The Hunga Tonga–Hunga Haʻapai eruption as seen by Japan’s Himawari-8 satellite on 15 January 2022. Top image: Eruption at 4:20 UTC (about 15 minutes into the eruption); Middle image: Eruption at 4:50 UTC (45 minutes into the eruption); Bottom image: Eruption at 5:40 UTC (1 hour 35 minutes into the eruption). Image credit: Simon Proud / STFC RAL Space / NCEO / JMA.
Using images captured by satellites, researchers in the University of Oxford’s Department of Physics and RAL Space have confirmed that the January 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano produced the highest-ever recorded plume. The colossal eruption is also the first to have been directly observed to have broken through to the mesosphere layer of the atmosphere. The results have been published today in the journal Science.
On 15 January 2022, Hunga Tonga-Hunga Ha’apai a submarine volcano in the Tongan archipelago in the southern Pacific Ocean, violently erupted. The explosion was one of the most powerful ever observed, sending shock waves around the world and triggering devastating tsunamis that left thousands homeless. A towering column of ash and water was ejected into the atmosphere — but until now, scientists lacked an accurate way to measure just how tall this was.
Normally, the height of a volcanic plume can be estimated by measuring the temperature recorded at the top by infrared-based satellites and comparing this to a reference vertical temperature profile. This is because in the troposphere (the first and lowest layer of the Earth’s atmosphere), temperature decreases with height. But if the eruption is so large that the plume penetrates into the next layer of the atmosphere (the stratosphere), this method becomes ambiguous because the temperature begins to increase again with height (due to the ozone layer absorbing solar ultraviolet radiation).
To overcome this problem, the researchers used a novel method based on a phenomenon called ‘the parallax effect’. This is the apparent difference in an object’s position when viewed from multiple lines of sight. You can see this for yourself by closing your right eye, and holding out one hand with the thumb raised upwards. If you then switch eyes, so that your left is closed and your right is open, your thumb will appear to shift slightly against the background. By measuring this apparent change in position and combining this with the known distance between your eyes, you can calculate the distance to your thumb.
The location of the Tonga volcano is covered by three geostationary weather satellites, so the researchers were able to apply the parallax effect to the aerial images these captured. Crucially, during the eruption itself, the satellites recorded images every 10 minutes, enabling the rapid changes in the plume’s trajectory to be documented.
The results showed that the plume reached an altitude of 57 kilometres at its highest extent. This is significantly higher than the previous record-holders: the 1991 eruption of Mount Pinatubo in the Philippines (40 km at its highest point), and the 1982 eruption of El Chichón in Mexico (31 km). It also makes the plume the first observational evidence of a volcanic eruption injecting material through the stratosphere and directly into the mesosphere, which starts at about 50 km above the Earth’s surface.
Lead author Dr Simon Proud (University of Oxford, RAL Space and the National Centre for Earth Observation), said: ‘It’s an extraordinary result as we have never seen a cloud of any type this tall before. Furthermore, the ability to estimate the height in the way we did (using the parallax method) is only possible now that we have good satellite coverage. It wouldn’t have been possible a decade or so ago.’
The Oxford researchers now intend to construct an automated system to compute the heights of volcano plumes using the parallax method. Co-author Dr Andrew Prata from the Sub-department of Atmospheric, Oceanic & Planetary Physics added: ‘We’d also like to apply this technique to other eruptions and develop a dataset of plume heights that can be used by volcanologists and atmospheric scientists to model the dispersion of volcanic ash in the atmosphere. Further science questions that we would like to understand are: Why did the Tonga plume go so high? What will be the climate impacts of this eruption? And what exactly was the plume composed of?’
Besides the University of Oxford, the study also involved the Rutherford Appleton Laboratory and National Centre for Earth Observation in Harwell, and Munich University of Applied Sciences.
Reference:
Simon R. Proud, Andrew T. Prata, Simeon Schmauß. The January 2022 eruption of Hunga Tonga-Hunga Ha’apai volcano reached the mesosphere. Science, 2022; 378 (6619): 554 DOI: 10.1126/science.abo4076
Scallop Pleuronectites from the Triassic period with fluorescent colour pattern; left under normal light, right under UV light. Photo: Klaus Wolkenstein
UV light makes it possible to see intricate structures of fossils that are barely visible in normal daylight. This method has often been used on the fossilised seashells from the Earth’s current geological era to reveal patterns of colour that had long since faded away. Now, research by a scientist from the University of Göttingen shows that fluorescent colour patterns can even be found in shells that are around 240 million years old, from the Earth’s Mesozoic Era. This makes them the oldest fluorescent colour patterns found so far. The results of this study have been published in the journal Palaeontology.
In fossils from the Mesozoic Era, traces of colour patterns are very rarely observed. However, the investigation with UV light of scallops from the Triassic period — right from the beginning of the Mesozoic Era — shows that colour patterns are preserved much more frequently than previously thought. UV light, which is invisible to the human eye, excites organic compounds in the fossils causing them to glow. This reveals a surprising variety of colour patterns: different variations of stripes, zigzags and flame patterns. The diversity of colour patterns is similar to those of today’s seashells found on a beach.
However, the colour patterns of today’s scallops do not show any fluorescence. “In the case of the Triassic shells, fluorescent compounds were only formed in the course of fossilisation through oxidation of the original pigments,” explains Dr Klaus Wolkenstein from the Geosciences Centre at the University of Göttingen, who is currently carrying out research at the University of Bonn. Surprisingly, the fossil shells show different fluorescent colours, depending on the region where they were found. “The colour spectrum ranges from yellow to red with all the transitions in between, which suggests that there were clear regional differences in the fossilisation of these scallops,” adds Wolkenstein.
Reference:
Klaus Wolkenstein. Fluorescent colour patterns in the basal pectinid Pleuronectites from the Middle Triassic of Central Europe: origin, fate and taxonomic implications of fluorescence. Palaeontology, 2022; 65 (5) DOI: 10.1111/pala.12625
There are several theories about how the Earth and the Moon were formed, most involving a giant impact. They vary from a model where the impacting object strikes the newly formed Earth a glancing blow and then escapes, through to one where the collision is so energetic that both the impactor and the Earth are vaporized.
Now scientists at the University of Leeds and the University of Chicago have analysed the dynamics of fluids and electrically conducting fluids and concluded that the Earth must have been magnetized either before the impact or as a result of it.
They claim this could help to narrow down the theories of the Earth-Moon formation and inform future research into what really happened.
Professor David Hughes, an applied mathematician in the School of Mathematics at the University of Leeds, said: “Our new idea is to point out that our theoretical understanding of the Earth’s magnetic field today can actually tell us something about the very formation of the Earth-Moon system.
“At first glance, this seems somewhat surprising, and previous theories had not recognized this potentially important connection.”
This new assessment is based on the resilience of Earth’s magnetic field, which is maintained by a rotating and electrically conducting fluid in the outer core, known as a geodynamo.
Professor Fausto Cattaneo, an astrophysicist at the University of Chicago, said: “A peculiar property of the Earth’s dynamo is that it can maintain a strong magnetic field but not amplify a weak one.
The scientists therefore concluded that if the Earth’s field were to get switched off, or even reduced to a very small level, it would not have the capability to kick in again.
“It is this remarkable feature that allows us to make deductions about the history of the early Earth; including, possibly, how the Moon was formed,” added Professor Cattaneo.
Professor Hughes added: “And if that is true, then you have to think, where did the Earth’s magnetic field come from in the first place?
“Our hypothesis is that it got to this peculiar state way back at the beginning, either pre-impact or as an immediate result of the impact.
“Either way, any realistic model of the formation of the Earth-Moon system must include magnetic field evolution. ”
Reference:
Fausto Cattaneo, David W. Hughes. How was the Earth–Moon system formed? New insights from the geodynamo. Proceedings of the National Academy of Sciences, 2022; 119 (44) DOI: 10.1073/pnas.2120682119
Paleohistological transverse sections of select elements of (A) large- and (B) medium-bodied individuals of the Eutaw ornithomimosaurs, and (C) relative body-size of the Eutaw ornithomimosaurs within known ornithomimosaur taxa through a geological time. Credit: Tsogtbaatar et al., CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
Ostrich-like dinosaurs called ornithomimosaurs grew to enormous sizes in ancient eastern North America, according to a study published October 19, 2022 in the open-access journal PLOS ONE by Chinzorig Tsogtbaatar of the North Carolina Museum of Natural Sciences and colleagues.
During the Late Cretaceous Period, North America was split by a seaway into two landmasses: Laramidia to the west and Appalachia to the east. But fossils from Appalachia are rare, and therefore ancient ecosystems from this region are poorly understood. In this study, Chinzorig and colleagues describe new fossils of ornithomimosaur dinosaurs from the Late Cretaceous Eutaw Formation of Mississippi.
Ornithomimosaurs, the so-called “bird-mimic” dinosaurs, were superficially ostrich-shaped with small heads, long arms, and strong legs. The new fossils, including foot bones, are around 85 million years old, making them a rare glimpse into a poorly known interval of North American dinosaur evolution
By comparing the proportions of these fossils and the patterns of growth within the bones, the authors determined that the fossils likely represent two different species of ornithomimosaurs, one relatively small and one very large. They estimate the larger species to have weighed over 800 kg, and the individual examined was likely still growing when it died. This makes it among the largest ornithomimosaurs known.
These fossils provide valuable insights into the otherwise poorly understood dinosaur ecosystems of Late Cretaceous eastern North America. They also shed light on ornithomimosaur evolution; giant body sizes and multiple species living side-by-side are recurring trends for these dinosaurs across North America and Asia. Further study will hopefully elucidate the reasons behind the success of these life strategies.
The authors add: “The co-existence of medium- and large-bodied ornithomimosaur taxa during the Late Cretaceous Santonian of North America does not only provide key information on the diversity and distribution of North American ornithomimosaurs from the Appalachian landmass, but it also suggests broader evidence of multiple cohabiting species of ornithomimosaurian dinosaurs in Late Cretaceous ecosystems of Laurasia.”
Reference:
Chinzorig Tsogtbaatar, Thomas Cullen, George Phillips, Richard Rolke, Lindsay E. Zanno. Large-bodied ornithomimosaurs inhabited Appalachia during the Late Cretaceous of North America. PLOS ONE, 2022; 17 (10): e0266648 DOI: 10.1371/journal.pone.0266648
Note: The above post is reprinted from materials provided by PLOS.
New research analyzing pieces of the most ancient rocks on the planet adds some of the sharpest evidence yet that Earth’s crust was pushing and pulling in a manner similar to modern plate tectonics at least 3.25 billion years ago. The study also provides the earliest proof of when the planet’s magnetic north and south poles swapped places.
The two results offer clues into how such geological changes may have resulted in an environment more conducive to the development of life on the planet.
The work, described in PNAS and led by Harvard geologists Alec Brenner and Roger Fu, focused on a portion of the Pilbara Craton in western Australia, one of the oldest and most stable pieces of the Earth’s crust. Using novel techniques and equipment, the researchers show that some of the Earth’s earliest surface was moving at a rate of 6.1 centimeters per year and 0.55 degrees every million years.
That speed more than doubles the rate the ancient crust was shown to be moving in a previous study by the same researchers. Both the speed and direction of this latitudinal drift leaves plate tectonics as the most logical and strongest explanations for it.
“There’s a lot of work that seems to suggest that early in Earth’s history plate tectonics wasn’t actually the dominant way in which the planet’s internal heat gets released as it is today through the shifting of plates,” said Brenner, a Ph.D. candidate in the Graduate School of Arts and Sciences and member of Harvard’s Paleomagnetics Lab. “This evidence lets us much more confidently rule out explanations that don’t involve plate tectonics.”
For example, the researchers can now argue against phenomena called “true polar wander” and “stagnant lid tectonics,” which can both cause the Earth’s surface to shift but aren’t part of modern-style plate tectonics. The results lean more toward plate tectonic motion because the newly discovered higher rate of speed is inconsistent with aspects of the other two processes.
In the paper, the scientists also describe what’s believed to be the oldest evidence of when Earth reversed its geomagnetic fields, meaning the magnetic North and South Pole flipped locations. This type of flip-flop is a common occurrence in Earth’s geologic history with the pole’s reversing 183 times in the last 83 million years and perhaps several hundred times in the past 160 million years, according to NASA.
The reversal tells a great deal about the planet’s magnetic field 3.2 billion years ago. Key among these implications is that the magnetic field was likely stable and strong enough to keep solar winds from eroding the atmosphere. This insight, combined with the results on plate tectonics, offers clues to the conditions under which the earliest forms of life developed.
“It paints this picture of an early earth that was already really geodynamically mature,” Brenner said. “It had a lot of the same sorts of dynamic processes that result in an Earth that has essentially more stable environmental and surface conditions, making it more feasible for life to evolve and develop.”
Today, the Earth’s outer shell consists of about 15 shifting blocks of crust, or plates, which hold the planet’s continents and oceans. Over eons the plates drifted into each other and apart, forming new continents and mountains and exposing new rocks to the atmosphere, which led to chemical reactions that stabilized Earth’s surface temperature over billions of years.
Evidence of when plate tectonics started is hard to come by because the oldest pieces of crust are thrust into the interior mantle, never to resurface. Only 5 percent of all rocks on Earth are older than 2.5 billion years old, and no rock is older than about 4 billion years.
Overall, the study adds to growing research that tectonic movement occurred relatively early in Earth’s 4.5-billion-year history and that early forms of life came about in a more moderate environment. Members of the project revisited the Pilbara Craton in 2018, which stretches about 300 miles across. They drilled into the primordial and thick slab of crust there to collect samples that, back in Cambridge, were analyzed for their magnetic history.
Using magnetometers, demagnetizing equipment, and the Quantum Diamond Microscope — which images the magnetic fields of a sample and precisely identifies the nature of the magnetized particles — the researchers created a suite of new techniques for determining the age and way the samples became magnetized. This allows the researchers to determine how, when, and which direction the crust shifted as well as the magnetic influence coming from Earth’s geomagnetic poles.
The Quantum Diamond Microscope was developed in a collaboration between Harvard researchers in the Departments of Earth and Planetary Sciences (EPS) and of Physics.
For future studies, Fu and Brenner plan keep their focus on the Pilbara Craton while also looking beyond it to other ancient crusts around the world. They hope to find older evidence of modern-like plate motion and when the Earth’s magnetic poles flipped.
“Finally being able to reliably read these very ancient rocks opens up so many possibilities for observing a time period that often is known more through theory than solid data,” said Fu, professor of EPS in the Faculty of Arts and Sciences. “Ultimately, we have a good shot at reconstructing not just when tectonic plates started moving, but also how their motions — and therefore the deep-seated Earth interior processes that drive them — have changed through time.”
Reference:
Alec R. Brenner, Roger R. Fu, Andrew R. C. Kylander-Clark, George J. Hudak, Bradford J. Foley. Plate motion and a dipolar geomagnetic field at 3.25 Ga. Proceedings of the National Academy of Sciences, 2022; 119 (44) DOI: 10.1073/pnas.2210258119
Note: The above post is reprinted from materials provided by Harvard University. Original written by Juan Siliezar.
Jeholornis was a raven-sized bird that lived 120 million years ago, among the earliest examples of dinosaurs evolving into birds, in what’s now China. The fossils that have been found are finely preserved but smashed flat, the result of layers of sediment being deposited over the years. That means that no one’s been able to get a good look at Jeholornis’s head. But in a new study, researchers digitally reconstructed a Jeholornis skull, revealing details about its eyes and brain that shed light on its vision and sense of smell.
“Jeholornis is my favorite Cretaceous bird, it has a lot of unusual, primitive traits, and it helps shed light on the bigger story of how different birds evolved,” says Jingmai O’Connor, associate curator of fossil reptiles at the Field Museum and one of the authors of the paper describing the discovery in the Zoological Journal of the Linnean Society. “This study is the first time we’re really getting at what this bird’s skull looked like, what its brain must have been like, which is really exciting.”
The study’s first author, Han Hu, went through roughly 100 fossils at China’s Shandong Tianyu Museum of Nature and selected the one with the best-preserved skull — still a little flattened, but intact. “It is very difficult to find the right skull among around 100 fossils, since we won’t know if one skull will provide us the information we want before the scanning, and due to the costs of high quality scanning, we couldn’t scan all those specimens to choose the best one. However, I chose this one because at least from the exposed surface, it is relatively complete, and which is also important is that this skull is preserved to be isolated from other parts of its body,” says Hu, a researcher at the Department of Earth Sciences, University of Oxford, UK. “This is very helpful since we usually won’t chop the skull off from the skeleton if they are articulated — no one wants to hurt these previous fossils, but an isolated skull will reduce the size of the scanning area, which will increase the scanning quality a lot. Luckily, the specimen we chose here for this project is nearly a perfect one — it provided us so much unknown information after the digital reconstruction.”
“These bones were kind of like the bottom of a bag of potato chips — they weren’t completely crushed, but the pieces were compacted,” says O’Connor. “So we were able to CT scan them — essentially taking a bunch of X-rays and stacking them together to form a 3D image — and then digitally re-articulate them and reconstruct the skull from all these bones.”
“We were able to see different features of the skull that had never been seen before in Jeholornis, and we were even able to extrapolate what its brain looked like,” says co-author and Field Museum postdoctoral researcher Matteo Fabbri.
The brain itself isn’t preserved — soft tissues rarely are — but bird and dinosaur brains tend to nest neatly within their skulls. Knowing the shape and dimensions of a fossil bird’s skull, therefore, tells us a lot about its brain, kind of like how a glove gives a decent approximation of how a hand is shaped. What’s more, brain structures are conserved across species and over time — things like olfactory bulbs and the cerebellum in the same general spots whether you’re looking at the brain of a frog, a human, or a fossil bird.
Thanks to the long-standing placements of these structures, the researchers were able to determine how Jeholornis’s brain compares with modern birds and dinosaurs (or, strictly speaking, non-avian dinosaurs — all birds, including Jeholornis, are dinosaurs, but not all dinosaurs are birds).
“Jeholornis’s brain morphology is transitional, in-between what we see in non-avian dinosaurs and what we see in modern birds,” says Fabbri. “If you look at the skulls of dinosaurs, what you see is a spot for a very reptile-like brain, meaning that they have very large olfactory bulbs, and the optic lobes that are in the midbrain are reduced. They probably had a very good sense of smell and not great sight, which is very reptilian. And on the other hand, if you look at modern birds, they do the reverse. They have small olfactory bulbs, and very large optic lobes. Jeholornis falls in the middle.”
Jeholornis had bigger olfactory bulbs than most modern birds, meaning that it probably relied more on its sense of smell than birds today (with the exception of a few keen-smellers, like vultures). Jeholornis’s strong sense of smell makes sense in the context of another recent study by the team, showing that Jeholornis is the earliest-known fruit-eating animal. “As fruits ripen, they release lots of chemicals,” says O’Connor. “We can’t prove it yet, but having a better sense of smell might have helped Jeholornis find fruit.”
In addition to a brain adapted for smelling, the researchers found that Jeholornis was likely better at seeing in the daytime than at night. Birds have bones called scleral rings that help determine how much light goes into their eyes. Species that need to see at night, like owls, have wider scleral ring openings relative to their eye sockets, to let in more light; birds that are active during the day have narrower openings for light to go through, like the aperture on a camera. Jeholornis’s scleral rings seem to indicate that it was most active during the day.
All of these skull features ladder up to a better understanding of this early bird’s lifestyle and the role it played in its ecosystem. “Reconstructing a skull is painstaking work, and as people are starting to put in the time to do it, It’s becoming more and more clear that the evolution of birds was more complicated than what we expected,” says Fabbri. “It’s not just different from dinosaurs and modern birds, it’s different from other early birds too. It’s not a straightforward evolutionary story.”
“The same as Jingmai, Jeholornis is also one of my favorite birds. Its special position as one of the most primitive birds during the dinosaur-bird transition determines that completing its story will reveal the true scenery of that critical evolutionary period, and also, tell us why and how the modern birds — the only living dinosaurs — evolved to be what we see now.” says Hu.
Reference:
Han Hu, Yan Wang, Matteo Fabbri, Jingmai K O’Connor, Paul G Mcdonald, Stephen Wroe, Xuwei Yin, Xiaoting Zheng, Zhonghe Zhou, Roger B J Benson. Cranial osteology and palaeobiology of the Early Cretaceous bird Jeholornis prima (Aves: Jeholornithiformes). Zoological Journal of the Linnean Society, 2022; DOI: 10.1093/zoolinnean/zlac089
Derbyshire fossil study reveals insights into Peak District’s 12 million year-old climatic past
A decade-long study into unique rocks near a Derbyshire village has been uncovering the secrets of what the county and the Peak District might have looked like under a much warmer and wetter past.
Although first studied over 10 years ago, the most recent investigation into geological deposits near Brassington was initiated in 2019, with an international team of researchers from Northumbria University, the British Geological Survey, Morehead State University in the USA and CONICET in Argentina now assessing their latest findings.
The complex techniques used can analyse the fossil pollen of plants and spores of fungi captured within the rock layer, helping to form a picture of past habitats and reconstruct likely climatic conditions far beyond our most recent understanding of the Peak District.
With plants and fungi generally favouring particular conditions, researchers are able to determine what the environment may have looked like some 12 million years ago.
The results and insights are unique to the study location in Derbyshire, as there are no other rocks of a similar age anywhere else in the UK.
Gaining similar understanding to life and climate in Europe so far back would likely require analysis of rocks from Germany or the Netherlands and then assuming these were the same for Derbyshire and the Peak District.
The results from the Derbyshire site and similar studies have gone on to suggest that the UK may get wetter with climate change. Today Derbyshire has a mean annual temperature of around 8°C with up to 1000mm of rain a year, 12 million years ago it was 12-18°C with 1200-1400mm of rain. This doubling of temperature was with atmospheric carbon dioxide levels similar to those predicted for 2060. These differences in temperature and rainfall would fundamentally change the entire landscape. This highlights how important carbon capture is to avoid extreme changes in climate.
With some of the most extensive upland landscapes and peat bogs in the UK and globally, the Peak District is already at the forefront of carbon capture or ‘sequestration’ through conservation management and restoration programmes, but also has a role to play in mitigating the potential localised impacts of climate change through natural flood management.
Dr. Matthew Pound from Northumbria University, which was behind the study, said: “Fossil plants and fungi can tell us a lot about a place – even from 12 million years ago. That’s why when choosing a nice sunny holiday you’d always pick palm trees over Christmas trees, and why I always end up with green tomatoes in the north of England! The study suggests an anticipated warmer climate for the UK and therefore a wetter UK, which of course has implications for all of us; but also provides an opportunity to ensure landscapes like the Peak District and Derbyshire can be part of that resilience, not just for local communities but at scale as we manage the carbon in our environment.”
Anna Badcock, Team Leader for Cultural Heritage at the Peak District National Park added: “This work is incredibly powerful in helping us communicate ideas about landscape change. Researchers use fossil pollen for reconstructing past environments and understanding human impacts on landscape, but this is recent in geological terms. It’s wonderful that advances in this kind of analysis can also be used to help us understand climate and environments millions of years ago – we still have such an extraordinary amount to learn from fungi and plants, and about how our environments adapt.”
Chris Dean, Head of Moors for the Future Partnership based in the Peak District National Park added: “This study shows how our climate is changing, and with that comes an increased risk of flooding as we see more frequent extreme storm events. Moorland restoration and effective natural flood management strategies, such as planting sphagnum moss and blocking gullies to slow the flow of rainfall to the valleys, have never been more important.”
What is the structure of the Earth? For starters, it consists of several layers: the crust, the upper and lower mantle, and the core. The mantle makes up most of our planet’s volume—84%. The lower mantle represents 55% of the Earth’s volume—it is also hotter and denser than the upper mantle.
The lower mantle has played an important role in the Earth’s evolution, including how Earth has cooled over billions of years, how materials have been circulated, and how water is stored and transported from/to the deep interior over a geologic time scale.
For more than seven decades, the mineralogy of the lower mantle has been studied extensively. The decades of studies, including laboratory experiments, computational simulations, and the study of inclusions in deep diamonds, led to the conclusion that the lower mantle consists of three main minerals: bridgmanite, ferropericlase, and davemaoite.
In a study recently published in Nature, a team of scientists—including Byeongkwan Ko, former Ph.D. student at ASU, now a postdoctoral researcher at Michigan State University, and Sang-Heon Dan Shim, Professor at the School of Earth and Space Exploration and a Navrotsky Professor of Materials Research at ASU have completed a new high-pressure experiment employing some different styles of heating to reveal an additional mineral residing in the lower mantle.
Among these three main minerals, two minerals bridgmanite and davemaoite have both so-called perovskite-type crystal structures. This structure is also widely known in physics, chemistry, and materials engineering, as some materials with the perovskite-type structure have shown superconductivity.
At shallow depths, minerals with similar crystal structures often merge and become single minerals, typically under a high-temperature environment. For example, mineral diopside has both calcium and magnesium, and is stable in the crust. Despite the structural similarity, however, existing studies have shown that davemaoite, rich in calcium, and bridgmanite, rich in magnesium, remain separate throughout the lower mantle.
“Why davemaoite and bridgmanite do not merge to one despite the fact that they have very similar atomic-scale structures? This question has fascinated researchers over two decades,” said Shim. “Many attempts have been made to find conditions where these two minerals merge, yet the answer from experiments has been consistently two separate minerals. This where we felt we need some fresh new ideas in experiments.”
The new experiment was an opportunity for the research group to try various heating techniques to compare methods. Instead of increasing temperature slowly in conventional high-pressure experiments, they increased temperature very fast to the high temperature related to the lower mantle, reaching 3000–3500 F within a second. The reason for this was that once two perovskite-structured minerals form it becomes very difficult for them to merge even if they enter into temperature conditions where a single perovskite mineral should be stable.
By heating the samples fast to target temperatures, Ko and Shim were able to avoid formation of two perovskite-structured minerals at low temperatures. Once they reach the temperature of the lower mantle, they monitor what minerals form for 15–30 min using X-ray beams at the Advanced Photon Source. They found that only single perovskite mineral forms, unexpected from the previous experiments. They found that at sufficiently high temperatures greater than 3500 F, davemaoite and bridgmanite become a single mineral in the perovskite-type structure.
“It has been believed that a large size difference between calcium and magnesium, the major cations of davemaoite and bridgmanite, respectively, should hinder these two minerals from merging,” said Ko. “But our study shows that they can overcome such difference in hot environments.”
The experiments suggest that the deeper lower mantle with sufficiently high temperature should have a mineralogy different from the shallower lower mantle. Because the mantle was much warmer in early Earth, the group’s new results indicate that most of the lower mantle had a single perovskite-structured mineral then, which means the mineralogy differed from the present-day lower mantle.
This new observation has a range of substantial impacts on our understanding of the deep Earth. Many seismic observations have shown that the deeper lower mantle properties are different from the shallower lower mantle. The changes are reported to be gradual. The merge of bridgmanite and davemaoite is shown to be gradual in the research group’s experiments.
Also, the properties of a rock with three main minerals, bridgmanite, ferropericlase, and davemaoite, does not match well with the properties of the deeper lower mantle. Ko and collaborators predict that these unresolved problems can be explained by a merge of bridgmanite and davemaoite to a new single perovskite-structured mineral.
Reference:
Byeongkwan Ko et al, Calcium dissolution in bridgmanite in the Earth’s deep mantle, Nature (2022). DOI: 10.1038/s41586-022-05237-4
In 2010, two of the study’s authors—David Shuster of UC Berkeley (left) and Yosemite Park geologist Greg Stock (right)—collected rock samples from the rim of Yosemite Valley, where the granite has eroded only slowly over the last 50 million years. In the distance is the upper Merced River valley. Former UC Berkeley graduate student Johnny Webb is at center. Credit: Kurt Cuffey, UC Berkeley
First-time visitors to Yosemite Valley gape in awe at the sheer granite wall of El Capitan and the neatly sliced face of Half Dome, aware, perhaps vaguely, that rain and glaciers must have taken a long time to cut and sculpt that landscape. But how long?
Did it all start 50 million years ago, when the granite through which the valley cuts was first exposed to the elements? Was it 30 million years ago, when data suggest canyons in the southern Sierra Nevada began to form? Did the valley only begin to form after the Sierra tilted toward the west some 5 million years ago, or was it mostly due to glaciers that formed in a cooling climate 2 to 3 million years ago?
Geologists from the University of California, Berkeley, employed a novel technique of rock analysis to get a more precise answer, and concluded that much of Yosemite Valley’s impressive depth was carved since 10 million years ago, and most likely even more recently — over the past 5 million years. This shaves about 40 million years off the oldest estimates.
Rivers performed the initial carving in a preexisting shallow valley, they determined, and then both rivers and ice contributed recently.
While the scientists are unable to be more precise, the new estimate is the first to be based on an experimental study of the granite rocks in and near Yosemite, rather than on inferences based on what was going on elsewhere in the Sierra Nevada.
“Yosemite Valley is one of the most famous topographic features on the planet,” said glaciologist Kurt Cuffey, UC Berkeley professor of geography and of earth and planetary science. “And of course, if you go to Yosemite Park and read the signage, they will give you numbers for when it became a deep canyon. But up until this project, every single claim about how old this valley is, when it formed a deep canyon, was just based on assumptions and speculation.”
Yosemite National Park geologist Greg Stock admits that the story told about the origin of the park’s iconic granite topography has been a little vague, because geologists still do not agree about what has happened since the Sierra’s signature granite formed underground between about 80 and 100 million years ago, up to 10 kilometers (6 miles) under a mountain range that looked a lot different than it does today.
“We know that the Sierra was a high mountain range 100 million years ago, when the granite was forming at depth. It was a chain of volcanoes that might have looked a bit like the Andes Mountains in South America,” Stock said. “The question really is whether the elevation has just been coming down through erosion since that time or whether it came down some and then was uplifted again more recently. At this point, based on studies I’ve done for most of my career and supported by this study, I see a lot of evidence for recent uplift happening sometime in the last 5 million years.”
That uplift, which happened at the same time that earthquakefaulting in the eastern Sierra Nevada created an escarpment several kilometers high, steepened the western slopes and rivers, causing them to incise valleys more quickly.
Cuffey, UC Berkeley geochemist David Shuster and their colleagues, including Stock, published the findings this week in the journal Geological Society of America Bulletin.
Shuster, a professor of earth and planetary science, developed a technique 15 years ago that he thought at the time might shed light on the origins of the valley, something that has fascinated both him and Cuffey since they first saw Yosemite as kids. Shuster, a California native, has visited it since early childhood. Cuffey, from central Pennsylvania, made his first trip to the park at the age of 15.
Much of what they remember learning is that the valley was carved by glaciers, giving short shrift to what happened before Ice Age glaciers arrived in the Pleistocene some 2.5 million years ago.
“What I learned from the signage in the valley when I was a kid wasn’t quite right, given what the scientific literature said at the time. Nevertheless, the topography has been interpreted to be significantly modified by ice,” Shuster said. “How to quantify that with geochronological tools, rather than just make up a story about it based on geomorphology, is one thing we were trying to do here.”
Shuster’s technique, called helium-4/helium-3 thermochronometry, reconstructs the temperature history of a sample of rock based on the spatial distribution of natural helium-4 in minerals, which is measured by comparison to an artificially-produced uniform distribution of helium-3. Because temperature increases with depth underground, the temperature history can tell when a rock was uncovered as the landscape eroded.
“The temperature of the rock is a function of the surface lowering down into it,” Shuster said. “It’s very analogous to removing a down comforter — the rock beneath it progressively gets colder. This progression through time with the rock cooling is what we get from the geochemistry and thermochronometry.”
The expectation is that granite bedrock exposed on the broad uplands of the Sierra should show a long history of cool surface temperatures, since they’ve been exposed for tens of millions of years longer than bedrock more recently exposed on the floor of Tenaya Canyon, which feeds into Yosemite Valley from the northeast.
The experiments, conducted at the Berkeley Geochronology Center, indicated that, while rock from the uplands has been close to the surface for about 50 million years, bedrock at the bottom of Tenaya Canyon has been exposed much more recently. The temperature history of the rock obtained from the bottom of Tenaya Canyon — from an exposed area of bedrock at the base of Half Dome — indicates that it was more than a kilometer underground 10 million years ago, and most likely only 5 million years ago. This means that a kilometer of rock was eroded away since that time.
“This upland surface that people are familiar with from parts of the Tioga Road and Tuolumne Meadows — that’s a very old landscape,” said Cuffey, who is the Martin Distinguished Chair in Ocean, Earth and Climate Science. “The question is: What about the deep canyon? Is that also very old, or is it relatively young? And what we found in our study, our big contribution, is that it’s fairly young. The best guess for the timing is in the last 3 to 4 million years, but maybe as far back as 10 million years for the start of the rapid incision.”
Bedrock studies
The geologists collected samples of granite bedrock from nearby highlands and the bottom of Tenaya Canyon, but not from the bedrock bottom of Yosemite Valley itself, which lies buried under about 500 meters (1/3 mile) of sediment that today forms the valley floor. But since the two formed at the same time, one can infer the timing of the formation of Yosemite Valley from the time of the scouring of Tenaya Canyon.
“The brief history of Yosemite Valley would be that there was some kind of valley in place for tens of millions of years — a river-carved canyon associated with the ancient Sierra Nevada. And then, in the last 5 million years or so, renewed uplift of the range through westward tilting caused rivers to steepen and deepen the canyons that they were in,” Stock said. “So, that probably carved out more of Yosemite Valley and may have started forming Tenaya Canyon. And then in the last 2 to 3 million years, as the climate cooled and glaciers came down through Tenaya Canyon and into Yosemite Valley, they further sculpted the rock, deepening those valleys. And in the case of Yosemite Valley, widening it out considerably. So, there’s some component of an old Yosemite Valley. But I think this recent work shows that much more of that topography is younger, rather than older.”
Stock, who has held the position of park geologist for 17 years and is the park’s first geologist, said the new study will revise how the park tells the geological history of Yosemite Valley.
“The timing of this new study is perfect in the sense that, over the next several years, we’re hoping to completely redo the Geology Hut displays at Glacier Point. I’m very excited to include these new results in those displays,” he said. “It’s a perfect place to tell that story, because there’s a view straight up Tenaya Canyon.”
Reference:
Kurt M. Cuffey, Alka Tripathy-Lang, Matthew Fox, Greg M. Stock, David L. Shuster. Late Cenozoic deepening of Yosemite Valley, USA. GSA Bulletin, 2022; DOI: 10.1130/B36497.1
Using Mössbauer spectroscopy, Osaka Metropolitan University scientists investigate the iron ion status of pyroxenes, a major group of rock-forming silicate minerals. Their study revealed that in pyroxene crystals consisting of roughly 50% calcium, the tensor that determines the ratios of iron ions at the Mössbauer spectral peaks is independent of the iron content but dependent on the calcium content. Credit: Shinoda, OMU
Pyroxenes are a major group of rock-forming silicate minerals that generally contain calcium, magnesium, and iron. Given their abundance, elucidating the physical properties of pyroxenes is deemed vital in the study of rocks and minerals.
A research group led by Professor Keiji Shinoda from the Graduate School of Science at Osaka Metropolitan University investigated the status of iron ions in monoclinic pyroxenes, a type of calcium-rich pyroxenes, using Mössbauer spectroscopy on thin sections of single crystals. Their study revealed that in pyroxene crystals consisting of roughly 50% calcium, the tensor that determines the ratios of iron ions at the Mössbauer spectral peaks in the M1 sites — one of two types of cation positions in the pyroxene crystal structure — is independent of the iron content but dependent on the calcium content.
The results of this research have clarified one of the physical properties of pyroxenes. These findings might facilitate detailed future analysis of iron using Mössbauer spectroscopy on mineral flakes.
“We had expected that the tensor that determines the ratios at the Mössbauer spectral peaks would change if the iron solid solution component changed,” explained Professor Shinoda. “However, we were surprised to find that the tensor properties actually varied according to the content of calcium, rather than that of iron. This study’s findings provide practical data for researchers who are conducting detailed analysis of iron by Mössbauer spectroscopy on mineral flakes.”
Reference:
Daiki Fukuyama, Keiji Shinoda, Daigo Takagi, Yasuhiro Kobayashi. Compositional dependence of intensity and electric field gradient tensors for Fe2+ at the M1 site in Ca–rich pyroxene by single crystal Mössbauer spectroscopy. Journal of Mineralogical and Petrological Sciences, 2022; 117 (1) DOI: 10.2465/jmps.220506
Mount Edgecumbe rises in the foreground with Crater Ridge behind and to the north on May 19, 2022. Photo by Max Kaufman/Alaska Volcano Observatory
Magma beneath long-dormant Mount Edgecumbe volcano in Southeast Alaska has been moving upward through Earth’s crust, according to research the Alaska Volcano Observatory rapidly produced using a new method.
The new approach at the observatory could lead to earlier detection of volcanic unrest in Alaska.
At Mount Edgecumbe, computer modeling based on satellite imagery shows magma is rising to about 6 miles from a depth of about 12 miles and has caused earthquakes and significant surface deformation.
“That’s the fastest rate of volcanic deformation that we currently have in Alaska,” said the research paper’s lead author, Ronni Grapenthin, a University of Alaska Fairbanks associate professor of geodesy.
“And while it is not uncommon for volcanoes to deform, the activity at Edgecumbe is unusual because reactivation of dormant volcanic systems is rarely observed,” he said.
An eruption is not imminent, Grapenthin said.
The findings by researchers at the UAF Geophysical Institute and the U.S. Geological Survey were published Oct. 10 in the journal Geophysical Research Letters.
The Alaska Volcano Observatory collaborated with the Alaska Satellite Facility, another Geophysical Institute unit, to process data in the cloud — a first for the volcano team.
Cloud computing uses remote servers to store data and provide computing services so a researcher does not have to download and sort data to process it, something that can take weeks or months.
The research team began its work as soon as a swarm of earthquakes was noticed at Mount Edgecumbe on April 11, 2022. Researchers analyzed the previous 7 1/2 years of ground deformation detected in satellite radar data.
Four days later, on April 15, the team had a preliminary result: An intrusion of new magma was causing the earthquakes. A small number of earthquakes began under Edgecumbe in 2020, but the cause was ambiguous until the deformation results were produced.
Additional data processing confirmed the preliminary finding. The Alaska Volcano Observatory informed the public on April 22, less than two weeks after the latest batch of Edgecumbe earthquakes was reported.
“We’ve done these kinds of analyses before, but new streamlined cloud-based workflows cut weeks or months of analysis down to just days,” said David Fee, the Alaska Volcano Observatory’s coordinating scientist at the Geophysical Institute.
Mount Edgecumbe, at 3,200 feet, is on Kruzof Island on the west side of Sitka Sound. It is part of the Mount Edgecumbe Volcanic Field, which includes the domes and crater of adjacent Crater Ridge.
Most striking for the researchers was an area of ground uplift on southern Kruzof Island 10.5 miles in diameter and centered 1.5 miles east of the volcano. The upward deformation began abruptly in August 2018 and continued at a rate of 3.4 inches annually, for a total of 10.6 inches through early 2022.
Subsequent computer modeling indicated the cause was the intrusion of new magma.
The new deformation-based analysis will allow for earlier detection of volcanic unrest, because ground deformation is one of its earliest indicators. Deformation can occur without accompanying seismic activity, making ground uplift a key symptom to watch.
The volcano observatory is applying the new approach to other volcanoes in Alaska, including Trident Volcano, about 30 miles north of Katmai Bay. The volcano is showing signs of elevated unrest.
Mount Edgecumbe isn’t showing signs of an imminent eruption, Grapenthin said.
“This magma intrusion has been going on for three-plus years now,” he said. “Prior to an eruption we expect more signs of unrest: more seismicity, more deformation, and — importantly — changes in the patterns of seismicity and deformation.”
The researchers say the magma is likely reaching an upper chamber through a near-vertical conduit. But they also believe the magma is precluded from moving further upward by thick magma already in the upper chamber.
The new magma is forcing the entire surface up instead.
Mount Edgecumbe is 15 miles west of Sitka, which has a population of about 8,500 residents.
The volcano last erupted 800 to 900 years ago, as cited in Lingít oral history handed down by Herman Kitka. A group of Tlingits in four canoes had camped on the coast about 15 or 20 miles south of some large smoke plumes, according to the account. A scouting party in a canoe was sent to investigate the smoke and reported “a mountain blinking, spouting fire and smoke.”
Others involved in the research include Franz Meyer, chief scientist of the Alaska Satellite Facility; UAF graduate students Yitian Cheng, Mario Angarita and Darren Tan; and Aaron Wech of the U.S. Geological Survey.
The Alaska Volcano Observatory is a joint program of the Geophysical Institute, U.S. Geological Survey and the Alaska Division of Geological and Geophysical Surveys.
Reference:
Ronni Grapenthin, Yitian Cheng, Mario Angarita, Darren Tan, Franz J. Meyer, David Fee, Aaron Wech. Return from Dormancy: Rapid inflation and seismic unrest driven by transcrustal magma transfer at Mt. Edgecumbe (L’úx Shaa) Volcano, Alaska. Geophysical Research Letters, 2022; DOI: 10.1029/2022GL099464
A depiction of an asteroid heading toward Earth, with the moon in the background. (Image credit: Juan Gartner via Getty Images)
A Curtin-led research team has found asteroid impacts on the Moon millions of years ago coincided precisely with some of the largest meteorite impacts on Earth, such as the one that wiped out the dinosaurs.
The study also found that major impact events on Earth were not stand-alone events, but were accompanied by a series of smaller impacts, shedding new light on asteroid dynamics in the inner solar system, including the likelihood of potentially devastating Earth-bound asteroids.
The international research team studied microscopic glass beads aged up to two billion years old that were found in lunar soil brought back to Earth in December 2020 as part of the Chinese National Space Agency’s Chang’e-5 Lunar mission. The heat and pressure of meteorite impacts created the glass beads and so their age distribution should mimic the impacts, revealing a timeline of bombardments.
Textural range of Chang’e-5 glass beads. (A) Homogeneous (type 1a) glass with no clasts, schlieren, vesicles, or metal. Slight adhering regolith. (B) Sphere of homogeneous (type 1a) glass with metal around the rim. (C and D) Type 2 spheres with increasing proportion of schlieren, metal, and vesicles. (E and F) Type 3 spheres with partially digested clasts, schlieren, metal, and vesicles.
Lead author Professor Alexander Nemchin, from Curtin University’s Space Science and Technology Centre (SSTC) in the School of Earth and Planetary Sciences, said the findings imply that the timing and frequency of asteroid impacts on the Moon may have been mirrored on Earth, telling us more about the history of evolution of our own planet.
“We combined a wide range of microscopic analytical techniques, numerical modelling, and geological surveys to determine how these microscopic glass beads from the Moon were formed and when,” Professor Nemchin said.
“We found that some of the age groups of the lunar glass beads coincide precisely with the ages of some of the largest terrestrial impact crater events, including the Chicxulub impact crater responsible for the dinosaur extinction event.
“The study also found that large impact events on Earth such as the Chicxulub crater 66 million years ago could have been accompanied by a number of smaller impacts. If this is correct, it suggests that the age-frequency distributions of impacts on the Moon might provide valuable information about the impacts on the Earth or inner solar system.”
Co-author Associate Professor Katarina Miljkovic, also from Curtin’s SSTC, said future comparative studies could give further insight into the geological history of the Moon.
“The next step would be to compare the data gleaned from these Chang’e-5 samples with other lunar soils and crater ages to be able to uncover other significant Moon-wide impact events which might in turn reveal new evidence about what impacts may have affected life on Earth,” Associate Professor Miljkovic said.
The international collaboration was supported by the Australian Research Council and involved researchers from Australia, China, USA, UK and Sweden including co-authors Dr Marc Norman from the Australian National University, Dr Tao Long from the Beijing SHRIMP Center at the Chinese Academy of Geological Sciences and PhD student Yuqi Qian from the China University of Geosciences.
Reference:
Tao Long, Yuqi Qian, Marc D. Norman, Katarina Miljkovic, Carolyn Crow, James W. Head, Xiaochao Che, Romain Tartèse, Nicolle Zellner, Xuefeng Yu, Shiwen Xie, Martin Whitehouse, Katherine H. Joy, Clive R. Neal, Joshua F. Snape, Guisheng Zhou, Shoujie Liu, Chun Yang, Zhiqing Yang, Chen Wang, Long Xiao, Dunyi Liu, Alexander Nemchin. Constraining the formation and transport of lunar impact glasses using the ages and chemical compositions of Chang’e-5 glass beads. Science Advances, 2022; 8 (39) DOI: 10.1126/sciadv.abq2542
Fossil specimen Ro-59.9 is littered with microscopic cavities. Some of them look as if tiny raspberries had once slumbered inside them, each of them just two hundredths of a millimeter in size. The fossilized leaf comes from the Rott fossil site near Bonn and is more than 20 million years old. At the moment, it is not possible to say to which plant species it belongs.
Perhaps that will change soon. Because the position and shape of the cavities are like a kind of fingerprint: they can be used to identify fossil plant remains. “Until now, it was not known how these cavities were formed,” explains Mahdieh Malekhosseini from the Institute of Geosciences at the University of Bonn. “For example, it was believed that they came from algae or pollen from other plants that somehow got onto the leaf during fossilization. But after analyzing hundreds of these structures, we can rule that out. Instead, we were able to show that calcium oxalate crystals are responsible for the depressions.”
Calcium oxalate is formed by very many living plants; it is considered one of the most common biominerals. What functions it fulfills has not yet been conclusively clarified. However, it is suspected that the crystals serve as calcium stores. In addition, because they are formed in the leaf but often penetrate the leaf surface as they grow, they probably repel pests. “Many insects have an aversion to calcium oxalate — they don’t like to walk on it,” explains Prof. Dr. Jes Rust, who supervised the study. “Some plants also seem to use the crystals as microlenses to use sunlight more efficiently for photosynthesis.”
The crystals are very sensitive to acid. They therefore dissolve during fossilization and can no longer be detected in the millions of years old finds. Often, however, imprints remain in the places where they have sat (in biology one speaks of “druses”). Sometimes organic material or other minerals also accumulate in these depressions, which then sit like tiny beads in the fossil leaf.
“We studied the microstructure of the pits and their distribution on fossil leaves whose species affiliation we knew,” Malekhosseini explains. “In addition, we looked at calcium oxalate crystals in the leaves of present-day plants. We found clear parallels in closely related species. For example, the crystal imprints in a fossil ginkgo leaf strongly resemble the calcium oxalate deposits of a present-day ginkgo in distribution and structure.”
Important insights into evolution
It was already known from the fossils of bare-seeded plants such as firs or pines that they sometimes show imprints of calcium oxalate crystals. However, this was not known of angiosperms — which are most flowers and deciduous trees. “This is a completely new field of research,” explains Jes Rust. “Among other things, we now want to investigate how the ability to form calcium oxalate crystals has developed over the course of evolution.” In doing so, the researchers want to focus on periods when environmental conditions changed rapidly — such as temperature or the intensity of UV radiation. “If the distribution of the drusen also changes after such incisions, then we can draw conclusions about the biological function of the crystals,” says Rust.
Reference:
Mahdieh Malekhosseini, Hans-Jürgen Ensikat, Victoria E. McCoy, Torsten Wappler, Maximilian Weigend, Lutz Kunzmann, Jes Rust. Traces of calcium oxalate biomineralization in fossil leaves from late Oligocene maar deposits from Germany. Scientific Reports, 2022; 12 (1) DOI: 10.1038/s41598-022-20144-4
A new study of a tiny Triassic fossil reptile first discovered over 100 years ago in the north east of Scotland has revealed it to be a close relative of the species that would become pterosaurs — iconic flying reptiles of the age of the dinosaurs.
The research, published in Nature, was carried out by a team of scientists led by Dr Davide Foffa, Research Associate at National Museums Scotland, and now a Research Fellow at the University of Birmingham. Working together with colleagues at Virginia Tech, the team used Computed Tomography (CT) to provide the first accurate whole skeleton reconstruction of Scleromochlus taylori.
The results reveal new anatomical details that conclusively identify it as a close pterosaur relative. It falls within a group known as Pterosauromorpha, comprising an extinct group of reptiles called lagerpetids together with pterosaurs.
Living approximately 240 -210 million years ago, lagerpetids were a group of relatively small (cat or small dog-sized) active reptiles. Schleromochlus was smaller still at under 20 centimetres in length. The results support the hypothesis that the first flying reptiles evolved from small, likely bipedal ancestors.
The finding settles a century-long debate. There had previously been disagreement as to whether the reptile, Scleromochlus, represented an evolutionary step in the direction of pterosaurs, dinosaurs or else some other reptilian offshoot.
The fossil of Scleromochlus is poorly preserved in a block of sandstone, which has made it difficult to study in sufficient detail to properly identify its anatomical features. The fossil is one of a group known as the Elgin Reptiles, comprising Triassic and Permian specimens found in the sandstone of the Morayshire region of north east Scotland around the town of Elgin.
The specimens are held mostly in the collections of National Museums Scotland, Elgin Museum and the Natural History Museum. The latter holds Scleromochlus, which was originally found at Lossiemouth.
Dr Foffa said: “It’s exciting to be able to resolve a debate that’s been going on for over a century, but it is far more amazing to be able to see and understand an animal which lived 230 million years ago and its relationship with the first animals ever to have flown. This is another discovery which highlights Scotland’s important place in the global fossil record, and also the importance of museum collections that preserve such specimens, allowing us to use new techniques and technologies to continue to learn from them long after their discovery.”
Professor Paul Barrett at the Natural History Museum said: “The Elgin reptiles aren’t preserved as the pristine, complete skeletons that we often see in museum displays. They’re mainly represented by natural moulds of their bone in sandstone and — until fairly recently — the only way to study them was to use wax or latex to fill these moulds and make casts of the bones that once occupied them. However, the use of CT scanning has revolutionized the study of these difficult specimens and has enabled us to produce far more detailed, accurate and useful reconstructions of these animals from our deep past.”
Professor Sterling Nesbitt at Virgina Tech said: “Pterosaurs were the first vertebrates to evolve powered flight and for nearly two centuries, we did not know their closest relatives. Now we can start filling in their evolutionary history with the discovery of tiny close relatives that enhance our knowledge about how they lived and where they came from”
In additional to National Museums Scotland, the Natural History Museum and Virginia Tech, the study also involved the Universities of Birmingham, Bristol and Edinburgh as well as the Chinese Academy of Sciences.
Reference:
Davide Foffa, Emma M. Dunne, Sterling J. Nesbitt, Richard J. Butler, Nicholas C. Fraser, Stephen L. Brusatte, Alexander Farnsworth, Daniel J. Lunt, Paul J. Valdes, Stig Walsh, Paul M. Barrett. Scleromochlus and the early evolution of Pterosauromorpha. Nature, 2022; DOI: 10.1038/s41586-022-05284-x
The miles-wide asteroid that struck Earth 66 million years ago wiped out nearly all the dinosaurs and roughly three-quarters of the planet’s plant and animal species.
It also triggered a monstrous tsunami with mile-high waves that scoured the ocean floor thousands of miles from the impact site on Mexico’s Yucatan Peninsula, according to a new University of Michigan-led study.
The study, scheduled for online publication Oct. 4 in the journal AGU Advances, presents the first global simulation of the Chicxulub impact tsunami to be published in a peer-reviewed scientific journal. In addition, U-M researchers reviewed the geological record at more than 100 sites worldwide and found evidence that supports their models’ predictions about the tsunami’s path and power.
“This tsunami was strong enough to disturb and erode sediments in ocean basins halfway around the globe, leaving either a gap in the sedimentary records or a jumble of older sediments,” said lead author Molly Range, who conducted the modeling study for a master’s thesis under U-M physical oceanographer and study co-author Brian Arbic and U-M paleoceanographer and study co-author Ted Moore.
The review of the geological record focused on “boundary sections,” marine sediments deposited just before or just after the asteroid impact and the subsequent K-Pg mass extinction, which closed the Cretaceous Period.
“The distribution of the erosion and hiatuses that we observed in the uppermost Cretaceous marine sediments are consistent with our model results, which gives us more confidence in the model predictions,” said Range, who started the project as an undergraduate in Arbic’s lab in the Department of Earth and Environmental Sciences.
The study authors calculated that the initial energy in the impact tsunami was up to 30,000 times larger than the energy in the December 2004 Indian Ocean earthquake tsunami, which killed more than 230,000 people and is one of the largest tsunamis in the modern record.
The team’s simulations show that the impact tsunami radiated mainly to the east and northeast into the North Atlantic Ocean, and to the southwest through the Central American Seaway (which used to separate North America and South America) into the South Pacific Ocean.
In those basins and in some adjacent areas, underwater current speeds likely exceeded 20 centimeters per second (0.4 mph), a velocity that is strong enough to erode fine-grained sediments on the seafloor.
In contrast, the South Atlantic, the North Pacific, the Indian Ocean and the region that is today the Mediterranean were largely shielded from the strongest effects of the tsunami, according to the team’s simulation. In those places, the modeled current speeds were likely less than the 20 cm/sec threshold.
For the review of the geological record, U-M’s Moore analyzed published records of 165 marine boundary sections and was able to obtain usable information from 120 of them. Most of the sediments came from cores collected during scientific ocean-drilling projects.
The North Atlantic and South Pacific had the fewest sites with complete, uninterrupted K-Pg boundary sediments. In contrast, the largest number of complete K-Pg boundary sections were found in the South Atlantic, the North Pacific, the Indian Ocean and the Mediterranean.
“We found corroboration in the geological record for the predicted areas of maximal impact in the open ocean,” said Arbic, professor of earth and environmental sciences who oversaw the project. “The geological evidence definitely strengthens the paper.”
Of special significance, according to the authors, are outcrops of the K-Pg boundary on the eastern shores of New Zealand’s north and south islands, which are more than 12,000 kilometers (7,500 miles) from the Yucatan impact site.
The heavily disturbed and incomplete New Zealand sediments, called olistostromal deposits, were originally thought to be the result of local tectonic activity. But given the age of the deposits and their location directly in the modeled pathway of the Chicxulub impact tsunami, the U-M-led research team suspects a different origin.
“We feel these deposits are recording the effects of the impact tsunami, and this is perhaps the most telling confirmation of the global significance of this event,” Range said.
The modeling portion of the study used a two-stage strategy. First, a large computer program called a hydrocode simulated the chaotic first 10 minutes of the event, which included the impact, crater formation and initiation of the tsunami. That work was conducted by co-author Brandon Johnson of Purdue University.
Based on the findings of previous studies, the researchers modeled an asteroid that was 14 kilometers (8.7 miles) in diameter, moving at 12 kilometers per second (27,000 mph). It struck granitic crust overlain by thick sediments and shallow ocean waters, blasting a roughly 100-kilometer-wide (62-mile-wide) crater and ejecting dense clouds of soot and dust into the atmosphere.
Two and a half minutes after the asteroid struck, a curtain of ejected material pushed a wall of water outward from the impact site, briefly forming a 4.5-kilometer-high (2.8-mile-high) wave that subsided as the ejecta fell back to Earth.
Ten minutes after the projectile hit the Yucatan, and 220 kilometers (137 miles) from the point of impact, a 1.5-kilometer-high (0.93-mile-high) tsunami wave — ring-shaped and outward-propagating — began sweeping across the ocean in all directions, according to the U-M simulation.
At the 10-minute mark, the results of Johnson’s iSALE hydrocode simulations were entered into two tsunami-propagation models, MOM6 and MOST, to track the giant waves across the ocean. MOM6 has been used to model tsunamis in the deep ocean, and NOAA uses the MOST model operationally for tsunami forecasts at its Tsunami Warning Centers.
“The big result here is that two global models with differing formulations gave almost identical results, and the geologic data on complete and incomplete sections are consistent with those results,” said Moore, professor emeritus of earth and environmental sciences. “The models and the verification data match nicely.”
According to the team’s simulation:
One hour after impact, the tsunami had spread outside the Gulf of Mexico and into the North Atlantic.
Four hours after impact, the waves had passed through the Central American Seaway and into the Pacific.
Twenty-four hours after impact, the waves had crossed most of the Pacific from the east and most of the Atlantic from the west and entered the Indian Ocean from both sides.
By 48 hours after impact, significant tsunami waves had reached most of the world’s coastlines.
For the current study, the researchers did not attempt to estimate the extent of coastal flooding caused by the tsunami.
However, their models indicate that open-ocean wave heights in the Gulf of Mexico would have exceeded 100 meters (328 feet), with wave heights of more than 10 meters (32.8 feet) as the tsunami approached North Atlantic coastal regions and parts of South America’s Pacific coast.
As the tsunami neared those shorelines and encountered shallow bottom waters, wave heights would have increased dramatically through a process called shoaling. Current speeds would have exceeded the 20 centimeters per second threshold for most coastal areas worldwide.
“Depending on the geometries of the coast and the advancing waves, most coastal regions would be inundated and eroded to some extent,” according to the study authors. “Any historically documented tsunamis pale in comparison with such global impact.”
A follow-up study is planned to model the extent of coastal inundation worldwide, Arbic said. That study will be led by Vasily Titov of the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Lab, who is a co-author of the AGU Advances paper.
In addition to Range, Arbic, Moore, Johnson and Titov, the study authors are Alistair Adcroft of Princeton University, Joseph Ansong of the University of Ghana, Christopher Hollis of Victoria University of Wellington, Christopher Scotese of the PALEOMAP Project, and He Wang of NOAA’s Geophysical Fluid Dynamics Laboratory and the University Corporation for Atmospheric Research.
Funding was provided by the National Science Foundation and the University of Michigan Associate Professor Support Fund, which is supported by the Margaret and Herman Sokol Faculty Awards. The MOM6 simulations were carried out on the Flux supercomputer provided by the University of Michigan Advanced Research Computing Technical Services.
Reference:
Molly M. Range, Brian K. Arbic, Brandon C. Johnson, Theodore C. Moore, Vasily Titov, Alistair J. Adcroft, Joseph K. Ansong, Christopher J. Hollis, Jeroen Ritsema, Christopher R. Scotese, He Wang. The Chicxulub Impact Produced a Powerful Global Tsunami. AGU Advances, 2022; 3 (5) DOI: 10.1029/2021AV000627
The skull of Ichthyosaurs Hauffiopteryx typicus from the Strawberry Bank Lagerstätt, one of the specimens that were the subject of this study Credit: Bath Royal Literary and Scientific Institution Collections
Early Jurassic ichthyosaur juveniles show predatory specialisations, scientists at the University of Bristol have revealed.
Their findings, published today in Journal of Anatomy, suggest that physical differences in their snouts show they evolved to have different diets and were not competing for the same resource.
Ichthyosaurs, the classic ‘sea dragons’, were dolphin-shaped marine predators that fed on fish and squid-like swimming shellfish. The ichthyosaurs of the Lower Jurassic, some 185 million years ago, are renowned because the first specimens were found over 200 years ago at Lyme Regis in southern England, by the celebrated fossil collector and palaeontologist Mary Anning. Some of her specimens have long, slender snouts and others have short, broad snouts.
“Functional studies need excellent three-dimensional specimens,” said Matt Williams of Bath Royal Literary and Scientific Institution, “and the Lower Jurassic ichthyosaur fossils from Strawberry Bank in Ilminster are just that. Mary Anning’s fossils are amazing, but they are mostly squashed flat.”
“Our idea was to CT scan the specimens,” said Dr Ben Moon, of Bristol’s School of Earth Sciences and a supervisor of the study. “The scans allow us to make a detailed, 3D model of the skull in the computer, and it can then be tested for the likely forces experienced during biting.”
“After we had the models, we could stress test them,” said supervisor Andre Rowe. “We tested and confirmed the hypothesis that the slender-snouted ichthyosaur had a quick but weak bite, and the broad-snouted ichthyosaur had a slow but powerful bite.”
“Confirming the supposition was important,” added author Professor Michael Benton. “It’s important we apply rigorous scientific approaches such as these engineering analyses. The two species of ichthyosaur presumably chased fast-moving prey (the fast biter) and slower, tough-shelled prey (the slow, powerful biter).
Sarah Jamison-Todd, who completed the work as part of her MSc in Palaeobiology said: “I learned about CT scanning, model construction, and biomechanical testing using standard engineering software that is used to test how buildings and large structures bend.”
Prof Benton concluded: “Modern predators like sharks and killer whales tend to eat anything they can, so it is exciting to be able to show that in the Jurassic there were definite specialisations. The work can be extended to explore other marine reptiles such as plesiosaurs and crocodiles, so we get a detailed picture of these amazing and alien worlds of the Jurassic oceans.”
Reference:
Sarah Jamison‐Todd, Benjamin C. Moon, Andre J. Rowe, Matt Williams, Michael J. Benton. Dietary niche partitioning in Early Jurassic ichthyosaurs from Strawberry Bank. Journal of Anatomy, 2022; DOI: 10.1111/joa.13744
The diamond from Botswana revealed to the scientists that considerable amounts of water are stored in the rock at a depth of more than 600 kilometres. Photo: Tingting Gu, Gemological Institute of America, New York, NY, USA
The transition zone (TZ) is the name given to the boundary layer that separates the Earth’s upper mantle and the lower mantle. It is located at a depth of 410 to 660 kilometres. The immense pressure of up to 23,000 bar in the TZ causes the olive-green mineral olivine, which constitutes around 70 percent of the Earth’s upper mantle and is also called peridot, to alter its crystalline structure. At the upper boundary of the transition zone, at a depth of about 410 kilometres, it is converted into denser wadsleyite; at 520 kilometres it then metamorphoses into even denser ringwoodite.
“These mineral transformations greatly hinder the movements of rock in the mantle,” explains Prof. Frank Brenker from the Institute for Geosciences at Goethe University in Frankfurt. For example, mantle plumes — rising columns of hot rock from the deep mantle — sometimes stop directly below the transition zone. The movement of mass in the opposite direction also comes to standstill. Brenker says, “Subducting plates often have difficulty in breaking through the entire transition zone. So there is a whole graveyard of such plates in this zone underneath Europe.”
However, until now it was not known what the long-term effects of “sucking” material into the transition zone were on its geochemical composition and whether larger quantities of water existed there. Brenker explains: “The subducting slabs also carry deep-sea sediments piggy-back into the Earth’s interior. These sediments can hold large quantities of water and CO2. But until now it was unclear just how much enters the transition zone in the form of more stable, hydrous minerals and carbonates — and it was therefore also unclear whether large quantities of water really are stored there.”
The prevailing conditions would certainly be conducive to that. The dense minerals wadsleyite and ringwoodite can (unlike the olivine at lesser depths) store large quantities of water- in fact so large that the transition zone would theoretically be able to absorb six times the amount of water in our oceans. “So we knew that the boundary layer has an enormous capacity for storing water,” Brenker says. “However, we didn’t know whether it actually did so.”
An international study in which the Frankfurt geoscientist was involved has now supplied the answer. The research team analysed a diamond from Botswana, Africa. It was formed at a depth of 660 kilometres, right at the interface between the transition zone and the lower mantle, where ringwoodite is the prevailing mineral. Diamonds from this region are very rare, even among the rare diamonds of super-deep origin, which account for only one percent of diamonds. The analyses revealed that the stone contains numerous ringwoodite inclusions — which exhibit a high water content. Furthermore, the research group was able to determine the chemical composition of the stone. It was almost exactly the same as that of virtually every fragment of mantle rock found in basalts anywhere in the world. This showed that the diamond definitely came from a normal piece of the Earth’s mantle. “In this study we have demonstrated that the transition zone is not a dry sponge, but holds considerable quantities of water,” Brenker says, adding: “This also brings us one step closer to Jules Verne’s idea of an ocean inside the Earth.” The difference is that there is no ocean down there, but hydrous rock which, according to Brenker, would neither feel wet nor drip water.
Hydrous ringwoodite was first detected in a diamond from the transition zone as early as 2014. Brenker was involved in that study, too. However, it was not possible to determine the precise chemical composition of the stone because it was too small. It therefore remained unclear how representative the first study was of the mantle in general, as the water content of that diamond could also have resulted from an exotic chemical environment. By contrast, the inclusions in the 1.5 centimetre diamond from Botswana, which the research team investigated in the present study, were large enough to allow the precise chemical composition to be determined, and this supplied final confirmation of the preliminary results from 2014.
The transition zone’s high water content has far-reaching consequences for the dynamic situation inside the Earth. What this leads to can be seen, for example, in the hot mantle plumes coming from below, which get stuck in the transition zone. There, they heat up the water-rich transition zone, which in turn leads to the formation of new smaller mantle plumes that absorb the water stored in the transition zone. If these smaller water-rich mantle plumes now migrate further upwards and break through the boundary to the upper mantle, the following happens: The water contained in the mantle plumes is released, which lowers the melting point of the emerging material. It therefore melts immediately and not just before it reaches the surface, as usually happens. As a result, the rock masses in this part of the Earth’s mantle are no longer as tough overall, which gives the mass movements more dynamism. The transition zone, which otherwise acts as a barrier to the dynamics there, suddenly becomes a driver of the global material circulation.
Reference:
Tingting Gu, Martha G. Pamato, Davide Novella, Matteo Alvaro, John Fournelle, Frank E. Brenker, Wuyi Wang, Fabrizio Nestola. Hydrous peridotitic fragments of Earth’s mantle 660 km discontinuity sampled by a diamond. Nature Geoscience, 2022; DOI: 10.1038/s41561-022-01024-y
GOES-West satellite image of Tonga volcanic eruption, 2022. Credit: NASA Worldview, NOAA / NESDIS / STAR
The catastrophic eruption of the Hunga Tonga-Hunga Ha’apai volcano in 2022 triggered a special atmospheric wave that has eluded detection for the past 85 years. Researchers from the University of Hawai’i (UH) at Manoa, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), and Kyoto University relied on state-of-the-art observational data and computer simulations to discover the existence of Pekeris waves — fluctuations in air pressure that were theorized in 1937 but never proven to occur in nature, until now.
The eruption in the South Pacific earlier this year released what was likely the most powerful explosion the world has experienced since the famous 1883 eruption of Mt. Krakatau in Indonesia. The rapid release of energy excited pressure waves in the atmosphere that quickly spread around the world.
The atmospheric wave pattern close to the eruption was quite complicated, but thousands of miles away the disturbances were led by an isolated wave front traveling horizontally at over 650 miles an hour as it spread outward. The air pressure perturbations associated with the initial wave front was seen clearly on thousands of barometer records throughout the world.
“The same behavior was observed after the Krakatau eruption and in the early 20th century a physical theory for this wave was developed by the English scientist Horace Lamb,” said Kevin Hamilton, emeritus professor of atmospheric science at the UH Manoa School of Ocean and Earth Science and Technology. “These motions are now known as Lamb waves. In 1937, the American-Israeli mathematician and geophysicist Chaim Pekeris expanded Lamb’s theoretical treatment and concluded that a second wave solution with a slower horizontal speed should also be possible. Pekeris tried to find evidence for his slower wave in the pressure observations after the Krakatau eruption but failed to produce a convincing case.”
In the recent study, published in the Journal of the Atmospheric Sciences, the team of scientists applied a broad range of tools now available including geostationary satellite observations, computer simulations and extremely dense networks of air pressure observations to successfully identify the Pekeris wave in the atmosphere following the Tonga eruption.
Lead author, Shingo Watanabe, deputy director of the JAMSTEC Research Center for Environmental Modeling, performed computer simulations of the response to the Tonga eruption.
“When we investigated the computer simulated and observed pulses over the entire Pacific basin, we found that the slower wave front could be seen over broad regions and that its properties matched those predicted by Pekeris almost a century ago,” said Hamilton.
Once the Pekeris wave was identified in the post-eruption aftermath the researchers realized that this result had more general implications for the motions in the atmosphere. Specifically, they predicted that there should be set of corresponding global oscillations or modes of the atmosphere on times scales of several hours to days. Analysis of long records of atmospheric pressure by study co-author Takatoshi Sakazaki, associate professor in the Graduate School of Science of Kyoto University, revealed the presence of the predicted set of oscillations.
“In our paper we propose a standard terminology of Lamb wave and Pekeris wave for the two solutions,” said Hamilton. “Chaim Pekeris later became world famous and is today regarded as ‘the father of Israeli geophysics’, but he did his calculation of the volcanic wave response as a very young researcher at MIT where he was known for his admiration for the earlier work of Lamb. It is fitting that our discovery and our proposed nomenclature would permanently connect Chaim Pekeris with his scientific hero, Horace Lamb.”
Reference:
Shingo Watanabe, Kevin Hamilton, Takatoshi Sakazaki, Masuo Nakano. First Detection of the Pekeris Internal Global Atmospheric Resonance: Evidence from the 2022 Tonga Eruption and from Global Reanalysis Data. Journal of the Atmospheric Sciences, 2022; DOI: 10.1175/JAS-D-22-0078.1
Scientists who drilled deeper into an undersea earthquake fault than ever before have found that the tectonic stress in Japan’s Nankai subduction zone is less than expected, according to a study from researchers at The University of Texas at Austin and University of Washington.
The findings, published in the journal Geology, are a puzzle because the fault produces a great earthquake almost every century and was thought to be building for another big one.
“This is the heart of the subduction zone, right above where the fault is locked, where the expectation was that the system should be storing energy between earthquakes,” said Demian Saffer, director of the University of Texas Institute for Geophysics (UTIG) who co-led the research and scientific mission that drilled the fault. “It changes the way we’re thinking about stress in these systems.”
Although the Nankai fault has been stuck for decades, the study shows that it is not yet showing major signs of pent-up tectonic stress. According to Saffer, that doesn’t alter the long-term outlook for the fault, which last ruptured in 1946 — when it caused a tsunami that killed thousands — and is expected to do so again during the next 50 years.
Instead, the findings will help scientists home in on the link between tectonic forces and the earthquake cycle and potentially lead to better earthquake forecasts, both at Nankai and other megathrust faults such as Cascadia in the Pacific Northwest.
“Right now, we have no way of knowing if the big one for Cascadia — a magnitude 9 scale earthquake and tsunami — will happen this afternoon or 200 years from now,” said Harold Tobin, a researcher at the University of Washington who is the first author of the paper. “But I have some optimism that with more and more direct observations like this, we can start to recognize when something anomalous is occurring and that the risk of an earthquake is heightened in a way that could help people prepare.”
Megathrust faults such as Nankai, and the tsunamis they generate, are among the most powerful and damaging on the globe, but scientists say they currently have no reliable way of knowing when and where the next big one will hit.
The hope is that by directly measuring the force felt between tectonic plates pushing on each other — tectonic stress — scientists can learn when a great earthquake is ready to happen.
However, the nature of tectonics means that the great earthquake faults are found in deep ocean, miles under the seafloor, making them incredibly challenging to measure directly. Saffer and Tobin’s drilling expedition is the closest scientists have come.
Their record-breaking attempt took place in 2018 aboard a Japanese scientific drilling ship, the Chikyu, which drilled 2 miles into the tectonic plate before the borehole got too unstable to continue, a mile short of the fault.
Nevertheless, the researchers gathered invaluable data about subsurface conditions near the fault, including stress. To do that, they measured how much the borehole changed shape as the Earth squeezed it from the sides, then pumped water to see what it took to force its walls back out. That told them the direction and strength of horizontal stress felt by the plate pushing on the fault.
Contrary to predictions, the horizontal stress expected to have built since the most recent great earthquake was close to zero, as if it had already released its pent-up energy.
The researchers suggested several explanations: It could be that the fault simply needs less pent-up energy than thought to slip in a big earthquake, or that the stresses are lurking nearer to the fault than the drilling reached. Or it could be that the tectonic push will come suddenly in the coming years. Either way, the researchers said the drilling showed the need for further investigation and long-term monitoring of the fault.
The research was funded by the Integrated Ocean Drilling Program and the Japan Agency for Marine-Earth Science and Technology. UTIG is a research unit of UT Austin’s Jackson School of Geosciences.
Reference:
Harold J. Tobin, Demian M. Saffer, David A. Castillo, Takehiro Hirose. Direct constraints on in situ stress state from deep drilling into the Nankai subduction zone, Japan. Geology, 2022; DOI: 10.1130/G49639.1
Artistic reconstruction of Mbiresaurus raathi (in the foreground) with the rest of the Zimbabwean animal assemblage in the background. It includes two rhynchosaurs (at front right), an aetosaur (at left), and a herrerasaurid dinosaur chasing a cynodont (at back right). Illustration courtesy of Andrey Atuchin.
An international team of paleontologists led by Virginia Tech has discovered and named a new, early dinosaur. The skeleton — incredibly, mostly intact — was first found by a graduate student in the Virginia Tech Department of Geosciences and other paleontologists over the course of two digs, in 2017 and 2019.
The findings of this new sauropodomorph — a long-necked dinosaur — newly named Mbiresaurus raathi were been published today in the journal Nature. The skeleton is, thus far, the oldest dinosaur skeleton ever found in Africa. The animal is estimated to have been 6 feet long with a long tail. It weighed anywhere from 20 to 65 pounds.The skeleton, missing only some of the hand and portions of the skull, was found in northern Zimbabwe.
“The discovery of Mbiresaurus raathi fills in a critical geographic gap in the fossil record of the oldest dinosaurs and shows the power of hypothesis-driven fieldwork for testing predictions about the ancient past,” said Christopher Griffin, who graduated in 2020 with a Ph.D. in geosciences from the Virginia Tech College of Science.
Griffin added, “These are Africa’s oldest-known definitive dinosaurs, roughly equivalent in age to the oldest dinosaurs found anywhere in the world. The oldest known dinosaurs — from roughly 230 million years ago, the Carnian Stage of the Late Triassic period — are extremely rare and have been recovered from only a few places worldwide, mainly northern Argentina, southern Brazil, and India.”
Sterling Nesbitt, associate professor of geosciences, also is an author on the study. “Early dinosaurs like Mbiresaurus raathi show that the early evolution of dinosaurs is still being written with each new find and the rise of dinosaurs was far more complicated than previously predicted,” he said.
The international team at the heart of this discovery include paleontologists fromtheNational Museums and Monuments of Zimbabwe, the Natural History Museum of Zimbabwe, and Universidade de São Paulo, São Paulo, Brazil.
Found alongside Mbiresaurus were an assortment of Carnian-aged fossils, including a herrerasaurid dinosaur, early mammal relatives such as cynodonts, armored crocodylian relatives such as aetosaurs, and, in Griffin’s description, “bizarre, archaic reptiles” known as rhynchosaurs, again typically found in South America and India from this same time period.
(Mbiresaurus is derived from Shona and ancient Greek roots. “Mbire” is the name of the district where the animal was found and also is the name of an historic Shona dynasty that ruled the region. The name “raathi” is in honor of Michael Raath, a paleontologist who first reported fossils in northern Zimbabwe.)
From their findings, Mbiresaurus stood on two legs and its head was relatively small head like its dinosaur relatives. It sported small, serrated, triangle-shaped teeth, suggesting that it was an herbivore or potentially omnivore.
Part of the 2019 expedition team in Harare, capital of Zimbabwe, before fieldwork. Left to right: Kudzie Madzana, Edward Mbambo, Sterling Nesbitt, George Malunga, Christopher Griffin, Darlington Munyikwa.
“We never expected to find such a complete and well-preserved dinosaur skeleton,” said Griffin, now a post-doctorate researcher at Yale University. “When I found the femur of Mbiresaurus, I immediately recognized it as belonging to a dinosaur and I knew I was holding the oldest dinosaur ever found in Africa. When I kept digging and found the left hip bone right next to the left thigh bone, I had to stop and take a breath — I knew that a lot of the skeleton was probably there, still articulated together in life position.”
Nesbitt, who is a member of the Virginia Tech Global Change Center, part of the Fralin Life Sciences Institute, added, “Chris did an outstanding job figuring out a place to test his ideas about early dinosaur evolution, went there, found incredible fossils, and put it all together in a fantastic collaboration that he initiated.”
A theory on dinosaur dispersal
In addition to the discovery of Mbiresaurus, the group of researchers also have a new theory on dinosaur migration, including the when and where.
Africa, like all continents, was once part of the supercontinent called Pangea. The climate across Pangea is thought to have been divided into strong humid and arid latitudinal belts, with more temperate belts spanning higher latitudes and intense deserts across the lower tropics of Pangea. Scientists previously believed that these climate belts influenced and constrained animal distribution across Pangea, said Griffin.
“Because dinosaurs initially dispersed under this climatic pattern, the early dispersal of dinosaurs should therefore have been controlled by latitude,” Griffin said. “The oldest dinosaurs are known from roughly the same ancient latitudes along the southern temperate climate belt what was at the time, approximately 50 degrees south.”
Griffin and others from the Paleobiology and Geobiology Research Group at Virginia Tech purposefully targeted northern Zimbabwe as the country fell along this same climate belt, bridging a geographic gap between southern Brazil and India during the Late Triassic Age.
More so, these earliest dinosaurs were restricted by climatic bands to southern Pangea, and only later in their history dispersed worldwide. To bolster this claim, the research team developed a novel data method of testing this hypothesis of climatic dispersal barriers based on ancient geography and the dinosaurian family tree. The breakdown of these barriers, and a wave of northward dispersal, coincided with a period of intense worldwide humidity, or the Carnian Pluvial Event.
After this, barriers returned, mooring the now-worldwide dinosaurs in their distinct provinces across Pangea for the remainder of the Triassic Period, according to the team. “This two-pronged approach combines hypothesis-driven predictive fieldwork with statistical methods to independently support the hypothesis that the earliest dinosaurs were restricted by climate to just a few areas of the globe,” Griffin said.
Brenen Wynd, also a doctoral graduate of the Department of Geosciences, helped build the data model. “The early history of dinosaurs was a critical group for this kind of problem. Not only do we have a multitude of physical data from fossils, but also geochemical data that previously gave a really good idea of when major deserts were present,” he said. “This is the first time where those geochemical and fossil data have been supported using only evolutionary history and the relationships between different dinosaur species, which is very exciting.”
A boon for Zimbabwe and Virginia Tech paleontology
The unearthing of one of the earliest dinosaurs ever found — and most of it fully intact — is a major win for the Natural History Museum of Zimbabwe. “The discovery of the Mbiresaurus is an exciting and special find for Zimbabwe and the entire paleontological field,” said Michel Zondo,a curator and fossil preparer at the museum. “The fact that the Mbiresaurus skeleton is almost complete, makes it a perfect reference material for further finds. It is the first sauropodomorph find of its size from Zimbabwe, otherwise most of our sauropodomorph finds from here are usually of medium- to large-sized animals.”
Darlington Munyikwa, deputy executive director of the National Museums and Monuments of Zimbabwe, added,”The unfolding fossil assemblage from the Pebbly Arkose Formation in the Cabora Bassa Basin, which was hitherto known for paucity of animal fossils, is exciting. A number of fossil sites [are] waiting for future exploration were recorded, highlighting the potential of the area to add more valuable scientific material.”
Much of the Mbiresaurus specimen is being kept in Virginia Tech’s Derring Hall as the skeleton is cleaned and studied. All of the Mbiresaurus skeleton and the additional found fossilswill be permanently kept at Natural History Museum of Zimbabwe in Bulawayo, Zimbabwe.
“This is such an exciting and important dinosaur find for Zimbabwe, and we have been watching the scientific process unfold with great pride,”saidMoira Fitzpatrick, the museum’s director. She was not involved in the study. “It has been a pleasure to work with Dr. Griffin,and we hope the relationship will continue well into the future.”
The discovery of Mbiresaurus also marks another highpoint for the Paleobiology and Geobiology Research Group. In 2019, Nesbitt authored a paper detailing the newly named tyrannosauroid dinosaur Suskityrannus hazelae. Incredibly, Nesbitt discovered the fossil at age 16 as a high school student participating in a dig expedition in New Mexico in 1998.
“Our group seeks out equal partnerships and collaborations all over the world and this project demonstrates a highly successful and valued collaboration,” Nesbitt said. “We will continue studying the many fossils from the same areas as where the new dinosaur came from and explore the fossil beds further.”
Funding for the dig and follow-up research came from several sources, including National Geographic Society, the U.S. National Science Foundation, Geological Society of America, Paleontological Society, Virginia Tech Graduate School, Virginia Tech Department of Geosciences, and the Fundação de Amparo à Pesquisa do Estado de São Paulo in Brazil.
Reference:
Christopher T. Griffin, Brenen M. Wynd, Darlington Munyikwa, Tim J. Broderick, Michel Zondo, Stephen Tolan, Max C. Langer, Sterling J. Nesbitt, Hazel R. Taruvinga. Africa’s oldest dinosaurs reveal early suppression of dinosaur distribution. Nature, 2022; DOI: 10.1038/s41586-022-05133-x
