Tracking down the asteroid that sealed the fate of the dinosaurs

Geoscientists from the University of Cologne have led an international study to determine the origin of the huge piece of rock that hit the Earth around 66 million years ago and permanently changed the climate. The scientists analysed samples of the rock layer that marks the boundary between the Cretaceous and Paleogene periods. This period also saw the last major mass extinction event on Earth, in which around 70 percent of all animal species became extinct. The results of the study published in Science indicate that the asteroid formed outside Jupiter's orbit during the early development of our solar system.

According to a widely accepted theory, the mass extinction at the Cretaceous-Paleogene boundary was triggered by the impact of an asteroid at least 10 kilometres in diameter near Chicxulub on the Yucatán Peninsula in Mexico.

On impact, the asteroid and large quantities of earth rock vaporized.

Fine dust particles spread into the stratosphere and obscured the sun.

This led to dramatic changes in the living conditions on the planet and brought photosynthetic activity to a halt for several years.

The dust particles released by the impact formed a layer of sediment around the entire globe.

This is why the Cretaceous-Paleogene boundary can be identified and sampled in many places on Earth.

It contains high concentrations of platinum-group metals, which come from the asteroid and are otherwise extremely rare in the rock that forms the Earth's crust.

By analysing the isotopic composition of the platinum metal ruthenium in the cleanroom laboratory of the University of Cologne's Institute of Geology and Mineralogy, the scientists discovered that the asteroid originally came from the outer solar system.

"The asteroid's composition is consistent with that of carbonaceous asteroids that formed outside of Jupiter's orbit during the formation of the solar system," said Dr Mario Fischer-Gödde, first author of the study.

The ruthenium isotope compositions were also determined for other craters and impact structures of different ages on Earth for comparison. This data shows that within the last 500 million years, almost exclusively fragments of S-type asteroids have hit the Earth. In contrast to the impact at the Cretaceous-Paleogene boundary, these asteroids originate from the inner solar system. Well over 80 percent of all asteroid fragments that hit the Earth in the form of meteorites come from the inner solar system. Professor Dr Carsten Münker, co-author of the study, added: "We found that the impact of an asteroid like the one at Chicxulub is a very rare and unique event in geological time. The fate of the dinosaurs and many other species was sealed by this projectile from the outer reaches of the solar system."

Read more at Science Daily

What turned Earth into a giant snowball 700m years ago? Scientists now have an answer

Australian geologists have used plate tectonic modelling to determine what most likely caused an extreme ice-age climate in Earth's history, more than 700 million years ago.

The study, published in Geology, helps our understanding of the functioning of the Earth's built-in thermostat that prevents the Earth from getting stuck in overheating mode.

It also shows how sensitive global climate is to atmospheric carbon concentration.

"Imagine the Earth almost completely frozen over," said the study's lead author, ARC Future Fellow Dr Adriana Dutkiewicz.

"We now think we have cracked the mystery: historically low volcanic carbon dioxide emissions, aided by weathering of a large pile of volcanic rocks in what is now Canada; a process that absorbs atmospheric carbon dioxide."

The project was inspired by the glacial debris left by the ancient glaciation from this period that can be spectacularly observed in the Flinders Ranges in South Australia.

A recent geological field trip to the Ranges, led by co-author Professor Alan Collins from the University of Adelaide, prompted the team to use the University of Sydney EarthByte computer models to investigate the cause and the exceptionally long duration of this ice age.

The extended ice age, also called the Sturtian glaciation after the 19th century European colonial explorer of central Australia, Charles Sturt, stretched from 717 to 660 million years ago, a period well before the dinosaurs and complex plant life on land existed.

Dr Dutkiewicz said: "Various causes have been proposed for the trigger and the end of this extreme ice age, but the most mysterious aspect is why it lasted for 57 million years -- a time span hard for us humans to imagine."

The team went back to a plate tectonic model that shows the evolution of continents and ocean basins at a time after the breakup of the ancient supercontinent Rodina.

They connected it to a computer model that calculates CO2 degassing of underwater volcanoes along mid-ocean ridges -- the sites where plates diverge and new ocean crust is born.

They soon realised that the start of the Sturtian ice age precisely correlates with an all-time low in volcanic CO2 emissions.

In addition, the CO2 outflux remained relatively low for the entire duration of the ice age.

Dr Dutkiewicz said: "At this time, there were no multicellular animals or land plants on Earth. The greenhouse gas concentration of the atmosphere was almost entirely dictated by CO2 outgassing from volcanoes and by silicate rock weathering processes, which consume CO2."

Co-author Professor Dietmar Müller from the University of Sydney said: "Geology ruled climate at this time. We think the Sturtian ice age kicked in due to a double whammy: a plate tectonic reorganisation brought volcanic degassing to a minimum, while simultaneously a continental volcanic province in Canada started eroding away, consuming atmospheric CO2.

"The result was that atmospheric CO2 fell to a level where glaciation kicks in -- which we estimate to be below 200 parts per million, less than half today's level."

The team's work raises intriguing questions about Earth's long-term future.

A recent theory proposed that over the next 250 million years, Earth would evolve towards Pangea Ultima, a supercontinent so hot that mammals might become extinct.

However, the Earth is also currently on a trajectory of lower volcanic CO2 emissions, as continental collisions increase and the plates slow down.

Read more at Science Daily

Source rocks of the first real continents

Geoscientists have uncovered a missing link in the enigmatic story of how the continents developed -- a revised origin story that doesn't require the start of plate tectonics or any external factor to explain their formation. Instead, the findings published last week in Nature Communications, rely solely on internal geological forces that occurred within oceanic plateaus that formed during the first few hundred million years of Earth's history.

A major hurdle in understanding how the continents formed during the Archean Eon (four to 2.5 billion years ago) has been identifying the building blocks of Earth's early crust.

Much of the "new" Archean crust formed during this period comprised a very distinct association of three types of granitoid rocks -- tonalite, trondhjemite and granodiorite (TTG).

Understanding what went into making TTGs and the magmas they formed from has been difficult, because so many geological processes occurred between their initial melting and ultimate crystallization.

Earlier researchers focused on the trace element composition of these rocks, hoping to find clues about TTG magmas and their source.

"We tracked a specific set of trace elements that aren't affected by alteration and pristinely preserve signatures from the original magma that made new TTG crust," said Dr. Matthijs Smit, associate professor and Canada Research Chair at the University of British Columbia's (UBC) Department of Earth, Ocean and Atmospheric Sciences.

"These elements allowed us to look back through the chemical changes that TTG magmas go through and trace the melt compositions back to their initial state and source -- most likely a sort of gabbro."

"Funnily enough, many people have varieties of this type of rock as a kitchen countertop," Dr. Smit says.

"In a way, many people are preparing their dinner on the type of rock that was responsible for making our modern continents."

The Archean TTG crust is still part of the continents today.

For instance, in North America they make up much of the Canadian Interior between the Cordillera mountain belt in the west and the Grenville and Appalachian mountain belts in the east.

The majority of Ontario, Quebec, Manitoba, Saskatchewan, Northwest Territories and Nunavut is made up of Archean crustal fragments that are dominated by TTGs and their slightly younger and more evolved granite counterparts.

"All of these rocks -- and especially their combination -- can be explained by the model we present," said Dr. Smit.

"Ours is a simple model in which TTGs, as well as the younger rocks that TTGs are typically associated with, resulted from the slow burial, thickening and melting of precursor crust that likely resembled oceanic plateaus. The continental crust was destined to develop the way it did, because it kept getting buried further and the rocks at its base had no choice but to melt. In doing so, they made the TTGs that proved a winning recipe for continental survival and growth."

The UBC researchers' discovery of a stand-alone "intra-crustal" mechanism to make TTGs dispels the long-standing theory that Archean TTGs are formed in Earth's first subduction zones and mark the start of plate tectonics.

"There's always been a 'chicken-and-egg' question of which came first -- the start of plate tectonics or TTG magmatism to make new continental crust," says Dr. Smit.

"We show that these things may actually not be directly related. The recognition of the type of source rock makes this leap possible and also takes away the need to have other mechanisms, such as meteorite impact, explain the growth of the first real continents."

Read more at Science Daily

Geoscientists map changes in atmospheric CO2 over past 66 million years

Today atmospheric carbon dioxide is at its highest level in at least several million years thanks to widespread combustion of fossil fuels by humans over the past couple centuries.

But where does 419 parts per million (ppm) -- the current concentration of the greenhouse gas in the atmosphere -- fit in Earth's history?

That's a question an international community of scientists, featuring key contributions by University of Utah geologists, is sorting out by examining a plethora of markers in the geologic record that offer clues about the contents of ancient atmospheres. Their initial study was published this week in the journal Science, reconstructing CO2 concentrations going back through the Cenozoic, the era that began with the demise dinosaurs and rise of mammals 66 million years ago.

Glaciers contain air bubbles, providing scientists direct evidence of CO2 levels going back 800,000 years, according to U geology professor Gabe Bowen, one of the study's corresponding authors. But this record does not extend very deep into the geological past.

"Once you lose the ice cores, you lose direct evidence. You no longer have samples of atmospheric gas that you can analyze," Bowen said. "So you have to rely on indirect evidence, what we call proxies. And those proxies are tough to work with because they are indirect."

"Proxies" in the geologic record

These proxies include isotopes in minerals, the morphology of fossilized leaves and other lines of geological evidence that reflect atmospheric chemistry. One of the proxies stems from the foundational discoveries of U geologist Thure Cerling, himself a co-author on the new study, whose past research determined carbon isotopes in ancient soils are indicative of past CO2 levels.

But the strength of these proxies vary and most cover narrow slices of the past. The research team, called the Cenozoic CO2 Proxy Integration Project, or CenCO2PIP, and organized by Columbia University climate scientist Bärbel Hönisch, set out to evaluate, categorize and integrate available proxies to create a high-fidelity record of atmospheric CO2.

"This represents some of the most inclusive and statistically refined approaches to interpreting CO2 over the last 66 million years," said co-author Dustin Harper, a U postdoctoral researcher in Bowen's lab. "Some of the new takeaways are we're able to combine multiple proxies from different archives of sediment, whether that's in the ocean or on land, and that really hasn't been done at this scale."

The new research is a community effort involving some 90 scientists from 16 countries. Funded by dozens of grants from multiple agencies, the group hopes to eventually reconstruct the CO2 record back 540 million years to the dawn of complex life.

At the start of the Industrial Revolution -- when humans began burning to coal, then oil and gas to fuel their economies -- atmospheric CO2 was around 280 ppm. The heat-trapping gas is released into the air when these fossil fuels burn.

Looking forward, concentrations are expected to climb up to 600 to 1,000 ppm by the year 2100, depending on the rate of future emissions. It is not clear exactly how these future levels will influence the climate.

But having a reliable map of past CO2 levels could help scientists more accurately predict what future climates may look like, according to U biology professor William Anderegg, director the U's Wilkes Center for Climate & Policy.

"This is an incredibly important synthesis and has implications for future climate change as well, particularly the key processes and components of the Earth system that we need to understand to project the speed and magnitude of climate change," Anderegg said.

Today's 419 ppm is the highest CO2 in 14 million years

At times in the past when Earth was a far warmer place, levels of CO2 were much higher than now. Still, the 419 ppm recorded today represents a steep and perhaps dangerous spike and is unprecedented in recent geologic history.

"By 8 million years before present, there's maybe a 5% chance that CO2 levels were higher than today," Bowen said, "but really we have to go back 14 million years before we see levels we think were like today."

In other words, human activity has significantly altered the atmosphere within the span of a few generations. As a result, climate systems around the globe are showing alarming signs of disruption, such as powerful storms, prolonged drought, deadly heat waves and ocean acidification.

A solid understanding of atmospheric CO2 variation through geological time is also essential to deciphering and learning from various features of Earth's history. Changes in atmospheric CO2 and climate likely contributed to mass extinctions, as well as evolutionary innovations.

Read more at Science Daily

Carbon dioxide -- not water -- triggers explosive basaltic volcanoes

Geoscientists have long thought that water -- along with shallow magma stored in Earth's crust -- drives volcanoes to erupt. Now, thanks to newly developed research tools at Cornell, scientists have learned that gaseous carbon dioxide can trigger explosive eruptions.

A new model suggests that basaltic volcanoes, typically located on the interior of tectonic plates, are fed by a deep magma within the mantle, stored about 20 to 30 kilometers below Earth's surface.

The research, which offers a clearer picture of our planet's deep internal dynamics and composition, with implications for improving volcanic-hazards planning, will publish August 7, 2023 at 3:00pm ET in the Proceedings of the National Academy of Sciences.

"We used to think all the action happened in the crust," said senior author Esteban Gazel, the Charles N. Mellowes Professor in Engineering in the Department of Earth and Atmospheric Sciences, in Cornell Engineering. "Our data implies the magma comes directly from the mantle -- passing fast through the crust - driven by the exsolution (the process phase of separating gas from liquid) of carbon dioxide.

"This completely changes the paradigm of how these eruptions happen," Gazel said. "All volcanic models had been dominated by water as the main eruption driver, but water has little to do with these volcanoes. It's carbon dioxide that brings this magma from the deep Earth."

About four years ago, Gazel and Charlotte DeVitre, Ph.D. '22, now a postdoctoral researcher at University of California, Berkeley, developed a high-precision carbon dioxide densimeter (which measures density in a tiny vessel) for Raman spectroscopy (a device that examines scattered photons through a microscope).

The natural samples -- microscopic-sized carbon dioxide rich bubbles trapped in crystals emanating from the volcanic eruption -- are then measured via Raman and quantified applying the newly developed densimeter. Essentially, the scientists are examining a microscopic time capsule to provide a history of the magma. This new technique is critical for near real-time precise estimations of magma storage, tested during the 2021 eruption in Las Palmas, in the Canary Islands by Gazel's group.

Further, the scientists developed methods to assess the effect of laser heating on carbon-dioxide rich inclusions (found swathed in the crystals), and to accurately assess melt inclusion and bubble volumes. They also developed an experimental reheating method to increase accuracy and properly account for carbon dioxide trapped as carbonate crystals inside the bubbles.

"The method of development and instrument design were challenging, especially during the height of the pandemic," Gazel said.

Using these new tools, the scientists scrutinized volcanic deposits from the Fogo volcano in Cabo Verde, west of Senegal in the Atlantic Ocean. They found a high concentration of volatiles in the micro-sized melt inclusions encased within the magnesium-iron silicate crystals. The higher amount of carbon dioxide enclosed in the crystals suggested that the magma was stored tens of kilometers below the surface -- within the Earth's mantle.

The group also discovered that this process is connected to the deep mantle source that supply these volcanoes.

This implies that eruptions such as Fogo's volcanic flareups start and are fed from the mantle, effectively bypassing storage in the Earth's crust and driven by deep carbon dioxide, according to the paper.

"These magmas have extremely low viscosities and come directly from the mantle," DeVitre said. "So here, viscosity and water cannot play the common roles that they do in shallower and/or more silicic (rich in silica) volcanic systems. Rather at Fogo volcano the magma must be driven up fast by the carbon dioxide and this likely plays a significant role in its explosive behavior. This is a major step in our understanding of the controls on basaltic explosivity."

Comprehending magma storage helps best prepare society for future eruptions, said Gazel, who is also a faculty fellow at the Cornell Atkinson Center for Sustainability.

"As deep magma storage will not be detected by ground deformation until the melt is close to surface," he said, "this has important repercussions to our understanding of volcanic hazards. We need to understand the drivers of these eruptions. The only way to see these processes now is by observing earthquakes, but earthquakes don't tell you exactly what's happening."

Said Gazel: "With precise measurements that tell us where eruptions start, where magmas melt and where they are stored -- and what triggers the eruption -- we can develop a much better plan for future eruptions."

Read more at Science Daily

Insolation affected ice age climate dynamics

In past ice ages, the intensity of summer insolation affected the emergence of warm and cold periods and played an important role in triggering abrupt climate changes, a study by climate researchers, geoscientists, and environmental physicists suggests. Using stalagmites in the European Alps, they were able to demonstrate that warm phases appeared primarily when the summer insolation reached maxima in the Northern Hemisphere. Study participants included scientists from Germany, Austria, and Switzerland led by researchers from Heidelberg University and the GFZ German Research Centre for Geosciences Potsdam.

Past ice ages in the Northern Hemisphere were marked by sudden transitions between cold and warm phases, each lasting several thousand years. The reason for these fluctuations has yet to be resolved, but research does point to effects relating to the size of the continental ice sheets. Greenland ice records 25 such warm-cold cycles between 115,400 and 14,700 years ago. Investigating stalagmites in the Melchsee-Frutt cave system in the Swiss Alps, the researchers were able to investigate for the first time and with high precision 16 such fluctuations in the penultimate glacial period 185,000 to 130,000 years ago.

Stalagmites in caves are crucial archives in climate research and offer clues as to changes in temperature, precipitation, and vegetation cover. "We are able to precisely determine their age and hence analyse the chronological sequence of abrupt ice age climate fluctuations, which we identify using oxygen isotope values," explains Prof. Dr Norbert Frank of the Institute of Environmental Physics at Heidelberg University. "Our investigations targeted whether, in addition to ice volumes in the Northern Hemisphere, orbitally driven changes in the global distribution of insolation could have influenced the abrupt changes in climate," states study head Dr Jens Fohlmeister, who earned his doctorate in environmental physics at Heidelberg University and worked at the GFZ German Research Centre for Geosciences Potsdam and the Potsdam Institute for Climate Impact Research during the investigations.

The researchers studied the transitions of warm-cold cycles in the penultimate ice age by analysing the age and oxygen isotope composition of stalagmites from the Melchsee-Frutt cave system. "Based on the newly acquired data, we were able to show that warm phases occurred mainly during the peak phase of summer insolation in the Northern Hemisphere, even when the sea level, which is dependent on the volume of the continental ice sheets, remained close to its minimum during peak glacial periods," explains Dr Fohlmeister. Model simulations confirmed these findings. In accordance with the research data from the cave system, the simulations predict the frequency as well as the duration of warm phases at the corresponding sea level and existing insolation.

Read more at Science Daily

Shrinking Arctic glaciers are unearthing a new source of methane

As the Arctic warms, shrinking glaciers are exposing bubbling groundwater springs which could provide an underestimated source of the potent greenhouse gas methane, finds new research published today in Nature Geoscience.

The study, led by researchers from the University of Cambridge and the University Centre in Svalbard, Norway, identified large stocks of methane gas leaking from groundwater springs unveiled by melting glaciers.

The research suggests that these methane emissions will likely increase as Arctic glaciers retreat and more springs are exposed. This, and other methane emissions from melting ice and frozen ground in the Arctic, could exacerbate global warming.

"These springs are a considerable, and potentially growing, source of methane emissions -- one that has been missing from our estimations of the global methane budget until now," said Gabrielle Kleber, lead author of the research who is from Cambridge's Department of Earth Sciences.

Scientists are concerned that additional methane emissions released by the Arctic thaw could ramp-up human-induced global warming. The springs the researchers studied hadn't previously been recognized as a potential source of methane emissions.

Kleber spent nearly three years monitoring the water chemistry of more than a hundred springs across Svalbard, where air temperatures are rising two times faster than the average for the Arctic. She likens Svalbard to the canary in the coal mine of global warming, "Since it is warming faster than the rest of the Arctic, we can get a preview of the potential methane release that could happen at a larger scale across this region."

Professor Andrew Hodson, study co-author from the University Centre in Svalbard said, "Living in Svalbard exposes you to the front-line of Arctic climate change. I can't think of anything more stark than the sight of methane outgassing in the immediate forefield of a retreating glacier."

Previously, research has centred on methane release from thawing permafrost (frozen ground). "While the focus is often on permafrost, this new finding tells us that there are other pathways for methane emissions which could be even more significant in the global methane budget," said study co-author Professor Alexandra Turchyn, also from Cambridge's Department of Earth Sciences.

Hodson added, "Until this work was conducted, we didn't understand the source and pathways of this gas because we were reading about studies from completely different parts of the Arctic where glaciers are absent."

The methane-delivering springs they identified are fed by a plumbing system hidden beneath most glaciers, which taps into large groundwater reserves within the underlying sediments and surrounding bedrock. Once the glaciers melt and retreat, springs appear where this groundwater network punches through to the surface.

The researchers found that methane emissions from glacial groundwater springs across Svalbard could exceed 2,000 tonnes over the course of a year -- which equates to roughly 10% of the methane emissions resulting from Norway's annual oil and gas energy industry.

This source of methane will likely become more significant as more springs are exposed, said Kleber, "If global warming continues unchecked then methane release from glacial groundwater springs will probably become more extensive."

Glacial groundwater springs aren't always easy to recognize, so Kleber trained her eye to pick them out from satellite images. Zooming in on the areas of land exposed by the retreat of 78 glaciers across Svalbard, Kleber looked for tell-tale blue trickles of ice where groundwater had leaked to the surface and frozen. She then travelled to each of these sites by snowmobile to take samples of the groundwater at locations where the ice had blistered due to pressurized water and gas build up.

When Kleber and the team profiled the chemistry of the water feeding these springs, they found that all bar one of the sites studied were highly concentrated with dissolved methane -- meaning that, when the spring water reaches the surface, there is plenty of excess methane that can escape to the atmosphere.

The researchers also identified localized hotspots of methane emissions, which were closely related to the type of rock from which the groundwater emerges. Certain rocks like shale and coal contain natural gases, including methane, produced by the breakdown of organic matter when the rocks formed. This methane can move upwards through fractures in the rock and into the groundwater.

"In Svalbard we are beginning to understand the complex and cascading feedbacks triggered by glacier melt -- it seems likely that there are more outcomes like this which we have yet to uncover," said Kleber.

Read more at Science Daily

Geoscientists shed a light on life's evolution 800 million years ago

Is nitrate responsible for algae, flowers, and even your neighbors?

A team of Virginia Tech geoscientists have unearthed evidence that may indicate yes.

The team's findings, recently published in Science Advances, reveal an increase in biologically available nitrogen during the time that marine eukaryotes -- organisms whose cells have a nucleus -- became dominate. Complex eukaryotic cells evolved into multicellular organisms and are credited for ushering in a whole new era for life on Earth, including animals, plants, and fungi.

"Where we sit today, with life as it is on the planet, is the sum total of all the events that happened in the past," said Ben Gill, an associate professor of sedimentary geochemistry and co-author on the paper. "And this is a key event where we shift from dominantly prokaryotic ecosystems -- cells that are much simpler than the ones in our bodies -- to eukaryotes. If that did not happen, we would not be here today."

Previous research focused on phosphorus' role in the rise of eukaryotes, but Junyao Kang, a doctoral student in the Department of Geosciences and lead author of the paper, was curious about the part nitrogen played in this event.

"This data is unique because nitrogen isotope data are virtually nonexistent from the early Neoproterozoic time period, or between a billion and 800 million years ago," said Kang.

Collaborating with the Nanjing University in Najing, China, Kang has spent two years working to understand what drove the rise of eukaryotes through nitrogen isotope analysis of rock samples from the North China Craton. Home to rocks dating back 3.8 billion years ago, the region was once covered by an ocean.

"We had some rough ideas of when eukaryotes became ecologically successful," said Shuhai Xiao, professor of geobiology and a paper co-author. "They had been there for a long time in a low-key status until about 820 million years ago, when they became abundant."

Kang decided he wanted to learn why. He took the data from the rock samples, entered it into a larger database, and analyzed it across a longer time scale that spanned different geographic locations.

"Once we did this kind of integration and put it into a big picture, we saw the rise of nitrates through time, which happened around 800 million years ago," said Kang.

Solid collaboration

A collaborative, international approach was key to connecting this new data with biological events, mostly notably, the rise of eukaryotes.

Gill and Rachel Reid, also a College of Science geochemist and co-author of the paper, provided critical analyses through resources, including the mass spectrometer in the Geoscience Stable Isotope Lab at Virginia Tech. An elemental analyzer coupled to the mass spectrometer allowed the researchers to extract pure nitrogen gas from the samples for analysis.

Gill specializes in reconstructing present and past chemical cycles on our planet. He collaborates with paleontologists to study the record of life preserved in the geological record and examines what potential environmental drivers might have enabled changes in life through history.

Reid, who generally focuses her research on Earth's more recent events, had a special opportunity to offer her nitrogen isotope expertise to these ancient fossils.

Feifei Zhang, a geochemist at Nanjing University, was the paper's fourth co-author. Zhang provided insights on how much oxygen would have been available in the oceans during the time when nitrate increased in abundance.

All of the Virginia Tech authors are affiliated members of the Fralin Life Sciences Institute's Global Change Center, with Kang serving as a Ph.D. fellow in the Interfaces of Global Change graduate program. The center brings together experts from diverse disciplines to solve these complex global challenges and train the next generation of leaders.

Past, present, and future

Xiao, who has helped excavate and study some of the most ancient fossils from around the world, said this type of study gives him hope for future discoveries. The team members look forward to collaborating with NASA on future grants, such as the exobiology program supporting their current research.

He also credits University Libraries at Virginia Tech for its support of open-access publications, such as Science Advances, to provide a vetted selection of research, freely available to readers.

"We can link the dots from the nitrogen isotopic compositions in the ancient past and then go to the next step and infer how much nitrate was available for organisms," said Xiao. "And then we tie that with the fossil data to show that there's a relationship."

While ancient oceans are long gone, what happened in ancient oceans are recorded in rocks, and studying these rocks provides a link from our Earth's history to the present and to the future.

Read more at Science Daily

New geosciences study shows Triassic fossils that reveal origins of living amphibians

The smallest of newly found fossils can upend what paleontologists know about our history.

A team of paleontologists from Virginia Tech and the U.S. Petrified Forest National Park, among others, have discovered the first "unmistakable" Triassic-era caecilian fossil -- the oldest-known caecilian fossils -- thus extending the record of this small, burrowing animal by roughly 35 million years. The find also fills a gap of at least 87 million years in the known historical fossil record of the amphibian-like creature.

The fossil was first co-discovered by Ben Kligman, a doctoral student in the Department of Geosciences, part of the Virginia Tech College of Science, at Arizona's Petrified Forest National Park during a dig in 2019. Named by Kligman as Funcusvermis gilmorei, the fossil extends the history of caecilians 35 million years back to Triassic Period, roughly 250 million to 200 million years ago.

Prior to this new study, published today in the journal Nature, only 10 fossil caecilian occurrences were known, dating back to the Early Jurassic Period, about 183 million years ago. However, previous DNA studies estimated evolutionary origins of caecilians back to the Carboniferous or Permian eras, some 370 million to 270 million years ago, according to Kligman, marking that 87-million-year gap. However, no such fossils had been found.

"The discovery of the oldest caecilian fossils highlights the crucial nature of new fossil evidence. Many of the biggest outstanding questions in paleontology and evolution cannot be resolved without fossils like this," said Kligman, who previously discovered a 220-million-year-old species of cynodont or stem-mammal, a precursor of modern-day mammals. "Fossil caecilians are extraordinarily rare, and they are found accidentally when paleontologists are searching for the fossils of other more common animals. Our discovery of one was totally unexpected, and it transformed the trajectory of my scientific interests."

The discovery of the fossils was made in 2019 by Kligman and Petrified Forest National Park student intern Xavier Jenkins, now a Ph.D. student at Idaho State University, while the duo was processing fossiliferous sediment from the park's nicknamed Thunderstorm Ridge via a microscope. Funcusvermis was found in a layer of the Chinle Formation dated to approximately 220 million years ago, when Arizona was positioned near the equator at the central part of the supercontinent Pangaea, Kligman said. This region at the time was subject to a hot, humid climate. Today, Arizona is still hot, but has low humidity.

"Seeing the first jaw under the microscope, with its distinctive double row of teeth, sent chills down my back," Kligman said. "We immediately knew it was a caecilian, the oldest caecilian fossil ever found, and a once-in-a-lifetime discovery."

Previous to this find, the 87-million-year gap in the fossil record hid the early evolutionary history of caecilians, leading to a decades-long debate amongst scientists over the relationships of caecilians to their amphibian relatives, frogs and salamanders.

"Funcusvermis extends the humid equatorial pattern of occurrence seen in all known fossil and living caecilians, suggesting that the biogeographic history of caecilians has been guided by restriction to these ecological settings, likely due to physiological constraints linked to humidity, and constrained by the drift of continental plates into and out of the humid-equatorial zone after the fragmentation of Pangaea," Kligman said.

Modern caecilians are limbless amphibians with cylindrical bodies with a compact, bullet-shaped skull that helps them burrow underground. Now exclusively home to South and Central America, Africa, and southern Asia, caecilians spend their lives burrowing in leaf-litter or soil searching for prey such as worms and insects. This underground existence has made studying caecilians difficult for scientists. Kligman, tongue in cheek, describes modern caecilians as an "eyeless sock puppet with the body of a worm."

Funcusvermis actually shares skeletal features related more with early frog and salamander fossils, strengthening evidence for a shared origin and close evolutionary relationship between caecilians and these two groups. Funcusvermis also shares skeletal features with an ancient group of amphibians known to paleontologists as dissorophoid temnospondyls. Kligman adds, "Unlike living caecilians, Funcusvermis lacks many adaptations associated with burrowing underground, indicating a slower acquisition of features associated with an underground lifestyle in the early stages of caecilian evolution."

Name that tune

Now, here's the fun part: The genus name 'Funcusvermis' was inspired by the Ohio Players' 1972 song "Funky Worm" from their album Pleasure, a favorite song of the authors that was often played while excavating fossils at Thunderstorm Ridge. 'Funcus' is derived from the Latinized form of the English word Funky for the upbeat, rhythmic form of dance music, while 'vermis' is derived from the Latin word for worm. (It's an excellent song, by the way. Instant earworm, so to speak.)

The species name, gilmorei, honors Ned Gilmore, the collections manager at the Academy of Natural Sciences of Philadelphia's Drexel University. (Kligman is from Philadelphia and volunteered with Gilmore's herpetology wet collection as an undergraduate student. "He was an important mentor who helped inspire my interest in fossils and amphibians," Kligman said.)

Co-authors on the study include Michelle Stocker, an assistant professor, and Sterling Nesbitt, an associate professor, in the Virginia Tech Department of Geosciences and members of the Global Change Center that is part of the Fralin Life Sciences Institute. Other authors include Adam Marsh, lead paleontologist; Matthew Smith, museum curator; and William Parker, chief of science and resource management, all at the Petrified Forest National Park; and Bryan Gee, postdoctoral fellow at the University of Washington's Burke Museum and Department of Biology.

"As the eponymous song says, it's the funkiest worm in the world," Marsh quipped.

Stocker added, "What we collect really determines what we can say about which animals that were present, how many of them there were, and what they looked like. Without using these methods for fossil collection and analysis we would be missing out on knowing so many important aspects of this Triassic ecosystem. Now that we have a search image of what bones to look for and how to look for them, it will be exciting to see what other fossil localities preserve these early lissamphibians."

Nesbitt said finds such as this can reset the game board on paleontology, in the best sense of the phrase. "This find clearly demonstrates that some fossils that you can barely see can greatly change our understanding of entire groups that you can see today," he said.

What's happened since 2019

At the Petrified Forest National Park, where the initial discovery was found in 2019, the lower jaws of at least 70 individuals of Funcusvermis have been recovered as of summer 2022, making the area "the most abundant fossil caecilian-producing bonebed ever discovered," Kligman said.

Only a handful of bones of Funcusvermis have been found, including upper and lower jaws, a vertebra, and part of a hind-limb, Kligman said. All of the found bones were disarticulated, not as complete skeletons. Without complete skeletons, Kligman and his fellow researchers cannot exactly determine the body length of Funcusvermis, but inferences from isolated elements, such as the lower jaw being less than a quarter of an inch long, indicate that Funcusvermis was a tiny animal.

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Analysis of particles of the asteroid Ryugu delivers surprising results

In December 2020, a small landing capsule brought rock particles from the asteroid Ryugu to Earth -- material from the beginnings of our solar system. The Japanese space probe Hayabusa 2 had collected the samples. Geoscientist Professor Frank Brenker and his team from Goethe University Frankfurt were among the first researchers wordwide allowed literally to "shed light" on these scientifically precious samples. In the process, they discovered areas with a massive accumulation of rare earths and unexpected structures. As part of an international research collaboration, they have now reported on this in the scientific journal Science.

Frank Brenker and his team are world leaders in a method that makes it possible to analyse the chemical composition of material in a three-dimensional and entirely non-destructive way and without complicated sample preparation -- yet with a resolution of under 100 nanometres. Resolution expresses the smallest perceptible difference between two measured values. The method's long name is "Synchrotron Radiation induced X-Ray Fluorescence Computed Tomography," in short SR-XRF-CT.

Japan had chosen Ryugu (English: Dragon's Palace) as the probe's destination because it is an asteroid which, due to its high carbon content, promised to deliver particularly extensive information about the origin of life in our solar system. The analyses conducted on 16 particles by the researchers together with the scientists in Frankfurt have now shown that Ryugu is composed of CI-type material. These are very similar to the Sun in terms of their chemical composition. So far, CI-material has only rarely been found on Earth -- material of which it was unclear how much it had been altered or contaminated when entering Earth's atmosphere or upon impact with our planet. Furthermore, the analysis confirms the assumption that Ryugu originated from a parent asteroid which formed in the outer solar nebula.

Until now, scientists had assumed that there was hardly any transport of material within the asteroid due to the low temperatures during the formation of the CI material in the early days of the solar system and therefore scarcely any possibility for a massive accumulation of elements. By means of SR-XRF-CT, however, the researchers in Frankfurt found a fine vein of magnetite -- an iron oxide mineral -- and hydroxyapatite, a phosphate mineral, in one of the grains of the asteroid. Other groups of scientists established that the structure and other magnetite-hydroxyapatite regions in the Ryugu samples must have formed at a surprisingly low temperature of under 40 °C. This finding is fundamental for interpreting almost all the results that the analysis of the Ryugu samples has generated and will generate in future.

In areas of the samples containing hydroxyapatite, Frank Brenker's team additionally detected rare earth metals -- a group of chemical elements indispensable today for alloys and glassware for high-tech applications, among others. "The rare earths occur in the hydroxyapatite of the asteroid in concentrations 100 times higher than elsewhere in the solar system," says Brenker. What's more, he says, all the elements of the rare earth metals have accumulated in the phosphate mineral to the same degree -- which is also unusual. Brenker is convinced: "This equal distribution of rare earths is a further indication that Ryugu is a very pristine asteroid that represents the beginnings of our solar system."

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How to look thousands of kilometers deep into the Earth

Researchers led by Sergey Lobanov from the GFZ German Research Centre for Geosciences have developed a new method to measure the density of silicon dioxide (SiO2) glass, one of the most important materials in industry and geology, at pressures of up to 110 gigapascals, 1.1 million times higher than normal atmospheric pressure. Instead of employing highly focused X-rays at a synchrotron facility, they used a white laser beam and a diamond anvil cell. The researchers report on their new and simple method in the current issue of Physical Review Letters.

The problem of density measurement under extreme conditions

In geosciences, the density of minerals, rocks, and melts at pressures up to several million atmospheres and temperatures of several thousand degrees is of critical importance because it governs the long-term planetary evolution as well as volcanic processes. But how can the density of a material be measured at such extreme conditions? To answer this question for a crystalline mineral or a rock, scientists use X-ray diffraction with which one measures the spacing between the periodically arranged atoms. There is, however, a problem if the material has a disordered structure, i.e. is non-crystalline, like glasses or molten rocks. In this case, the volume of the sample has to be measured directly -- the density of a material equals its mass divided by volume. However, such measurements are extremely difficult because of the tiny volume of the sample brought to high pressure. Previously, these measurements required large scale X-ray facilities and highly specialized equipment, thus being very expensive. Now, a team led by scientist Sergey Lobanov of the GFZ German Research Centre for Geosciences is introducing a new method in which a laser the size of a shoebox allows them to measure the volume of samples brought to pressures similar to that at the depth of more than 2000 km in the Earth.

Inside the Earth, the rock is under unimaginably high pressure, up to several million times higher than normal atmospheric pressure. However, contrary to widespread belief, the Earth's mantle is not liquid, but solid. The rock behaves in a viscoplastic fashion: It moves centimeter by centimeter per year, but it would burst under a hammer blow. Nevertheless, the slow movements drive the Earth's crustal plates and tectonics, which in turn trigger volcanism. Chemical changes, for example, caused by water squeezed out of subducted crustal plates, can change the melting point of the rock in such a way that suddenly molten magma is formed. When this magma makes its way to the Earth's crust and to the surface, volcanic eruptions occur.

Density of disordered materials

No instrument in the world can penetrate the Earth's mantle to study such processes in detail. Therefore, one must rely on calculations, seismic signals and laboratory experiments to learn more about the Earth's interior. A diamond anvil cell can be used to generate the extremely high pressures and temperatures that prevail there. The samples explored in it are smaller than the tip of a pin. Their volume is in the sub nanoliter range (e.g. at least 10 million times smaller than 1 milliliter). When material is compressed under such high pressures, the internal structure changes. To analyze this precisely, X-rays are used on crystals to generate diffraction patterns. This allows conclusions to be drawn about the volume of the crystal lattice and thus also the density of the material. Non-crystalline materials, such as glasses or molten rocks, have so far kept their innermost secrets to themselves. This is because for disordered materials X-ray diffraction does not provide direct information on their volume and density.

Simple trick: measurement with laser instead of X-ray beam

Using a simple trick, researchers led by Sergey Lobanov have now succeeded in measuring the refractive index and density of silicon dioxide (SiO2) glass, one of the most important materials in industry and geology, at pressures of up to 110 gigapascals. This is a pressure that prevails at a depth of more than 2,000 kilometers in the Earth's interior and is 1.1 million times higher than normal atmospheric pressure. The researchers used a multicolor laser to measure the brightness of its reflection from the pressurized sample. The brightness of the laser reflection contained information on the refractive index, a fundamental material property that describes how light slows down and bends as it travels through the material, but also the path length of the laser inside the sample. Materials with a high refractive index and density, such as diamonds and metals, typically appear bright and shiny to our eye. Instead of looking at the tiny samples with a naked eye, Lobanov and his colleagues used a powerful spectrometer to record changes in brightness at high pressure. These measurements yielded the refractive index of SiO2 glass and provided key information to quantify its density.

Significance of the density measurement of glasses for the geosciences

"Earth was a giant ball of molten rock 4.5 billion years ago. To understand how Earth has cooled and produced a solid mantle and crust, we need to know the physical properties of molten rocks at extreme pressure. However, studying melts at high pressure is extremely challenging and to circumvent some of these challenges geologists choose to study glasses instead of melts. Glasses are produced by quickly cooling hot but viscous melts. As a result, the structure of glasses often represents the structure of melts they were formed from. Previous measurements of glass density at high pressure required large and expensive synchrotron facilities that produce a tightly focused beam of X-rays that can be used to view the tiny sample in a diamond anvil cell. These were challenging experiments and only the densities of very few glasses have been measured to a pressure of 1 million atmospheres. We have now shown that the evolution of the sample volume and density of any transparent glass can be accurately measured up to pressures of at least 110 GPa using optical techniques," Lobanov says. "This can be done outside of synchrotron facilities and is therefore much easier and less costly. Our work thus paves the way to future studies of glasses that approximate Earth's present-day and long-gone melts. These future studies will provide new quantitative answers about the evolution of the early Earth as well as the driving forces behind volcanic eruptions."

New possibilities for the investigation of non-crystalline, initially non-transparent solids

Because the samples are extremely small and therefore ultra-thin, even materials that look like a lump of rock in large pieces become translucent. According to the researchers, these developments open up new possibilities for studying the mechanical and electronic properties of non-crystalline solids that appear nontransparent in larger volumes. According to the authors of the study, their findings have far-reaching implications for materials science and geophysics. In addition, this information could serve as a benchmark for computational studies of the transport properties of glasses and melts under extreme conditions.

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Climate signature identified in rivers globally

For decades geoscientists have been trying to detect the influence of climate on the formation of rivers, but up to now there has been no systematic evidence.

A new study, led by scientists from the University of Bristol and published today in the journal Nature, discovers a clear climatic signature on rivers globally that challenges existing theories.

If you walk from a river's source to its mouth, you walk a path that descends in elevation. In some rivers, this path will descend steeply out of the uplands, and then flatten out in the lowlands. This results in an elevational profile (which we call the long profile) that has a concave up shape, similar to the shape of the inside of a bowl as you trace it from the inside rim to the bottom. In contrast, a straight long profile descends evenly in elevation, like a ramp, along the path as you walk from the source to the mouth.

The new research by Chen et al. shows that while river long profiles tend to be concave up in humid regions, they become progressively straighter in drier regions.

Lead author Shiuan-An Chen from the University of Bristol's School of Geographical Sciences, said: "The long profile is formed gradually over tens of thousands to millions of years, so it tells a bigger story about the climate history of region. We would expect climate to affect the river long profile because it controls how much water flows in rivers and the associated force of water to move sediment along the riverbed."

Up until now scientists have lacked a large, systematic dataset of rivers that spans the range of climate zones on Earth, enabling full exploration of the links between climate and river form. The research team produced a new, freely available, database of river long profiles, generated from data originally collected by NASA's space shuttle. They used specialist software developed by co-author Dr Stuart Grieve at Queen Mary University of London to develop a new long profile database that includes over 330,000 rivers across the globe.

The study shows for the first time at the global scale that there are distinct differences in river long profile shapes across climate zones, and that the reason behind these differences lies in the expression of aridity in streamflow in rivers.

In humid regions, rivers tend to have flow in them all year round which continually moves sediment and erodes the overall profile into a concave up shape.

As the climate becomes progressively arid (from semi-arid, to arid, to hyper-arid), rivers only flow a few times per year when it rains, moving sediment infrequently.

Additionally, arid rivers tend to experience brief, intense rainstorms, which do not create flow over the entire river length.

These links between climate, streamflow and long profile shape are explained in the paper using a numerical model which simulates the evolution of river profiles over time in response to streamflow characteristics.

The authors show that regardless of all other potential controls on river profiles, streamflow characteristics have a dominant effect on the final profile shape. They demonstrate that the differences in the climatic expression of streamflow explain the variations in profile shape across climatic regions in their database.

Dr Katerina Michaelides, also from Bristol's School of Geographical Sciences, who led the research added:

"Traditional theory included in textbooks for decades describes that river long profiles evolve to be concave up. Existing theories are biased towards observations made in humid rivers, which are far better studied and more represented in published research than dryland rivers.

"Our study shows that many river profiles around the world are not concave up and that straighter profiles tend to be more common in arid environments."

"I think dryland rivers have been understudied and under-appreciated, especially given that drylands cover ~40% of the global land surface. Their streamflow expression gives unique insights into the climatic influence on land surface topography."

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Ancient animal species: Fossils dating back 550 million years among first animal trails

Three Gorges, Yantze River, China.

In a remarkable evolutionary discovery, a team of scientists co-led by a Virginia Tech geoscientist has discovered what could be among the first trails made by animals on the surface of the Earth roughly a half-billion years ago.

Shuhai Xiao, a professor of geosciences with the Virginia Tech College of Science, calls the unearthed fossils, including the bodies and trails left by an ancient animal species, the most convincing sign of ancient animal mobility, dating back about 550 million years. Named Yilingia spiciformis -- that translates to spiky Yiling bug, Yiling being the Chinese city near the discovery site -- the animal was found in multiple layers of rock by Xiao and Zhe Chen, Chuanming Zhou, and Xunlai Yuan from the Chinese Academy of Sciences' Nanjing Institute of Geology and Palaeontology.

The findings are published in the latest issue of Nature. The trials are from the same rock unit and are roughly the same age as bug-like footprints found by Xiao and his team in a series of digs from 2013 to 2018 in the Yangtze Gorges area of southern China, and date back to the Ediacaran Period, well before the age of dinosaurs or even the Pangea supercontinent. What sets this find apart: The preserved fossil of the animal that made the trail versus the unknowable guesswork where the body has not been preserved.

"This discovery shows that segmented and mobile animals evolved by 550 million years ago," Xiao said. "Mobility made it possible for animals to make an unmistakable footprint on Earth, both literally and metaphorically. Those are the kind of features you find in a group of animals called bilaterans. This group includes us humans and most animals. Animals and particularly humans are movers and shakers on Earth. Their ability to shape the face of the planet is ultimately tied to the origin of animal motility."

The animal was a millipede-like creature a quarter-inch to an inch wide and up to 4 inches long that alternately dragged its body across the muddy ocean floor and rested along the way, leaving trails as loing as 23 inches. The animal was an elongated narrow creature, with 50 or so body segments, a left and right side, a back and belly, and a head and a tail.

The origin of bilaterally symmetric animals -- known as bilaterians -- with segmented bodies and directional mobility is a monumental event in early animal evolution, and is estimated to have occurred the Ediacaran Period, between 635 and 539 million years ago. But until this finding by Xiao and his team, there was no convincing fossil evidence to substantiate those estimates. One of the recovered specimens is particularly vital because the animal and the trail it produced just before its death are preserved together.

Remarkably, the find also marks what may be the first sign of decision making among animals -- the trails suggest an effort to move toward or away from something, perhaps under the direction of a sophisticated central nerve system, Xiao said. The mobility of animals led to environmental and ecological impacts on the Earth surface system and ultimately led to the Cambrian substrate and agronomic revolutions, he said.

"We are the most impactful animal on Earth," added Xiao, also an affiliated member of the Global Change Center at Virginia Tech. "We make a huge footprint, not only from locomotion, but in many other and more impactful activities related to our ability to move. When and how animal locomotion evolved defines an important geological and evolutionary context of anthropogenic impact on the surface of the Earth."

Rachel Wood, a professor in the School of GeoSciences at University of Edinburgh in Scotland, who was not involved with the study, said, "This is a remarkable finding of highly significant fossils. We now have evidence that segmented animals were present and had gained an ability to move across the sea floor before the Cambrian, and more notably we can tie the actual trace-maker to the trace. Such preservation is unusual and provides considerable insight into a major step in the evolution of animals."

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From Earth's deep mantle, scientists find a new way volcanoes form

Volcanic eruption.

Far below Bermuda's pink sand beaches and turquoise tides, geoscientists have discovered the first direct evidence that material from deep within Earth's mantle transition zone -- a layer rich in water, crystals and melted rock -- can percolate to the surface to form volcanoes.

Scientists have long known that volcanoes form when tectonic plates (traveling on top of the Earth's mantle) converge, or as the result of mantle plumes that rise from the core-mantle boundary to make hotspots at Earth's crust. But obtaining evidence that material emanating from the mantle's transition zone -- between 250 to 400 miles (440-660 km) beneath our planet's crust -- can cause volcanoes to form is new to geologists.

"We found a new way to make volcanoes. This is the first time we found a clear indication from the transition zone deep in the Earth's mantle that volcanoes can form this way," said senior author Esteban Gazel, associate professor in the Department of Earth and Atmospheric Sciences at Cornell University. The research published in Nature.

"We were expecting our data to show the volcano was a mantle plume formation -- an upwelling from the deeper mantle -- just like it is in Hawaii," Gazel said. But 30 million years ago, a disturbance in the transition zone caused an upwelling of magma material to rise to the surface, forming a now-dormant volcano under the Atlantic Ocean and then forming Bermuda.

Using a 2,600-foot (over 700-meter) core sample -- drilled in 1972, housed at Dalhousie University, Nova Scotia -- co-author Sarah Mazza of the University of Münster, in Germany, assessed the cross-section for isotopes, trace elements, evidence of water content and other volatile material. The assessment provided a geologic, volcanic history of Bermuda.

"I first suspected that Bermuda's volcanic past was special as I sampled the core and noticed the diverse textures and mineralogy preserved in the different lava flows," Mazza said. "We quickly confirmed extreme enrichments in trace element compositions. It was exciting going over our first results ... the mysteries of Bermuda started to unfold."

From the core samples, the group detected geochemical signatures from the transition zone, which included larger amounts of water encased in the crystals than were found in subduction zones. Water in subduction zones recycles back to Earth's surface. There is enough water in the transition zone to form at least three oceans, according to Gazel, but it is the water that helps rock to melt in the transition zone.

The geoscientists developed numerical models with Robert Moucha, associate professor of Earth sciences at Syracuse University, to discover a disturbance in the transition zone that likely forced material from this deep mantle layer to melt and percolate to the surface, Gazel said.

Despite more than 50 years of isotopic measurements in oceanic lavas, the peculiar and extreme isotopes measured in the Bermuda lava core had not been observed before. Yet, these extreme isotopic compositions allowed the scientists to identify the unique source of the lava.

"If we start to look more carefully, I believe we're going to find these geochemical signatures in more places," said co-author Michael Bizimis, associate professor at the University of South Carolina.

Gazel explained that this research provides a new connection between the transition zone layer and volcanoes on the surface of Earth. "With this work we can demonstrate that the Earth's transition zone is an extreme chemical reservoir," said Gazel. "We are now just now beginning to recognize its importance in terms of global geodynamics and even volcanism."

Said Gazel: "Our next step is to examine more locations to determine the difference between geological processes that can result in intraplate volcanoes and determine the role of the mantle's transition zone in the evolution of our planet."

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Geoscientists reconstruct 'eye-opening' 900-year Northeastern U.S. climate record

Doctoral students Daniel Miller, in the water, with Helen Habicht and Benjamin Keisling, handle two recaptured sediment traps from an unusually deep lake in central Maine, where they collected 136 sediment samples spanning the 900-year time span to reconstruct the longest and highest-resolution climate record for the Northeastern United States to date.

Deploying a new technique for the first time in the region, geoscientists at the University of Massachusetts Amherst have reconstructed the longest and highest-resolution climate record for the Northeastern United States, which reveals previously undetected past temperature cycles and extends the record 900 years into the past, well beyond the previous early date of 1850.

First author Daniel Miller, with Helen Habicht and Benjamin Keisling, conducted this study as part of their doctoral programs with advisors geosciences professors Raymond Bradley and Isla Castañeda. As Miller explains, they used a relatively new quantitative method based on the presence of chemical compounds known as branched glycerol dialkyl glycerol tetra ethers (branched GDGTs) found in lakes, soils, rivers and peat bogs around the world. The compounds can provide an independent terrestrial paleo-thermometer that accurately assesses past temperature variability.

Miller says, "This is the first effort using these compounds to reconstruct temperature in the Northeast, and the first one at this resolution." He and colleagues were able to collect a total of 136 samples spanning the 900-year time span, many more than would be available with more traditional methods and from other locations that typically yield just one sample per 30-100 years.

In their results, Miller says, "We see essentially cooling throughout most of the record until the 1900s, which matches other paleo-records for North America. We see the Medieval Warm Period in the early part and the Little Ice Age in the 1800s." An unexpected observation was 10, 50-to-60-year temperature cycles not seen before in records from Northeast U.S., he adds, "a new finding and surprising. We're trying to figure out what causes that. It may be caused by changes in the North Atlantic Oscillation or some other atmospheric patterns. We'll be looking further into it."

He adds, "We're very excited about this. I think it's a great story of how grad students who come up with a promising idea, if they have enough support from their advisors, can produce a study with really eye-opening results." Details appear in a recent issue of the European Geophysical Union's open-access online journal, Climate of the Past.

The authors point out that paleo-temperature reconstructions are essential for distinguishing human-made climate change from natural variability, but historical temperature records are not long enough to capture pre-human-impact variability. Further, using conventional pollen- and land-based sediment samples as climate proxies can reflect confounding parameters rather than temperature, such as precipitation, humidity, evapo-transpiration and vegetation changes.

Therefore, additional quantitative paleo-temperature records are needed to accurately assess past temperature variability in the Northeast United States, the researchers point out. An independent terrestrial paleo-thermometer that relies on measuring two byproducts of processes carried out in branched GDGTs in lake sediment, a method first introduced two decades ago by researchers in The Netherlands, offered a promising alternative, Miller says.

Source organisms are not known for branch GDGTs, he points out, but they are thought to be produced in part by Acidobacteria. "These are compounds likely produced by different algae and bacteria communities in the membrane, or skin," he notes. "Just like for humans, the skin regulates the organism's body temperature and these compounds change in response to temperature. So if they grow in summer, they reflect that and the compounds are different than if they were produced in winter. We record the compounds to get the temperature curves. We found there seems to be a huge bloom of these organisms in the fall. After they die, they settle into the lake bottom. We think it's mainly a fall temperature that we're detecting."

For this work, Miller and colleagues constructed large plastic sediment traps and deployed them about ten feet below the surface of a small, 106-foot-deep lake in central Maine in May, 2014. They then dove under to collect a catchment bottle from the bottom of each trap every month in June, July, August and September, and the following May 2015.

Miller says, "This lake is very deep for its small area, with very steep sides. It doesn't seem to have much mixing of water layers by surface winds. We think that has helped to preserve a bottom water layer with no oxygen year-round, known as anoxia, which helps in the preservation of annual layers in the sediments at the bottom of the lake. It's rare for a lake to have such fine, thin lines that represent annual deposition, so all you have to do is count the lines to count the years. We double-checked our results with radiocarbon dating and other methods, and it turns out that reconstructing the temperature record this way was successful."

Miller and colleagues say this project enjoyed notable support from many quarters, including the UMass Amherst Alumni Association supporting student field work and data collection in Maine; the geology department at Bates College; funding from the U.S. Geological Survey; and at UMass Amherst, sophisticated biogeochemistry laboratory equipment and the Joe Hartshorn Memorial Award from the geosciences department, and other assistance from the Northeast Climate Adaptation Science Center.

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Plate tectonics not needed to sustain life

The artist's concept depicts Kepler-69c, a super-Earth-size planet in the habitable zone of a star like our sun, located about 2,700 light-years from Earth in the constellation Cygnus.

There may be more habitable planets in the universe than we previously thought, according to Penn State geoscientists, who suggest that plate tectonics -- long assumed to be a requirement for suitable conditions for life -- are in fact not necessary.

When searching for habitable planets or life on other planets, scientists look for biosignatures of atmospheric carbon dioxide. On Earth, atmospheric carbon dioxide increases surface heat through the greenhouse effect. Carbon also cycles to the subsurface and back to the atmosphere through natural processes.

"Volcanism releases gases into the atmosphere, and then through weathering, carbon dioxide is pulled from the atmosphere and sequestered into surface rocks and sediment," said Bradford Foley, assistant professor of geosciences. "Balancing those two processes keeps carbon dioxide at a certain level in the atmosphere, which is really important for whether the climate stays temperate and suitable for life."

Most of Earth's volcanoes are found at the border of tectonic plates, which is one reason scientists believed they were necessary for life. Subduction, in which one plate is pushed deeper into the subsurface by a colliding plate, can also aid in carbon cycling by pushing carbon into the mantle.

Planets without tectonic plates are known as stagnant lid planets. On these planets, the crust is one giant, spherical plate floating on mantle, rather than separate pieces. These are thought to be more widespread than planets with plate tectonics. In fact, Earth is the only planet with confirmed tectonic plates.

Foley and Andrew Smye, assistant professor of geosciences, created a computer model of the lifecycle of a planet. They looked at how much heat its climate could retain based on its initial heat budget, or the amount of heat and heat-producing elements present when a planet forms. Some elements produce heat when they decay. On Earth, decaying uranium produces thorium and heat, and decaying thorium produces potassium and heat.

After running hundreds of simulations to vary a planet's size and chemical composition, the researchers found that stagnant lid planets can sustain conditions for liquid water for billions of years. At the highest extreme, they could sustain life for up to 4 billion years, roughly Earth's life span to date.

"You still have volcanism on stagnant lid planets, but it's much shorter lived than on planets with plate tectonics because there isn't as much cycling," said Smye. "Volcanoes result in a succession of lava flows, which are buried like layers of a cake over time. Rocks and sediment heat up more the deeper they are buried."

The researchers found that at high enough heat and pressure, carbon dioxide gas can escape from rocks and make its way to the surface, a process known as degassing. On Earth, Smye said, the same process occurs with water in subduction fault zones.

This degassing process increases based on what types and quantities of heat-producing elements are present in a planet up to a certain point, said Foley.

"There's a sweet spot range where a planet is releasing enough carbon dioxide to keep the planet from freezing over, but not so much that the weathering can't pull carbon dioxide out of the atmosphere and keep the climate temperate," he said.

According to the researchers' model, the presence and amount of heat-producing elements were far better indicators for a planet's potential to sustain life.

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New insight into how Giant's Causeway and Devils Postpile were formed

This is the Giant's Causeway.

A new study by geoscientists at the University of Liverpool has identified the temperature at which cooling magma cracks to form geometric columns such as those found at the Giant's Causeway in Northern Ireland and Devils Postpile in the USA.

Geometric columns occur in many types of volcanic rocks and form as the rock cools and contracts, resulting in a regular array of polygonal prisms or columns.

Columnar joints are amongst the most amazing geological features on Earth and in many areas, including the Giant's Causeway, they have inspired mythologies and legends.

One of the most enduring and intriguing questions facing geologists is the temperature at which cooling magma forms these columnar joints.

Liverpool geoscientists undertook a research study to find out how hot the rocks were when they cracked open to form these spectacular stepping stones.

In a paper published in Nature Communications, researchers and students at the University's School of Environmental Sciences designed a new type of experiment to show how as magma cools, it contracts and accumulates stress, until it cracks. The study was performed on basaltic columns from Eyjafjallajökull volcano, Iceland.

They designed a novel apparatus to permit cooling lava, gripped in a press, to contract and crack to form a column. These new experiments demonstrated that the rocks fracture when they cool about 90 to 140?C below the temperature at which magma crystallises into a rock, which is about 980?C for basalts.

This means that columnar joints exposed in basaltic rocks, as observed at the Giant's Causeway and Devils Postpile (USA) amongst others, were formed around 840-890 ?C.

Yan Lavallée, Liverpool Professor of Volcanology who headed the research, said: "The temperature at which magma cools to form these columnar joints is a question that has fascinated the world of geology for a very long time. We have been wanting to know whether the temperature of the lava that causes the fractures was hot, warm or cold.

"I have spent over a decade pondering how to address this question and construct the right experiment to find the answer to this question. Now, with this study, we have found that the answer is hot, but after it solidified."

Dr Anthony Lamur, for whom this work formed part of his doctoral study, added: "These experiments were technically very challenging, but they clearly demonstrate the power and significance of thermal contraction on the evolution of cooling rocks and the development of fractures."

Dr Jackie Kendrick, a post-doctoral researcher in the Liverpool group said: "Knowing the point at which cooling magma fractures is critical, as -beyond leading to the incision of this stunning geometrical feature- it initiates fluid circulation in the fracture network. Fluid flow controls heat transfer in volcanic systems, which can be harnessed for geothermal energy production. So the findings have tremendous applications for both volcanology and geothermal research."

Understanding how cooling magma and rocks contract and fracture is central to understand the stability of volcanic constructs as well as how heat is transferred in the Earth.

Professor Lavallée added: "The findings shed light on the enigmatic observations of coolant loss made by Icelandic engineers as they drilled into hot volcanic rocks in excess of 800?C; the loss of coolant in this environment was not anticipated, but our study suggests that substantial contraction of such hot rocks would have opened wide fractures that drained away the cooling slurry from the borehole.

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Voyage from Earth's crust to its mantle and back again

Uranium isotopes leave a distinct 'fingerprint' in the sources of volcanic rocks, making it possible to gauge their age and origin. Geologists have gained a new understanding of how Earth's crust is recycled back into its interior based on these uranium isotopes.

From the beginning of time, uranium has been part of Earth and, thanks to its long-lived radioactivity, it has proven ideal to date geological processes and deduce Earth's evolution. Natural uranium consists of two long-lived isotopes uranium-238 and the lighter uranium-235. A new study of the global cycle of these uranium isotopes brings additional perspectives to the debate on how Earth has changed over billions of years as revealed in a recently published study in the journal Nature.

From early Earth history, the continental crust (Earth's thick solid outer skin that we live on) has accumulated mass from the underlying hot mantle. Most of the newly formed crust, however, is lost again. At mid-ocean ridges at the bottom ocean, where plates drift apart, new oceanic crust is constantly produced as basaltic rocks when hot volcanic lava emerges from the mantle and solidifies. The oceanic crust moves away from the mid-ocean-ridges and ultimately gets transported back into the underlying mantle through "subduction" at ocean trenches.

Uranium is enriched in the rocks of the continental crust; however, at Earth's surface, different environments over time have influenced its mobility. In an oxygen-free atmosphere, as prevailed on early Earth, uranium stayed immobile in rocks as tetravalent uranium (IV). Only after atmospheric oxygen was formed did uranium become oxidised to its mobile hexavalent uranium (VI). This more mobile uranium may then be released during the weathering and break-down of rocks and transported to the oceans in aqueous form. As the cooling oceanic crust moves away from the mid-ocean-ridges in the oceans, seawater eventually percolates through cracks in its rock and in the process uranium gets incorporated into the oceanic crust, in a similar way that a sponge takes up water.

"The radioactive nature of uranium isotopes has long been key in reconstructing early Earth history, but we now see that they also have another story to tell" explains Morten Andersen, a geochemist in the Department of Earth Sciences at ETH Zurich.

Uranium isotopes form specific signatures

For this work, conducted at the University of Bristol including Morten Andersen (now Earth Science, ETH Zurich) along with researchers from the Durham (UK), Wyoming and Rhode Island (US), used the 'fingerprint' carried in the ratio of the two uranium isotopes.

The specific "fingerprint" derived from the ratio of the uranium isotopes, relates to uranium oxidation processes at Earth's surface. In particular, the researchers found that a higher ratio of uranium-238 to uranium-235 is incorporated into the modern oceanic crust, when compared to the uranium isotope signature found in meteorites. The meteorites represent Earth's "building blocks" and, thus, yield the original uranium isotope composition of Earth as a whole, and also the undisturbed mantle. This uranium isotope "fingerprint" of the altered oceanic crust provides a way to trace uranium that has moved from the surface and back into Earth's interior through subduction.

In order to examine the uranium cycle (and the rock cycle), the researchers analysed mid-ocean ridge basalts (MORBs), the hot volcanic lava that is produced from the upper and well-mixed part of the mantle. The ratio of the uranium isotopes in MORBs can be compared with those found in ocean island basalts in places such as Hawaii and the Canary Islands. These islands are so-called "hot-spots" with lava formed from hot mantle plumes that up-well beneath the oceanic crust. Compared to the MORB mantle, the island basalts are made up of material transported to the surface from a much deeper, less well-mixed, mantle sources.

Heavy uranium from surface to the deep

The isotope ratios for uranium-238 to uranium-235 are significantly greater for MORBs than for ocean island basalts. The ratios are also higher than that found in meteorites. This suggests that the MORBs contain a "fingerprint" of the uranium from the oceanic crust, drawn down from the surface and into the upper part of Earth's mantle through subduction, according to Andersen.

Through convection -- slow movements of material in the upper mantle -- the material was eventually mixed around and carried to the area of the mid-ocean ridges and transported back to the surface in the lavas that make up MORBs.

In contrast, the island basalts' ratios of uranium-238 to uranium-235 correspond to those of the meteorites used in the study and showed that these rocks could not have the same mantle source as the MORBs. The researchers explain that ocean island lavas comes from a deeper, less mixed, mantle source and therefore any uranium added from the surface originates from a much earlier time in Earth's history, when the surface environment was very different from today.

Study co-author Heye Freymuth of the University of Bristol explains: "Although uranium was incorporated into the oceanic crust since the initial rise in atmospheric oxygen about 2.4 billion years ago, the ocean crust did not incorporate higher amounts of uranium-238 as the oceans did not yet have adequate supplies of oxygen."

Only during the second marked increase in atmospheric oxygen content 600 million years ago did the deep ocean become fully oxidised, which allowed the oceanic crust to gain the "fingerprint" of high uranium-238. So, despite the oceanic crust having been transported into Earth's mantle for a long time, the uranium isotope ratio of the subducted oceanic crust first differed from Earth's mantle only after the full oxidation of the oceans.

"An important result of this study is how changing conditions on Earth's surface and the increase of oxygen in the atmosphere influenced the composition of deep Earth. Our results suggest that due to changes over the past 600 million years, uranium was mobilised from the surface, transported into Earth's interior and distributed within the mantle," says Andersen.

Read more at Science Daily

Continent-Sized Scan Reveals US Underbelly

A continent-sized scan of North America is giving researchers the sharpest view yet of mysterious geological structures underneath the United States.

The impressive view comes from an ambitious experiment called EarthScope, which has scanned the country from California to Maine using hundreds of portable seismometers. (The next stop is Alaska.) Launched in 2004, the massive effort has already revealed new details about the geology of the western and central United States, such as the shape of Yellowstone's magma plume. Now, the first clear images of the entire continent are beginning to emerge, according to a study published Oct. 15 in the journal Geophysical Research Letters.

"This was the dream to start with," said Brandon Schmandt, lead study author and a seismologist at the University of New Mexico in Albuquerque.

The EarthScope process resembles snapping a CT scan of the Earth, with a field crew moving sensitive earthquake detectors across the surface and researchers constructing an image of the rocks below.

In the new study, Schmandt and his co-author, Fan-Chi Lin of the University of Utah, built a detailed, 3-D map of the Earth's upper mantle, which is the rocky layer between the crust and core. The results could help researchers solve some long-standing geologic puzzles. The mantle is not only a time capsule, preserving the history of crashing tectonic plates, but also a force that influences what happens at the surface.

Deep discoveries

Clues to geologic mysteries may lie hidden in the mantle, the study reports. One mystery is why there are a handful of 48-million-year-old volcanoes in Virginia, when no other volcanic features have formed on the East Coast since about 200 million years ago.

The East Coast has been a passive margin, with no colliding tectonic plates, for 200 million years, so the Virginia volcanoes are unusual features, Schmandt said. But it turns out that the mantle beneath the East Coast isn't as cold and dense as one might expect after so many millennia free from jostling.

The researchers found alternating zones within the mantle where earthquake waves shift gears, from fast-moving and slow-moving speeds and back. This differs from the more uniform mantle under the old and tectonically stable central United States. (Earthquake waves speed up and slow down when they hit rocks with different temperature, density or composition.)

The new model revealed that two of sites where seismic waves suddenly slow down match up with geological features on the Earth's surface. One is in the central Appalachians, centered directly below the Virginia volcanoes. The second, located in the northern Appalachians, lines up with a feature called the Great Meteor hotspot track in Canada, Schmandt said. The track is a chain of progressively younger volcanoes that starts in Canada and stretches out into the Atlantic Ocean.

Further work on the anomalies could help explain why Virginia's rare volcanoes appeared. For instance, Schmandt said he was impressed that 50 million years later, the mantle beneath the volcanoes is still altered by whatever process triggered the eruptions. "It's a little bit surprising to see these strong changes in a place that's been a passive margin for such a long time," Schmandt told Live Science.

To the south, a puzzling bite in the Appalachian Mountains called the Mississippi Embayment stands out sharply in the new model. The corner-shaped region of the embayment pokes northwest from the Mississippi River delta. Geologists have long argued over what created the embayment, which is concealed under miles of Mississippi River mud.

The new data suggests a piece of North America was ripped out long ago, then later replaced by another drifting chunk, perhaps a piece of an island chain similar to Japan. "It really looks like a different type of lithosphere in there," Schmandt said. Fragments of islands and other continents that smashed onto North America can appear as hotter mantle regions beyond the outline of the original continent.

Old history

Some of the clearest shapes in the new mantle map are ancient relics. Earlier studies have shown North America sits above a graveyard for discarded pieces of old ocean floor. The pieces of oceanic crust (or slabs) were consumed at a subduction zone offshore the West Coast. A subduction zone is where one plate sinks underneath another. "It's fascinating to see slabs that subducted 10 to 100 million years ago," Schmandt said. "It tells us what the driving forces were like in the past."

But beneath North America, the slabs of crust aren't sinking in the way scientists thought they would. Schmandt and Lin discovered fragments of old oceanic crust at about 310 miles (500 kilometers) depth under the central and eastern United States, whereas younger pieces of oceanic crust have dropped nearly twice that depth beneath the western United States. The researchers suggest a large piece of oceanic crust that subducted more than 40 million years ago broke into several large fragments, at least two of which foundered.

Read more at Discovery News

Earth's Magnetic Field Could Flip Within a Lifetime

A pilot looking down at her plane controls and realizing magnetic north is hovering somewhere over Antarctica may sound like a scene from a science-fiction movie, but new research suggests the idea isn't so far-fetched in the relatively near future.

A magnetic field shift is old news. Around 800,000 years ago, magnetic north hovered over Antarctica and reindeer lived in magnetic south. The poles have flipped several times throughout Earth's history. Scientists have estimated that a flip cycle starts with the magnetic field weakening over the span of a few thousand years, then the poles flip and the field springs back up to full strength again. However, a new study shows that the last time the Earth's poles flipped, it only took 100 years for the reversal to happen.

The Earth's magnetic field is in a weakening stage right now. Data collected this summer by a European Space Agency (ESA) satellite suggests the field is weakening 10 times faster than scientists originally thought. They predicted a flip could come within the next couple thousand years. It turns out that might be a very liberal estimate, scientists now say.

"We don't know whether the next reversal will occur as suddenly as this one did, but we also don't know that it won't," Paul Renne, director of the Geochronology Center at the University of California, Berkeley, said in a statement.

Geologists still are not sure what causes the planet's magnetic field to flip direction. Earth's iron core acts like a giant magnet and generates the magnetic field that envelops the planet. This helps protect against blasts of radiation that erupt from the sun and sometimes hurtle toward Earth. A weakening magnetic field could interrupt power grids and radio communication, and douse the planet in unusually high levels of radiation.

While the ESA satellite studied the magnetic field from above, Renne and a team of researchers studied it from below. The researchers dug through ancient lake sediments exposed at the base of the Apennine Mountains in Italy. Ash layers from long-ago volcanic eruptions are mixed into the sediment. The ash is made of magnetically sensitive minerals that hold traces of Earth's magnetic field lines, and the researchers were able to measure the direction the field was pointing.

Renne and colleagues then used a technique called argon-argon dating — which works because radioactive potassium-40 decays into argon-40 at a known rate — to determine the age of the rock sediment. The layers built up over a 10,000-year period, and the researchers could pinpoint where the poles flipped in the rock layers. The last flip happened around 786,000 years ago.

Sudden swap

The sediment layers also showed the magnetic field was unstable for about 6,000 years before the abrupt flip-flop. The period of instability included two low points in the field's strength, each of which lasted about 2,000 years.

Geologists don't know where the magnetic field is now in that reversal timescale or if this flip will even follow the same pattern as the last. The bottom line is that no one is sure when it's coming.

"We don't really know whether the next reversal is going to resemble the last one, so it's impossible to say whether we're just seeing the first of possibly several excursions (slight movements), or a true reversal," Renne told Live Science in an email.

Magnetic doomsday?

While a pole flip could cause a few technical issues, there's no need to panic. Scientists have combed the geological timeline for any evidence of catastrophes that might be related to a magnetic flip. They haven't found any.

The only havoc that a reversal would wreak is interference in the global electric grid. No direct evidence remains of past catastrophes triggered by a magnetic flip.

Read more at Discovery News