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Geologists take Earth’s inner temperature using erupted sea glass

A map of the World Ocean Floor. Credit: Library of Congress, Geography and Map Division
A map of the World Ocean Floor. Credit: Library of Congress, Geography and Map Division

If the Earth’s oceans were drained completely, they would reveal a massive chain of undersea volcanoes snaking around the planet. This sprawling ocean ridge system is a product of overturning material in the Earth’s interior, where boiling temperatures can melt and loft rocks up through the crust, splitting the sea floor and reshaping the planet’s surface over hundreds of millions of years.

Now geologists at MIT have analyzed thousands of samples of erupted material along ocean ridges and traced back their chemical history to estimate the temperature of the Earth’s interior.

Their analysis shows that the temperature of the Earth’s underlying ocean ridges is relatively consistent, at around 1,350 degrees Celsius—about as hot as a gas range’s blue flame. There are, however, “hotspots” along the ridge that can reach 1,600 degrees Celsius, comparable to the hottest lava.

The team’s results, appearing today in the Journal of Geophysical Research: Solid Earth, provide a temperature map of the Earth’s interior around ocean ridges. With this map, scientists can better understand the melting processes that give rise to undersea volcanoes, and how these processes may drive the pace of plate tectonics over time.

“Convection and plate tectonics have been important processes in shaping Earth history,” says lead author Stephanie Brown Krein, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “Knowing the temperature along this whole chain is fundamental to understanding the planet as a heat engine, and how Earth might be different from other planets and able to sustain life.”

Krein’s co-authors include Zachary Molitor, an EAPS graduate student, and Timothy Grove, the R.R. Schrock Professor of Geology at MIT.

A chemical history

The Earth’s interior temperature has played a critical role in shaping the planet’s surface over hundreds of millions of years. But there’s been no way to directly read this temperature tens to hundreds of kilometers below the surface. Scientists have applied indirect means to infer the temperature of the upper mantle—the layer of the Earth just below the crust. But estimates thus far are inconclusive, and scientists disagree about how widely temperatures vary beneath the surface.

For their new study, Krein and her colleagues developed a new algorithm, called ReversePetrogen, that is designed to trace a rock’s chemical history back in time, to identify its original composition of elements and determine the temperature at which the rock initially melted below the surface.

The algorithm is based on years of experiments carried out in Grove’s lab to reproduce and characterize the melting processes of the Earth’s interior. Researchers in the lab have heated up rocks of various compositions, reaching various temperatures and pressures, to observe their chemical evolution. From these experiments, the team has been able to derive equations—and ultimately, the new algorithm—to predict the relationships between a rock’s temperature, pressure, and chemical composition.

Krein and her colleagues applied their new algorithm to rocks collected along the Earth’s ocean ridges—a system of undersea volcanoes spanning more than 70,000 kilometers in length. Ocean ridges are regions where tectonic plates are spread apart by the eruption of material from the Earth’s mantle—a process that is driven by underlying temperatures.

“You could effectively make a model of the temperature of the entire interior of the Earth, based partly on the temperature at these ridges,” Krein says. “The question is, what is the data really telling us about the temperature variation in the mantle along the whole chain?”

Mantle map

The data the team analyzed include more than 13,500 samples collected along the length of the ocean ridge system over several decades, by multiple research cruises. Each sample in the dataset is of an erupted sea glass—lava that erupted in the ocean and was instantly chilled by the surrounding water into a pristine, preserved form.

Scientists previously identified the chemical compositions of each glass in the dataset. Krein and her colleagues ran each sample’s chemical compositions through their algorithm to determine the temperature at which each glass originally melted in the mantle.

In this way, the team was able to generate a map of mantle temperatures along the entire length of the ocean ridge system. From this map, they observed that much of the mantle is relatively homogenous, with an average temperature of around 1,350 degrees Celsius. There are however, “hotspots,” or regions along the ridge, where temperatures in the mantle appear significantly hotter, at around 1,600 degrees Celsius.

“People think of hotspots as regions in the mantle where it’s hotter, and where material may be melting more, and potentially rising faster, and we don’t exactly know why, or how much hotter they are, or what the role of composition is at hotspots,” Krein says. “Some of these hotspots are on the ridge, and now we may get a sense of what the hotspot variation is globally using this new technique. That tells us something fundamental about the temperature of the Earth now, and now we can think of how it’s changed over time.”

Krein adds: “Understanding these dynamics will help us better determine how continents grew and evolved on Earth, and when subduction and plate tectonics started—which are critical for complex life.”

Note: The above post is reprinted from materials provided by Massachusetts Institute of Technology.

Giant friction experiment at Kilauea volcano

A wide-angle aerial view looks southeast over Kīlauea’s summit caldera on July 22, 2021. Large cliffs formed during the 2018 collapses are visible on the left side of the photo. A recently active lava lake is visible in the lower right. (Image credit: M. Patrick, USGS)
A wide-angle aerial view looks southeast over Kīlauea’s summit caldera on July 22, 2021. Large cliffs formed during the 2018 collapses are visible on the left side of the photo. A recently active lava lake is visible in the lower right. (Image credit: M. Patrick, USGS)

On April 30, 2018, on the eastern flank of Hawaii’s Kīlauea volcano, lava suddenly drained from a crater that had been spewing lava for more than three decades. Then the floor of the crater, named Pu’u’ō’ō, dropped out.

Within 48 hours, the lava lake at Kīlauea’s summit 12 miles northwest of Pu’u’ō’ō began to fall as magma drained into the volcano’s plumbing. Soon, new cracks opened 12 miles east of Pu’u’ō’ō and molten lava spurted out, crept over roads, burned trees and torched power poles.

Over three months, Kīlauea spat out enough lava to fill 320,000 Olympic-sized swimming pools, destroyed more than 700 homes and displaced thousands of people. The summit landscape itself was transformed as its crater collapsed by as much as 1,500 feet throughout the summer in a way that scientists are only beginning to understand.

“In the entire 60 years of modern geophysical instrumentation of volcanoes, we’ve had only half a dozen caldera collapses,” said Stanford University geophysicist Paul Segall, lead author of a new study in Proceedings of the National Academy of Sciences that helps explain how these events unfold and finds evidence confirming the reigning scientific paradigm for how friction works on earthquake faults.

The results may help to inform future hazard assessments and mitigation efforts around volcanic eruptions. “Improving our understanding of the physics governing caldera collapses will help us to better understand the conditions under which collapses are possible and forecast the evolution of a collapse sequence once it begins,” said co-author Kyle Anderson, PhD ’12, a geophysicist with the U.S. Geological Survey who was part of the team working on-site at Kīlauea during the 2018 eruption.

The nature of friction

A key factor controlling the collapse of volcanic calderas — and the rupture of earthquake faults around the world — is friction. It’s ubiquitous in nature and our everyday lives, coming into play any time two surfaces move relative to each other. But interactions between surfaces are so complex that, despite centuries of study, scientists still don’t completely understand how friction behaves in different situations. “It’s not something that we can entirely predict using only equations. We also need data from experiments,” Segall said.

Scientists seeking to understand the role of friction in earthquakes usually run these experiments in labs using rock slabs barely larger than a door and often closer to the size of a deck of cards. “One of the big challenges in earthquake science has been to take these friction laws and the values that were found in the laboratory, and apply them to, say, the San Andreas Fault, because it’s such an enormous jump in scale,” said Segall, the Cecil H. and Ida M. Green Professor of Geophysics at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth).

In the new study, published July 23, Segall and Anderson examine the slipping and sticking of Kīlauea volcano’s collapse block — a chunk of crust five miles around and half a mile deep — to characterize friction at a much larger scale. “We set out to develop a mathematical model of that collapse, highly simplified, but using modern understanding of friction,” Segall said.

Kīlauea’s collapse

Kīlauea’s caldera collapsed not in one smooth descent, but rather like a sticky piston. Roughly every day and a half, the collapse block dropped by nearly eight feet in a matter of seconds, then stopped. That’s because as magma in the chamber below the caldera surged out to fissures in Kīlauea’s lower eastern flank, it took away support for the overlying rock. “Eventually, the pressure becomes low enough that the floor falls in and it starts collapsing, like a sinkhole,” Segall said.

By the time the 2018 Kīlauea eruption ended, the volcano’s piston-like collapse events repeated 62 times — with each one triggering an earthquake and every move tracked down to the millimeter every five seconds by an array of 20 global positioning system (GPS) instruments. During the first few dozen collapse events, the geometry of the rock surfaces changed, but they held stable for the final 30 halting descents.

The new research shows that for this type of eruption, when the eruptive vent is at a lower elevation, it leads to a bigger drop in pressure below the caldera block — which then makes it more likely that a collapse event will start. Once collapse initiates, the weight of the massive caldera block maintains pressure on the magma, forcing it to the eruption site. “If not for the collapse, the eruption would have undoubtedly ended much sooner,” Segall said.

Evolving friction

Segall and Anderson’s analysis of the trove of data from Kīlauea’s caldera collapse confirms that, even at the vast scale of this volcano, the ways different rock surfaces slip and slide past one another or stick at different speeds and pressures over time are very similar to what scientists have found in small-scale laboratory experiments.

Specifically, the new results provide an upper bound for an important factor in earthquake mechanics known as slip-weakening distance, which geophysicists use to calculate how faults become unstuck. This is the distance over which the frictional strength of a fault weakens before rupturing — something that’s central to accurate modeling of the stability and buildup of energy on earthquake faults. Laboratory experiments have suggested this distance could be as short as tens of microns — equivalent to the width of a hair spliced into a few dozen slivers — while estimates from real earthquakes indicate it could be as long as 20 centimeters.

The new modeling now shows this evolution occurs over no more than 10 millimeters, and possibly much less. “The uncertainties are bigger than they are in the lab, but the friction properties are completely consistent with what’s measured in the laboratory, and that’s very confirming,” Segall said. “It tells us that we’re okay taking those measurements from really small samples and applying them to big tectonic faults because they held true in the behavior we observed in Kīlauea’s collapse.”

The new work also adds realistic complexity to a mathematical piston model, proposed a decade ago by Japanese volcanologist Hiroyuki Kumagai and colleagues, to explain a large caldera collapse on Miyake Island, Japan. While the widely embraced Kumagai model assumed the volcano’s rock surfaces changed as if by flipping a switch from being stationary relative to each other to slipping past one another, the new modeling recognizes that the transition between “static” and “dynamic” friction is more complex and gradual. “Nothing in nature occurs instantaneously,” Segall said.

Reference:
Paul Segall, Kyle Anderson. Repeating caldera collapse events constrain fault friction at the kilometer scale. Proceedings of the National Academy of Sciences, 2021; 118 (30): e2101469118 DOI: 10.1073/pnas.2101469118

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

Sea levels influence eruptions on volcanic island

The cliffs of the volcanic island of Santorini showing the layers of deposits from past volcanic eruptions. Credit: co-author Dr. Ralf Gertisser (Keele University).
The cliffs of the volcanic island of Santorini showing the layers of deposits from past volcanic eruptions. Credit: co-author Dr. Ralf Gertisser (Keele University).

The rise and fall of sea levels influence the likelihood of volcanic eruptions on the Greek island of Santorini, new research led by Oxford Brookes University has discovered. Analysing the timings of eruptions over hundreds of thousands of years, the researchers found that a 40 metre fall in sea level is a crucial point beyond which eruptions are more likely to occur. The findings could have implications for millions of people living on volcanic islands around the world.

Santorini — cliffs reveal history of eruptions

The research on the popular tourist destination was led by Dr Christopher Satow, Senior Lecturer in Physical Geography at Oxford Brookes.

He says there are clues about past volcanic activity on Santorini in the layers of rock on the cliff face encircling the inner part of the island: “A huge eruption 3,600 years ago caused the centre of what was then a conical island to sink into the sea, revealing an extraordinarily detailed history of over 200 volcanic eruptions preserved within the remaining circle of cliffs.

“Comparing this eruption history to a sea level record allowed us to show for the first time that the sea level has had an important role in determining the timing of eruptions at Santorini, and probably at many other island volcanoes around the world.

“The mechanism is quite simple: falling sea levels remove mass from the Earth’s crust and the crust fractures as a result. These fractures allow magma to rise and feed eruptions at the surface.”

The researchers say that eruptions at hundreds of other volcanic islands around the world may also have been influenced by fluctuations in sea level. Dr Satow added: “Just as when you pull a plug out of the bath, the water level drops everywhere throughout the bath at the same time; in a similar way, sea level changes occur at the same time everywhere across the globe.”

Volcanic eruptions and climate change

Volcanic eruptions can change the climate, for example the eruption of the Philippines’ Mt. Pinatubo in 1992 resulted in a fall in global temperature of 0.5oC.

But Dr Satow says the climate also impacts on volcanic activity: “What is less well known is that on long timescales, the climate can also affect volcanoes. As ice sheets retreated across volcanic landscapes after the last ice age, the removal of mass changed the stress conditions in the Earth’s crust, allowing the fractures which feed volcanic eruptions to form more easily.

“As these ice sheets melted the global sea level rose rapidly, by around 100 meters, adding a significant mass to the crust around many volcanic islands which, in theory, should alter their eruptive activity.”

Dr Satow concludes: “57% of the world’s volcanoes are islands or are coastal, and are often home to large populations. Further vital research is needed to fully understand the effects of changing sea level on these volcanoes and the risks they pose to their populations.”

Dr Satow collaborated with researchers from Royal Holloway University of London, Keele University, the University of Oxford, Uppsala University in Sweden, the University of Portsmouth and the University of Leicester.

Reference:
Chris Satow, Agust Gudmundsson, Ralf Gertisser, Christopher Bronk Ramsey, Mohsen Bazargan, David M. Pyle, Sabine Wulf, Andrew J. Miles, Mark Hardiman. Eruptive activity of the Santorini Volcano controlled by sea-level rise and fall. Nature Geoscience, 2021; DOI: 10.1038/s41561-021-00783-4

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

Volcanic tremor and deformation at Kīlauea

A view of Kīlauea’s summit lava lake. The lava lake is contained within a crater, which is set within the larger Halema‘uma‘u Crater. New research aims to understand the activity that led to the eruption in 2018 in Kīlauea’s lower East Rift Zone. Credit: USGS
A view of Kīlauea’s summit lava lake. The lava lake is contained within a crater, which is set within the larger Halema‘uma‘u Crater. New research aims to understand the activity that led to the eruption in 2018 in Kīlauea’s lower East Rift Zone. Credit: USGS

Kīlauea in Hawaii is the best-monitored volcano in the world. The 2018 eruption was the largest in some 200 years, providing researchers with a plethora of new data to understand the volcano’s plumbing and behavior. Two new studies dig into data on volcanic tremor and deformation to better characterize the events leading up to and following the 2018 eruption.

In one study, Soubestre et al. used data from a permanent seismic network and tiltmeter located at Kīlauea’s summit and derived models of tremor source processes to examine how volcanic tremors related to the disappearance of a lava lake and subsidence in Halema’uma’u Crater at the beginning and throughout the 2018 eruption. Here the authors used a seismic network covariance matrix approach to enhance coherent signals and cut out noise to detect and locate the volcanic tremor sources.

The team identified three previously unidentified tremor sources, including long-period tremor during the period preceding the eruption associated with radiation from a shallow hydrothermal system on the southwest flank of Halema’uma’u Crater. The team picked up on two sets of gliding tremor in early and late May. Models show that the first set was linked to the intrusion of a rock piston into the hydrothermal system and the second was linked to changes in the gas content of magma within a dike below the crater affected by a dozen collapse events.

The second study focused on the period following the 2018 eruption. Here Wang et al. used GPS and interferometric synthetic aperture radar data to examine deformation around the caldera associated with the volcano’s known reservoirs—the shallow Halema’uma’u reservoir (HMM) and the deeper South Caldera reservoir (SC)—after the eruption ended in August of 2018. They documented inflation on the northwestern side of the caldera and deflation on the southeastern side of the caldera, indicating that the summit magma chambers are hydraulically distinct. The concurrent East Rift Zone (ERZ) inflation indicated dynamic magma transfer between the summit and the ERZ.

The authors presented a new physics-based model that uses differential equations to describe reservoir pressure and magma flux between the volcano’s reservoirs to simulate potential magmatic pathways of connectivity between the reservoirs and the ERZ. They used a dynamic inversion of the postcollapse GPS time series of surface displacement to estimate the conductivity of potential magmatic pathways.

The team found that the primary connective pathway in the postcollapse period that best fits the GPS data is a shallow connection between the HMM and the ERZ. The study doesn’t rule out a direct pathway between the SC and ERZ reservoirs but suggests that if it exists, it was significantly less active over the study period.

Reference:

  1. Jean Soubestre et al, Sources of Volcanic Tremor Associated With the Summit Caldera Collapse During the 2018 East Rift Eruption of Kīlauea Volcano, Hawai’i, Journal of Geophysical Research: Solid Earth (2021). DOI: 10.1029/2020JB021572
  2. Taiyi Wang et al, Post‐2018 Caldera Collapse Re‐Inflation Uniquely Constrains Kīlauea’s Magmatic System, Journal of Geophysical Research: Solid Earth (2021). DOI: 10.1029/2021JB021803

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

Skull of 340 million year old animal digitally recreated, revealing secrets of ancient amphibian

Skull fossils of amphibian. Credit: Field Museum of Natural History, Chicago
Skull fossils of amphibian. Credit: Field Museum of Natural History, Chicago

Researchers from the University of Bristol and University College London have used cutting-edge techniques to digitally reconstruct the skull of one of the earliest limbed animals.

Tetrapods include mammals, reptiles and amphibians—everything from salamanders to humans. Their origin represents a crucial time in animal evolution, from the development of limbs with digits and the shift from water on to land. The study, which was recently published in the Journal of Vertebrate Paleontology, depicts the reconstructed skull of a prehistoric amphibian, the 340-million year old Whatcheeria deltae, to reveal what this animal looked like and how it may have fed.

First discovered in Iowa in 1995, the fossils of Whatcheeria were originally squashed flat after being buried by mud at the bottom of an ancient swamp, but paleontologists were able to use computational methods to restore the bones to their original arrangement. The fossils were put through a CT scanner to create exact digital copies, and software was used to separate each bone from the surrounding rock. These digital bones were then repaired and reassembled to produce a 3D model of the skull as it would have appeared while the animal was alive.

The authors found that Whatcheeria possessed a tall and narrow skull quite unlike many other early tetrapods that were alive at the time. Lead author James Rawson, who worked on this project alongside his undergraduate degree in paleontology and evolution, said: “Most early tetrapods had very flat heads which might hint that Whatcheeria was feeding in a slightly different way to its relatives, so we decided to look at the way the skull bones were connected to investigate further.”

By tracing the connecting edges of the skull bones, known as sutures, the authors were able to figure out how this animal tackled its prey. Professor Emily Rayfield, of the University of Bristol’s School of Earth Sciences, who also worked on the study, said: “We found that the skull of Whatcheeria would have made it well-adapted to delivering powerful bites using its large fangs.”

Co-author Dr. Laura Porro said: “There are a few types of sutures that connect skull bones together and they all respond differently to various types of force. Some are better at dealing with compression, some can handle more tension, twisting and so on. By mapping these suture types across the skull, we can predict what forces were acting on it and what type of feeding may have caused those forces.”

The authors found that the snout had lots of overlapping sutures to resist twisting forces from struggling prey, while the back of the skull was more solidly connected to resist compression during biting.

Mr Rawson added: “Although this animal was still probably doing most of its hunting in the water, a bit like a modern crocodilian, we’re starting to see the sorts of adaptations that enabled later tetrapods to feed more efficiently on land.”

Reference:
James R. G. Rawson et al, Osteology and digital reconstruction of the skull of the early tetrapod Whatcheeria deltae, Journal of Vertebrate Paleontology (2021). DOI: 10.1080/02724634.2021.1927749

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

Icy waters of ‘Snowball Earth’ may have spurred early organisms to grow bigger

Two fossils of Brooksella alternata.
Two fossils of Brooksella alternata. Credits: Glenn Asakawa/CU Boulder; CC photo via Wikimedia Commons

A new study from CU Boulder finds that hundreds of millions of years ago, small single-celled organisms may have evolved into larger multicellular life forms to better propel themselves through icy waters.

The research was led by paleobiologist Carl Simpson and appears today in the journal The American Naturalist. It hones in on a question that’s central to the history of the planet: How did life on Earth, which started off teeny-tiny, get so big?

“Once organisms get big, they have a clear ecological advantage because the physics around how they capture food become totally different,” said Simpson, assistant professor in the Department of Geological Sciences at CU Boulder and the CU Museum of Natural History. “But the hard part for researchers has been explaining how they got big in the first place.”

In his latest study, Simpson draws on a series of mathematical equations to argue that this all-important shift may have come down to hydrodynamics — or the pursuit of a more efficient backstroke.

Roughly 750 million years ago, and for reasons that scientists are still debating, the planet became suddenly and dramatically colder — a period of time called “Snowball Earth.” To adapt to these frigid conditions, which can make swimming more difficult, small organisms like bacteria may have begun to glom together to form larger and more complex life.

Simpson still has a lot of work to do before he can prove his theory. But, the geologist said, the results could help to reveal how the ancestors of all modern multicellular life, from flowers to elephants and even people, first arose on Earth.

“By swimming together, these cells could remain small on an individual level but still produce more power,” Simpson said. “They become both bigger and faster as a group.”

Snowball Earth

Those successes took place at a seemingly inhospitable time in the planet’s past.

During “Snowball Earth,” the globe may have been all but recognizable. Ice sheets a half-mile thick or more may have blanketed the planet for as much as 70 million years, while temperatures in the oceans plummeted to less than 32 degrees Fahrenheit.

But even amid those frigid conditions, something spectacular happened: The first organisms made up of many different cells, not just one, began to emerge around the planet. Scientists still aren’t sure what those ancient multicellular organisms might have looked like. One theory suggests that they resembled Volvox, a type of algae that are common in oceans today and are shaped like a hollow sphere or snow globe.

“That’s something that has lodged in my mind for years,” Simpson said. “How do Snowball Earth and the rise of multicellular organisms go together?”

The answer to that counterintuitive problem may hinge on a little-known property of water.

Simpson explained that when saltwater gets colder, it also becomes several times thicker, or more viscous. Humans are too big to notice the change. But for organisms the size of modern-day bacteria, the difference can be huge.

“When you’re small, you’re stuck,” he said. “The water moves you.”

Taking a swim

The geologist ran a series of calculations to gauge how organisms of various shapes and sizes might fare in the oceans of Snowball Earth. And, in this case, bigger might be better.

Simpson said that modern-day bacteria and other single-celled organisms move around in aquatic environments using two different sets of tools: There are cilia — which are wavy, hair-like projections — and flagella — think the “tails” on sperm cells. Both of these tools would have been painfully slow in frigid ocean conditions, his results show.

If individual cells joined forces to make a bigger organism, in contrast, they could produce a lot more swimming power while keeping the energy needs of each cell low.

“The advantage of the multicellular strategy is that each cell stays small and has low metabolic requirements, but these cells can swim together,” Simpson said.

He’s currently testing the theory using experiments with modern algae in a lab and by digging deeper into Earth’s fossil record. One thing is clear, Simpson said: Once life forms got big, a whole new world of possibilities became available to them. Primitive animals like sponges, for example, survive not by floating in the ocean but by actively pumping water through their bodies.

“When you’re big, you now can move the water rather than the other way around,” Simpson said.

Reference:
Carl Simpson. Adaptation to a viscous Snowball Earth Ocean as a path to complex multicellularity. The American Naturalist, 2021; DOI: 10.1086/716634

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

Decline in CO2 cooled Earth’s climate more than 30 million years ago

Tree stomp in lignite deposits. Credit: Vittoria Lauretano
Tree stomp in lignite deposits. Credit: Vittoria Lauretano

New research led by the University of Bristol demonstrates that a decline in the concentration of atmospheric CO2 played a major role in driving Earth’s climate from a warm greenhouse into a cold icehouse world around 34 million years ago. This transition could be partly reversed in the next centuries due to the anthropogenic rise in CO2.

Between 40 and 34 million years ago, Earth’s climate underwent a major climatic transition. Before 40 million years ago, during the Eocene, Antarctica was covered by lush forests, but by 34 million years ago, in the Oligocene, these forests had been replaced by thick continental ice sheets, as we know Antarctica today. The main driver of this greenhouse to icehouse transition is widely debated, and little information is available about how climate changed on land. An international team led by Dr. Vittoria Lauretano and Dr. David Naafs at the University of Bristol used molecular fossils preserved in ancient coals to reconstruct land temperature across this transition.

The team used a new approach based on the distribution of bacterial lipids preserved in ancient wetland deposits. It was developed as part of the ERC-funded project, The Greenhouse Earth System (TGRES), which also funded this study. The TGRES PI and paper co-author Rich Pancost, from the University’s School of Chemistry, explained: ‘These compounds originally comprised the cell membranes of bacteria living in ancient wetlands, with their structures changing slightly to help the bacteria adapt to changing temperature and acidity. Those compounds can then be preserved for tens of millions of years, allowing us to reconstruct those ancient environmental conditions.’

To reconstruct temperature change across the greenhouse to icehouse transition, the team applied their new approach to coal deposits from the southeast Australian Gippsland Basin. These remarkable deposits span over 10 million years of Earth history and have been extensively characterized by collaborators on the study from the University of Melbourne, Dr. Vera Korasidis and Prof. Malcolm Wallace.

The new data show that land temperatures cooled alongside the ocean’s and by a similar magnitude of about 3C. To explore causes of that temperature decline, the team conducted climate model simulations, Crucially, only simulations that included a decline in atmospheric CO2 could reproduce a cooling consistent with the temperature data reconstructed from the coals.

These results provide further evidence that atmospheric CO2 plays a crucial role in driving Earth’s climate, including the formation of the Antarctic ice sheet.

“Eocene to Oligocene terrestrial Southern Hemisphere cooling caused by declining pCO2” is published in Nature Geoscience.

Reference:
Eocene to Oligocene terrestrial Southern Hemisphere cooling caused by declining pCO2, Nature Geoscience (2021). DOI: 10.1038/s41561-021-00788-z

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

The City of David and the sharks’ teeth mystery

Fossilised Squalicorax tooth Nr. #07815 from the Jerusalem site. Credit: Omri Lernau
Fossilised Squalicorax tooth Nr. #07815 from the Jerusalem site. Credit: Omri Lernau

Scientists have found an unexplained cache of fossilized shark teeth in an area where there should be none—in a 2900 year old site in the City of David in Jerusalem. This is at least 80 km from where these fossils would be expected to be found. There is no conclusive proof of why the cache was assembled, but it may be that the 80 million-year-old teeth were part of a collection, dating from just after the death of King Solomon. The same team has now unearthed similar unexplained finds in other parts of ancient Judea.

Presenting the work at the Goldschmidt Conference, lead researcher, Dr. Thomas Tuetken (University of Mainz, Institute of Geosciences) said:

“These fossils are not in their original setting, so they have been moved. They were probably valuable to someone; we just don’t know why, or why similar items have been found in more than one place in Israel”.

The teeth were found buried in material used to fill in a basement before conversion to a large Iron-Age house. The house itself was situated in the City of David, one of the oldest parts of Jerusalem, found nowadays in the largely Palestinian village of Silwan. They were found together with fish bones thrown away as food waste 2900 years ago, and other infill material such as pottery. Intriguingly, they were found together with hundreds of bullae—items used to seal confidential letters and packages—implying a possible connection with the administrative or governing class at some point. Normally archaeological material is dated according to the circumstances where it is found, and so at first it was assumed that the teeth were contemporary with the rest of the find. Dr. Tuetken said:

“We had at first assumed that the shark teeth were remains of the food dumped nearly 3000 years ago, but when we submitted a paper for publication, one of the reviewers pointed out that the one of the teeth could only have come from a Late Cretaceous shark that had been extinct for at least 66 million years. That sent us back to the samples, where measuring organic matter, elemental composition, and the crystallinity of the teeth confirmed that indeed all shark teeth were fossils. Their strontium isotope composition indicates an age of about 80 million years. This confirmed that all 29 shark teeth found in the City of David were Late Cretaceous fossils—contemporary with dinosaurs. More than that, they were not simply weathered out of the bedrock beneath the site, but were probably transported from afar, possibly from the Negev, at least 80 km away, where similar fossils are found”.

Since the first finds, the team have found other shark teeth fossils elsewhere in Israel, at the Maresha and Miqne sites. These teeth are also likely to have been unearthed and moved from their original sites.

Dr. Tuetken said:

“Our working hypothesis is that the teeth were brought together by collectors, but we don’t have anything to confirm that. There are no wear marks which might show that they were used as tools, and no drill holes to indicate that they may have been jewelry. We know that there is a market for shark’s teeth even today, so it may be that there was an Iron Age trend for collecting such items. This was a period of riches in the Judean Court. However, it’s too easy to put 2 and 2 together to make 5. We’ll probably never really be sure”.

The shark teeth which have been identified come from several species, including from the extinct Late Cretaceous group Squalicorax. Squalicorax, which grew to between 2 and 5 meters long, lived only during the Late Cretaceous period (which was the same period as the late dinosaurs), so acts as a reference point in dating these fossils.

Commenting, Dr. Brooke Crowley (University of Cincinnati) said:

“This research by Dr. Tuetken and colleagues is an excellent example of why it is so important to approach a research question with as few assumptions as possible, and how sometimes we have to revisit our initial assumptions. It also highlights how beneficial it can be to apply multiple tools to answer a research question. In this case, the authors used both strontium and oxygen isotopes, as well as X-ray diffraction and trace element analysis to establish most likely age and origin of the fossil teeth. It was a monumental of work but these efforts have revealed a much more interesting story about the people who lived in this region in the past. I am very excited by this work and hope that one day, we might be able to unravel the mystery of why these fossil teeth are being recovered from cultural deposits”.

Dr. Crowley was not involved in this work. The work relating to the Jerusalem finds has been published in the peer-reviewed journal Frontiers in Ecology and Evolution 8:570032. Dr. Crowley edited this paper for the journal.

Reference:
Thomas Tütken et al, Strontium and Oxygen Isotope Analyses Reveal Late Cretaceous Shark Teeth in Iron Age Strata in the Southern Levant, Frontiers in Ecology and Evolution (2021). DOI: 10.3389/fevo.2020.570032

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

Paleonursery offers rare, detailed glimpse at life 518 million years ago

Chuandianella ovata, an extinct shrimp-like crustacean.
Chuandianella ovata, an extinct shrimp-like crustacean.
IMAGE: Xianfeng Yang, Yunnan Key Laboratory for Palaeobiology, Yunnan University

All life on Earth 500 million years ago lived in the oceans, but scientists know little about how these animals and algae developed. A newly discovered fossil deposit near Kunming, China, may hold the keys to understanding how these organisms laid the foundations for life on land and at sea today, according to an international team of researchers.

The fossil deposit, called the Haiyan Lagerstätte, contains an exceptionally preserved trove of early vertebrates and other rare, soft-bodied organisms, more than 50% of which are in the larval and juvenile stages of development. Dating to the Cambrian geologic period approximately 518 million years ago and providing researchers with 2,846 specimens so far, the deposit is the oldest and most diverse found to date.

“It’s just amazing to see all these juveniles in the fossil record,” said Julien Kimmig, collections manager at the Earth and Mineral Sciences Museum & Art Gallery, Penn State. “Juvenile fossils are something we hardly see, especially from soft-bodied invertebrates.”

Xianfeng Yang, a paleobiologist at Yunnan University, China, led a team of Chinese researchers that collected the fossils at the research site. He measured and photographed the specimens and analyzed them with Kimmig. The researchers report the results of their study today (June 28) in the journal Nature Ecology and Evolution.

The researchers identified 118 species, including 17 new species, in the lagerstätte — a sedimentary deposit of extraordinary fossils with exceptional preservation that sometimes includes preserved soft tissues.

The species include the ancestors of modern-day insects and crustaceans, worms, trilobites, algae, sponges and early vertebrates related to jawless fish. The researchers also found eggs and an abundance of rare juvenile fossils with appendages still intact and their internal soft tissues visible.

The specimens are so well-preserved that they are revealing body parts never before seen, said Sara Kimmig, assistant research professor in the Earth and Environmental Systems Institute and facility director of the Laboratory for Isotopes and Metals in the Environment at Penn State.

“The site preserved details like 3D eyes, features that have never really been seen before, especially in such early deposits,” she said.

Scientists can use CT scanning on these 3D features to reconstruct the animals and extract even more information from the fossils, according to the researchers.

The lagerstätte contains several event beds, or layers in the sediment where the fossils are found. Each layer represents a single burial event. All species identified in the study are present in the lowest layer, with subsequent layers containing diverse species, but not to the extent of the lowest one.

The researchers think these intervals could represent boom and bust periods in the marine community. Many species might have come to the area — at the time located in deeper waters toward the center of the Kunming Gulf — seeking protection from strong ocean currents. However, a change in oxygen levels or storm events that caused sediment to flow down a slope and bury everything in its path may have caused extinctions.

The abundance of juvenile fossils, on the other hand, suggests that the Haiyan Lagerstätte could have been a paleonursery. The species found in the lagerstätte may have chosen to reproduce there due to the protection it provided from predators.

“Could these worms and jellyfish and bugs have developed something as sophisticated as a paleonursery to raise their young? Whatever the case may be, it’s fascinating to be able to parallel this behavior to that of modern animals,” Sara Kimmig said.

Scientists will be able to use this collection to study how these ancient animals developed from the larval to the adult stage.

“We’ll see how different body parts grew over time, which is something we currently do not know for most of these groups,” Julien Kimmig said. “And these fossils will give us more information on their relationships to modern animals. We will see if how these animals develop today is similar to how they developed 500 million years ago, or if something has changed throughout time.”

The developmental information will also provide insights into the relationships between animal groups, as similar developmental patterns may indicate a link between species, he added.

“The Haiyan Lagerstätte will be a wealth of knowledge moving forward for many researchers, not only in terms of paleontology but also in paleo-environmental reconstructions,” said Sara Kimmig. She and her colleagues would like to conduct geochemical analyses on the specimens and the sediments. These analyses could help them potentially recreate the environment and climate during the time that this lagerstätte was deposited.

The fossils will also allow the researchers to study how animals behaved 500 million years ago when the world was a bit warmer than today and use it as a proxy for where the world is headed in terms of animal behavior in a warmer environment.

“In this deposit, we found the ancestors to most modern animals, both marine and terrestrial,” Julien Kimmig said. “If the Haiyan Lagerstätte is actually a paleonursery, it means that this type of animal behavior has not changed much in 518 million years.”

Additional contributors to this study include Dayou Zhai and Yu Liu, Yunnan University; and Shanchi Peng, Chinese Academy of Sciences.

The National Natural Science Foundation of China, the State Key Laboratory of Palaeobiology and Stratigraphy at the Nanjing Institute of Geology and Palaeontology, and the Key Research Program of the Institute of Geology & Geophysics, Chinese Academy of Sciences, funded this research.

Reference:
Yang, X., Kimmig, J., Zhai, D. et al. A juvenile-rich palaeocommunity of the lower Cambrian Chengjiang biota sheds light on palaeo-boom or palaeo-bust environments. Nat Ecol Evol, 2021 DOI: 10.1038/s41559-021-01490-4

Note: The above post is reprinted from materials provided by Penn State. Original written by Francisco Tutella.

New model for shield volcano eruption

Nierra Negra Volcano on the Galapagos Islands
Nierra Negra Volcano on the Galapagos Islands (Photo: jkraft5, AdobeStock.com)

There are some large shield volcanoes in the world’s oceans where the lava is usually not ejected from the crater in violent explosions, but flows slowly out of the ground from long fissures. In the recent eruption of the Sierra Negra volcano in the Galapagos Islands, which lie just under a thousand kilometres off South America in the Pacific Ocean, one of these fissures was fed through a curved pathway in June 2018. This 15 kilometre-long pathway, including the kink, was created by the interaction of three different forces in the subsurface, Timothy Davis and Eleonora Rivalta from the GFZ German Research Centre for Geosciences in Potsdam, together with Marco Bagnardi and Paul Lundgren from NASA’s Jet Propulsion Laboratory in Pasadena, now explain based on computer models in the journal Geophysical Research Letters.

Even before the eruption, the geoscientists in California had seen in radar satellite data that the surface of the flank of the 1140-metre-high Sierra Negra volcano had bulged to a height of about two metres: this bulge, about five kilometres wide, stretched from the crater rim about ten kilometres in a west-northwest direction and turned at a right angle to the north-northeast near the coast. Timothy Davis and his team then found out what this structure and its perplexing bend were all about with the help of computer models.

Driving Force 1: Hotspot beneath the Galapagos Islands

As with many other volcanoes in the middle of the world’s oceans, a “hotspot” is hidden beneath the Galapagos Islands. For at least 20 million years, hot rock has been rising slowly from deep within the Earth’s interior, like a solid, but difficult-to-form plasticine. Like a blowtorch, this hotspot, up to 200 kilometres wide, melts its way through the solid crust of the Earth. This hot magma is a little lighter than the solid rock around it, so it keeps rising until it collects in a large cavity about two kilometres below the crater of the Sierra Negra volcano. “With a diameter of around six kilometres and a thickness of no more than one kilometre, this magma chamber resembles an oversized pancake of molten rock,” Timothy Davis describes this structure.

Driving Force 2: the Weight of the Volcano Rock

In the almost 13 years since the last eruption in October 2005, more and more magma has flowed into the chamber from below. There, the pressure rose and lifted the crater floor up to 5.20 metres. However, the enormous force of the gathering magma masses sought another way out. Deep underground, the viscous rock slowly crawled in a west-northwest direction. Another force plays an important role here: the enormous weight of the volcano’s rock masses presses from above on the magma flow that is just forming. As the shield volcano becomes flatter and flatter towards the outside, the pressure there also decreases. As the molten rock is pressed in the direction with lower pressure, it slowly swells outwards in a magma flow that is four kilometres wide but only about two metres high.

Driving Force 3: Buoyancy

Near the coastline, the flattening shield volcano presses ever more weakly on the now almost ten-kilometre-long magma corridor deep below the surface. There, a third force gains the upper hand. The magma is much lighter than the rock around the passage and was previously only prevented from swelling by the overlying weight of the shield volcano. Near the coastline, however, this buoyancy becomes stronger than the pressure of the rock from above. On top of that, the magma slope there tilts about ten degrees into the depths. Together, these forces change the direction in which the viscous rock is pressed and the magma slope bends towards the north-northeast.

The rock cracks, the volcano erupts

Still, the magma swelling under the crater continues to increase the pressure until the upward-pressing molten mass begins to crack the rock around the magma passage. At no more than walking speed, this magma-filled crack (dyke) is travelling deep underground towards the coastline. “The magma rising from the crack reaches the surface after a few days and continues to flow there as lava, which solidifies after some time,” Timothy Davis explains the subsequent course of the volcanic eruption.

Important prerequisite for prediction and hazard minimization

For the first time, the geophysicist was able to simulate such a tortuous magma propagation pathway feeding an eruption and determine the forces that control this. Timothy Davis and Eleonora Rivalta, together with their colleagues in California, have thus laid important foundations for research into such fissure eruptions. And they have taken a decisive step towards predicting such eruptions and thus reducing the dangers they pose.

Reference:
Timothy Davis, Marco Bagnardi, Paul Lundgren, Eleonora Rivalta. Extreme Curvature of Shallow Magma Pathways Controlled by Competing Stresses: Insights From the 2018 Sierra Negra Eruption. Geophysical Research Letters, 2021; 48 (13) DOI: 10.1029/2021GL093038

Note: The above post is reprinted from materials provided by GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre.

Supervolcano fed from Earth’s mantle caused crustal plates to rotate

A "Plume" in the Earth's mantle, i.e. a surge of hot material, caused the Indian Plate to spin off. (Graphic: Alisha Steinberger)
A “Plume” in the Earth’s mantle, i.e. a surge of hot material, caused the Indian Plate to spin off. (Graphic: Alisha Steinberger)

The plates of the Earth’s crust perform complicated movements that can be attributed to quite simple mechanisms. That is the short version of the explanation of a rift that began to tear the world apart over a length of several thousand kilometers 105 million years ago. The scientific explanation appears today in the journal Nature Geoscience.

According to the paper, a super volcano split the Earth’s crust over a length of 7,500 kilometers, pushing the Indian Plate away from the African Plate. The cause was a “plume” in the Earth’s mantle, i.e. a surge of hot material that wells upwards like an atomic mushroom cloud in super slow motion. It has long been known that the Indian landmass thus made its way northward and bumped into Eurasia. But a seemingly counterintuitive east-west movement of the continental plates was also part of the process. This is supported by calculations by a team led by Dutch scientist Douwe van Hinsbergen (Utrecht University) and Bernhard Steinberger (GFZ German Research Centre for Geosciences).

According to the findings, the Indian Plate did not simply move away from Africa, but rotated in the process. The reason for this is the subcontinent, whose land mass acts on the much larger continental plate like an axis around which the entire plate rotates. In the south, the scissors opened, in the north they closed — there, mountain-building processes and the subduction of crustal plates were induced.

This has dramatic effects up to the present time: The subduction processes continue and trigger earthquakes again and again in the Mediterranean region between Cyprus and Turkey. The traces of the plume and the supervolcano can still be identified today. They are flood basalts on Madagascar and in the southwest of India. They testify to immense volcanic activity fed by the mantle plume.

Bernhard Steinberger has calculated the movement and pressure that the super volcano near present-day Madagascar could cause further north on the Arabian Peninsula and in what is now the Mediterranean.

Reference:
Douwe J. J. van Hinsbergen, Bernhard Steinberger, Carl Guilmette, Marco Maffione, Derya Gürer, Kalijn Peters, Alexis Plunder, Peter J. McPhee, Carmen Gaina, Eldert L. Advokaat, Reinoud L. M. Vissers, Wim Spakman. A record of plume-induced plate rotation triggering subduction initiation. Nature Geoscience, 2021; DOI: 10.1038/s41561-021-00780-7

Note: The above post is reprinted from materials provided by GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre.

Longest known continuous record of the Paleozoic discovered in Yukon wilderness

Ordovician black shales of the Mount Hare Formation, Road River Group (approximately 465 million years old) rise above conglomerates of the Aberdeen Member. The dangerous rapids of Aberdeen Canyon (Nan Zhak Nadhàdlaii), created by the Peel River cutting through the resistant conglomerates, appear at bottom left. (Image credit: Erik Sperling)
Ordovician black shales of the Mount Hare Formation, Road River Group (approximately 465 million years old) rise above conglomerates of the Aberdeen Member. The dangerous rapids of Aberdeen Canyon (Nan Zhak Nadhàdlaii), created by the Peel River cutting through the resistant conglomerates, appear at bottom left. (Image credit: Erik Sperling)

Hundreds of millions of years ago, in the middle of what would eventually become Canada’s Yukon Territory, an ocean swirled with armored trilobites, clam-like brachiopods and soft, squishy creatures akin to slugs and squid.

A trove of fossils and rock layers formed on that ancient ocean floor have now been unearthed by an international team of scientists along the banks of the Peel River a few hundred miles south of the Arctic’s Beaufort Sea. The discovery reveals oxygen changes at the seafloor across nearly 120 million years of the early Paleozoic era, a time that fostered the most rapid development and diversification of complex, multi-cellular life in Earth’s history.

“It’s unheard of to have that much of Earth’s history in one place,” said Stanford University geological scientist Erik Sperling, lead author of a July 7 study detailing the team’s findings in Science Advances. Most rock formations from the Paleozoic Era have been broken up by tectonic forces or eroded over time. “There’s nowhere else in the world that I know of where you can study that long a record of Earth history, where there’s basically no change in things like water depth or basin type.”

Oxygen was scarce in the deep water of this and other oceans at the dawn of the Paleozoic, roughly 541 million years ago. It stayed scarce until the Devonian, roughly 405 million years ago, when, in a geological blink — no more than a few million years — oxygen likely rocketed to levels close to those in modern oceans and the diversity of life on Earth exploded. Big, predatory fish appeared. Primitive ferns and conifers marched across continents previously ruled by bacteria and algae. Dragonflies took flight. And all of this after nearly four billion years of Earth’s landscapes being virtually barren.

Scientists have long debated what might have caused the dramatic shift from a low oxygen world to a more oxygenated one that could support a diverse web of animal life. But until now, it has been difficult to pin down the timing of global oxygenation or the long-term, background state of the world’s oceans and atmosphere during the era that witnessed both the so-called Cambrian explosion of life and the first of Earth’s “Big Five” mass extinctions, about 445 million years ago at the end of the Ordovician.

“In order to make comparisons throughout these huge swaths of our history and understand long-term trends, you need a continuous record,” said Sperling, an assistant professor of geological sciences at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth).

Context for past life

With permission from the Na Cho Nyak Dun and Tetlit Gwitch’in communities in Yukon, Sperling’s team, which included researchers from Dartmouth College and the Yukon Geological Survey, spent three summers at the Peel River site. Arriving by helicopter, the research team hacked through brush with machetes beside Class VI rapids to collect hundreds of fist-sized samples of rock from more than a mile of interbedded layers of shale, chert and lime mudstone.

Back at Sperling’s lab at Stanford, a small army of summer undergraduates and graduate students worked over five summers to help analyze the fossils and chemicals entombed in the rocks. “We spent a lot of time splitting open rocks and looking at graptolite fossils,” Sperling said. Because graptolites evolved a vast array of recognizable body shapes relatively quickly, the pencil-like markings left by the fossils of these colony-dwelling sea creatures give geologists a way to date the rocks in which they’re found.

Once the researchers had finished identifying and dating graptolite fossils, they ground the rocks in a mill, then measured iron, carbon, phosphorus and other elements in the resulting powder to assess the ocean conditions at the time and place where the layers formed. They analyzed 837 new samples from the Peel River site, as well as 106 new samples from other parts of Canada and 178 samples from around the world for comparison.

Winners and losers

The data show low oxygen levels, or anoxia, likely persisted in the world’s oceans for millions of years longer than previously thought — well into the Phanerozoic, when land plants and early animals began to diversify. “The early animals were still living in a low oxygen world,” Sperling said. Contrary to long-held assumptions, the scientists found Paleozoic oceans were also surprisingly free of hydrogen sulfide, a respiratory toxin often found in the anoxic regions of modern oceans.

When oxygen eventually did tick upward in marine environments, it came about just as larger, more complex plant life took off. “There’s a ton of debate about how plants impacted the Earth system,” Sperling said. “Our results are consistent with a hypothesis that as plants evolved and covered the Earth, they increased nutrients to the ocean, driving oxygenation.” In this hypothesis, the influx of nutrients to the sea would have given a boost to primary productivity, a measure of how quickly plants and algae take carbon dioxide and sunlight, turn them into new biomass — and release oxygen in the process.

The change probably killed off graptolites. “Although more oxygen is really good for a lot of organisms, graptolites lost the low oxygen habitat that was their refuge,” Sperling said. “Any environmental change is going to have winners and losers. Graptolites might have been the losers.”

Reference:
Erik A. Sperling, Michael J. Melchin, Tiffani Fraser, Richard G. Stockey, Una C. Farrell, Liam Bhajan, Tessa N. Brunoir, Devon B. Cole, Benjamin C. Gill, Alfred Lenz, David K. Loydell, Joseph Malinowski, Austin J. Miller, Stephanie Plaza-Torres, Beatrice Bock, Alan D. Rooney, Sabrina A. Tecklenburg, Jacqueline M. Vogel, Noah J. Planavsky, Justin V. Strauss. A long-term record of early to mid-Paleozoic marine redox change. Science Advances, 2021; 7 (28): eabf4382 DOI: 10.1126/sciadv.abf4382

Note: The above post is reprinted from materials provided by Stanford University. Original written by Josie Garthwaite.

Researchers detail the most ancient bat fossil ever discovered in Asia

Upper molar of Altaynycteris aurora. Credit: Li Qiang
Upper molar of Altaynycteris aurora. Credit: Li Qiang

A new paper appearing in Biology Letters describes the oldest-known fragmentary bat fossils from Asia, pushing back the evolutionary record for bats on that continent to the dawn of the Eocene and boosting the possibility that the bat family’s “mysterious” origins someday might be traced to Asia.

A team based at the University of Kansas and China performed the fieldwork in the Junggar Basin — a very remote sedimentary basin in northwest China — to discover two fossil teeth belonging to two separate specimens of the bat, dubbed Altaynycteris aurora.

The new fossil specimens help scientists better understand bat evolution and geographic distribution and better grasp how mammals developed in general.

“Bats show up in the fossil record out of the blue about 55-ish million years ago — and they’re already scattered on different parts of the globe,” said lead author Matthew Jones, a doctoral student at the KU Biodiversity Institute and Department of Ecology & Evolutionary Biology. “Before this, the earliest bats are known from a couple of places in Europe — Portugal and southern France — and Australia. So, when they show up early in the fossil record as these fragmentary fossils they’re already effectively worldwide. By the time we get their earliest known full skeletons, they look modern — they can fly, and most of them are able to echolocate. But we don’t really know anything about this transitional period from non-bats to bats. We don’t even really know what their closest living relatives are among mammals. It’s a really big evolutionary mystery where bats came from and how they evolved and became so specialized.”

Jones’ co-authors were K. Christopher Beard, senior curator at the KU Biodiversity Institute and Foundation Distinguished Professor of Ecology & Evolutionary Biology at KU; and Qiang Li and Xijun Ni of the Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences and the Center for Excellence in Life and Paleoenvironment at the Chinese Academy of Sciences.

The ancient bat teeth were discovered through painstaking fieldwork in the Junggar Basin, where the KU researchers worked at an isolated field site established by their Chinese colleagues, one of two sites in the region the team hope will continue yielding interesting fossils.

“This was concerted effort over a long period of time by our Chinese colleagues,” Jones said.

“They suspected that there were fossiliferous deposits from the Paleocene and Eocene, and they spent several years going out there, identifying where to find fossils. Chris was a part of several seasons of fieldwork there. I was a part of one season of fieldwork there. What we did was collect a bunch of sediment to screen wash, which is sort of like panning for gold. You pour a bunch of sediment into a sievelike apparatus and let all the dirt and everything fall out, and you’re only left with particles of a certain size, but also fossils.”

Beard said the fieldwork was an outgrowth of long-standing relationships between the KU team and its Chinese counterparts.

“We’ve been fortunate enough to be able to host our Chinese colleagues here in Lawrence for extended research visits, and they’ve more than reciprocated by hosting us for research and fieldwork in China. This work in the Junggar Basin is really trailblazing work because the fossil record in this part of China is only just barely beginning to emerge, and this area is very removed and isolated. It’s just a giant empty place. There are some camels, some snakes and lizards, but you don’t see many people there. That remoteness makes the logistics to do fieldwork there quite difficult and expensive because you’ve got to bring in all your food and water from far outside — all of that hindered research in this area previously.”

Following the challenging fieldwork, the residue left behind from the screen washing at the site was sorted at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing.

“In 2017, after we got back from the field, Xijun said. ‘Hey, one of the technicians picking through this sediment thinks they found a bat,'” Jones said. “Knowing I was interested in bats, they showed it to me. The next year, the other tooth was found — so there’s two teeth.”

Through meticulous morphological analysis of the teeth, along with biostratigraphy — or analyzing the position of layers of fossil remains in the deposits — the authors were able to date the specimens to the advent of the Eocene, the earliest period when bat fossils have been found anywhere on Earth. Indeed, the presence of these ancient bat fossils in Asia bolsters a theory that bats could have emerged from there in the first place, then distributed themselves worldwide when they later developed flight.

More fieldwork in the area is ongoing, and Jones and Beard said they were hopeful to find even older specimens, perhaps even dating to the Paleocene, the epoch before the Eocene, when researchers believe bats probably originated. Yet the particulars of Altaynycteris aurora remain hazy — for instance, it’s impossible to say from teeth fragments if the animal could fly or echolocate.

“These teeth look intermediate, in between what we would expect a bat ancestor to look like — and in fact, what a lot of early Cenozoic insectivorous mammals to do look like — and what true bat looks like,” Jones said. “So, they have some features that are characteristic of bats that we can point to and say, ‘These are bats.’ But then they have some features that we can call for simplicity’s sake ‘primitive.'”

The researchers said the new fossils help fill in a gap to understanding the evolution of bats, which remains a puzzle to experts — and could teach us more about mammals in general.

“I can think of two mammal groups that are alive today that are really weird,” Beard said. “One of them is bats, because they fly — and that’s just ridiculous. The other one is whales, because they’re completely adapted to life in the ocean, they can swim, obviously, and they do a little bit of sonar echolocation themselves. We know a lot about transitional fossils for whales. There are fossils from places like Pakistan that were quadrupedal mammals that looked vaguely doglike. We have a whole sequence of fossils linking these things that were clearly terrestrial animals walking around on land, through almost every kind of transitional phase you can imagine, to a modern whale. This isn’t true for bats. For bats, literally you’ve got a normal mammal and then you’ve got bats — and anytime you’ve got a fossil record that’s a giant vacuum, we need work that can fill partly that. This paper is at least a step along that path.”

Reference:
Matthew F. Jones, Qiang Li, Xijun Ni, K. Christopher Beard. The earliest Asian bats (Mammalia: Chiroptera) address major gaps in bat evolution. Biology Letters, 2021; 17 (6): 20210185 DOI: 10.1098/rsbl.2021.0185

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

Earth’s climate life story, 3 billion years in the making

Boriana Kalderon-Asael conducts field work at a Middle-Upper Ordovician outcrop near Reedsville, Penn. Credit: Ashleigh Hood
Boriana Kalderon-Asael conducts field work at a Middle-Upper Ordovician outcrop near Reedsville, Penn. Credit: Ashleigh Hood

One of Earth’s greatest mysteries is how it transformed itself, ever so gradually, from a barren ball of rock into a launching pad for life.

Earth scientists have spent decades piecing together the relevant clues—identifying and studying the planet’s complex interplay of geological processes, atmospheric dynamics, and chemical cycles. In particular, scientists have studied the roles played by carbon and silicon in stabilizing Earth’s climate over a vast stretch of time.

Now a Yale-led study in the journal Nature provides an unprecedented look at this 3-billion-year-old story, told in ancient sediments from around the world.

“We wanted to advance our understanding of what processes have regulated Earth’s climate over geologic time scales,” said Noah Planavsky, an associate professor of Earth and planetary sciences in Yale’s Faculty of Arts and Sciences and co-corresponding author of the new study with Yale graduate student Boriana Kalderon-Asael and University College London researcher Philip Pogge von Strandmann.

“How the Earth’s climate has remained stable for the majority of the last 3 billion years is one of the most fundamental questions one can ask about how the Earth works,” Planavsky said.

At the root of Earth’s climate life story is its ability to remove carbon dioxide from the atmosphere and store it in rocks and sediments. We have plants to thank for that, the researchers said.

The emergence of plants on land and in the ocean led to gradual—but major—changes in how rocks and sediments weathered. These changes in weathering opened the door for sequestering carbon into the Earth itself.

“The result was a substantial decrease in carbon dioxide levels, which kept pace with the increasing luminosity of the sun as it aged, helping to ensure that the Earth remained persistently habitable to both simple and complex life forms,” Planavsky said.

Kalderon-Asael and Planavsky led an international team of researchers that gathered more than 600 sediment samples at roughly 100 sites worldwide. The researchers studied geochemical data found in lithium isotopes in the samples—a methodology used in other studies over the past decade to look at specific points in Earth’s recent and distant past.

The new study encompasses the entirety of Earth’s history, allowing researchers to document the evolution of how Earth regulated its climate.

“It gives us the whole picture,” said Kalderon-Asael, the study’s first author. “This began as a one-year project to look at a couple of sites. As we started to see the data come in, we added more collaborators and more samples until we were able to look at all of Earth’s history.”

In addition to the history lesson, the study offers a long-term perspective on the rapid changes in global climate today.

“Through all of the massive changes Earth has undergone—in the biosphere and in the amount of solar radiation it receives—it has remained habitable by making adjustments on extremely long time-scales,” Planavsky said. “It highlights how totally unprecedented the current shifts are in the carbon cycle.”

Reference:
Boriana Kalderon-Asael et al, A lithium-isotope perspective on the evolution of carbon and silicon cycles, Nature (2021). DOI: 10.1038/s41586-021-03612-1

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

A rock with many perspectives

The Alum Shale, here an example of a coastal deposit, consists of quartz and potassium Feldspar clasts as well as conspicuous Pyrite crystals (here: white) embedded in a clayey matrix. Scanning electron micrograph (scale: lower image edge length corresponds to approx. 40 μm). Credit: Schulz, GFZ
The Alum Shale, here an example of a coastal deposit, consists of quartz and potassium Feldspar clasts as well as conspicuous Pyrite crystals (here: white) embedded in a clayey matrix. Scanning electron micrograph (scale: lower image edge length corresponds to approx. 40 μm). Credit: Schulz, GFZ

The Alum Shale of Northern Europe not only has an eventful history of formation, connected with the microcontinent Baltica, it also holds great potential as an object of investigation for future research questions. Geologists use the rock to reconstruct processes of oil and gas formation, and even possible traces of past life on Mars can be identified with its help. Researchers at the German Research Centre for Geosciences Potsdam GFZ, together with colleagues from Canada, China, Switzerland and Denmark, have summarized the state of knowledge about the multi-layered rock. Their article was published in July in the journal Earth-Science Reviews.

The microcontinent ‘Baltica’

“This rock tells a story,” says Hans-Martin Schulz when he talks about the Northern European Alum Shale. It is the checkered history of a microcontinent called “Baltica”, which was located in the southern hemisphere about 500 million years ago. “The microcontinent is surrounded by a calm, shallow marginal sea,” says the scientist in the GFZ’s Organic Geochemistry Section, describing the situation in the period from the Middle Cambrian to the Lower Ordovician. Higher land plants do not yet exist, and the surface of Baltica is exposed to wind and weather. “Rocks weather, and debris and dust are carried into the sea. Together with components of algae and other microorganisms, they trickle through the layers of the calm marginal sea and settle layer by layer in the oxygen-free bottom water,” Schulz continues. These organic-mineral deposits fossilize and form the dark claystone that makes up today’s Alum Shale. Over millions of years, Baltica migrated northwards and is now integrated into northern Europe. “Almost half a billion years later, the Baltic Sea forms on Baltica,” Schulz concludes the first part of the story.

Oil and gas formation in phases

For three years, Schulz’s group and international colleagues have been combing through their own data and that of other research groups. In their comprehensive synopsis, they also describe the different phases of oil and gas formation during Baltica’s development. Parts of the microcontinent sink to depths of several thousand meters during migration. Oil forms under the influence of geothermal heat. “The oil that was generated at that time is now produced on the Swedish island of Gotland and in the Baltic Sea off the Polish coast,” Schulz explains.

Other parts of the microcontinent occur more near the surface, for example in what is now southern Sweden. There, about 300 million years ago, increased expansion of the earth’s crust takes place. Magma escapes, the heat of which causes further crude oil to form in the Alum Shale. “These rather regional deposits are enclosed in the rock,” the geologist describes. At the end of the last ice age, about ten thousand years ago, sweet meltwater penetrates the shale here. “It meets tiny inclusions of ancient seawater. They contain bacteria that have survived for millions of years,” Schulz describes. The fresh water awakens them to new activity, and further bacteria are possibly contained in the meltwater. The microbes decompose components of the oil and form methane gas.

Influence of uranium

And that’s not the end of the story: although there is still plenty of organic material, the oil-forming potential of the Alum Shale is declining. This is because it contains uranium, whose radiation alters the enclosed carbon compounds over long periods of time—”with fatal consequences for oil formation”, as Schulz says. “The long chains are split off,” he explains. “What remains are ring-shaped hydrocarbons, predominantly benzene rings, which are linked together.” These changes prevent the further formation of petroleum from the organic remnants of Cambrian and Ordovician life. The uranium probably originated in the rocks that were eroded on Baltica and settled in the sea. “And seawater also contains dissolved uranium, so some of the radioactive metal could have been absorbed by the sediments from it,” Schulz adds.

Alum shale has many talents

The GFZ researcher and his team are investigating the significance of the very high uranium concentrations in places in the Alum Shale: “Can organic material altered by uranium still feed a deep biosphere?” they are asking themselves in ongoing studies, for example. Or does the radioactive fission of hydrocarbons prevent microbes from surviving at great depths? And it is not only the influence of uranium on microbial life that interests him. “The Alum Shale is a rock with many talents,” Schulz says. “We can study numerous processes on it at different depths, at different degrees of maturity of the organic material, different uranium concentrations and sometimes extreme conditions.”

The Alum Shale may even have answers to the question of past life at a distance of 70 million kilometers from Earth: organic components have been found on Mars that have structural similarities to those found in the Alum Shale. And similar to the uranium-containing terrestrial mudstone, these molecules were exposed to the equally radioactive cosmic over long periods of time. “So these hydrocarbon compounds could be the altered remains of organisms similar to our earlier bacteria,” Schulz explains. “The Alum Shale serves as a Mars analog for us to interpret the possible traces of past life on our neighboring planet.”

Insights into final disposal of nuclear waste?

For us on Earth, another aspect of his research is topical: besides salts and granites, mudstone is a candidate for the final disposal of nuclear waste. “We also have ideas for future projects on this,” Schulz reveals. “At the core of this is the question of microbial life over long periods of time in the low-porosity, uranium-rich Alum Shale—but that story is on another page.”

Reference:
Hans-Martin Schulz et al, The Furongian to Lower Ordovician Alum Shale Formation in conventional and unconventional petroleum systems in the Baltic Basin – A review, Earth-Science Reviews (2021). DOI: 10.1016/j.earscirev.2021.103674

Note: The above post is reprinted from materials provided by Helmholtz Association of German Research Centres.

‘Fool’s gold’ not so foolish after all

Gold in pyrite
Gold in pyrite

Curtin University research has found tiny amounts of gold can be trapped inside pyrite, commonly known as ‘fool’s gold’, which would make it much more valuable than its name suggests.

This study, published in the journal Geology in collaboration with the University of Western Australia and the China University of Geoscience, provides an in-depth analysis to better understand the mineralogical location of the trapped gold in pyrite, which may lead to more environmentally friendly gold extraction methods.

Lead researcher Dr Denis Fougerouse from Curtin’s School of Earth and Planetary Sciences said this new type of “invisible” gold has not previously been recognised and is only observable using a scientific instrument called an atom probe.

“The discovery rate of new gold deposits is in decline worldwide with the quality of ore degrading, parallel to the value of precious metal increasing,” Dr Fougerouse said.

“Previously gold extractors have been able to find gold in pyrite either as nanoparticles or as a pyrite-gold alloy, but what we have discovered is that gold can also be hosted in nanoscale crystal defects, representing a new kind of “invisible” gold.

“The more deformed the crystal is, the more gold there is locked up in defects. The gold is hosted in nanoscale defects called dislocations — one hundred thousand times smaller than the width of a human hair — so a special technique called atom probe tomography is needed to observe it.”

Dr Fougerouse said the team also explored gold extraction methods and possible ways to obtain the trapped gold with less adverse impacts on the environment.

“Generally, gold is extracted using pressure oxidizing techniques (similar to cooking), but this process is energy hungry. We wanted to look into an eco-friendlier way of extraction,” Dr Fougerouse said.

“We looked into an extraction process called selective leaching, using a fluid to selectively dissolve the gold from the pyrite. Not only do the dislocations trap the gold, but they also behave as fluid pathways that enable the gold to be “leached” without affecting the entire pyrite.”

The study is supported by the Australian Research Council and the Science and Industry Endowment Fund. Dr Fougerouse is affiliated with The Institute for Geoscience Research (TIGeR), Curtin’s flagship Earth Sciences research institute.

Reference:
Denis Fougerouse, Steven M. Reddy, Mark Aylmore, Lin Yang, Paul Guagliardo, David W. Saxey, William D.A. Rickard, Nicholas Timms. A new kind of invisible gold in pyrite hosted in deformation-relateddislocations. Geology, 2021; DOI: 10.1130/G49028.1

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

Earth’s meteorite impacts over past 500 million years tracked

The asteroid belt between Jupiter and Mars is the main source of extraterrestrial material that lands on Earth. (Illustration: ESA/ATG Medialab)
The asteroid belt between Jupiter and Mars is the main source of extraterrestrial material that lands on Earth. (Illustration: ESA/ATG Medialab)

For the first time, a unique study conducted at Lund University in Sweden has tracked the meteorite flux to Earth over the past 500 million years. Contrary to current theories, researchers have determined that major collisions in the asteroid belt have not generally affected the number of impacts with Earth to any great extent.

Researchers have been studying geological series since the 19th century in order to reconstruct how flora, fauna and the climate have changed over millions of years. Until now, however, almost nothing has been known about ancient meteorite flux — which makes sense since impact is rare, and the battered celestial bodies quickly break down as they encounter Earth’s oxygen. A new study published in PNAS shows how researchers in Lund have reconstructed meteorite bombardment towards Earth over the past 500 million years.

“The research community previously believed that meteorite flux to Earth was connected to dramatic events in the asteroid belt. The new study, however, shows that the flux has instead been very stable,” says Birger Schmitz, professor of geology at Lund University.

To conduct the study, researchers at Lund University’s Astrogeobiology Laboratory dissolved almost ten tonnes of sedimentary rocks from ancient seabeds in strong acids because the sediment contains residue from the meteorites dating back to when they fell to Earth.

Meteorites contain a small fraction of a mineral, a chromium oxide, which is very resistant to degradation. The microscopic chromium oxide grains were sifted out in the laboratory and serve as time capsules with an abundance of information.

“The dissolved sediment represents 15 periods over the past 500 million years. In total, we have extracted chromium oxide from almost 10,000 different meteorites. Chemical analyses then enabled us to determine which types of meteorites the grains represent,” says Birger Schmitz.

A couple of thousand meteorites land on the Earth’s surface every year, and approximately 63,000 space rocks have been documented by science. The space rocks originate from the asteroid belt between Mars and Jupiter where battered celestial bodies from gigantic collisions revolve around the sun.

“We were very surprised to learn that only one of the 70 largest asteroid collisions that took place over the past 500 million years resulted in an increased flux of meteorites to Earth. For some reason, most of the rocks stay in the asteroid belt,” says Birger Schmitz.

The study not only upends generally accepted meteorite flux theories; it also provides entirely new perspectives on which types of celestial bodies are at greatest risk of colliding with Earth and where in the solar system they originate. From a geological time perspective, kilometre-sized celestial bodies collide with the Earth on a regular basis. One such event took place 66 million years ago, when a celestial body stretching over 10 kilometres in size hit the Yucatán Peninsula. The impact was part of the reason the Earth went dark and dinosaurs starved to death.

“Future impact from even a small asteroid for example in the sea close to a populated area could lead to disastrous outcomes. This study provides important understanding that we can use to prevent this from happening; for example, by attempting to influence the trajectory of rapidly approaching celestial bodies,” concludes Birger Schmitz.

Reference:
Fredrik Terfelt, Birger Schmitz. Asteroid break-ups and meteorite delivery to Earth the past 500 million years. Proceedings of the National Academy of Sciences, 2021; 118 (24): e2020977118 DOI: 10.1073/pnas.2020977118

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

Discovery of the oldest plant fossils on the African continent!

Uskiella spargen a small plant whose axes divide several times before bearing oval sporangia. Credit : Cyrille Prestianni
Uskiella spargen a small plant whose axes divide several times before bearing oval sporangia. Credit : Cyrille Prestianni

The analysis of very old plant fossils discovered in South Africa and dating from the Lower Devonian period documents the transition from barren continents to the green planet we know today. Cyrille Prestianni, a palaeobotanist at the EDDy Lab at the University of Liège (Belgium), participated in this study, the results of which have just been published in the journal Scientific Reports.

The greening of continents — or terrestrialisation — is undoubtedly one of the most important processes that our planet has undergone. For most of the Earth’s history, the continents were devoid of macroscopic life, but from the Ordovician period (480 million years ago) green algae gradually adapted to life outside the aquatic environment. The conquest of land by plants was a very long process during which plants gradually acquired the ability to stand upright, breathe in the air or disperse their spores. Plant fossils that document these key transitions are very rare. In 2015, during the expansion of the Mpofu Dam (South Africa), researchers discovered numerous plant fossils in geological strata dated to the Lower Devonian (420 — 410 million years ago), making this a truly exceptional discovery.

Cyrille Prestianni, a palaeobotanist at the EDDy Lab (Evolution and Diversity Dynamics Lab) at the University of Liège, explains: “The discovery quickly proved to be extraordinary, since we are in the presence of the oldest fossil flora in Africa and it is very diversified and of exceptional quality. It is thanks to a collaboration between the University of Liège, the IRSNB (Royal Belgian Institute of Natural Sciences) and the New Albany Museum (South Africa) that this incredible discovery could be studied. The study, which has just been published in the journal Scientific Reports, describes this particularly diverse fossil flora with no less than fifteen species analysed, three of which are new to science. Dr. Prestianni adds : ” This flora is also particularly interesting because of the quantity of complete specimens that have been discovered,” says the researcher. These plants are small, with the largest specimens not exceeding 10 cm in height. They are simple plants, consisting of axes that divide two or three times and end in reproductive structures called sporangia. ”

The fossil flora of Mpofu allows us today to imagine what the world might have been like when the largest plants were no taller than our ankle and almost no animals had yet been able to free themselves from the aquatic environment. It gives us a better understanding of how our Earth went from a red rock devoid of life to the green planet we know today. These plants, simple as they are, are a crucial step in the construction of the environments that hosted the first land animals, arthropods. They form the basis of the long history of life on Earth, which continues today from dense tropical forests to the arid tundra of the north.

Reference:
Robert W. Gess, Cyrille Prestianni. An early Devonian flora from the Baviaanskloof Formation (Table Mountain Group) of South Africa. Scientific Reports, 2021; 11 (1) DOI: 10.1038/s41598-021-90180-z

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

The Earth has a pulse — a 27.5-million-year cycle of geological activity, researchers say

The early Earth was hotter than it is today and this affected the strength of the crust and mantle.
The early Earth was hotter than it is today and this affected the strength of the crust and mantle.

Geologic activity on Earth appears to follow a 27.5-million-year cycle, giving the planet a “pulse,” according to a new study published in the journal Geoscience Frontiers.

“Many geologists believe that geological events are random over time. But our study provides statistical evidence for a common cycle, suggesting that these geologic events are correlated and not random,” said Michael Rampino, a geologist and professor in New York University’s Department of Biology, as well as the study’s lead author.

Over the past five decades, researchers have proposed cycles of major geological events — including volcanic activity and mass extinctions on land and sea — ranging from roughly 26 to 36 million years. But early work on these correlations in the geological record was hampered by limitations in the age-dating of geologic events, which prevented scientists from conducting quantitative investigations.

However, there have been significant improvements in radio-isotopic dating techniques and changes in the geologic timescale, leading to new data on the timing of past events. Using the latest age-dating data available, Rampino and his colleagues compiled updated records of major geological events over the last 260 million years and conducted new analyses.

The team analyzed the ages of 89 well-dated major geological events of the last 260 million years. These events include marine and land extinctions, major volcanic outpourings of lava called flood-basalt eruptions, events when oceans were depleted of oxygen, sea-level fluctuations, and changes or reorganization in the Earth’s tectonic plates.

They found that these global geologic events are generally clustered at 10 different timepoints over the 260 million years, grouped in peaks or pulses of roughly 27.5 million years apart. The most recent cluster of geological events was approximately 7 million years ago, suggesting that the next pulse of major geological activity is more than 20 million years in the future.

The researchers posit that these pulses may be a function of cycles of activity in the Earth’s interior — geophysical processes related to the dynamics of plate tectonics and climate. However, similar cycles in the Earth’s orbit in space might also be pacing these events.

“Whatever the origins of these cyclical episodes, our findings support the case for a largely periodic, coordinated, and intermittently catastrophic geologic record, which is a departure from the views held by many geologists,” explained Rampino.

In addition to Rampino, study authors include Yuhong Zhu of NYU’s Center for Data Science and Ken Caldeira of the Carnegie Institution for Science.

Reference:
Michael R. Rampino, Ken Caldeira, Yuhong Zhu. A pulse of the Earth: A 27.5-Myr underlying cycle in coordinated geological events over the last 260 Myr. Geoscience Frontiers, 2021; 12 (6): 101245 DOI: 10.1016/j.gsf.2021.101245

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

Mining precious rare-earth elements from coal fly ash with a reusable ionic liquid

Open cut hard rock mining, Kalgoorlie, Western Australia.
Open cut hard rock mining, Kalgoorlie, Western Australia. Credit: Stephen Codrington

Rare-earth elements are in many everyday products, such as smart phones, LED lights and batteries. However, only a few locations have large enough deposits worth mining, resulting in global supply chain tensions. So, there’s a push toward recycling them from non-traditional sources, such as waste from burning coal — fly ash. Now, researchers in ACS’ Environmental Science & Technology report a simple method for recovering these elements from coal fly ash using an ionic liquid.

While rare-earth elements aren’t as scarce as their name implies, major reserves are either in politically sensitive locations, or they are widely dispersed, which makes mining them challenging. So, to ensure their supply, some people have turned to processing other enriched resources. For instance, the ash byproduct from coal-fired power plants has similar elemental concentrations to raw ores. Yet, current methods to extract these precious materials from coal fly ash are hazardous and require several purification steps to get a usable product. A potential solution could be ionic liquids, which are considered to be environmentally benign and are reusable. One in particular, betainium bis(trifluoromethylsulfonyl)imide or [Hbet][Tf2N], selectively dissolves rare-earth oxides over other metal oxides. This ionic liquid also uniquely dissolves into water when heated and then separates into two phases when cooled. So, Ching-Hua Huang, Laura Stoy and colleagues at Georgia Tech wanted to see if it would efficiently and preferentially pull the desired elements out of coal fly ash and whether it could be effectively cleaned, creating a process that is safe and generates little waste.

The researchers pretreated coal fly with an alkaline solution and dried it. Then, they heated ash suspended in water with [Hbet][Tf2N], creating a single phase. When cooled, the solutions separated. The ionic liquid extracted more than 77% of the rare-earth elements from fresh material, and it extracted an even higher percentage (97%) from weathered ash that had spent years in a storage pond. Finally, rare-earth elements were stripped from the ionic liquid with dilute acid. The researchers found that adding betaine during the leaching step increased the amounts of rare-earth elements extracted. The team tested the ionic liquid’s reusability by rinsing it with cold water to remove excess acid, finding no change in its extraction efficiency through three leaching-cleaning cycles. The researchers say that this low-waste approach produces a solution rich in rare-earth elements, with limited impurities, and could be used to recycle precious materials from the abundance of coal fly ash held in storage ponds.

Reference:
Laura Stoy, Victoria Diaz, Ching-Hua Huang. Preferential Recovery of Rare-Earth Elements from Coal Fly Ash Using a Recyclable Ionic Liquid. Environmental Science & Technology, 2021; DOI: 10.1021/acs.est.1c00630

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

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