical data and geodynamic simulations, which suggest that the Earth may instead have had a motionless ‘lid’ on its surface – in contrast to the actively moving combination of plates we see today.

“We know that meteorite impacts had a huge effect on the inner solar system at this time,” says Associate Professor O’Neill, “you only need to look at the Moon to see that. What isn’t clear was how our own impact history might have affected the planet’s evolution.”

“We’ve seen evidence of some geological activity that suggests something like subduction acted on the early Earth – but this is hard to reconcile with other geodynamic simulations. But if we consider Earth as part of an evolving early solar system, as opposed to only looking at the planet in isolation, then this evolution starts to make more sense,” he added.

O’Neill also notes that while the magnetic field for much of Earth’s ancient history has been quite low, but recent work has suggested field strengths up to present-day values existed between around 4.0-4.1 billion years ago.

“This is a really important age in the inner solar system. Impacting studies have suggested a big disturbance in the asteroid populations at this time, with perhaps a big upswing in impacts on the Earth. Our simulations show that larger amounts of meteorite collisions with the planet around this time could have driven the subduction process, explaining the formation of many zircons around this period, as well as the increase in magnetic field strength.”

Overall, the study adds evidence towards the fact that meteorite impacts likely had a role in the formation of the Earth that we know today.

“This work shows there is a strong connection between impacts and geophysical evolution capable of drastically altering a planet’s evolution,” said coauthor Dr Simone Marchi from the Southwest Research Institute in the USA.

“One has to wonder, how much of the current Earth, and other terrestrial planets, is the result of collisions that took place eons ago?” Dr Marchi concluded.

Reference:
C. O’Neill et al. Impact-driven subduction on the Hadean Earth, Nature Geoscience (2017). DOI: 10.1038/ngeo3029

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

Geologists study the drying up of the Mediterranean Sea 5.96 million years ago

The white line represents the present-day Mediterranean coastline, blue regions show the submarine area in case of a 2km Mediterranean sea level lowering as it was proposed during the Messinian salinity crisis and red circles show the location of volcanic provinces whose activity was enhanced during the Messinian (the size of the circle is proportional the activity augmentation). Credit: UNIGE

We already know that climate change influences such Earth processes as erosion and fluctuations in sea levels. But do surface processes in turn have an influence on volcanic activity? This was the question raised by geologists from the University of Geneva (UNIGE, Switzerland) and international collaborators. The researchers analysed volcanic data from the Messinian salinity crisis in the Mediterranean Sea, when the Strait of Gibraltar was blocked and the Mediterranean temporarily isolated from the Atlantic. After observing a sharp rise in volcanic activity during this period, and testing various scenarios, the geologists concluded that the increase in magmatic activity could only be explained by the almost total drying out of the Mediterranean. These results, published in Nature Geoscience, reveal the influence of surface processes, largely controlled by climate, on volcanic activity.

It is known that the Strait of Gibraltar was temporarily shut during the Messinian Era (more precisely, from 5.96 to 5.33 million years ago) and that the Mediterranean Sea was isolated from the Atlantic. In fact, as far back as the 1970s, scientists have found layers of salt several hundred metres thick on the seabed. The only explanation is that there was very limited connection between the Mediterranean and the Atlantic. The scientists also discovered huge underwater canyons dating back to the same period, hollowed out by rivers running over land that is now submerged, suggesting that the sea level was much lower at the time. This also points to the massive drying up of the Mediterranean with enormous geographical and climatic disruption across the entire basin. This hypothesis, however, continues to be a source of debate.

Nevertheless, a team of UNIGE-led geologists has provided new evidence of the Mediterranean’s drying up and the forcing of surface processes on magmatic activity. “We understand that what happens at the Earth’s surface, such as a sudden sea level lowering, causes the pressure to change at depth and has an effect on magma production,” says Pietro Sternai, researcher in the Department of Earth Sciences in UNIGE’s Science Faculty. Given that the salinity crisis was capable of generating these changes in pressure, the geologists, working on the hypothesis that the Mediterranean dried out, studied the changes in volcanic activity during this period.

When a volcano erupts, the magma cools on the Earth’s surface and the minerals crystallise. Based on these silent witnesses of volcanic activity, the scientists were able to establish that there were 13 eruptions around the Mediterranean between 5.9 and 5.3 million years ago. This is over twice the average activity, which is around 4.5 eruptions over a longer time length encompassing the salinity crisis. Why is the figure so high? “The single logical explanation,” suggests Sternai, “is the hypothesis that the sea dried out, since this is the only event powerful enough to alter the Earth’s pressure and magmatic production over the entire Mediterranean.”

The geologists used numerical models to test the hypothesis that the Mediterranean dried up. They reproduced the history of the charging and discharging of the weight of water and sediment in the Mediterranean as it was drying out. Then they calculated the changes in pressure at depth and the impact on magma production.

Two scenarios were examined: The first factored in the salinity crisis with drastic lowering of the sea level, and the second excluded the drawdown. “The simulations showed that the only way to account for the proven increase in volcanic activity was that the level (and thus the weight) of the Mediterranean Sea dropped by about two kilometres,” explains Sternai. “I leave it to you to imagine what the landscape looked like.”

In addition to providing further evidence of the drying out of the Mediterranean, the research also demonstrates the impact of climate change on the deep Earth. Climate change influences magmatic production, in particular via the effects on erosion and hydrology, which modify the pressure exerted at the Earth’s surface on the deep layers. Although we have been aware of the impact of volcanism on the climate for quite some time, the results presented in the study have disclosed that the opposite is also possible. “This pioneering work opens up new perspectives for interdisciplinary studies about the coupling between the solid Earth and the fluid Earth, and—for example—involving volcanologists, geomorphologists and climatologists,” concludes Sternai.

Reference:
Pietro Sternai et al. Magmatic pulse driven by sea-level changes associated with the Messinian salinity crisis, Nature Geoscience (2017). DOI: 10.1038/ngeo3032

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

Diamonds show Earth still capable of ‘superhot’ surprises

Octaedral P-type diamond from Venetia with a garnet mineral inclusion. Credit: Michael Gress

Diamonds may be ‘forever’ but some may have formed more recently than geologists thought. A study of 26 diamonds, formed under extreme melting conditions in the Earth’s mantle, found two populations, one of which has geologically ‘young’ ages. The results show that certain volcanic events on Earth may still be able to create super-heated conditions previously thought to have only existed early in the planet’s history before it cooled. The findings may have implications for diamond prospecting.

Diamonds can be categorised by their inclusions: minerals trapped within the carbon crystal structure that give clues about the conditions and the rocks in which they formed. The studied diamonds contain harzburgitic inclusions, a type of peridotite ‒ the most common rock in Earth’s mantle ‒ which have experienced extreme temperatures and undergone very large amounts of melting.

The study led by researchers at the Vrije Universiteit (VU) Amsterdam used radioisotope analysis to date tiny inclusions trapped in diamonds from the Venetia mine in South Africa. Results showed that the diamonds had formed in at least two separate events. Nine of the diamonds had an age of around 3 billion years, and could be linked to volcanism caused by the break-up of an old continent that led to large-scale melting. However, surprisingly, ten diamonds were dated as just over a billion years old, correlating with a giant volcanic event at Umkondo in southern Zimbabwe, 1.1 billion years ago.

“Conventional thinking has been that the level of melting needed to create these diamonds could only happen early in the history of the Earth when it was much hotter. We show that this is not the case and that some harzburgitic diamonds are much younger than assumed. We propose that our younger set of diamonds formed in a special environment where a major plume from the deep mantle was raised towards the surface and underwent extensive melting as the pressure reduced,” said Janne Koornneef, who led the study, published today in Nature Communications.

Gareth Davies, co-author of the study, commented, “This is a fascinating insight into the inner workings of planet Earth. While young diamonds are formed in other types of rocks and conditions in the mantle, it’s very unexpected to find harzburgitic diamonds linked to relatively recent geological activity. As harzburgitic rocks are important markers for diamond prospecting, the findings may have implications for the geological environments where we look for new diamond mines.”

The analysis of the diamonds at VU Amsterdam was funded by Europlanet 2020 Research Infrastructure and the research was funded by the European Research Council. The De Beers Group of Companies donated the diamonds used in this study.

Reference:
Janne M. Koornneef, Michael U. Gress, Ingrid L. Chinn, Hielke A. Jelsma, Jeff W. Harris, Gareth R. Davies. Archaean and Proterozoic diamond growth from contrasting styles of large-scale magmatism. Nature Communications, 2017; 8 (1) DOI: 10.1038/s41467-017-00564-x

Note: The above post is reprinted from materials provided by Europlanet Media Centre.

Early trilobites had stomachs, new fossil study finds

This photo is of a specimen of the trilobite Palaeolenus lantenoisi from the Guanshan Biota in southern Yunnan Province, China. Rarely are internal organs preserved in fossils, but this specimen shows the digestive system preserved as reddish iron oxides. The digestive system is comprised of a crop (inflated region at top of specimen), lateral glands, and a central canal that runs along the length of the body; the iron oxides that extend beyond the fossil are the remains of gut contents that were extruded during preservation. Credit: F. Chen

Exceptionally preserved trilobite fossils from China, dating back to more than 500 million years ago, have revealed new insights into the extinct marine animal’s digestive system. Published today in the journal PLOS ONE, the new study shows that at least two trilobite species evolved a stomach structure 20 million years earlier than previously thought.

“Trilobites are one of the first types of animals to show up in large numbers in the fossil record,” said lead author Melanie Hopkins, an assistant curator in the Division of Paleontology at the American Museum of Natural History. “Their exoskeletons were heavy in minerals, and so they preserved really well. But like all fossils, it’s very rare to see the preservation of soft tissues like organs or appendages in trilobites, and because of this, our knowledge of the trilobite digestive system comes from a small number of specimens. The new material in this study really expands our understanding.”

Trilobites are a group of extinct marine arthropods — distantly related to the horseshoe crab — that lived for almost 300 million years. They were extremely diverse, with about 20,000 species, and their fossil exoskeletons can be found all around the world. Most of the 270 specimens analyzed in the new study were collected from a quarry in southern Kunming, China, during an excavation led by Hopkins’ co-author, Zhifei Zhang, from Northwest University in Xi’an.

Previous research suggests that two body plans existed for trilobite digestive systems: a tube that runs down the length of the trilobite’s body with lateral digestive glands that would have helped process the food; or an expanded stomach, called a “crop,” leading into a simple tube with no lateral glands. Until now, only the first type had been reported from the oldest trilobites. Based on this, researchers had proposed that the evolution of the crop came later in trilobite evolutionary history and represented a distinct type of digestive system.

The Chinese trilobite fossils, about 20 percent of which have soft tissue preservation, are dated to the early Cambrian, about 514 million years ago. Contradictory to the previously proposed body plans, the researchers identified crops in two different species within this material. In addition, they found a single specimen that has both a crop and digestive glands — suggesting that the evolution of trilobite digestive systems is more complex than originally proposed.

The study backs up an earlier announcement made by a separate research team, which found evidence for the unusual crop and gland pairing in a single juvenile trilobite specimen from Sweden from the late Cambrian. But the Chinese material presents the oldest example of this complex digestive system in a mature trilobite, wiping away doubts that the dual structures might just be part of the animal’s early development.

“This is a very rigorous study based on multiple specimens, and it shows that we should start thinking about this aspect of trilobite biology and evolution in a different way,” Hopkins said.

Reference:
Melanie J. Hopkins, Feiyang Chen, Shixue Hu, Zhifei Zhang. The oldest known digestive system consisting of both paired digestive glands and a crop from exceptionally preserved trilobites of the Guanshan Biota (Early Cambrian, China). PLOS ONE, 2017; 12 (9): e0184982 DOI: 10.1371/journal.pone.0184982

Note: The above post is reprinted from materials provided by American Museum of Natural History.

Big herbivorous dinosaurs ate crustaceans as a side dish

Dark crustacean shell fragment embedded in coprolite, or fossilized dinosaur feces. Credit: University of Colorado

Some big plant-eating dinosaurs roaming present-day Utah some 75 million years ago were slurping up crustaceans on the side, a behavior that may have been tied to reproductive activities, says a new University of Colorado Boulder study.

The evidence for the crustacean-chowing dinosaurs comes from fossilized feces samples known as coprolites, said Associate Professor Karen Chin, curator of paleontology at CU Boulder’s Museum of Natural History. Dating to the late Cretaceous Period, the coprolites were discovered in Grand Staircase-Escalante National Monument in southern Utah by a team from the Denver Museum of Nature & Science who invited Chin out to their dig.

From what we know about dinosaurs, this was a totally unexpected behavior,” said Chin. “It was such a surprising discovery we wondered what the motivation could have been.”

Chin said the Utah coprolites were similar to those she has examined from Montana — which likely were from duck-billed dinosaurs known as hadrosaurs — in that both were similar in size and held jumbled fragments of rotting wood. A closer look at some of the Utah coprolites also turned up thick bits and pieces of fossilized shell, an indication crustaceans were living in the decaying, coniferous wood, she said.

Because crustacean shells turned up in at least 10 coprolite samples in three different stratigraphic layers of the national monument over a distance of about 13 miles, Chin thinks their ingestion by the dinosaurs was purposeful and would have provided valuable protein and calcium sources.

A paper on the subject was published Sept. 21 in the journal Scientific Reports. Study co-authors included Professor Emeritus Rodney Feldmann and doctoral student Jessica Tashman of Kent State University in Kent, Ohio. Funding for the project came from both CU Boulder and Kent State University.

Examples of modern crustaceans, which have hard exoskeletons, include lobsters, crab, shrimp and crayfish. Some of the coprolites examined were probably around two gallons in volume, Chin said.

The size of the crustacean shell bits in the coprolites indicate the crustaceans were at least two inches in length and perhaps larger, said Chin. Individual crustaceans comprised from 20 to 60 percent of the width of a common hadrosaur beak, suggesting it was unlikely the crustaceans were unwittingly swallowed, she said.

“While it is difficult to prove intent regarding feeding strategies, I suspect these dinosaurs targeted rotting wood because it was a great source of protein in the form of insects, crustaceans and other invertebrates,” said Chin. “If we take into account the size of the crustaceans and that they were probably wriggling when they were scooped up, the dinosaurs would have likely been aware of them and made a choice to ingest them.”

Even though the team is unable to determine what kind of crustaceans they were, fossil crab claws have been found in the same area in a slightly older geologic formation. Present-day Utah appears to have been next to or near a sea during the Cretaceous Period, said Chin.

Chin also suspects the consumption of crustaceans may have been a seasonal dietary shift, perhaps tied to breeding and egg-laying activities of dinosaurs. She notes contemporary bird species — which are technically avian dinosaurs — often consume more protein and calcium during the breeding season to support successful reproduction.

“If we found one coprolite with a crustacean fossil in it, that would be a really interesting scientific discovery,” Chin said. “But it wouldn’t necessarily indicate a recurring feeding behavior. We now have multiple coprolites with crustacean fossils, showing that at least some types of herbivorous dinosaurs occasionally engaged in this unanticipated feeding strategy.”

The researchers sliced the coprolite material into thin sections that were then analyzed with an electron microprobe to determine their chemical composition — in this case they found a preponderance of calcium, said Chin.

Hadrosaurs were one of the most common dinosaur type of the Cretaceous, growing up to 30 feet long and weighing up to three tons. Some species had characteristic crests on their heads. They also had specialized teeth for grinding plant material, and are thought by some paleontologists to have roamed in herds and nurtured their young.

Reference:
Karen Chin, Rodney M. Feldmann, Jessica N. Tashman. Consumption of crustaceans by megaherbivorous dinosaurs: dietary flexibility and dinosaur life history strategies. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-11538-w

Note: The above post is reprinted from materials provided by University of Colorado at Boulder.

Dino-killing asteroid’s impact on bird evolution

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

Human activities could change the pace of evolution, similar to what occurred 66 million years ago when a giant asteroid wiped out the dinosaurs, leaving modern birds as their only descendants. That’s one conclusion drawn by the authors of a new study published in Systematic Biology.

Cornell University Ph.D. candidate Jacob Berv and University of Bath Prize Fellow Daniel Field suggest that the meteor-induced mass extinction (a.k.a. the K-Pg event) led to an acceleration in the rate of genetic evolution among its avian survivors. These survivors may have been much smaller than their pre-extinction relatives.

“There is good evidence that size reductions after mass extinctions may have occurred in many groups of organisms,” says Berv. “All of the new evidence we have reviewed is also consistent with a Lilliput Effect affecting birds across the K-Pg mass extinction.” Paleontologists have dubbed this phenomenon the “Lilliput Effect” — a nod to the classic tale Gulliver’s Travels.

“Smaller birds tend to have faster metabolic rates and shorter generation times,” Field explains. “Our hypothesis is that these important biological characters, which affect the rate of DNA evolution, may have been influenced by the K-Pg event.”

The researchers jumped into this line of inquiry because of the long-running “rocks and clocks” debate. Different studies often report substantial discrepancies between age estimates for groups of organisms implied by the fossil record and estimates generated by molecular clocks. Molecular clocks use the rate at which DNA sequences change to estimate how long ago new species arose, assuming a relatively steady rate of genetic evolution. But if the K-Pg extinction caused avian molecular clocks to temporarily speed up, Berv and Field say this could explain at least some of the mismatch. “Size reductions across the K-Pg extinction would be predicted to do exactly that,” says Berv.

“The bottom line is that, by speeding up avian genetic evolution, the K-Pg mass extinction may have temporarily altered the rate of the avian molecular clock,” says Field. “Similar processes may have influenced the evolution of many groups across this extinction event, like plants, mammals, and other forms of life.”

The authors suggest that human activity may even be driving a similar Lilliput-like pattern in the modern world, as more and more large animals go extinct because of hunting, habitat destruction, and climate change.

“Right now, the planet’s large animals are being decimated — the big cats, elephants, rhinos, and whales,” notes Berv. “We need to start thinking about conservation not just in terms of functional biodiversity loss, but about how our actions will affect the future of evolution itself.”

Reference:
Jacob S. Berv, Daniel J. Field. Genomic Signature of an Avian Lilliput Effect across the K-Pg Extinction. Systematic Biology, 2017; DOI: 10.1093/sysbio/syx064

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

Lumbering giants had agile ancestors “Dinosaur evolution”

Sauropods were colossal grazers, but their ancestors were light-footed predators — as revealed by studies of their braincases. Credit: Image courtesy of Ludwig-Maximilians-Universität München

The best known sauropod dinosaurs were huge herbivorous creatures, whose brain structures were markedly different from those of their evolutionary predecessors, for the earliest representatives of the group were small, lithe carnivores.

The sauropod group of dinosaurs included the largest animals that have ever walked the Earth — up to 40 meters long and weighing as much as 90 tons. Evolutionarily speaking, they were obviously very successful, giving rise to a diverse and widely distributed array of plant-eating species. These forms were characterized by a small head, a long and highly flexible neck that allowed them — like modern giraffes — to graze the tops of the tallest trees, and a massive body that made mature specimens invulnerable to predators. The sauropods survived for well over 100 million years before succumbing to the meteorite that snuffed out the dinosaurs at the end of the Cretaceous Era.

However, the early representatives of the lineage that led to these lumbering giants were strikingly different in form and habits. For a start, they were carnivores — like Saturnalia tupiniquim, an early sauropod dinosaur that was about the same size as a modern wolf. Recent work carried out by researchers for Ludwig-Maxilians-Universitaet (LMU) in Munich in collaboration with colleagues in Brazil now confirms this scenario and adds new details to the story. Most of the evidence for the early members of the Sauropodomorpha comes from their type of dentition. Now paleontologists Mario Bronzati and Oliver Rauhut, who are based at LMU and the Bavarian State Collection for Paleontology and Geology in Munich, have used computer tomography (CT) to analyze fossil skull bones assigned to S. tupiniquim. The high-resolution images of the cranial bones provided by this technique enabled them to deduce the overall surface morphology of the brain. The results suggest that despite being capable of consuming both meat and plants, S. tupiniquim could have followed a purely predatory lifestyle. The new findings appear in Scientific Reports.

The fossil material used in the study was discovered in Brazil over 20 years ago. It comes from a geological formation that dates back to the Triassic Era, and is about 230 million years old. According to the authors of the study, these are the oldest dinosaur bones that have been successfully reassembled with the aid of computer tomography at sufficiently high resolution to permit the reconstruction of the gross anatomy of the brain.

The evolution of the so-called Sauropodomorpha, of which Saturnalia tupiniquim is an early representative, and the Sauropoda sensu stricto, is marked by a clear tendency towards extension of the neck region, which is accompanied by reduction of the size of the skull — with a corresponding decrease in the volume of the brain — relative to the skeleton as a whole. Saturnalia tupiniquim stands at the beginning of this process. But the new study reveals that, unlike the case in the true sauropods, a specific area in the cerebellum, which encompasses the two lobes known as the flocculus and paraflocculus, is particularly prominent in the brain of S. tupiniquim. These structures are known to play an important role in controlling voluntary movements of the head and neck, and are involved in regulating the oculomotor system, which stabilizes the animal’s field of view.

Bronzati, Rauhut and their co-authors therefore argue that these features enabled S. tupiniquim to adopt a predatory lifestyle. Their findings strongly suggest that, in contrast to the true sauropods, it had a bipedal gait. Moreover, it was nimble enough to hunt, seize and kill its prey — thanks to its inferred ability to track moving objects with its eyes and to execute rapid movements of its head and neck in a coordinated and precise fashion. With the aid of CT-based reconstruction of the surface anatomy of the brain, the researchers now hope to retrace other stages in the evolution of the sauropodomorphs.

Reference:
Mario Bronzati, Oliver W. M. Rauhut, Jonathas S. Bittencourt, Max C. Langer. Endocast of the Late Triassic (Carnian) dinosaur Saturnalia tupiniquim: implications for the evolution of brain tissue in Sauropodomorpha. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-11737-5

Note: The above post is reprinted from materials provided by Ludwig-Maximilians-Universität München.

Bite force research reveals dinosaur-eating frog

An individual Ceratophrys cranwelli biting a force transducer. Leather strips glued to ends of bite bars provide a natural surface that encourages high-effort biting and avoids damage to teeth and bones. The strips also indicate a bite point for standardization of bite-force performance

Scientists say that a large, now extinct, frog called Beelzebufo that lived about 68 million years ago in Madagascar would have been capable of eating small dinosaurs.

The conclusion comes from a study of the bite force of South American horned frogs from the living genus Ceratophrys, known as Pacman frogs for their characteristic round shape and large mouth, similar to the video game character Pac-Man. Due to their attractive body colouring, voracious appetite, and comically huge heads, horned frogs are very popular in the international pet trade.

Published today in the Nature journal Scientific Reports, the scientists from University of Adelaide, California State Polytechnic University — Pomona, University of California — Riverside and UCL, University College London found that living large South American horned frogs have similar bite forces to those of mammalian predators.

“Unlike the vast majority of frogs which have weak jaws and typically consume small prey, horned frogs ambush animals as large as themselves — including other frogs, snakes, and rodents. And their powerful jaws play a critical role in grabbing and subduing the prey,” says Dr Marc Jones, researcher at the University of Adelaide’s School of Biological Sciences and honorary researcher at the South Australian Museum.

The study found that small horned frogs, with head width of about 4.5cm, can bite with a force of 30 newtons (N) or about 3 kg or 6.6 lbs. A scaling experiment, comparing bite force with head and body size, calculated that large horned frogs that are found in the tropical and subtropical moist lowland forests of South America, with a head width of up to 10 cm, would have a bite force of almost 500 N. This is comparable to reptiles and mammals with a similar head size.

“This would feel like having 50 litres of water balanced on your fingertip,” says Professor Kristopher Lappin, Professor of Biological Sciences at California State Polytechnic University — Pomona.

Based on their scaling relationship, the scientists estimated the bite force of the giant extinct frog Beelzebufo — which is in many ways similar to living horned frogs — may have had a bite up to 2200 N, comparable to formidable mammalian predators such as wolves and female tigers.

“At this bite force, Beelzebufo would have been capable of subduing the small and juvenile dinosaurs that shared its environment,” says Dr Jones.

The scientists measured bite force using a custom-made force transducer, a device which accurately measures the force applied to two plates covered with leather when an animal bites them.

“This is the first time bite force has been measured in a frog,” says Professor Lappin. “And, speaking from experience, horned frogs have quite an impressive bite, and they tend not to let go. The bite of a large Beelzebufo would have been remarkable, definitely not something I would want to experience firsthand.”

Sean Wilcox, a PhD candidate at the University of California — Riverside, says: “Many people find horned frogs hilarious because of their big heads and fat, round bodies. Yet, these predators have given us a rare opportunity to learn something more about the biology of a huge extinct frog.”

Reference:
A. Kristopher Lappin, Sean C. Wilcox, David J. Moriarty, Stephanie A. R. Stoeppler, Susan E. Evans, Marc E. H. Jones. Bite force in the horned frog (Ceratophrys cranwelli) with implications for extinct giant frogs. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-11968-6

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

3-D analysis of dog fossils sheds light on domestication debate

3D plot of PC1–3 mandible shape variation. Black: dogs, dark grey: Alaskan wolves, light grey: European wolves, dark red: Ivolgin fossils, green: Ust’-Polui fossils, purple: Pleistocene Alaskan wolves, cyan: 1600CE fossil dogs, orange: unknown Alaskan fossil canids, pink: 1600CE fossil wolf. Credit: Scientific Reports

In an effort to settle the debate about the origin of dog domestication, a technique that uses 3-D scans of fossils is helping researchers determine the difference between dogs and wolves.

In the ongoing debate, one camp believes dogs were domesticated in the Paleolithic age (more than 17,000 years ago), when humans were hunter-gatherers. The other camp believes domestication occurred in the Neolithic age (17,000 to 7,000 years ago), when humans first established agriculture and civilizations.

Abby Grace Drake, a senior lecturer in the Department of Ecology and Evolutionary Biology, and her colleagues have been analyzing 3-D scans of ancient fossil canid mandibles to determine whether they belong to dogs or wolves. The answer, they find, is not so simple.

The researchers found that in the early stages of domestication, the skull changed shape but evolution of the mandible lagged behind and did not co-evolve with the skull. Their study is reported in the Aug. 25 issue of the journal Scientific Reports.

“A lot of the fossil evidence for the date of dog domestication is based on morphological [structural] analysis of mandibles,” said Drake, the paper’s first author. Robert Losey, an anthropologist at the University of Alberta, Canada, is a senior co-author of the paper. “Our study shows that when you measure modern dog mandibles and wolf mandibles using 3-D measurements you can distinguish them, and yet when we looked at these fossil mandibles, they don’t look like dogs or wolves.”

Wolves have fairly straight mandibles while dog mandibles are curved, structural features that become evident in a 3-D scan. In a proof of principle, when analyzing the 3-D structures of mandibles of modern dogs, Drake and colleagues correctly classified 99.5 percent of the samples as being dog or wolf.

However, 3-D analysis of fossil records from four ancient sites, two from Russia and two from Alaska, found that most of those fossil mandibles could not be classified as either dog or wolf, even though features in canid skulls from the same sites as well as other data proved that the samples were dog remains.

Other evidence also showed that these canids were domesticated: The remains were found within human dwellings, remains at both the Russian sites revealed butchery marks, indicating that they were eaten, and isotope analysis of canid and human remains from one of the sites – Ust’-Polui, in the Russian Arctic – showed canids and humans were both eating fish, and humans were feeding their canids.

Since mandibles do not appear to evolve as rapidly as the skull, the results show they are not reliable for identifying early dog fossils, Drake said.

Four of 26 fossil mandibles from Ust’-Polui, which was occupied from 250 B.C. to 150 B.C., were identified as dogs, while three of the mandibles from the site were identified as wolves.

At another site, Ivolgin, in southern Russia, occupied between 300 B.C. and 200 B.C., none of the 20 mandibles were identified as dogs, though 8 were identified as wolves. All of the skulls found at these sites, 12 from Ivolgin and five from Ust’-Polui, were clearly identified as dogs.

Canid fossils of wolves and dogs from the Alaskan sites from 1600 CE were used as controls and to compare genetic testing against the structural 3-D data.

A 2015 paper by Drake and Michael Coquerelle, an anthropologist at the University Rey Juan Carlos in Alcorcon, Spain, and a co-author on the current paper, used the 3-D technique to refute a claim that dogs existed 30,000 years ago. That claim was based on linear caliper measurements of skulls. Linear measurements are inaccurate because dog and wolf skull sizes overlap, Drake said. On the other hand, 3-D analysis of skulls uses landmarks across the skull to identify differences between dogs and wolves in the angle of the muzzle, or snout, and in the angling of the eye orbits.

“The earliest dogs I’ve seen in my analysis are from 7,000 to 9,000 years ago,” Drake said.

Reference:
Abby Grace Drake et al, Three-Dimensional Geometric Morphometric Analysis of Fossil Canid Mandibles and Skulls, Scientific Reports (2017). DOI: 10.1038/s41598-017-10232-1

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

Scenes From Around Mexico Capital as Earthquake Struck

19 Sep 2017 ــــ Thousands of people tore through Mexico City in terror as a powerful 7.1-magnitude earthquake toppled buildings and trapped residents on the anniversary of a devastating 1985 tremor.

The giant quake, which is believed to have killed at least 44 people, sent panicked office workers streaming into the streets as skyscrapers swayed and bridges collapsed.

Hospital staff evacuated wards across the city at 1:15pm local time (7:15pm GMT) – shading babies in incubators under trees as horrified patients watched brick walls crumble around them.

The US Geological Survey said the quake had a magnitude of 7.1 and was centred near the Puebla state town of Raboso, about 76 miles south east of Mexico City.

The capital’s mayor said there were reports of people trapped in collapsed and burning buildings.

Scientists locate potential magma source in Italian supervolcano

Scientists have now pinpointed the location of the hot zone where hot materials rose to feed the caldera during its last period of activity in the 1980s. Credit: University of Aberdeen

Scientists have found the first direct evidence of a so-called ‘hot zone’ feeding a supervolcano in southern Italy that experts say is nearing eruption conditions.

Campi Flegrei is a volcanic caldera to the west of Naples that last erupted centuries ago.

The area has been relatively quiet since the 1980s when the injection of either magma or fluids in the shallower structure of the volcano caused a series of small earthquakes.

Using seismological techniques, scientists have now pinpointed the location of the hot zone where hot materials rose to feed the caldera during this period.

The study was led by Dr Luca De Siena at the University of Aberdeen in conjunction with the INGV Osservatorio Vesuviano, the RISSC lab of the University of Naples, and the University of Texas at Austin. The research provides a benchmark that may help predict how and where future eruptions could strike.

“One question that has puzzled scientists is where magma is located beneath the caldera, and our study provides the first evidence of a hot zone under the city of Pozzuoli that extends into the sea at a depth of 4 km,” Dr De Siena said.

“While this is the most probable location of a small batch of magma, it could also be the heated fluid-filled top of a wider magma chamber, located even deeper.”

Dr De Siena’s study suggests that magma was prevented from rising to the surface in the 1980s by the presence of a 1-2 km-deep rock formation that blocked its path, forcing it to release stress along a lateral route.

While the implications of this are still not fully understood, the relatively low amount of seismic activity in the area since the 1980s suggests that pressure is building within the caldera, making it more dangerous.

“During the last 30 years the behaviour of the volcano has changed, with everything becoming hotter due to fluids permeating the entire caldera,” Dr De Siena explained.

“Whatever produced the activity under Pozzuoli in the 1980s has migrated somewhere else, so the danger doesn’t just lie in the same spot, it could now be much nearer to Naples which is more densely populated.

“This means that the risk from the caldera is no longer just in the centre, but has migrated. Indeed, you can now characterise Campi Flegrei as being like a boiling pot of soup beneath the surface.

“What this means in terms of the scale of any future eruption we cannot say, but there is no doubt that the volcano is becoming more dangerous.

“The big question we have to answer now is if it is a big layer of magma that is rising to the surface, or something less worrying which could find its way to the surface out at sea.”

Reference:
Luca De Siena et al. Source and dynamics of a volcanic caldera unrest: Campi Flegrei, 1983–84, Scientific Reports (2017). DOI: 10.1038/s41598-017-08192-7

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

Scientists produce best estimate of Earth’s composition

Representative Image: Deep Earth

Scientists at ANU have produced the best estimate of Earth’s elemental composition which will help them understand how the Earth formed 4.6 billion years ago.

The Solar System began as a dense blob in a molecular cloud of hydrogen gas and dust that collapsed under its own gravity, forming the early Sun, Earth and other planets.

Co-researcher Associate Professor Charley Lineweaver said the Earth’s chemical composition was set at that early stage of formation.

“The four most abundant elements – iron, oxygen, silicon and magnesium – make up more than 90 per cent of the Earth’s mass, but working out exactly what the Earth is made of is tricky,” said Dr Lineweaver from the Research School of Earth Sciences and the Research School of Astronomy and Astrophysics at ANU.

“Seismological studies of earthquakes inform us about the Earth’s core, mantle and crust, but it’s hard to convert this information into an elemental composition.

“Our deepest drilling has only scratched the surface down to 10 kilometres of our 6,400 kilometre radius planet. Rocks at the surface only come from as deep as the upper mantle.”

The research is published in the international journal Icarus and is available here.

Lead author ANU PhD scholar Haiyang Wang said the team made the most comprehensive estimates of the Earth’s composition based on a meta-analysis of previous estimates of the mantle and core, and a new estimate of the core’s mass.

“Our work focused on getting realistic uncertainties so that our reference model can be used in future comparisons of the Earth with the Sun, or with Mars or with any other body in the Solar System,” said Mr Wang from the ANU Research School of Astronomy and Astrophysics.

Co-researcher Professor Trevor Ireland from the ANU Research School of Earth Sciences said planetary scientists would find many uses for this new composition record.

“This will have far-reaching importance, not only for planetary bodies in our Solar System but also other star systems in the universe,” he said.

Haiyang Wang has received the Prime Minister’s Australia Asia Award to support his PhD research at ANU.

Reference:
Haiyang S. Wang et al. The elemental abundances (with uncertainties) of the most Earth-like planet, Icarus (2017). DOI: 10.1016/j.icarus.2017.08.024

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

Changes in Earth’s crust caused oxygen to fill the atmosphere

Matthijs Smit of the University of British Columbia examines ancient rocks from the deep crust in Norway during the summer of 2017. Credit: Matthijs Smit

Scientists have long wondered how Earth’s atmosphere filled with oxygen. UBC geologist Matthijs Smit and research partner Klaus Mezger may have found the answer in continental rocks that are billions of years old.

“Oxygenation was waiting to happen,” said Smit. “All it may have needed was for the continents to mature.”

Earth’s early atmosphere and oceans were devoid of free oxygen, even though tiny cyanobacteria were producing the gas as a byproduct of photosynthesis. Free oxygen is oxygen that isn’t combined with other elements such as carbon or nitrogen, and aerobic organisms need it to live. A change occurred about three billion years ago, when small regions containing free oxygen began to appear in the oceans. Then, about 2.4 billion years ago, oxygen in the atmosphere suddenly increased by about 10,000 times in just 200 million years. This period, known as the Great Oxidation Event, changed chemical reactions on the surface of the Earth completely.

Smit, a professor in UBC’s department of earth, ocean & atmospheric sciences, and colleague, professor Klaus Mezger of the University of Bern, were aware that the composition of continents also changed during this period. They set out to find a link, looking closely at records detailing the geochemistry of shales and igneous rock types from around the world — more than 48,000 rocks dating back billions of years.

“It turned out that a staggering change occurred in the composition of continents at the same time free oxygen was starting to accumulate in the oceans,” Smit said.

Before oxygenation, continents were composed of rocks rich in magnesium and low in silica — similar to what can be found today in places like Iceland and the Faroe Islands. But more importantly, those rocks contained a mineral called olivine. When olivine comes into contact with water, it initiates chemical reactions that consume oxygen and lock it up. That is likely what happened to the oxygen produced by cyanobacteria early in Earth’s history.

However, as the continental crust evolved to a composition more like today’s, olivine virtually disappeared. Without that mineral to react with water and consume oxygen, the gas was finally allowed to accumulate. Oceans eventually became saturated, and oxygen crossed into the atmosphere.

“It really appears to have been the starting point for life diversification as we know it,” Smit said. “After that change, the Earth became much more habitable and suitable for the evolution of complex life, but that needed some trigger mechanism, and that’s what we may have found.”

As for what caused the composition of continents to change, that is the subject of ongoing study. Smit notes that modern plate tectonics began at around the same time, and many scientists theorize that there is a connection.

Smit and Mezger published their findings today in the journal Nature Geoscience. The research was funded by the Natural Sciences and Engineering Research Council.

Reference:
Matthijs A. Smit & Klaus Mezger. Earth’s early O2 cycle suppressed by primitive continents. Nature Geosceince, 2017 DOI: 10.1038/ngeo3030

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

Tidal and mangrove deposits during the Oligo-Miocene in the South China Sea

Thick succession of mangrove-derived mudrock and associated coal, underlying tidally influenced channel sandstone. Nyalau Formation, Bintulu, Sarawak. Credit: M.H. Amir Hassan

A study on 22–18 million-year-old tidal deposits reveals insights on the significance of mangrove organic carbon sequestration in the South China Sea at geological time scales.

A collaborative study between geoscientists at the Department of Geology, University of Malaya, and the Department of Earth Science and Engineering, Imperial College London, have shown that tidally-generated deposits form significantly thick successions in the Neogene Sarawak Basin. In addition, tidal modelling using reconstructed palaeogeographic maps show that the South China Sea experienced the highest tides on Earth during the Oligo-Miocene, which explains the predominance of tidal deposits in the region. The work also highlights the importance of mangrove organic carbon burial in the South China Sea region as a major component of the global carbon cycle, and the importance of geologic processes (working at the scale of millions of years) in the sequestration of organic carbon.

The study (which is published in a special publication of the Geological Society, London) analysed 72 m of sedimentary rock of the Nyalau Formation exposed around Bintulu, Sarawak, and over 2,000 m of core samples extracted from oil-bearing fields of the Balingian Province, offshore Sarawak (courtesy of PETRONAS). The team has concluded that 22 – 18 million years ago, the Sarawak Basin formed a large, embayed coast, with numerous rivers supplying sediment to the basin. Abundant tidal signatures in the deltaic sediments indicate significant tidal influence.

The results of the sedimentological analysis were also published in Nature Communications, led by Imperial College with collaborations from University of Malaya, University of York and Brunei Darussalam. The researchers looked at the distribution of mangrove coals and mudrocks, which are closely associated with the tidal deposits. Widespread distribution of tidal and mangrove deposits (ranging in age between 15.5 to 11.7 Ma) indicate a predominantly tidally-influenced setting for the South China Sea shelf and associated coastline during the Oligo-Miocene. Oligo-Miocene age, mangrove-derived coals and mudrocks are also widespread throughout the peripheral South China Sea basins, where they form important oil-and-gas source rocks.

Utilizing data on the volume of hydrocarbons (oil and gas) in place, the total volume of sediments that have accumulated in the South China Sea basins and the subsidence history of the basins since the Oligocene, the authors estimate that the organic carbon storage in peripheral South China Sea basins exceeded 4,000 Gt, or equivalent to 2,000 p.p.m of atmospheric CO2.

The researchers are now in the process expanding the work by collecting more data in the northern Borneo region, especially in poorly accessible locations, in order to refine the current palaeogeographic and palaeohydrodynamic models for the Neogene South China Sea.

Reference:
Meor H. Amir Hassan et al. Sedimentology and stratigraphic architecture of a Miocene retrogradational, tide-dominated delta system: Balingian Province, offshore Sarawak, Malaysia, Geological Society, London, Special Publications (2016). DOI: 10.1144/SP444.12

Meor H. Amir Hassan et al. Sedimentology and stratigraphic development of the upper Nyalau Formation (Early Miocene), Sarawak, Malaysia: A mixed wave- and tide-influenced coastal system, Journal of Asian Earth Sciences (2012). DOI: 10.1016/j.jseaes.2012.12.018

Daniel S. Collins et al. Tidal dynamics and mangrove carbon sequestration during the Oligo–Miocene in the South China Sea, Nature Communications (2017). DOI: 10.1038/ncomms15698

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

Lava flows from Kamokuna ocean entry, Hawai’i

August 31, 2017 ـــ These flows are about a 45 minute hike inland from the Kamokuna ocean entry and are inside the park boundary.

Video Copyright © NPS/Janice Wei

Kamokuna ocean entry

Kamokuna ocean entry is a Lava deltas, similar to river deltas form wherever sufficient sub-aerial flows of lava enter standing bodies of water. The lava cools and breaks up as it encounters the water, with the resulting fragments filling in the adjacent seabed topography such that the flow can move further offshore sub-aerially. Lava deltas are generally associated with large-scale, effusive type basaltic volcanism.

Lava deltas are found mainly associated with volcanic islands, particularly those formed at hotspots as they produce the necessary effusive basaltic flows.

The largest lava delta systems known are associated with formation of volcanic type passive margins. Just prior to break-up along the northern Atlantic in the late Paleocene, massive eruptions occurred along the eventual line of break-up. This volcanism, part of the North Atlantic Igneous Province, led to the formation of two extensive lava escarpments, interpreted as deltas, extending from the Faeroes onto the More Margin (the Faeroe-Shetland escarpment) and the Vøring escarpment on the Vøring margin, a combined distance of approximately 1000 km. As these deltas were prograding into water of relatively constant depth, they were able to extend as much as 25 km from their original vents.

Ancestor of sea reptile super-predators found in Germany

Credit: Uppsala universitet

A new species of extinct sea monster from the Early Jurassic has been identified by a team of German and Swedish researchers. The fossilized bones were found in a clay pit near the city of Bielefeld in Germany. The findings will be published in the journal Alcheringa.

The fossilized bones of a plesiosaur, an extinct long-necked marine reptile from the Age of Dinosaurs, have been identified by paleontologists from the Naturkunde-Museum Bielefeld in Germany and Uppsala University in Sweden. The remains are about 190 million years old and were excavated in the early 1980s.

The new find was named Arminisaurus schuberti after the ancient Germanic chieftain Arminius, who defeated the Roman legions at Teutoburg Forest near Bielefeld in 9 AD, and Siegfried Schubert, the amateur paleontologist who secured the specimen for scientific study.

Another extinct sea reptile from Germany was named by the same research team only last month.

“Plesiosaurs were amongst the most successful marine predators from the Age of Dinosaurs. Some, such as the famous Liopleurodon, were colossal predators up to 15 metres long. They were the equivalent of White sharks and Killer whales in the oceans today” said Sven Sachs, a researcher at the Naturkunde-Museum Bielefeld and author on the study.

By comparison, Arminisaurus was small, only about 3-4 metres long, and probably hunted fish, squid and other small prey in the ancient seas that covered Germany during the Jurassic period.

The preserved bones of Arminisaurus were broken up by mining machinery, but enough was recovered to classify the animal as an early relative of later Jurassic plesiosaur super predators known as pliosaurids. About 40 percent of the skeleton was recovered, including parts of the skull, vertebrae and limb bones.

“Arminisaurus is significant because it dates from a timeframe early in the Jurassic, during which we have very few identifiable plesiosaur fossils” said Benjamin Kear, Curator of Vertebrate Palaeontology at the Museum of Evolution at Uppsala University, and author on the study. “Only two other plesiosaur fossils have ever been named from this mysterious interval in plesiosaurian evolution, making Arminisaurus a very important new addition for the global record of the group”.

The study also showed that Arminisaurus shared features with plesiosaurs that lived 50 million years later, during the Cretaceous period. This information will help unravel the radiation of these bizarre marine reptiles, and shed light on the early diversity of the gigantic pliosaurids.

The paper describing Arminisaurus is published in a forthcoming special issue of the Australasian palaeontology journal Alcheringa, which showcases some of the latest research on ancient marine reptiles. The skeleton will be put on display as a centerpiece in the Naturkunde-Museum Bielefeld in Bielefeld, Germany.

Reference:
Sven Sachs et al. A rare new Pliensbachian plesiosaurian from the Amaltheenton Formation of Bielefeld in northwestern Germany, Alcheringa: An Australasian Journal of Palaeontology (2017). DOI: 10.1080/03115518.2017.1367419

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

Measuring the strength of olivine, the most abundant mineral in the Earth’s mantle

Olivine, the most abundant mineral found in the Earth’s mantle, is considered to be a robust model of the interior of the Earth’s composition. Credit: Evan Krape/ University of Delaware

University of Delaware professor Jessica Warren and colleagues from Stanford University, Oxford University and University of Pennsylvania, reported new data that material size-effects matter in plate tectonics.

Plate tectonics, the way the Earth’s plates move apart and come back together, has been used since the 1960s to explain the location of volcanoes and earthquakes.

The study published Wednesday, Sept. 13 in the American Association for the Advancement of Science journal Science Advances, resolves 40 years of disagreement in datasets about the strength of olivine, the most abundant mineral found in the upper 250 miles or so of the Earth, known as the mantle.

“Measuring the strength of olivine is critical to understanding how strong tectonic plates are, which, in turn, matters to how plates break and create subduction zones like those along the Cascadia plate, which runs down the west coast of Canada to the west coast of the United States,” said Warren, a geologist in the College of Earth, Ocean, and Environment. It’s also important for understanding how plates move around over the million-year time scales.

The paper demonstrated that olivine’s strength is size-sensitive and that olivine is stronger the smaller the volume that is measured, something that has been known in materials science for many metals and ceramics, but has not been studied in a geological material before.

Warren explained that the problem with studying rocks on the earth’s surface is that they are no longer subjected to the high pressures found inside the earth that cause materials to flow (like ice in a glacier). Recreating these elevated pressures in the laboratory is difficult, making it hard for scientists to study material strength in the lab.

The researchers used a technique, called instrumented nanoindentation, to measure olivine’s strength. The technique allowed them to recreate pressure conditions similar to those inside the earth by pressing a diamond tip that was carefully machined to a specific geometry into the olivine crystal to measure the material’s response. The diamond tips ranged in size from 5 to 20 microns (0.000001 meter). The researchers performed hundreds of indentation tests on tiny olivine crystals less than a centimeter square and found that the olivine crystal became weaker as the size of the diamond tip increased.

To validate this size-effect, the researchers reviewed the available literature data on the strength of olivine to determine the sizes and areas that had been tested in previous experiments dating to the late 1970s. The size-effect showed up in the old data, too.

“The reason 40 years’ worth of data don’t agree from one experiment to the next is because scientists were measuring different sizes or areas of olivine,” Warren said. “But if you plot the same information as a function of the sample size, the datasets, in fact agree, and display the same general trend — the larger the indentation in the material tested, the weaker the olivine becomes.”

Now that Warren and her colleagues understand this size-effect, they are turning their attention to how temperature affects the strength of olivine, and more broadly, on where tectonic plates might break and give rise to potential subduction zones.

Temperatures inside the earth are much hotter than on the surface and can range from 1,470 to 2,200 degrees Fahrenheit (800 to 1,200 degrees Celsius).

The team also will consider what role water plays in the structure of olivine minerals and rocks in the earth. According to Warren, current estimates suggest the earth contains the equivalent of 50 percent to 4 times the amount of water found in the global ocean.

“When geologists look at how faults buckle and deform, it is at a very small length scale where conditions in size effect really matter, just like our olivine tests in the laboratory,” Warren said. “But this size effect disappears when you get to a large enough length scale on tectonic plates, so we need to consider other things like when temperature and water begin to play a role.”

Reference:
Size effects resolve discrepancies in 40 years of work on low-temperature plasticity in olivine. DOI: 10.1126/sciadv.1701338

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

Celebrity fossil reveals all for science

Agnostus pisiformis. Credit: Esben Horn

With the help of an artist, a geology professor at Lund University in Sweden has figuratively speaking breathed life into one of science’s most well-known fossil species; Agnostus pisiformis. The trilobite-like arthropod lived in huge numbers in Scandinavia a half-billion years ago. Today, this extinct species provides important clues for science in several ways.

Despite its small size, Agnostus pisiformis is a remarkable and useful fossil. The extinct animal was just one centimetre in size when adult, but has been found exceptionally well-preserved and in large numbers. And it is not only the outer hard shells — even the animal’s soft tissue has been found so well preserved that it is possible to create extremely detailed sculptures that show what the tiny creature looked like.

“The sculptures have been greatly scaled up and show the animal’s complete anatomy down to the smallest detail, including all the extremities and antennae,” says Mats E. Eriksson, geology professor at Lund University.

Eriksson’s research focuses mainly on microscopic fossils and attempts, among other things, to reconstruct ecosystems that are several hundred million years old.

The sculptures were created in connection with a research article he wrote on Agnostus pisiformis. He was assisted by the Danish artist and designer, Esben Horn, whose company, 10 Tons, specialises in producing lifelike sculptures of both extant and extinct organisms for museums and institutions around the world.

The ancient Agnostus pisiformis is mainly known from Scandinavia, but it has been recorded also elsewhere, for example in England and Russia. Due to the fact that the species only lived for a limited period of time just over 500 million years ago, it is possible to use the fossilto date various rocks, which explains why Agnostus pisiformis is a celebrity within science.

However, the species is not only useful for researchers as a time reference, as it also gives them valuable insights into ancient life on Earth. This fossil is so well-preserved and occursin such large numbers that it is possible to understand its complete development, from juvenile to adult.

“The incredible degree of preservational detail means that we can grasp the entire anatomy of the animal, which in turn reveals a lot about its ecology and mode of life,” says Mats E. Eriksson.

He now hopes that the sculptures of Agnostus pisiformis will become part of a travelling exhibition on the long lost faunas that existed in the oceans more than 500 million years ago. He wants to spread the knowledge about early lifeduring what he regards as a very exciting time in Earth history. He also wants to highlight that palaeontology, that is, the study of fossils, is not just about dinosaurs.

“There were actually ecosystems seething with fantastic and bizarre life forms several hundred million years before the dinosaurs even appeared,” concludes Mats E. Eriksson.

Reference:
Mats E. Eriksson, Esben Horn. Agnostus pisiformis — a half a billion-year old pea-shaped enigma. Earth-Science Reviews, 2017; 173: 65 DOI: 10.1016/j.earscirev.2017.08.004

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

Tectonic plates ‘weaker than previously thought,’ say scientists

Researchers experimented on olivine crystals to help determine the strength of tectonic plates. Credit: Lars Hansen

Experiments carried out at Oxford University have revealed that tectonic plates are weaker than previously thought. The finding explains an ambiguity in lab work that led scientists to believe these rocks were much stronger than they appeared to be in the natural world. This new knowledge will help us understand how tectonic plates can break to form new boundaries.

Study co-author Lars Hansen, Associate Professor of Rock and Mineral Physics in Oxford University’s Department of Earth Sciences, said: “The strength of tectonic plates has been a major target of research for the past four decades. For plate tectonics to work, plates must be able to break to form new plate boundaries. Significant effort has gone into measuring the strength of the key olivine-rich rocks that make up plates using laboratory experiments.

“Unfortunately, those estimates of rock strength have been significantly greater than the apparent strength of plates as observed on Earth. Thus, there is a fundamental lack of understanding of how plates can actually break to form new boundaries. Furthermore, the estimates of rock strength from laboratory experiments exhibit considerable variability, reducing confidence in using experiments to estimate rock properties.”

The new research, published in the journal Science Advances, uses a technique known as ‘nanoindentation’ to resolve this discrepancy and explain how the rocks that make up tectonic plates can be weak enough to break and form new plate boundaries.

Dr Hansen said: “We have demonstrated that this variability among previous estimates of strength is a result of a special length-scale within the rocks – that is, the strength depends on the volume of material being tested. To determine this we used nanoindentation experiments in which a microscopic diamond stylus is pressed into the surface of an olivine crystal. These experiments reveal that the strength of the crystal depends on the size of the indentation.

“This concept translates to large rock samples, for which the measured strength increases as the size of the constituent crystals decreases. Because most previous experiments have used synthetic rocks with crystal sizes much smaller than typically found in nature, they have drastically overestimated the strength of tectonic plates. Our results therefore both explain the wide range of previous estimates of rock strength and provide confirmation that the strength of the rocks that make up tectonic plates is low enough to form new plate boundaries.”

The study was an international collaboration involving scientists from Stanford University, the University of Pennsylvania, Oxford University and the University of Delaware.

Dr Hansen added: “This result has implications beyond forming tectonic plate boundaries. Better predictions of the strength of rocks under these conditions will help inform us on many dynamic processes in plates. For instance, we now know that the evolution of stresses on earthquake-generating faults likely depends on the size of the individual crystals that make up the rocks involved. In addition, flexing of plates under the weight of volcanoes or large ice sheets, a process intimately linked to sea level on Earth, will also ultimately depend on crystal size.”

Reference:
“Size effects resolve discrepancies in 40 years of work on low-temperature plasticity in olivine” Science Advances (2017). DOI: 10.1126/sciadv.1701338

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

‘Mysterious’ ancient creature was definitely an animal, research confirms

A Dickinsonia fossil was first described in 1947. Credit: Alex Liu

It lived well over 550 million years ago, is known only through fossils and has variously been described as looking a bit like a jellyfish, a worm, a fungus and lichen. But was the ‘mysterious’ Dickinsonia an animal, or was it something else?

A new study by researchers at the universities of Oxford, Cambridge, Bristol, and the British Geological Survey provides strong proof that Dickinsonia was an animal, confirming recent findings suggesting that animals evolved millions of years before the so-called Cambrian Explosion of animal life.

The study is published in the journal Proceedings of the Royal Society B.

Lead author on the paper is Dr Renee Hoekzema, a PhD candidate in Oxford University’s Mathematical Institute who carried out this research while completing a previous PhD in Oxford’s Department of Earth Sciences. She said: “Dickinsonia belongs to the Ediacaran biota – a collection of mostly soft-bodied organisms that lived in the global oceans between roughly 580 and 540 million years ago. They are mysterious because despite there being around 200 different species, very few of them resemble any living or extinct organism, and therefore what they were, and how they relate to modern organisms, has been a long-standing palaeontological mystery.”

In 1947, Dickinsonia became one of the first described Ediacaran fossils and was initially thought to be an organism similar to a jellyfish. Since then, its strange body plan has been compared to that of a worm, a placozoan, a bilaterian and several non-animals including fungi, lichens and even entirely extinct groups.

Co-author Dr Alex Liu, from the Department of Earth Sciences at the University of Cambridge, said: “Discriminating between these different hypotheses has been difficult, as there are so few morphological features in Dickinsonia to compare to modern organisms. In this study we took the approach of looking at populations of this organism, including assumed juvenile and adult individuals, to assess how it grew and to try to work out how to classify it from a developmental perspective.”

The research was carried out on the basis of a widely held assumption that growth and development are ‘conserved’ within lineages – in other words, the way a group of organisms grows today would not have changed significantly from the way its ancestors grew millions of years ago.

Dickinsonia is composed of multiple ‘units’ that run down the length of its body. The researchers counted the number of these units in multiple specimens, measured their lengths and plotted these against the relative ‘age’ of the unit, assuming growth from a particular end of the organism. This data produced a plot with a series of curves, each of which tracked how the organism changed in the size and number of units with age, enabling the researchers to produce a computer model to replicate growth in the organism and test previous hypotheses about where and how growth occurred.

Dr Hoekzema said: “We were able to confirm that Dickinsonia grows by both adding and inflating discrete units to its body along its central axis. But we also recognised that there is a switch in the rate of unit addition versus inflation at a certain point in its life cycle. All previous studies have assumed that it grew from the end where each “unit” is smallest, and was therefore considered to be youngest. We tested this assumption and interpreted our data with growth assumed from both ends, eventually coming to the conclusion that people have been interpreting Dickinsonia as having grown at the wrong end for the past 70 years.

“When we combined this growth data with previously obtained information on how Dickinsonia moved, as well as some of its morphological features, we were able to reject all non-animal possibilities for its original biological affinity and show that it was an early animal, belonging to either the Placozoa or the Eumetazoa.

“This is one of the first times that a member of the Ediacaran biota has been identified as an animal on the basis of positive evidence.”

Dr Liu added: “This finding demonstrates that animals were present among the Ediacaran biota and importantly confirms a number of recent findings that suggest animals had evolved several million years before the “Cambrian Explosion” that has been the focus of attention for studies into animal evolution for so long.

“It also allows Dickinsonia to be considered in debates surrounding the evolution and development of key animal traits such as bilateral symmetry, segmentation and the development of body axes, which will ultimately improve our knowledge of how the earliest animals made the transition from simple forms to the diverse range of body plans we see today.”

Reference:
Renee S. Hoekzema et al, Quantitative study of developmental biology confirms Dickinsonia as a metazoan, Proceedings of the Royal Society B: Biological Sciences (2017). DOI: 10.1098/rspb.2017.1348

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

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