Curtin researchers have developed a new technique by studying the age of ancient grains of sand from beaches, rivers and rocks from around the world to reveal previously hidden details of the Earth’s distant geological past.
Lead researcher Dr Milo Barham, from the Timescales of Mineral Systems Group within Curtin’s School of Earth and Planetary Sciences, said the team devised a metric, which determines the ‘age distribution fingerprint’ of minerals known as zircon within sand, shedding new light on the evolution of the Earth’s surface over the last few billion years.
“While much of the original geological record is lost to erosion, durable minerals like zircon form sediments that effectively gather information from these lost worlds to paint a vivid picture of the planet’s history, including changing environments, the development of a habitable biosphere, the evolution of continents, and the accumulation of mineral resources at ancient plate boundaries,” Dr Barham said.
“This new approach allows a greater understanding of the nature of ancient geology in order to reconstruct the arrangement and movement of tectonic plates on Earth through time.
“The world’s beaches faithfully record a detailed history of our planet’s geological past, with billions of years of Earth’s history imprinted in the geology of each grain of sand and our technique helps unlock this information.”
Co-author Professor Chris Kirkland, also from the Timescales of Mineral Systems Group within Curtin’s School of Earth and Planetary Sciences, said the new method can be used to trace the Earth’s history with greater detail than previously achievable.
“Zircons contain chemical elements that allow us to date and reconstruct the conditions of mineral formation. Much like human population demographics trace the evolution of countries, this technique allows us to chart the evolution of continents by identifying the particular age population demographics of zircon grains in a sediment,” Professor Kirkland said.
“The way the Earth recycles itself through erosion is tracked in the pattern of ages of zircon grains in different geological settings. For example, the sediment on the west and east coasts of South America are completely different because there are many young grains on the west side that were created from crust plunging beneath the continent, driving earthquakes and volcanoes in the Andes. Whereas, on the east coast, all is relatively calm geologically and there is a mix of old and young grains picked up from a diversity of rocks across the Amazon basin.”
Dr Barham and Professor Kirkland are affiliated with The Institute for Geoscience Research (TIGeR), Curtin’s flagship Earth Sciences research institute and the research was funded by the Minerals Research Institute of Western Australia.
Reference:
M. Barham, C.L. Kirkland, A.D. Handoko. Understanding ancient tectonic settings through detrital zircon analysis. Earth and Planetary Science Letters, 2022; 583: 117425 DOI: 10.1016/j.epsl.2022.117425
Note: The above post is reprinted from materials provided by Curtin University. Original written by Lucien Wilkinson.
Kimberlites are complex rocks that came to the Earth’s surface from great depths. The picture shows a thin section of a carbonate-rich kimberlite. (Photograph: David Swart / Messengers of the Mantle Exhibition)
The rapid development of fauna 540 million years ago has permanently changed the Earth — deep into its lower mantle. A team led by ETH researcher Andrea Giuliani found traces of this development in rocks from this zone.
It is easy to see that the processes in the Earth’s interior influence what happens on the surface. For example, volcanoes unearth magmatic rocks and emit gases into the atmosphere, and thus influence the biogeochemical cycles on our planet.
What is less obvious, however, is that the reverse is also true: what happens on the Earth’s surface effect the Earth’s interior — even down to great depths. This is the conclusion reached by an international group of researchers led by Andrea Giuliani, SNSF Ambizione Fellow in the Department of Earth Sciences at ETH Zurich, in a new study published in the journal Science Advances. According to this study, the development of life on our planet affects parts of Earth’s lower mantle.
In their study, the researchers examined rare diamond-bearing volcanic rocks called kimberlites from different epochs of the Earth’s history. These special rocks are messengers from the lowest regions of the Earth’s mantle. Scientists measured the isotopic composition of carbon in about 150 samples of these special rocks. They found that the composition of younger kimberlites, which are less than 250 million years old, varies considerably from that of older rocks. In many of the younger samples, the composition of the carbon isotopes is outside the range that would be expected for rocks from the mantle.
The researchers see a decisive trigger for this change in composition of younger kimberlites in the Cambrian Explosion. This relatively short phase — geologically speaking — took place over a period of few tens of million years at the beginning of the Cambrian Epoch, about 540 million years ago. During this drastic transition, almost all of today’s existing animal tribes appeared on Earth for the first time. “The enormous increase in life forms in the oceans decisively changed what was happening on the Earth’s surface,” Giuliani explains. “And this in turn affected the composition of sediments at the bottom of the ocean.”
From the oceans to the mantle and back
For the Earth’s lower mantle, this changeover is relevant because some of the sediments on the seafloor, in which material from dead living creatures is deposited, enter the mantle through plate tectonics. Along the subduction zones, these sediments — along with the underlying oceanic crust — are transported to great depths. In this way, the carbon that was stored as organic material in the sediments also reaches the Earth’s mantle. There the sediments mix with other rock material from the Earth’s mantle and after a certain time, estimated to at least 200-300 million years, rise to the Earth’s surface again in other places — for example in the form of kimberlite magmas.
It is remarkable that changes in marine sediments leave such profound traces, because overall, only small amounts of sediment are transported into the depths of the mantle along a subduction zone. “This confirms that the subducted rock material in the Earth’s mantle is not distributed homogeneously, but moves along specific trajectories,” Giuliani explains.
The Earth as a total system
In addition to carbon, the researchers also examined the isotopic composition of other chemical elements. For example, the two elements strontium and hafnium showed a similar pattern to carbon. “This means that the signature for carbon cannot be explained by other processes such as degassing, because otherwise the isotopes of strontium and hafnium would not be correlated with those of carbon,” Giuliani notes.
The new findings open the door for further studies. For example, elements such as phosphorus or zinc, which were significantly affected by the emergence of life, could also provide clues as to how processes at the Earth’s surface influence the Earth’s interior. “The Earth is really a complex overall system,” Giuliani says. “And we now want to understand this system in more detail.”
Reference:
Andrea Giuliani, Russell N. Drysdale, Jon D. Woodhead, Noah J. Planavsky, David Phillips, Janet Hergt, William L. Griffin, Senan Oesch, Hayden Dalton, Gareth R. Davies. Perturbation of the deep-Earth carbon cycle in response to the Cambrian Explosion. Science Advances, 2022; 8 (9) DOI: 10.1126/sciadv.abj1325
Note: The above post is reprinted from materials provided by ETH Zurich. Original written by Felix Würsten.
By examining earthquake models from a fresh perspective, Cornell University engineers now show that the earthquake fracture energy — once thought to relate to how faults in the Earth’s crust weaken — is related to how quakes stop.
This modeling revelation could help science inch closer to making accurate earthquake forecasts.
“We realized that observations we thought were related to how faults weaken are actually data related to how an earthquake stops,” said Greg McLaskey, assistant professor in the School of Civil and Environmental Engineering, in the College of Engineering. “We’ve observed that earthquake fracture energy is more related to the overall rupture style — such as crack-like or pulse-like rupture — instead of a specific slip-weakening relationship (the way the crust weakens when plates slide past each other).”
The work, “Earthquake Breakdown Energy Scaling Despite Constant Fracture Energy,” was published Feb. 22 in Nature Communications. In addition to McLaskey, the lead author was Chun-Yu (Huey) Ke, Ph.D. ’21, and David S. Kammer at the Institute for Building Materials, ETH Zu?rich, Switzerland. The research was supported by the National Science Foundation.
Research over the past 25 years has focused on earthquake fracture energy or breakdown energy usually estimated from ground shaking, McLaskey said.
That research had linked earthquake fracture energy to the way the Earth’s crust weakens during an earthquake. But by studying large-scale rock experiments — at the Bovay Laboratory Complex — between two two-ton granite slabs, the researchers at Cornell found that those models may have been slightly askew.
The lab’s computer models suggested that those seismic observations are not directly related to fracture energy, but instead, the new research indicated, the seismic observations depend on how the earthquake ends, as related to either a pulse-like or crack-like rupture style.
For a pulse-like rupture, the fault resembles an inchworm moving along a surface. The inchworm doesn’t jump, McLaskey said, and only a little bit moves at a time. In a crack-style rupture, the fault resembles a zipper.
Seismologists have been measuring the fracture energy (sometimes called breakdown energy) of earthquakes. “That parameter of an earthquake should not be interpreted as a weakening of the crust,” he said, “but whether the earthquake rupture is a pulse or a crack.”
When earthquakes do occur, they end. The slipped part of the fault tapers off and eventually merges with part of the crust that is not ruptured. “Think of a car approaching a stop sign,” he said. “You don’t stop abruptly. You see the sign and you apply the brakes — but the factor we’ve introduced is whether you’re coming to a stop sign going uphill, downhill or on a flat surface.”
The engineers found that when they slammed on the experimental brakes, they could not get the ruptures to stop. “The only way we could get our ruptures in the lab to stop is by making ‘a hill,’ so to speak,” McLaskey said. “We introduced that factor into our model and it began to make sense.”
Earthquakes are unpredictable, he said, discussing early warning technology used around the world in Japan and Mexico, and now being developed in California.
“If you get a 1-second warning because of sensors that there will be an earthquake — maybe a 10-second warning — you’ll be lucky,” he said.
“One of the reasons why it is difficult to predict earthquakes is because scientific modeling equations don’t always add up,” McLaskey said. “This paper is a step in the right direction. We’re getting a better understanding of these models — hopefully leading to an ability to predict earthquakes.”
McLaskey is a faculty fellow at the Cornell Atkinson Center for Sustainability.
Reference:
Chun-Yu Ke, Gregory C. McLaskey, David S. Kammer. Earthquake breakdown energy scaling despite constant fracture energy. Nature Communications, 2022; 13 (1) DOI: 10.1038/s41467-022-28647-4
Note: The above post is reprinted from materials provided by Cornell University. Original written by Blaine Friedlander.
Earth’s thin crust softens considerably when it dives down into the Earth attached to a tectonic plate. That is demonstrated by X-ray studies carried out using DESY’s X-ray source PETRA III on a mineral which occurs in large quantities in basaltic crust. This softening can even cause the crust to peel away from the underlying plate, as an international team led by Hauke Marquardt from the University of Oxford reports in the scientific journal Nature. The delaminated crust has different physical properties from the rest of the mantle, which may explain anomalies in the speed with which seismic waves propagate through the mantle.
For the first time, the scientists have managed to measure the deformation of the mineral davemaoite under the conditions that prevail inside the Earth’s mantle. “Davemaoite belongs to the widespread group of materials known as perovskites, but it is only formed from other minerals at depths of about 550 kilometres and beyond, due to the increasing pressure and temperature,” explains lead author Julia Immoor from the Bavarian Research Institute of Experimental Geochemistry and Geophysics at the University of Bayreuth. The existence of the mineral had been predicted for decades, but it was not until 2021 that a natural sample of it was found. Davemaoite differs from other perovskites in its cubic crystal structure, among other things. At great enough depths, it can account for about a quarter of the descending basaltic oceanic crust.
Using a special apparatus at DESY’s Extreme Conditions Beamline (P02.2) at PETRA III, the team has now succeeded in artificially producing davemaoite and examining it with X-rays. To do this, the scientists heated finely ground wollastonite (CaSiO3) to around 900 degrees Celsius at high pressure, until davemaoite was formed. The mineral was then deformed by applying an increasing pressure of up to 57 gigapascals — around 570,000 times atmospheric pressure at sea level — and examined using X-rays. These parameters correspond to the conditions encountered at depths of up to 1300 kilometres.
“Our measurements show that davemaoite is surprisingly soft within Earth’s lower mantle,” reports Hauke Marquardt, who led the research. “This observation completely changes our ideas about the dynamic behaviour of subducting slabs in the lower mantle.” The dynamics in these so-called subduction zones, where one tectonic plate dives underneath another, depend very much on how hard the minerals present are. Being surprisingly soft, davemaoite can cause the descending crust to detach from the underlying plate, whereby the subduction process then proceeds separately for the crust and the remaining plate.
Scientists have long speculated about such a detachment because the separated crust could cause the characteristic changes in the velocities of seismic waves that are observed at different depths. Until now, however, it has been unclear what causes could lead to such a delamination. “I am glad that the experimental setup we have come up with here is able to help solve important questions linked to processes occurring deep inside our planet,” says DESY’s Hanns-Peter Liermann, who is in charge of the Extreme Conditions Beamline at PETRA III and a co-author of the study.
Researchers from the Universities of Bayreuth, Oxford and Utah, as well as from the GFZ German Research Centre for Geosciences in Potsdam, the California Institute of Technology and DESY were involved in the study. The project was funded in part by Deutsche Forschungsgemeinschaft DFG.
Reference:
J. Immoor, L. Miyagi, H.-P. Liermann, S. Speziale, K. Schulze, J. Buchen, A. Kurnosov & H. Marquardt. Weak cubic CaSiO3 perovskite in the Earth’s mantle. Nature, 2022 DOI: 10.1038/s41586-021-04378-2
Evidence suggests an asteroid impact that killed off most dinosaurs might have happened in spring. Credit: Joschua Knüppe
The asteroid which killed nearly all of the dinosaurs struck Earth during springtime. This conclusion was drawn by an international team of researchers after having examined thin sections, high-resolution synchrotron X-ray scans, and carbon isotope records of the bones of fishes that died less than 60 minutes after the asteroid impacted. The team presents its findings in the journal Nature.
The researchers from Uppsala University in Sweden, Vrije Universiteit (VU) in Amsterdam, Vrije Universiteit in Brussels (VUB), and the European Synchrotron Radiation Facility (ESRF) in France turned to the unique Tanis locality in North Dakota (United States) to find fossilised paddlefishes and sturgeons which were direct casualties of the so-called Chicxulub meteorite impact that also marked the last day of the dinosaurs. The impact rocked the continental plate and caused massive standing waves in water bodies. These mobilised enormous volumes of sediment that engulfed fishes and buried them alive while impact spherules rained down from the sky, less than an hour after impact.
Fossil fishes in the Tanis event deposit were pristinely preserved, with their bones showing almost no signs of geochemical alteration. The synchrotron X-ray data, which are made available for anyone to explore, confirms that filtered-out impact spherules are still stuck in their gills. Even soft tissues have been preserved!
Selected fish bones were studied for the reconstruction of latest Cretaceous seasonality. “These bones registered seasonal growth very much like trees do” says Sophie Sanchez of Uppsala University and the ESRF.
“The retrieved growth rings not only captured the life histories of the fishes but also recorded the latest Cretaceous seasonality and thus the season in which the catastrophic extinction occurred,” states senior author Jeroen van der Lubbe of the VU in Amsterdam.
An additional line of evidence was provided by the distribution, shapes and sizes of the bone cells, which are known to fluctuate with the seasons as well. “In all studied fishes, bone cell density and volumes can be traced over multiple years. These were on the rise but had not yet peaked during the year of death,” says Dennis Voeten of Uppsala University.
One of the studied paddlefishes was subjected to stable carbon isotope analysis to reveal its annual feeding pattern. The availability of zooplankton, its prey of choice, oscillated seasonally and peaked between spring and summer.
“This temporary increase of ingested zooplankton enriched the skeleton of its predator with the heavier 13C carbon isotope relative to the lighter 12C carbon isotope,” explains Suzan Verdegaal-Warmerdam of the VU Amsterdam. “The carbon isotope signal across the growth record of this unfortunate paddlefish confirms that the feeding season had not yet climaxed — death came in spring,” infers Melanie During from Uppsala University and the VU Amsterdam and lead author of the publication.
The end-Cretaceous mass extinction represents one of the most selective extinctions in the history of life that saw the demise of all non-avian dinosaurs, pterosaurs, ammonites, and most marine reptiles, while mammals, birds, crocodiles, and turtles survived. Because we now know that the extinction must have abruptly started during northern-hemisphere spring, we start to understand that this event took place during particularly sensitive life stages of Latest Cretaceous organisms, including the onset of reproduction cycles. And because southern-hemisphere autumn coincides with spring in the Northern Hemisphere, the preparation for winter may have just protected organisms in the Southern Hemisphere.
“This crucial finding will help to uncover why most of the dinosaurs died out while birds and early mammals managed to evade extinction,” concludes Melanie During.
Reference:
Melanie A. D. During, Jan Smit, Dennis F. A. E. Voeten, Camille Berruyer, Paul Tafforeau, Sophie Sanchez, Koen H. W. Stein, Suzan J. A. Verdegaal-Warmerdam, Jeroen H. J. L. van der Lubbe. The Mesozoic terminated in boreal spring. Nature, 2022; DOI: 10.1038/s41586-022-04446-1
Researchers discover first evidence indicating dinosaur respiratory infection
A group of researchers from around the country, including University of New Mexico Research Assistant Professor Ewan Wolff, discovered the first evidence of a unique respiratory infection in the fossilized remains of a dinosaur that lived nearly 150 million years ago.
Researchers examined the remains of an immature diplodocid — a long-necked herbivorous sauropod dinosaur, like “Brontosaurus” — dating back to the Late Jurassic Period of the Mesozoic Era. The dinosaur nicknamed “Dolly,” discovered in southwest Montana, had evidence of an infection in the area of its neck vertebrae.
They study, led by Cary Woodruff of the Great Plains Dinosaur Museum, identified never before seen abnormal bony protrusions that had an unusual shape and texture. These protrusions were located in an area of each bone where they would have been penetrated by air sacs. Air sacs are non-oxygen exchanging parts of the respiratory system in modern birds that are also present in dinosaurs. The air sacs would have ultimately connected to “Dolly’s” lungs and formed part of the dinosaur’s complex respiratory system. CT imaging of the irregular protrusions revealed that they were made of abnormal bone that most likely formed in response to an infection.
“We’ve all experienced these same symptoms — coughing, trouble breathing, fever and here’s a 150-million-year-old dinosaur that likely felt as miserable as we all do when we’re sick.” Woodruff said.
Researchers say these findings are significant because Dolly was considered a non-avian dinosaur, and sauropods, like Dolly, did not evolve to become birds; only avian theropods evolved into birds. The authors speculate this respiratory infection could have been caused by a fungal infection similar to aspergillosis, a common respiratory illness that affects birds and reptiles today and can lead to bone infections. In addition to documenting the first occurrence of such a respiratory infection in a dinosaur, this fossilized infection also has important anatomical implications for the respiratory system of sauropod dinosaurs.
“This fossil infection in Dolly not only helps us trace the evolutionary history of respiratory-related diseases back in time, but it also gives us a better understanding of what kinds of diseases dinosaurs were susceptible to,” Woodruff said.
“This would have been a remarkably, visibly sick sauropod,” Wolff said. “We always think of dinosaurs as big and tough, but they got sick. They had respiratory illnesses like birds do today, in fact, maybe even the same devastating infections in some cases.”
The researchers suggest that if Dolly had been infected with an aspergillosis-like respiratory infection, it likely experienced flu or pneumonia-like symptoms such as weight loss, coughing, fever and breathing difficulties. As aspergillosis can be fatal in birds if untreated, a potentially similar infection in Dolly could have ultimately caused the death of the animal.
“We have to continue to expand our knowledge of ancient diseases. If we look hard enough, we may begin to understand more about the evolution of immunity and infectious disease,” Wolff said. “When we work together between multiple specialties — veterinarians, anatomists, paleontologists, paleopathologists, and radiologists we can come away with a more complete picture of ancient disease.”
The research group included: Cary Woodruff, a paleopathologist/veterinarian — Ewan Wolff (University of New Mexico, Albuquerque, N.M.), a veterinarian — Sophie Dennison (TeleVet Imaging Solutions, Oakton, V.a.), and two paleontologists who are also medical anatomists — Mathew Wedel (Western University of Health Sciences, Pomona, Calif) and Lawrence Witmer (Ohio University Heritage College of Osteopathic Medicine, Athens, Ohio).
Reference:
D. Cary Woodruff, Ewan D. S. Wolff, Mathew J. Wedel, Sophie Dennison, Lawrence M. Witmer. The first occurrence of an avian-style respiratory infection in a non-avian dinosaur. Scientific Reports, 2022; 12 (1) DOI: 10.1038/s41598-022-05761-3
Illustration by Cindy Joli, Julio Francisco Garza Lorenzo, and René Dávila Rodríguez.
Approximately 80 miles from the westernmost reach of China’s Great Wall, paleontologists found relics of an even more ancient world. Over the last two decades, teams of researchers unearthed more than 100 specimens of fossil birds that lived approximately 120 million years ago, during the time of the dinosaurs. However, many of these fossils have proved difficult to identify: they’re incomplete and sometimes badly crushed. In a new paper published in the Journal of Systematics and Evolution, researchers examined six of these fossils and identified two new species. And as a fun side note, one of those new species had a movable bony appendage at the tip of its lower jaw that may have helped the bird root for food.
“It was a long, painstaking process teasing out what these things were,” says Jingmai O’Connor, the study’s lead author and the associate curator of vertebrate paleontology at Chicago’s Field Museum. “But these new specimens include two new species that increase our knowledge of Cretaceous bird faunas, and we found combinations of dental features that we’ve never seen in any other dinosaurs.”
“These fossils come from a site in China that has produced fossils of birds that are pretty darned close to modern birds, but all the bird fossils described thus far haven’t had skulls preserved with the bodies,” says co-author Jerry Harris of Utah Tech University. “These new skull specimens help fill in that gap in our knowledge of the birds from this site and of bird evolution as a whole.”
All birds are dinosaurs, but not all dinosaurs are birds; a small group of dinosaurs evolved into birds that coexisted with other dinosaurs for 90 million years. Modern birds are the descendants of the group of birds that survived the extinction that killed the rest of the dinosaurs, but many prehistoric birds went extinct then too. O’Connor’s work focuses on studying different groups of early birds to figure out why some survived while others went extinct.
The fossil site in northwestern China, called Changma, is an important place for researchers like O’Connor studying bird evolution. It’s the second-richest Mesozoic (time of the dinosaurs) fossil bird site in the world, but more than half of the fossils found there belong to the same species, Gansus yumenensis.Determining which fossils are Gansus and which ones aren’t is tricky; the six specimens that O’Connor and her colleagues examined in this study are primarily just skulls and necks, parts not preserved in known specimens of Gansus. The fossils were also somewhat smushed by their time deep in the Earth, which made analyzing them difficult.
“The Changma site is a special place,” says study co-author Matt Lamanna of Pittsburgh’s Carnegie Museum of Natural History. “The fossil-bearing rocks there tend to split into thin sheets along ancient bedding planes. So, when you’re digging, it’s like you’re literally turning back the pages of history, layer by layer uncovering animals and plants that haven’t seen the light of day in roughly 120 million years.”
“Because the specimens were pretty flattened, CT-scanning them and fully segmenting them could take years and might not even give you that much information, because these thin bones are flattened into almost the same plane, and then it just becomes almost impossible to figure out where the boundaries of these bones are,” says O’Connor. “So we had to kind of work with what was exposed.” Through painstaking work, the researchers were able to identify key features in the birds’ jaws that showed that two of the six specimens were unknown to science.
The new species (or, more accurately, new genera — genus is a step above species in the order scientists use to name organisms) are called Meemannavis ductrix and Brevidentavis zhangi. Meemannavis is named for Meemann Chang, a Chinese paleontologist who became the first woman to lead the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing. The name Brevidentavis means “short-toothed bird.” Like Gansus, both Meemannavis and Brevidentavis are ornithuromorph birds — the group that contains modern birds. Like today’s birds, Meemannavis was toothless. Brevidentavis, on the other hand, had small, peg-like teeth packed close together in its mouth. Along with those teeth came another strange feature.
“Brevidentavis is an ornithuromorph bird with teeth, and in ornithuromorphs with teeth, there’s a little bone at the front of the jaw called the predentary, where its chin would be if birds had chins,” explains O’Connor. In a previous study on the predentary in another fossil bird, the authors figured out, by CT-scanning the bone and staining it with chemicals, that the predentary bone underwent stress and also found a kind of cartilage that only forms when there’s movement.
“In this earlier study, we were able to tell that the predentary was capable of being moved, and that it would have been innervated — Brevidentavis wouldn’t just have been able to move its predentary, it would have been able to feel through it,” says O’Connor. “It could have helped them detect prey. We can hypothesize that these toothed birds had little beaks with some kind of movable pincer at the tip of their jaws in front of the teeth.”
Brevidentavis isn’t the first fossil bird discovered with a predentary that might have been used in this way, but its existence, along with Meemannavis, helps round out our understanding of the diversity of prehistoric birds, especially in the Changma region.
The study also helps shed light on the most common bird from the site, Gansus, since at least four of the other specimens examined probably belong to this species. “Gansus is the first known true Mesozoic bird in the world, as Archaeopteryx is more dinosaur-like, and now we know what its skull looks like after about 40 years,” notes Hai-Lu You of the IVPP.
“These amazing fossils are like a lockpick allowing us to open the door to greater knowledge of the evolutionary history of the skull in close relatives of living birds,” says Tom Stidham, a co-author from the IVPP. “At a time when giant dinosaurs still roamed the land, these birds were the products of evolution experimenting with different lifestyles in the water, in the air, and on land, and with different diets as we can see in some species having or lacking teeth. Very few fossils of this geological age provide the level of anatomical detail that we can see in these ancient bird skulls.”
“These discoveries strengthen the hypothesis that the Changma locality is unusual in that it is dominated by ornithuromorph birds, which is uncommon in the Cretaceous,” says O’Connor. “Learning about these relatives of modern birds can ultimately help us understand why today’s birds made it when the others didn’t.”
Reference:
Jingmai K. O’Connor, Thomas A. Stidham, Jerald D. Harris, Matthew C. Lamanna, Alida M. Bailleul, Han Hu, Min Wang, Hai‐Lu You. Avian skulls represent a diverse ornithuromorph fauna from the Lower Cretaceous Xiagou Formation, Gansu Province, China. Journal of Systematics and Evolution, 2022; DOI: 10.1111/jse.12823
In July 2019, a series of earthquakes including two major shocks of magnitude 6.4 and 7.1 a day apart struck near Ridgecrest, CA, between Los Angeles and Las Vegas. For local residents, it was a violent interruption to the Fourth of July holiday. For seismologists, it was a rare opportunity to study how earthquakes damage the Earth’s crust.
The earthquake zone — which belongs to a network of faults called the Eastern California Shear Zone — is sparsely populated and arid, without much in the way of vegetation or buildings to obscure the surface. But it is also well-covered by satellite and remote imagery and accessible to geologists who could be on the scene well before evidence of crust damage disappeared.
UC Davis doctoral student Alba Rodríguez Padilla was among the scientists studying the site, along with Professor Mike Oskin, Department of Earth and Planetary Sciences, Christopher Milliner, California Institute of Technology and Andreas Plesch of Harvard University. They mapped the surface rupture from LIDAR data and aerial imagery collected by prior studies, and compared the rupture maps to other datasets to explore the distribution of rock damage from the earthquakes. Their findings are published Feb. 24 in Nature Geoscience.
“We not only have aridity helping here, improvements in imaging technique and resolution, together with collecting a large spatial data footprint, are what make the Ridgecrest coverage cutting edge,” Rodríguez Padilla said.
Inelastic deformation
The rock surrounding the fault suffered from “inelastic deformation,” meaning it was deformed and broken rather than returning to its original configuration. The deformation was highest within 100 meters of the fault, with widespread, low-intensity damage up to 20 kilometers (16 miles) away.
This deformation leaves the rock around the fault less rigid than before, softening the crust. This softening dissipates energy from future earthquakes, increases permeability and focuses deformation.
The study provides a better understanding of how damage from earthquakes accumulates and might affect future events, Rodríguez Padilla said.
The study was funded by the Southern California Earthquake Center, which is supported by NSF and the U.S. Geological Survey. Rodríguez Padilla was partly supported by a NASA fellowship.
Reference:
Alba M. Rodriguez Padilla, Michael E. Oskin, Christopher W. D. Milliner, Andreas Plesch. Accrual of widespread rock damage from the 2019 Ridgecrest earthquakes. Nature Geoscience, 2022; DOI: 10.1038/s41561-021-00888-w
Nearly 10 yrs of drone surveys at Merapi volcano highlights the importance of hydrothermal weakening and structures hidden beneath younger lavas. A fracture system that formed in 2012 was subsequently buried under new lava in 2018. Only a year later, the new lava dome that formed in 2018 showed signs of instability and collapse along the previously buried fracture system, implying that hidden weaknesses may be a key factor in controlling hazardous volcano collapse. Credit: Darmawan et al., (2022)
Lava domes form at the top of many volcanoes when viscous lava erupts. When they become unstable, they can collapse and cause a hazard. An international team of researchers has analyzed summit dome instabilities at the Merapi Volcano, Indonesia. The researchers hope that by understanding the inner processes, volcano collapses can be better forecasted.
Catastrophic volcano collapses and associated explosions, like the famous collapse of Mt St Helens in 1980, are widely considered as unpredictable. This is because the physical properties, stress conditions, and internal structure of volcanoes and the lava domes on top of many volcanoes are not well understood and can change rapidly from one day to another.
A new study jointly led by Gadja Mata University in Yogyakarta Indonesia, Uppsala University in Sweden, and the German Research Center GFZ at Potsdam is now able to explain summit dome instabilities and associated pyroclastic flows at Merapi volcano, Indonesia. The study combines novel drone-based photogrammetry surveillance over several years with mineralogical, geochemical, and mechanical rock strength measurements.
The research demonstrated that a horseshoe-shaped fracture zone in the volcanoes summit region that formed in 2012 and which guided intense gas emission in the past was subsequently buried by renewed lava outpourings in 2018. The new lava dome that has been forming since 2018 started to show signs of instability in 2019 and the researchers were able to show that the summit dome of the volcano is currently collapsing along this now-hidden fracture zone. The research team then considered the changes that must have occurred along this now buried fracture zone from long term gas flux by measuring the composition and physical properties along similar fracture zones in the volcano’s summit region, and concludes that weakened rocks of the hidden fracture zone are likely the main cause for the location of the ongoing summit instabilities at Merapi.
This finding now offers an opportunity for monitoring teams at volcanoes to better forecast locations of potential volcano collapse by employing long-term remote sensing monitoring techniques to assess the hazards associated with summit dome and edifice failure and collapses at active volcanoes worldwide.
Reference:
Darmawan et al. Hidden mechanical weaknesses within lava domes provided by buried high-porosity hydrothermal alteration zones. Scientific Reports, DOI: 10.1038/s41598-022-06765-9
Note: The above post is reprinted from materials provided by Uppsala University.
The astonishing force of the Tonga volcanic eruption in January 2022 shocked the world, but the fact that this underwater volcano actually erupted came as less of a surprise to geoscientists using satellite data to study changes in the temperature deep below Earth’s surface. As part of the effort to understand the complexities of Earth’s interior, scientists working within ESA’s Science for Society 3D Earth project, have developed a state-of-the art model of the lithosphere, which is a term to describe Earth’s brittle crust and the top part of the upper mantle, and the sub-lithospheric upper mantle down to 400 km depth. The model combines different satellite data, such as gravity data from ESA’s GOCE mission, with in-situ observations, primarily seismic tomography. The model that show differences in temperature, or thermal structures, indicated that the Tonga volcano was due to erupt at some point. Credit: ESA/Planetary Visions
The astonishing force of the Tonga volcanic eruption shocked the world, but the fact that this underwater volcano actually erupted came as less of a surprise to geoscientists using satellite data to study changes in the temperature deep below Earth’s surface.
The cataclysmic explosion of the Hunga Tonga-Hunga Ha’apai volcano in January is reported to have been the biggest eruption recorded anywhere on the planet in 30 years. It sent a plume of ash soaring into the sky, left the island nation of Tonga smothered in ash, sonic booms were heard as far away as Alaska and tsunami waves raced across the Pacific Ocean.
While the Tonga eruption was powerful but short, last year’s eruption of the Cumbre Vieja volcano on the Spanish Canary Island of La Palma was less explosive but lasted for almost three months.
Although different, both of these recent eruptions remind us all of how devastating nature can be. A better understanding of the natural processes that are occurring deep below our feet might bring the possibility of predicting eruptions a little closer.
This is one of the aims of ESA’s Science for Society 3D Earth project where an international group of geoscientists joined forces to develop a state-of-the art global model of the lithosphere, which is a term to describe Earth’s brittle crust, the top part of the upper mantle and the sub-lithospheric upper mantle down to 400 km depth. The model combines different satellite data, such as gravity data from ESA’s GOCE, with in-situ observations, primarily seismic tomography.
In their model that shows differences in temperature, or the thermal structure, of Earth’s upper mantle, the researchers could see that these volcanoes would erupt at some point. Predicting exactly when this would happen is, however, more difficult.
Javier Fullea, from Complutense University of Madrid, said, “Our WINTERC-G model, which uses in-situ tomographic and GOCE satellite gravity data, shows a branch of the Azores plume. It is visible from the surface down to a depth of 400 km, at the base of the upper mantle. The plume flows southeast towards Madeira and the Canary Islands surrounding the cold mantle beneath the north Atlantic’s African margin.
“Across the globe, we see that the Hunga Tonga volcano is located in a back arc basin, created by the subduction of the Tonga slab. Back arc volcanoes are associated with the cold slab being melted by the mantle as the slab slides down into the mantle.”
Sergei Lebedev, from the University of Cambridge in the UK, adds, “From such models and seismic tomography, we see structures rising from great depth beneath the Canary Islands. These anomalies reflect hot material rising to the surface of Earth and are referred to as hotspots or plumes and are a constant source for the volcanos at the surface.
“The origin of the Hunga Tonga-Hunga Ha’apai volcano is different. It is a part of the Tonga–Kermadec arc, where the edge of the Pacific tectonic plate dives beneath the Australian Plate. Here, our imaging shows the layer of hydrated, partially molten rock above the plunging Pacific Plate, which feeds the volcanoes of the arc.”
But where do these thermal anomalies come from?
The answer lies even deeper, at a depth of around 2800 km, and is associated with structures at the core–mantle boundary: the Large-Low Seismic Velocity Provinces (LLSVPs). These prominent continent-sized structures appear to have a big impact on how the surface behaves.
Clint Conrad, from Norway’s Centre for Earth Evolution Dynamics, said, “There is a link between the flow in the mantle, where convection cells drive plate tectonics, and major plume locations. The flow along the core–mantle boundary pushes plume material against the LLSVPs, forming the plumes. In models, this flow is driven by downwelling slabs that surround the two LLSVPs. The Canary Islands, for example, site above the edge of the African LLSVP.”
However, the exact origin and build-up of the LLSVPs remains elusive. At the recent 4D Earth Science meeting alternative concepts and ideas were discussed using satellite data and seismological models, which will hopefully lead to more detailed studies of Earth interior in the near future.
Bart Root from TU Delft, one of the organizers, summarizes, “Clearly a multidisciplinary approach is needed, where different types of satellite data are combined with seismological data in a common way to address the exact structure of Earth’s deep interior.”
ESA’s Diego Fernandez noted, “I’m happy to see that ESA’s FutureEO Science for Society project is yielding results that will further improve our understanding of the deep-lying sources of the events such as we’ve just seen in La Palma and Tonga.
“It is worth noting that data from the GOCE satellite has been key to this research. GOCE, which mapped variations in Earth’s gravity field with extreme detail and precision, completed its mission in orbit back in 2013—and scientists still rely on the data. This is another example of the benefits our satellite missions bring well beyond their life in orbit.”
The pink pumice, and its thermal history, provides an insight into underwater eruptions.
In research published in the Nature portfolio journal Communications Earth and Environment, the researchers including Professor Scott Bryan, Dr Michael Jones and PhD candidate Joseph Knafelc, were intrigued by the occurrence of pink pumice within the massive pumice raft that resulted from the Havre 2012 deep-sea eruption.
The publication of the new research comes after the recent dramatic explosion of the Hunga Tonga Hunga Ha’apai volcano in Tonga, about 1200 km north of the Havre volcano, which has sharply brought the world’s attention to the explosive potential and hazards associated with submarine eruptions.
Professor Bryan, who has been studying pumice rafts for more than 20 years, said the pink pumice produced in the 2012 Havre eruption revealed insights into how magma can shoot out and up from underwater volcanoes.
“Unlike Hunga Tonga-Hunga Ha’apai, Havre is in a much more remote location. Its summit is 900m below sea level, and the nearest populated areas are around 800km away on the North Island of New Zealand,” Professor Bryan said.
When the volcano erupted in 2012, there was no one to see it happen. But the colour of the pumice tells the story of what happened.
Joseph Knafelc, lead author of the research, said the new model put forward in the research challenged the known depth limits for explosive eruptions.
“The common theory is that underwater eruptions, particularly in deep water such as at Havre, cannot be explosive and instead make lava flows on the seafloor,” Mr Knafelc said.
“But few submarine eruptions have been able to be observed, and past studies had failed to consider the existence of the pink pumice in the pumice raft.
“The colour in this case is critical — the pink to red colour tells us the pumice had to be ejected into the air at temperatures above 700 °C for tiny iron minerals to then oxidise and cause the reddening.
“The problem is that it was an underwater eruption that had to push up through nearly 1 km of ocean. The only way it can do this is if the eruption was very powerful and able to punch through the ocean water and produce an eruption column in the air.”
The research details how the core of the eruption was a powerful jet and able to be shielded from the surrounding water.
“The pink pumice and its thermal history tell us that the core of the eruption column was untouched by the cooling effects of the ocean water,” Professor Bryan said.
“An explosive eruption column could get hot pumice into the atmosphere in as little as a few seconds.
“This was a very powerful eruption. The problem is that previous studies had not recognised or downplayed the explosive potential of submarine eruptions even in very deep water and thus the hazards posed by submarine eruptions.
“As a timely reminder, we recently witnessed in Tonga the power of, and devastation and impact from, explosive submarine eruptions, the effects of which could be detected around the world.”
The research team included Professor Andrew Berry and Dr Guil Mallman from the Australian National University, Professor David Gust and Dr Henrietta Cathey from QUT, Dr Eric Ferré, from the University of Louisiana at Lafayette, and Daryl Howard from the Australian Synchrotron. QUT researchers are from the QUT Earth and Atmospheric School and the Central Analytical Research Facility (CARF).
Reference:
Joseph Knafelc, Scott E. Bryan, Michael W. M. Jones, David Gust, Guil Mallmann, Henrietta E. Cathey, Andrew J. Berry, Eric C. Ferré, Daryl L. Howard. Havre 2012 pink pumice is evidence of a short-lived, deep-sea, magnetite nanolite-driven explosive eruption. Communications Earth & Environment, 2022; 3 (1) DOI: 10.1038/s43247-022-00355-3
Drone images of craters formed at Sheep Mountain. Credit: Kent Sundell, Casper College.
Several dozen small impact craters, 10-70-m in size, have been discovered in southeastern Wyoming. A team of U.S. and German geoscientists found these ancient craters in exposed sedimentary layers from the Permian period (280 million years ago). After discovering the first craters, the team initially suspected that they are a crater-strewn field, formed by the breakup of an asteroid that entered the atmosphere. However, with the discovery of more and more craters over a wide area, this interpretation was ruled out.
Many of the craters are clustered in groups and are aligned along rays. Furthermore, several craters are elliptical, allowing the reconstruction of the incoming paths of the impactors. The reconstructed trajectories have a radial pattern.
“The trajectories indicate a single source and show that the craters were formed by ejected blocks from a large primary crater,” said project leader Thomas Kenkmann, professor of geology at the University of Freiburg, Germany. “Secondary craters around larger craters are well known from other planets and moons but have never been found on Earth,”
The team calculated the ballistic trajectories and used mathematical simulations to model the formation of the craters. All of the craters found so far are located 150-200 km from the presumed primary crater and were formed by blocks that were 4-8-m in size that struck the Earth at speeds of 700-1000 m/s. The team estimate that the source crater is about 50-65 km in diameter and should be deeply buried under younger sediments in the northern Denver basin near the Wyoming-Nebraska border.
Reference:
Thomas Kenkmann, Louis Müller, Allan Fraser, Doug Cook, Kent Sundell, Auriol S.P. Rae. Secondary cratering on Earth: The Wyoming impact crater field. GSA Bulletin, 2022; DOI: 10.1130/B36196.1
The Kumano Pluton in southern Japan appears as a red bulge (indicating dense rock) in the center of a new 3D visualization by The University of Texas at Austin. The pluton is large enough to interfere with the nearby Nankai subduction zone and the region’s earthquakes. Credit: Adrien Arnulf
Thanks to 20 years of seismic data processed through one of the world’s most powerful supercomputers, scientists have created the first complete, 3D visualization of a mountain-size rock called the Kumano Pluton buried miles beneath the coast of southern Japan. They can now see the rock could be acting like a lightning rod for the region’s megaquakes, diverting tectonic energy into points along its sides where several of the region’s largest earthquakes have happened.
Scientists have known about the pluton for years but were aware of only small portions of it. Thanks to new research by an international team of scientists led by The University of Texas at Austin, researchers now have a view of the entire subterranean formation and its effect on the region’s tectonics.
The findings will provide critical information for a major new Japanese government-funded project to find out whether another major earthquake is building in the Nankai subduction zone, where the pluton is located, said Shuichi Kodaira, director of the Japan Agency for Marine-Earth Science and Technology and a co-author of the study published Feb. 3 in the journal Nature Geoscience.
“We cannot predict exactly when, where, or how large future earthquakes will be, but by combining our model with monitoring data, we can begin estimating near-future processes,” said Kodaira, who was among the scientists who first spotted signs of the Kumano Pluton in 2006. “That will provide very important data for the Japanese public to prepare for the next big earthquake.”
The full extent of the Kumano Pluton was revealed using the LoneStar5 supercomputer at UT’s Texas Advanced Computing Center to piece together 20 years of seismic data into a single high-definition 3D model.
“The fact that we can make such a large discovery in an area that is already well studied is, I think, eye opening to what might await at places that are less well monitored,” said Adrien Arnulf, a research assistant professor at the University of Texas Institute for Geophysics and the study’s lead author.
The model shows the region around the Nankai subduction zone, with the Earth’s crust bending under the pluton’s weight. In another unexpected finding, the pluton was seen diverting buried groundwater into the Earth’s interior. The researchers think the pluton’s interference with the wider subduction zone is influencing the tectonic forces that cause earthquakes.
Seismic imaging uses sound waves to create pictures of the Earth’s subsurface. Over the years, Japan’s vast network of sensors has collected millions of seismic recordings from thousands of locations along the Nankai subduction zone. The sensors are primarily used to record earthquakes and tremors, but the team widened their search to include chance recordings of passing scientific surveys using a technique Arnulf and coauthor Dan Bassett, a research scientist at GNS Science, had perfected while working on small-scale projects in New Zealand. The researchers compiled the massive amounts of information into a single data set and turned it into a 3D model with the help of LoneStar5.
In addition to shedding light on how the pluton may be influencing how and where earthquakes occur, the study is a major demonstration of how big data could revolutionize earthquake science. Arnulf envisions the same methods being used to make regional-scale images in other areas, such as northeast Japan, New Zealand, and Cascadia in the U.S. Pacific Northwest — all of which have subduction zones known to host the Earth’s largest earthquakes.
The research was funded by the U.S. National Science Foundation. Additional co-authors include scientists at Scripps Institution of Oceanography at the University of California, San Diego. UTIG is a research unit of the UT Jackson School of Geosciences.
Reference:
Adrien F. Arnulf, Dan Bassett, Alistair J. Harding, Shuichi Kodaira, Ayako Nakanishi, Gregory Moore. Upper-plate controls on subduction zone geometry, hydration and earthquake behaviour. Nature Geoscience, 2022; DOI: 10.1038/s41561-021-00879-x
Minerals are visible in rock samples from the coast of Oman. Scientists said these rocks may reveal new information about subduction, an important tectonic process on Earth. Credit: Joshua Garber / Penn State.
Ancient rocks on the coast of Oman that were once driven deep down toward Earth’s mantle may reveal new insights into subduction, an important tectonic process that fuels volcanoes and creates continents, according to an international team of scientists.
“In a broad sense this work gives us a better understanding of why some subduction zones fail while others set up as long-term, steady-state systems,” said Joshua Garber, assistant research professor of geosciences at Penn State.
Subduction occurs when two tectonic plates collide, and one is forced under the other. Where oceanic and continental plates meet, the denser oceanic plates normally subduct and descend into the mantle, the scientists said.
Occasionally, oceanic plates move on top, or obduct, forcing continental plates down toward the mantle instead. But the buoyancy of the continental crust can cause the subduction to fail, carrying the material back toward the surface along with slabs of oceanic crust and upper mantle called ophiolites, the scientists said.
“The Samail Ophiolite on the Arabian Peninsula is one of the largest and best exposed examples on the surface of the Earth,” Garber said. “It’s one of the best studied, but there have been disagreements about how and when the subduction occurred.”
The team, led by Penn State scientists, investigated the timing of the subduction using nearby rocks from the Saih Hatat formation in Oman, which was subducted under the Samail Ophiolite, according to the researchers.
Heat and pressure from the process created garnet, zircon and rutile crystals in a key suite of highly metamorphosed rocks that saw the most extreme conditions during subduction. Using state-of-the-art dating techniques, including measuring isotopic dates and trace elements, the scientists determined these minerals all formed at roughly the same time 81 to 77 million years ago.
“What’s interesting about this is that they were all dated by slightly different methods, but they all gave us essentially the same results,” Garber said. “This tells us that all the minerals in the rocks have a coherent story. They all record the same metamorphic episode at the same time.”
The findings, published in the Journal of Geophysical Research: Solid Earth, dispute previous results that estimated the event began 110 million years ago and happened in separate phases, the scientists said.
“What our findings suggest is that this continental material was not subducted deep into the mantle a long time before the ophiolite formed as previously thought,” Garber said. “Our data supports a nice sequence of events that happened in a tighter window and that makes more geological sense.”
The scientists said the subduction of the continental margin occurred after the obduction of the Samail Ophiolite. The most deeply subducted continental material was likely anchored to more dense rocks, and when this anchor broke, the buoyant continental rocks exhumed, first quickly, and then slowly during a lengthy residence in the lower to middle crust. It eventually become exposed in tectonic windows through the ophiolite.
“Subduction is a really big part of plate tectonics on Earth,” Garber said. “It’s the major recycling mechanism for surface material to the deeper mantle, so understanding how they eventually evolve into stable subduction zones or how they end very quickly is of great interest. I think here we’ve nailed down why this subduction zone ended and the sequence of events that came with it.”
Also contributing to this work from Penn State was Andrew Smye, assistant professor of geosciences.
Matthew Rioux, assistant teaching professor, Bradley Hacker, professor emeritus, and Andrew Kylander-Clark, senior development engineer, at the University of California, Santa Barbara; Michael Searle, professor at Oxford University; Jeff Vervoort, professor at Washington State University; and Clare Warren, professor at the Open University also contributed.
The National Science Foundation and an ExxonMobil/Geological Society of America graduate student research grant provided funding.
Reference:
Joshua M. Garber, Matthew Rioux, Michael P. Searle, Andrew R. C. Kylander‐Clark, Bradley R. Hacker, Jeff D. Vervoort, Clare J. Warren, Andrew J. Smye. Dating Continental Subduction Beneath the Samail Ophiolite: Garnet, Zircon, and Rutile Petrochronology of the As Sifah Eclogites, NE Oman. Journal of Geophysical Research: Solid Earth, 2021; 126 (12) DOI: 10.1029/2021JB022715
Note: The above post is reprinted from materials provided by Penn State. Original written by Matthew Carroll.
A magnitude 8.2 earthquake was “hidden” within a magnitude 7.5 earthquake in 2021, sending a mysterious tsunami around the world, according to a new study in Geophysical Research Letters. Credit: Zhe Jia and AGU
Scientists have uncovered the source of a mysterious 2021 tsunami that sent waves around the globe.
In August 2021, a magnitude 7.5 earthquake hit near the South Sandwich Islands, creating a tsunami that rippled around the globe. The epicenter was 47 kilometers below the Earth’s surface—too deep to initiate a tsunami—and the rupture was nearly 400 kilometers long, which should have generated a much larger earthquake.
Seismologists were puzzled and sought to understand what really happened that day in the remote South Atlantic.
A new study revealed the quake wasn’t a single event, but five, a series of sub-quakes spread out over several minutes. The third sub-quake was a shallower, slower magnitude 8.2 quake that hit just 15 kilometers below the surface. That unusual, “hidden” earthquake was likely the trigger of the worldwide tsunami.
The study was published in the AGU journal Geophysical Research Letters, which publishes short-format, high-impact papers with implications that span the Earth and space sciences.
Because the South Sandwich Islands earthquake was complex, with multiple sub-quakes, its seismic signal was difficult to interpret, according to lead study author Zhe Jia, a seismologist at the California Institute of Technology. The magnitude 8.2 quake was hidden within the tangle of seismic waves, which interfered with each other over the course of the event. The hidden quake’s signal wasn’t clear until Jia filtered the waves using a much longer period, up to 500 seconds. Only then did the 200-second-long quake, which Jia said accounted for over 70% of the energy released during the earthquake, become clear.
“The third event is special because it was huge, and it was silent,” Jia said. “In the data we normally look at [for earthquake monitoring], it was almost invisible.”
Predicting hazards for complex earthquakes can be difficult, as the South Sandwich Islands quake demonstrates. The USGS initially reported the magnitude 7.5 quake and only added the 8.2 event the following day, as the surprise tsunami lapped on shores up to 10,000 kilometers away from its point of origin.
“We need to rethink our way to mitigate earthquake-tsunami hazards. To do that, we need to rapidly and accurately characterize the true size of big earthquakes, as well as their physical processes,” Jia said.
Because this type of earthquake can result in unexpected tsunami, it’s critical to improve our predictions. “With these complex earthquakes, the earthquake happens and we think, ‘Oh, that wasn’t so big, we don’t have to worry.’ And then the tsunami hits and causes a lot of damage,” said Judith Hubbard, a geologist at the Earth Observatory of Singapore who was not involved in the study. “This study is a great example of how we can understand how these events work, and how we can detect them faster so we can have more warning in the future.”
Sneaky seismic signals
When an earthquake hits, it sends waves of vibration through the Earth. The global network of earthquake monitors uses those seismic waves to pinpoint the time, location, depth and magnitude of an earthquake. Common monitoring often focuses on short- and medium-periods of waves, Jia said, and longer periods can be left out. But even incorporating long periods into monitoring, on its own, isn’t enough to catch complex earthquakes with messy seismic signals.
“It’s hard to find the second earthquake because it’s buried in the first one,” Jia said. “It’s very seldom complex earthquakes like this are observed. … And if we don’t use the right dataset, we cannot really see what was hidden inside.”
A simple earthquake can easily be pinpointed and described, Jia said. But a messy one needs to be carefully broken down into its constituent parts, to find out what unique combination of simpler earthquakes built up the complex one.
Jia and his colleagues developed an algorithm to tease apart the seismic signals during those messy earthquakes. By “decomposing” complex earthquake signals into simpler forms, using waves over different periods (varying from 20 to 500 seconds long), the algorithm can identify the location and properties of different sub-earthquakes. It’s akin to someone with perfect pitch hearing five dissonant notes struck at once, yet being able to identify each individual note.
“I think a lot of people are daunted by trying to work on events like this,” said Hubbard. “That somebody was willing to really dig into the data to figure it out is really useful.”
Both Jia and Hubbard noted a long-term goal is to automate the detection of such complex earthquakes, as we can for simple earthquakes. For the 2021 quake, the tsunami was small by the time it reached shores, and most of the permanent residents of the remote, volcanic islands are penguins. But complex earthquakes can pose significant hazards if they generate larger tsunami or strike in a densely populated region.
Reference:
Zhe Jia et al, The 2021 South Sandwich Island M w 8.2 Earthquake: A Slow Event Sandwiched Between Regular Ruptures, Geophysical Research Letters (2022). DOI: 10.1029/2021GL097104
A series of earthquakes and aftershocks shook the Ridgecrest area in Southern California in 2019. Distributed acoustic sensing (DAS) using fiber-optic cables enables high-resolution subsurface imaging, which can explain the observed site amplification of earthquake shaking. Credit: Yang et al., 2022
How much the ground moves during an earthquake strongly depends on properties of rock and soil just beneath Earth’s surface. Modeling studies suggest that ground shaking is amplified in sedimentary basins, on which populated urban areas are often located. However, imaging near-surface structure around urban areas at high resolution has been challenging.
Yang et al. have developed a new approach of using distributed acoustic sensing (DAS) to construct a high-resolution image of near-surface structure. DAS is an emerging technique that can transform existing fiber-optic cables into seismic arrays. By monitoring changes in how light pulses scatter as they travel through the cable, scientists can calculate small strain changes in the material surrounding the fiber. In addition to recording earthquakes, DAS has proven useful in a variety of applications, such as naming the loudest marching band at the 2020 Rose Parade and uncovering dramatic changes in vehicular traffic during COVID-19 stay-at-home orders.
Prior researchers repurposed a 10-kilometer stretch of fiber to detect aftershocks following the magnitude 7.1 Ridgecrest earthquake in California in July 2019. Their DAS array detected about six times as many small aftershocks as conventional sensors did during a 3-month period.
In the new study, the researchers analyzed continuous seismic data produced by traffic. The DAS data allowed the team to develop a near-surface shear velocity model with a subkilometer resolution two orders of magnitude higher than typical models. This model revealed that along the length of the fiber, sites where aftershocks produced more ground motion generally corresponded with where shear velocity was lower.
Such fine-scale seismic hazard mapping could improve urban seismic risk management, especially in cities where fiber-optic networks may already be present, the authors suggest.
Reference:
Yan Yang et al, Sub‐Kilometer Correlation Between Near‐Surface Structure and Ground Motion Measured With Distributed Acoustic Sensing, Geophysical Research Letters (2021). DOI: 10.1029/2021GL096503
The edges of Earth’s tectonic plates, centered over the Pacific Ocean. Colors indicate whether plates are scraping past (yellow), diving under (green), or pulling away (red) from one another. Study site near New Zealand marks the location of a newly forming subduction zone. Credit: Brandon Shuck/University of Texas Institute for Geophysics
One longstanding enigma in geology is how one tectonic plate can break Earth’s rock-hard shell and begin diving under another in the process known as subduction.
Now, a new study describes how a small break in one tectonic plate was squeezed and pulled over millions of years until it unzipped and set in motion a runaway geologic process. The study, of an emerging subduction zone off New Zealand, was just published in the journal Nature Geoscience.
“We now know how subduction nucleated and how fast it’s growing,” said lead author Brandon Shuck. “That’s important to know because subduction is the main driver of plate tectonics. It builds mountains, forms new oceans and drives chemical cycling from the deep earth all the way to the atmosphere.” Shuck did the work for his doctoral thesis at the University of Texas Jackson School of Geosciences; he is now a postdoctoral research scientist at Columbia University’s Lamont-Doherty Earth Observatory.
Earth is believed to be the only planet in the Solar System to undergo subduction, which is key to the cycling of carbon that makes life possible here. “We do believe that subduction didn’t always happen on Earth, so understanding how [it] initiates today is a critical step to understanding how our world eventually became a habitable planet,” said the study’s coauthor Harm Van Avendonk, a senior research scientist at the University of Texas.
The research began in 2018 aboard Lamont-Doherty’s research vessel Marcus G. Langseth off New Zealand, where Shuck and his shipmates endured weeks of bad weather to gather detailed seismic images of the seafloor.
Onshore, Shuck matched the images with rock samples from other ocean expeditions. This provided a geologic timeline to reconstruct an unzipping plate. According to his reconstruction, a small break appeared in the Australian plate around 16 million years ago, which slowly grew as it collided with other tectonic plates. When the break had unzipped far enough, the heavier portion of the plate broke through the earth’s rocky shell (known as the lithosphere), setting it on a downward conveyor that has continued for the last 8 million years. Today, the new subducting margin is about 300 miles long.
“That’s pretty small at the scale of global tectonics,” Shuck said. “But it’s going to keep growing all the way down to Antarctica.” he predicted. “Once it gets that big, more than 1,000 miles long, it could change the motion of neighboring tectonic plates.”
For now, the only sign on the surface is a handful of volcanoes near New Zealand’s South Island. Most emerged in the last hundred thousand years. They are likely to grow into a longer volcanic chain as the split spreads south in the future, Shuck said.
Shuck’s study reconciles two opposing ideas about how subduction starts: with the gradual back and forth of plates bumping against one another, or by plates spontaneously and rapidly collapsing under their own weight. The new research suggests that sometimes the two ideas might both be part of the equation.
“The work shows that there may, instead, be multiple scenarios driving subduction initiation,” said Fabio Crameri, a Swiss geophysicist who wrote a Nature Geoscience commentary accompanying the study. “Even if the same scenario isn’t true for every subduction zone, their model challenges our current systems for classifying subduction zone initiation and highlights the need for 4D modeling.”
Reference:
Brandon Shuck et al, Stress transition from horizontal to vertical forces during subduction initiation, Nature Geoscience (2022). DOI: 10.1038/s41561-021-00880-4
Images of different fossil remains of Abditosaurus kuehnei at the Orcau-1 site (a), the excavation process (b and c) and the neck after fossil preparation (d).
Researchers from the Institut Català de Paleontologia Miquel Crusafont (ICP), the Conca Dellà Museum (MCD), the Universitat Autònoma de Barcelona (UAB), the University of Zaragoza (UNIZAR) and the NOVA University of Lisbon (UNL) have described the new species of titanosaur dinosaur Abditosaurus kuehnei from the remains excavated at the Orcau-1 site, in the southern Pyrenees (Catalonia, Spain). The semiarticulated 70.5-million-year-old skeleton is the most complete specimen of this herbivorous group of dinosaurs discovered so far in Europe. Moreover, Abditosaurus is the largest titanosaur species found in the Ibero-Armorican island — an ancient region nowadays comprising Iberia and the south of France — representing a senescent individual estimated to be 17,5 meters in length with body mass of 14,000 kg.
The size of this giant is one of the most surprising facts to researchers. “Titanosaurs from the Upper Cretaceous of Europe tend to be small or medium-sized due to their evolution in insular conditions,” explained Bernat Vila, paleontologist at the ICP leading the research. During the Upper Cretaceous (between 83 and 66 million years ago), Europe was a large archipelago made up of dozens of islands. The species that evolved there tend to be relatively small, or even dwarves compared to their relatives living in large landmasses, due primarily to the limitation of food resources in islands. “It is a recurring phenomenon in the history of life on Earth, we have several examples worldwide in the fossil record of this evolutionary trend. That’s why we were astonished by the large dimensions of this specimen,” said Vila.
The fieldwork conducted over several decades unearthed 53 skeletal elements of the specimen. These include several teeth, vertebrae, ribs, and limb, scapular and pelvic bones, as well as a semiarticulated fragment of the neck formed by 12 cervical vertebrae. “We were really lucky, it is unusual to find such complete specimens in the Pyrenees due to its troubled geologic history,” explains Àngel Galobart, ICP researcher and director of the Conca Dellà Museum (Isona, Catalonia).
The excavation of the neck in 2014 was a technical challenge. Once prepared for extraction, the neck was encased in a large block of polyurethane foam, becoming one of the largest jackets ever excavated in Europe.
The history of the research that has led to the description of the new species dates back to 1954, when German paleontologist Walter Kühne collected the first remains and sent them to Madrid. The site fell into oblivion until 1986, when some more remains began to be extracted until a great storm forced the cancellation of the excavation. Subsequently, fieldwork on the site fell again into oblivion until a paleontologist from the ICP resumed systematic excavations in Orcau-1. The story of this finding was featured in the 2017 documentary “Europe’s last giant.” The generic name Abditosaurus means ‘forgotten reptile’ and the specific epithet kuehnei is a tribute to its discoverer.
In their article published in Nature Ecology & Evolution, researchers conclude that Abditosaurus belongs to a group of saltasaurine titanosaurs from South America and Africa, different from the rest of European titanosaurs that are characterized by a smaller size. These authors hypothesize that the Abditosaurus lineage reached the Ibero-Armorican island taking advantage of a global drop in sea level that reactivated ancient migration routes between Africa and Europe.
“Other evidence support the migration hypothesis,” explains Albert Sellés, paleontologist at the ICP and co-author of the article. “In the same site we have found eggshells of dinosaur species known to have inhabited Gondwana, the southernmost continent.”
The new finding is a major advance in the understanding of the evolution of sauropod dinosaurs at the end of the Cretaceous and brings a new perspective to the phylogenetic and paleobiogeographic puzzle of sauropods in the last 15 million years before their extinction.
In addition to Vila, Sellés and Galobart, Novella Razzolini (Institut Català de Paleontologia Miquel Crusafont and Conca Dellà Museum), Miguel Moreno (Museu de Lurinhã and NOVA University of Lisbon), Iñaki Canudo (Aragosaurus-IUCA Group, University of Zaragoza) and Alejandro Gil (Universitat Autònoma de Barcelona) participated in this study.
“During the Jurassic and Cretaceous, Iberia was the point of connection between Eurasia, Africa and North America. Studying how Abditosaurus relates to the fauna of these continents helps us to understand when there were connections between them, and when they became isolated,” says Miguel Moreno, researcher at the Museu de Lurinhã and NOVA University of Lisbon that has performed the paleobiogeographic study.
The large Cretaceous herbivores
Titanosaurs are a group of sauropod dinosaurs that become very diverse and abundant in the terrestrial ecosystems of the Cretaceous. All of them were quadrupeds and phytophagous. Titanosaurs had a small and pointed skull, with small nail-shaped teeth used to uproot vegetation. Their body was robust, with forelimbs shorter than the hindlimbs and a long necks and tails. Some species sported a skin covered with bony plates named osteoderms that may have served as a protective shield or as a reserve of calcium.
The paleontological sites within the Catalan Pyrenees have provided exceptional dinosaur fossils over the last century. Research is especially significant as its fossil record includes the last vertebrate faunas, including non-avian dinosaurs, that lived in Europe right before the global extinction event that took place 66 million years ago.
On the ICP: The Institut Català de Paleontologia Miquel Crusafont (ICP) is a CERCA center (Centres de Recerca de Catalunya, Generalitat de Catalunya) ascribed to to the Universitat Autònoma de Barcelona (UAB) and devoted to research in vertebrate and human paleontology at the highest international level, as well as the conservation and dissemination of the Catalan paleontological heritage. It is constituted as a public foundation with a board of trustees made up of the Government of Catalonia and the UAB.
Reference:
Bernat Vila, Albert Sellés, Miguel Moreno-Azanza, Novella L. Razzolini, Alejandro Gil-Delgado, José Ignacio Canudo, Àngel Galobart. A titanosaurian sauropod with Gondwanan affinities in the latest Cretaceous of Europe. Nature Ecology & Evolution, 2022; DOI: 10.1038/s41559-021-01651-5
A view of the graben, which emerged near the Holuhraun lava field in Iceland. The western boundary of the graben is seen in the foreground, in the center-right portion of the image, where the land begins to dip down. Credit: Stephan Kolzenburg
At the boundaries between tectonic plates, narrow rifts can form as Earth’s crust slowly pulls apart.
But how, exactly, does this rifting happen?
Does pressure from magma rising from below ground force the land apart? Or is a rift just a rip, created mainly by the pulling motion of tectonic plates that are drifting away from each other?
A study in the journal Geology explores these questions and sheds new light on how this process works.
Past research has pointed to magma as a key driver in rifting events. But as the new findings highlight, “We have to be a bit more nuanced and acknowledge that rift processes do not have to operate identically across the entire globe,” says lead scientist Stephan Kolzenburg, Ph.D., assistant professor of geology in the University at Buffalo College of Arts and Sciences.
Study tells the story of a newly formed rift in Iceland
The new study was published in November 2021. It describes how a trench-like structure called a rift-graben opened in 2014 in Iceland near what is now known as the Holuhraun lava field, in a region that straddles the tectonic boundary between the North American and Eurasian plates. A graben forms when a chunk of land sags downward as the land on both sides of it moves away, creating a chasm called a rift.
The team concluded that in this particular case, the slow drift of tectonic plates, and not pressure from a magma chamber along the rift, was the driver.
The graben formed within a period of a few days, and then, “it just stayed like that, and it didn’t care about anything else that happened in the magmatic plumbing system,” Kolzenburg says. “The graben was remarkably stable even though lots of dynamic processes were happening underneath, such as pressure changes in the magmatic feeder system of the eruption.”
Magma leaked through the rift once it was open, but that magma didn’t appear to be the main force behind the initial creation of the rift, Kolzenburg says.
The study benefited from the work of an international group of scientists who had been closely monitoring Holuhraun and the surrounding region, documenting seismic activity and the volume of magma emerging during a period of unrest from 2014-15. Kolzenburg’s team compared this information to digital elevation models that detailed how the area’s topography changed over time, capturing the graben’s sudden appearance and tracking the landscape for nearly five years after the graben’s formation.
Not all rifts are created the same way
The findings apply specifically to the graben the team studied. In other rift zones, different dynamics may be at play, including in the Afar Region of Ethiopia, where magma is believed to play a more important role in driving rift formation, Kolzenburg says.
As he and co-authors write in their 2021 paper in Geology, “In concert, the data suggest that while some rifts may be magmatically controlled, not all rift zones require the presence of a deep-seated pressurized magma chamber to control their dynamics.”
The study was a collaboration between Kolzenburg, Julia Kubanek at the European Space Agency, Mariel Dirscherl and Ernst Hauber at the German Aerospace Center, Christopher W. Hamilton at the University of Arizona, Stephen. P. Scheidt at Howard University and Ulrich Münzer at Ludwig-Maximilians-Universität.
Reference:
S. Kolzenburg et al, Solid as a rock: Tectonic control of graben extension and dike propagation, Geology (2021). DOI: 10.1130/G49406.1
True body shape of the ancient Megalodon remains a mystery. (Phillip Sternes/UCR/DePaul)
A new study leaves large tooth marks in previous conclusions about the body shape of the Megalodon, one of the largest sharks that ever lived.
The study, which makes use of a pioneering technique for analyzing sharks, has now been published in the international journal Historical Biology.
Megalodons swam the Earth roughly 15 to 3.6-million years ago, and are often portrayed as super-sized monsters in films such as 2018’s “The Meg.” While there is no dispute that they existed or that they were gigantic, Otodus megalodon are known only from their fossilized teeth and vertebrae. Based on this evidence, studies suggest they reached lengths of up to 65 feet.
Unfortunately, additional fossil evidence from which to draw conclusions about their bodies, such as a complete skeleton, has not yet been discovered.
“The cartilage in shark bodies doesn’t preserve well, so there are currently no scientific means to support or refute previous studies on O. megalodon body forms,” said Phillip Sternes, a UCR organismal biologist and lead author on the study.
Traditionally, researchers have modeled Megalodon bodies on those of modern great white sharks. Great whites are partially warm blooded and belong to the lamniform shark order. Megalodons also belong to this order, and it is believed they shared this partial warm bloodedness with great whites.
It was previously thought having some warm blood is an advantage that could expand sharks’ swimming range, unlike other fish dependent on water temperature. However, it is now believed to increase swimming speed.
“Great whites are among the fastest swimming sharks, so Megalodons were likely also big, fast sharks you would not want to run into in the open ocean,” said Sternes.
There are eight families of Lamniformes, and 15 species. Previous research took five species of warm-blooded Lamniformes, averaged their fin and body shapes and proposed a general model for Megalodons.
Sternes and his colleagues wanted to understand whether the five species used to determine Megalodon’s shape differed somehow from the rest of the order, which includes some sharks that are cold blooded.
The researchers compared the five species to each other, and to the rest of the lamniform order. Using detailed field guide drawings, they performed quantitative comparisons of the sharks’ fin, head and body shapes.
They found no general patterns that would allow them to tease out body shape differences.
“Warm bloodedness does not make you a differently shaped shark,” Sternes said. “I encourage others to explore ideas about its body shape, and to search for the ultimate treasure of a preserved Megalodon fossil. Meanwhile, this result clears up some confusion about previous findings and opens the door to other ideas once again.”
While others typically use actual organisms or photos of organisms for such comparisons, Sternes pioneered the use of this two-dimensional drawing technique on sharks.
“The purpose of field guides is to identify a species, so the drawings must be accurate representations,” he said. “It’s a technique widely used in biology and works well for sharks since some specimens exist only in remote places.”
Sternes hopes that others use the technique to study snakes, birds and other animals with specimens that may be difficult to collect. He also hopes others will continue to search for a better understanding of the Megalodon.
“This study may appear to be a step backward in science,” said Kenshu Shimada, study co-author and DePaul University paleobiology professor. “But the continued mystery makes paleontology, the study of prehistoric life, a fascinating and exciting scientific field.”
Reference:
Phillip C. Sternes, Jake J. Wood, Kenshu Shimada. Body forms of extant lamniform sharks (Elasmobranchii: Lamniformes), and comments on the morphology of the extinct megatooth shark, Otodus megalodon, and the evolution of lamniform thermophysiology. Historical Biology, 2022; 1 DOI: 10.1080/08912963.2021.2025228
