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Pterosaur hatchlings needed their parents, trove of eggs reveals

A fossilised pterosaur mandible
A fossilised pterosaur mandible is displayed at a museum in Hami, in northwestern China’s Xinjiang region.

The largest collection of fossilized pterosaur eggs ever found has shown that pterosaurs, the airborne cousins of dinosaurs, could not fly right away and needed care from their parents, researchers said Thursday.

Pterosaurs were reptiles, and the first creatures—after insects—to evolve powered flight, meaning they flapped their wings to stay aloft instead of simply jumping and gliding.

First known to exist as many as 225 million years ago, they went extinct along with the dinosaurs about 65 million years ago.

Until now, scientists had found some pterosaur eggs with remains inside, including three in Argentina and five in China.

But the latest report in the peer-reviewed US journal Science is based on the biggest collection to date—215 fossilized eggs that were found in a 10-foot (three-meter) long sandstone block in northwestern China’s Hami City, Xinjiang Uygur Autonomous Region.

“Since these are extremely fragile fossils, we were very surprised to find so many in the same place,” Brazilian paleontologist Alexander Kellner told AFP.

“Because of this discovery, we can talk about the behavior of these animals for the first time.”

Needed their parents

Sixteen of the eggs contained fossilized remains of a pterosaur species known as Hamipterus tianshanensis.

As adults, these creatures would have stood about four feet tall, with a wingspan of 11 feet.

None of the eggs held a full set of pterosaur bones, likely because pieces were lost over the years due to storms and floods.

But scientists did find partial wing and skull bones, along with one complete lower jaw, which fill in aspects of pterosaurs’ life cycle that have been poorly understood until now.

Using three-dimensional computed tomography scans, they discovered intact and well-developed thigh bones suggesting the creatures “benefited from functional hind legs shortly after hatching,” said the report.

But their chest muscles were weak.

“This shows that when pterosaurs hatched, they could walk but not fly,” said Kellner.

“They needed their parents. This is one of the biggest discoveries we have made.”

Nesting behavior

Adult pterosaur bones were also scattered across the site, a sign that they returned to the same nesting spots over time, much the same as modern day sea turtles.

The massive numbers of eggs and bones point to major storms thrashing the site, submerging the eggs in a lake where they floated briefly before sinking and becoming buried alongside adult skeletons.

Researchers also noted that the cracked exterior of the eggs resembled the fragile softness of lizard eggs.

“All are deformed to a certain extent, which indicate their pliable nature,” said the study.

One of the young pterosaurs was estimated to be “at least two years old and still growing at the time of its death, supporting the growing body of evidence that pterosaurs had long incubation periods.”

An accompanying article in the journal Science, written by D. Charles Deeming of the University of Lincoln, called the study “remarkable for the number of eggs in association with adults and juvenile pterosaurs that it reports on.”

However, many questions remain, including whether the size of each clutch was really two as previous studies have suggested, just how the pterosaurs concealed their eggs, whether beneath vegetation or sand or soil, and why so many of the eggs appear dehydrated.

“Hopefully additional finds of equally spectacular fossils will help us answer such questions,” he wrote.

Reference:
X. Wang el al., “Egg accumulation with 3D embryos provides insight into the life history of a pterosaur,” Science (2017). DOI: 10.1126/science.aan2329

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

Time between world-changing volcanic super-eruptions less than previously thought

The Toba caldera was the site of a massive super-eruption 75,000 years ago.
The Toba caldera was the site of a massive super-eruption 75,000 years ago. Credit: NASA/METI/AIST/Japan Space Systems, and U.S./Japan ASTER Science Team.

After analysing a database of geological records dated within the last 100,000 years, a team of scientists from the University of Bristol has discovered the average time between so-called volcanic super-eruptions is actually much less than previously thought.

Volcanoes and bolides, such as asteroids, are geohazards powerful enough to be destructive on a global scale.

One recent assessment described them as capable of returning humanity to a pre-civilization state.

The largest explosive eruptions are termed ‘super-eruptions’, and produce in excess of 1,000 gigatons of erupted mass, enough to blanket an entire continent with volcanic ash, and change global weather patterns for decades.

The team from the University of Bristol’s Schools of Earth Sciences and Mathematics estimated how often the largest explosive eruptions happen. Their analysis indicates that the average time between super-eruptions is only slightly longer than the age of our civilization — dating from the Agricultural Revolution 12,000 years ago.

Jonathan Rougier, Professor of Statistical Science, said: “The previous estimate, made in 2004, was that super-eruptions occurred on average every 45 — 714 thousand years, comfortably longer than our civilization.

“But in our paper just published, we re-estimate this range as 5.2 — 48 thousand years, with a best guess value of 17 thousand years.”

According to geological records, the two most recent super-eruptions were between 20 and 30 thousand years ago.

Professor Rougier added: “On balance, we have been slightly lucky not to experience any super-eruptions since then.

“But it is important to appreciate that the absence of super-eruptions in the last 20 thousand years does not imply that one is overdue. Nature is not that regular.

“What we can say is that volcanoes are more threatening to our civilization than previously thought.”

Our civilization will change in unimaginable ways over the next thousand years, and there are many other ways in which it might suffer a catastrophic blow well before the next super-eruption.

On that basis, Professor Rougier says there is little need to plan now for a super-eruption, especially with many other pressing issues to address, which will affect the current and the next generation of humans. But large eruptions, which are much more frequent, can still be devastating for communities and even countries, and careful planning is a crucial part of disaster risk reduction.

Regarding the paper, Professor Rougier explained: “As well as improving our understanding of global volcanism, our paper develops relatively simple techniques to analyse incomplete and error-prone geological and historical records of rare events.

“These difficulties are ubiquitous in geohazards, and we expect our approach will be used for reappraising other types of hazard, such as earthquakes.”

Reference:
J. Rougier, S. Sparks, K. Cashman, and S. Brown. The global magnitude-frequency relationship for large explosive volcanic eruptions. Earth and Planetary Science Letters, 2017 (in press). DOI: 10.1016/j.epsl.2017.11.015

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

Parkfield segment of San Andreas fault may host occasional large earthquakes

Parkfield Segment, San Andreas fault
Parkfield Segment, San Andreas fault

Although magnitude 6 earthquakes occur about every 25 years along the Parkfield Segment of the San Andreas Fault, geophysical data suggest that the seismic slip induced by those magnitude 6 earthquakes alone does not match the long-term slip rates on this part of the San Andreas fault, researchers report November 28 in the Bulletin of the Seismological Society of America (BSSA).

The Parkfield section of the fault could rupture simultaneously with a magnitude 7.7 earthquake on the fault segment immediately to the south. These southern earthquakes — the latest of which was the 1857 Fort Tejon earthquake — appear to occur about every 140 to 300 years. Using these data, Sylvain Michel of the University of Cambridge, UK and colleagues calculate that an earthquake occurring on the Parkfield segment during these simultaneous ruptures could reach the equivalent of a magnitude 6.4 to 7.5 earthquake, and help to close the “slip budget” on the fault.

Michel and colleagues compared the amount of slip in earthquakes on the Parkfield segment of the fault with the between-earthquake accumulation of seismic moment (a measure of earthquake size that is related to the fault area, amount of fault slip, and the material strength). The buildup of this seismic moment between earthquakes is called the “moment deficit,” which is available for release during the next earthquake.

The seismic moment released from the six earthquakes of about magnitude 6 that have occurred on the Parkfield fault segment since 1857 would only account for about 12 percent of the available moment deficit, Michel said. “This analysis shows that balancing the moment budget on the Parkfield segment of the San Andreas fault probably requires more frequent or larger earthquakes than what the instrumental and historical data suggest,” he and his colleagues write in the BSSA paper.

The Parkfield segment has been studied intensely by seismologists, especially as it forms the transition zone between the “creeping” northern half of the fault and its “locked” southern portion. Michel and colleagues took advantage of the wealth of geophysical data that have been collected in this region, using a catalog of earthquakes that have occurred in the area and models of the fault slip rate inferred from surface deformation given by Global Positioning System (GPS) and satellite observations of ground changes. The detailed information allowed the researchers to apply the slip budget concept to assessing the seismic potential of the fault, and thus the frequency of earthquakes.

After concluding that the Parkfield segment must host occasional large earthquakes under the slip budget model, they calculated the likely occurrence of these large earthquakes over 30-year and 200-year periods.

Michel and colleagues report that the probability of an earthquake of magnitude 6 or more is equal to about 43 percent over the span of 30 years, and 96 percent over the span of 200 years.

The findings will help seismologists further examine how earthquakes on the Parkfield segment might occur in the future, the researchers said. For instance, their data could be used to explore whether locked patches of the fault separately host magnitude 6 or smaller earthquakes, and if larger, less frequent earthquakes might rupture across patches.

Reference:
Sylvain Michel, Jean‐Philippe Avouac, Romain Jolivet, Lifeng Wang. Seismic and Aseismic Moment Budget and Implication for the Seismic Potential of the Parkfield Segment of the San Andreas Fault. Bulletin of the Seismological Society of America, 2017; DOI:10.1785/0120160290

Note: The above post is reprinted from materials provided by Seismological Society of America.

Eruption clues: Researchers create snapshot of volcano plumbing

Mount Etna in Italy
Mount Etna in Italy is a modern example of alkaline volcanism. Credit: Shawn Appel on Unsplash

Much like a forensic team recreates a scene to determine how a crime was committed, researchers at the University of New Hampshire are using scientific sleuthing to better understand the journey of magma, or molten rock, in one of Europe’s largest and most active volcanoes, Mount Etna. Researchers applied several techniques, in a new way, to create a more accurate picture of the volcano’s plumbing system and how quickly the magma rises to the top to cause an eruption. Their findings contribute to our understanding of how and when volcanoes erupt.

In their study, recently published in the journal Geochemical Perspective Letters, the UNH team set out to determine if the magma lingers below in pockets of the volcano or if it pushes up all at once. To put the pieces of the puzzle together, they combined three approaches previously not used together to reconstruct the ancient magma plumbing system by looking for chemical signatures in lava rock collected from flows on the surface. They looked at the minerals and the trace elements in the rocks because the tracers can help identify where the minerals have been by how they crystallized.

“As magma moves up through Earth’s crust beneath the volcano, it starts to crystallize,” says Sarah Miller, of UNH’s department of Earth sciences and lead author of the study. “Some elements move rapidly and some more slowly, so there is a chemical record of events in those crystals that can help us determine their journey.”

Extracting the timing and magma source information for ancient volcanism demonstrates how long-lived pre-eruptive processes of transport and storage work at Mount Etna. The researchers found a range of crystallization depths, suggesting there were discrete sites beneath the volcano where the rising magma crystallized. Their chemical forensic work showed two interesting things about the volcano. First, the source that produced magma in the ancient Mount Etna is much the same as what happens in Mount Etna in the present-day. Secondly, they showed that the crystals were virtually chemically identical to the lavas in which they erupted. This second finding suggests that in Mount Etna the length of time for crystal storage beneath the volcano is likely relatively short, a result which could help provide insight with recent findings for larger more explosive eruptive systems like Yellowstone.

“This proof-of-concept work puts us in a position to apply our approach more widely to other volcanoes,” said Julie Bryce, professor and chair of Earth sciences and a co-author of this paper. “Our work advances ways we can examine and think about volcanic plumbing systems beneath frequently active volcanic centers. Reconstructing the dynamics of these plumbing systems, and knowing how long-lived they are, helps in anticipating future changes in eruptive potential.”

The University of New Hampshire is a flagship research university that inspires innovation and transforms lives in our state, nation and world. More than 16,000 students from all 50 states and 71 countries engage with an award-winning faculty in top ranked programs in business, engineering, law, liberal arts and the sciences across more than 200 programs of study. UNH’s research portfolio includes partnerships with NASA, NOAA, NSF and NIH, receiving more than $100 million in competitive external funding every year to further explore and define the frontiers of land, sea and space.

Reference:
S.A. Miller et al. Magma dynamics of ancient Mt. Etna inferred from clinopyroxene isotopic and trace element systematics, Geochemical Perspectives Letters (2017). DOI: 10.7185/geochemlet.1735

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

Research shows North Texas earthquakes occurring on ‘dead’ faults

The post-2008 seismicity has occurred both in areas that were seismically active before 2008 (for example, the Mississippi embayment) and in regions with no pre-2008 historical or instrumental seismicity (for example, FWB).
The post-2008 seismicity has occurred both in areas that were seismically active before 2008 (for example, the Mississippi embayment) and in regions with no pre-2008 historical or instrumental seismicity (for example, FWB). The two study areas are outlined and represented in Figs. 2 and 6. Credit: Modified with permissions from Rubinstein and Mahani (13).

Recent earthquakes in the Fort Worth Basin – in the rural community of Venus and the Dallas suburb of Irving – occurred on faults that had not been active for at least 300 million years, according to research led by SMU seismologist Beatrice Magnani.

The research supports the assertion that recent North Texas earthquakes were induced, rather than natural – a conclusion entirely independent of previous analyses correlating seismicity to the timing of wastewater injection practices, but that corroborates those earlier findings. The full study, “Discriminating between natural vs induced seismicity from long-term deformation history of intraplate faults,” published by Science Advances.

“To our knowledge this is the first study to discriminate natural and induced seismicity using classical structural geology analysis techniques,” said Magnani, associate professor of geophysics in SMU’s Huffington Department of Earth Sciences. Co-authors for the study include Michael L. Blanpied, associate coordinator of the USGS Earthquake Hazard program, and SMU seismologists Heather DeShon and Matthew Hornbach.

The results were drawn from analyzing the history of fault slip (displacement) over the lifetime of the faults. The authors analyzed seismic reflection data, which allow “mapping” of the Earth’s subsurface from reflected, artificially generated seismic waves. Magnani’s team compared data from the North Texas area, where several swarms of felt earthquakes have been occurring since 2008, to data from the Midwestern U.S. region that experienced major earthquakes in 1811 and 1812 in the New Madrid seismic zone.

Frequent small earthquakes are still recorded in the New Madrid seismic zone, which is believed to hold the potential for larger earthquakes in the future.

“These North Texas faults are nothing like the ones in the New Madrid Zone – the faults in the Fort Worth Basin are dead,” Magnani said. “The most likely explanation for them to be active today is because they are being anthropogenically induced to move.”

In the New Madrid seismic zone, the team found that motion along the faults that are currently active has been occurring over many millions of years. This has resulted in fault displacements that grow with increasing age of sedimentary formations.

In the Fort Worth Basin, along faults that are currently seismically active, there is no evidence of prior motion over the past (approximately) 300 million years. “The study’s findings suggest that that the recent Fort Worth Basin earthquakes, which involve swarms of activity on several faults in the region, have been induced by human activity,” said USGS scientist Blanpied.

The findings further suggest that these North Texas earthquakes are not simply happening somewhat sooner than they would have otherwise on faults continually active over long time periods. Instead, Blanpied said, the study indicates reactivation of long-dormant faults as a consequence of waste fluid injection.

Seismic reflection profiles in the Venus region used for this study were provided by the U.S. Geological Survey Earthquake Hazards Program. Seismic reflection profiles for the Irving area are proprietary. Magnani and another team of scientists collected seismic reflection data used for this research during a 2008-2011 project in the northern Mississippi embayment, home to the New Madrid seismic zone.

Reference:
Discriminating between natural versus induced seismicity from long-term deformation history of intraplate faults. DOI: 10.1126/sciadv.1701593

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

Feathered dinosaurs were even fluffier than we thought

Depiction of Anchiornis and its contour feather.
Rebecca Gelernter’s new depiction of Anchiornis and its contour feather. Credit: Rebecca Gelernter

A University of Bristol-led study has revealed new details about dinosaur feathers and enabled scientists to further refine what is potentially the most accurate depiction of any dinosaur species to date.

Birds are the direct descendants of a group of feathered, carnivorous dinosaurs that, along with true birds, are referred to as paravians — examples of which include the infamous Velociraptor.

Researchers examined, at high resolution, an exceptionally-preserved fossil of the crow-sized paravian dinosaur Anchiornis — comparing its fossilised feathers to those of other dinosaurs and extinct birds.

The feathers around the body of Anchiornis, known as contour feathers, revealed a newly-described, extinct, primitive feather form consisting of a short quill with long, independent, flexible barbs erupting from the quill at low angles to form two vanes and a forked feather shape.

The observations were made possible by decay processes that separated some of these feathers from the body prior to burial and fossilisation, making their structure easier to interpret.

Such feathers would have given Anchiornis a fluffy appearance relative to the streamlined bodies of modern flying birds, whose feathers have tightly-zipped vanes forming continuous surfaces. Anchiornis’s unzipped feathers might have affected the animal’s ability to control its temperature and repel water, possibly being less effective than the vanes of most modern feathers. This shaggy plumage would also have increased drag when Anchiornis glided.

Additionally, the feathers on the wing of Anchiornis lack the aerodynamic, asymmetrical vanes of modern flight feathers, and the new research shows that these vanes were also not tightly-zipped compared to modern flight feathers. This would have hindered the feather’s ability to form a lift surface. To compensate, paravians like Anchiornis packed multiple rows of long feathers into the wing, unlike modern birds, where most of the wing surface is formed by just one row of feathers.

Furthermore, Anchiornis and other paravians had four wings, with long feathers on the legs in addition to the arms, as well as elongated feathers forming a fringe around the tail. This increase in surface-area likely allowed for gliding before the evolution of powered flight.

To assist in reconstructing the updated look of Anchiornis, scientific illustrator Rebecca Gelernter worked with Evan Saitta and Dr Jakob Vinther, from the University of Bristol’s School of Earth Sciences and School of Biological Sciences, to draw the animal as it was in life.

The new piece represents a radical shift in dinosaur depictions and incorporates previous research.

The color patterns for Anchiornis are known from fossilised pigment studies, the outline of the flesh of the animal has been constructed by examining fossils under laser fluorescence, and previous work has described the multi-tiered layering of the wing feathers.

Evan Saitta said: “The novel aspects of the wing and contour feathers, as well as fully-feathered hands and feet, are added to the depiction.

“Most provocatively, Anchiornis is presented in this artwork climbing in the manner of hoatzin chicks, the only living bird whose juveniles retain a relic of their dinosaurian past, a functional claw.

“This contrasts much previous art that places paravians perched on top of branches like modern birds.

“However, such perching is unlikely given the lack of a reversed toe as in modern perching birds and climbing is consistent with the well-developed arms and claws in paravians.

“Overall, our study provides some new insight into the appearance of dinosaurs, their behavior and physiology, and the evolution of feathers, birds, and powered flight.”

Rebecca Gelernter added: “Paleoart is a weird blend of strict anatomical drawing, wildlife art, and speculative biology. The goal is to depict extinct animals and plants as accurately as possible given the available data and knowledge of the subject’s closest living relatives.

“As a result of this study and other recent work, this is now possible to an unprecedented degree for Anchiornis. It’s easy to see it as a living animal with complex behaviours, not just a flattened fossil.

“It’s really exciting to be able to work with the scientists at the forefront of these discoveries, and to show others what we believe these fluffy, toothy almost-birds looked like as they went about their Jurassic business.”

Reference:
E. Saitta, R. Gelernter and J. Vinther. Additional information on the primitive contour and wing feathering of paravian dinosaurs. Paleontology, 2017. DOI: 10.1111/pala.12342

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

When magma prevents volcanic eruptions

Following a large caldera-forming eruption some magma remains in the magma reservoir.
Following a large caldera-forming eruption some magma remains in the magma reservoir.This magma cools, its viscosity increases, and when new magma is injected, the magma left over after the caldera-forming eruption stops the fresh magma from propagating to the surface and promotes caldera resurgence. Credit: UNIGE / Roma Tre

A spectacular proof of our planet’s activity, calderas are huge topographic depressions, similar to flat-bottomed craters, with a diameter of several tens of kilometres. They are formed by large volcanic eruptions, and sometimes experience an inflation of their floor of up to a kilometre, caused by magma injection. This well-known process, dubbed “caldera resurgence,” has been observed several times and yet remains one of the least understood in volcanology. But why, after an eruption, does the arrival of new magma not produce another major eruption, but instead resurgence? A team of researchers from the University of Roma Tre, Italy, and the University of Geneva (UNIGE), Switzerland, shows that the non-erupted magma left after the caldera-forming eruption behaves as a “rubber sheet” that inhibits the rise to the surface of the newly injected magma. The research is published in Nature Communications.

A caldera forms when a magma chamber is partially emptied by a large eruption and its roof collapses, producing a depression at the surface. After this catastrophic event, in a slow process that can last thousands of years, the caldera floor may start to lift disproportionately but without eruption. Resurgence does not immediately follow caldera formation, suggesting that it is not driven by the residual magma left in the reservoir after collapse, but rather by the injection of new magma.

The magma behaves as a rubber sheet

“The magma is not entirely removed from the magma chamber during the caldera-forming eruption. We used thermal modelling to determine how this residual magma evolves over time, and what role it plays in the resurgence process,” explains Luca Caricchi, associate professor at the Department of Earth Sciences of the UNIGE Faculty of Science. The magma, hotter than the rocks surrounding the magma chamber, cools progressively and its viscosity increases. The higher viscosity of the leftover magma, with respect to the newly injected magma, makes it behave as a rubber sheet, stopping the propagation of the new magma to the surface.

These results were corroborated by experiments. The leftover magma was replaced by a silicone layer and the newly injected magma by less viscous vegetable oil. The contrast in viscosity between these two materials is equivalent to the contrast observed between the two magmas in nature. “Independently of the depth of the silicone layer, its presence always impedes the propagation of the newly injected magma to the surface,” says Federico Galetto, researcher at the Department of Science of the University of Roma Tre.

The model developed by the researchers provides a theoretical framework to account for the transition from magma eruption to accumulation. Valerio Acocella, associate professor at the Department of Eart Sciences of the University of Roma Tre, adds, “The process we discuss is essential not only to develop resurgence, but also for the formation of the magma reservoirs responsible for the largest eruptions on Earth.”

Reference:
Federico Galetto et al, Caldera resurgence driven by magma viscosity contrasts, Nature Communications (2017). DOI: 10.1038/s41467-017-01632-y

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

New Genus of Extinct Horses in North America

Two skulls of the new genus Haringtonhippus from Nevada (upper) and Texas (lower).
Two skulls of the new genus Haringtonhippus from Nevada (upper) and Texas (lower). Credit: Photos by Eric Scott

An international team of researchers has discovered a previously unrecognized genus of extinct horses that roamed North America during the last ice age.

The new findings, published November 28 in the journal eLife, are based on an analysis of ancient DNA from fossils of the enigmatic “New World stilt-legged horse” excavated from sites such as Natural Trap Cave in Wyoming, Gypsum Cave in Nevada, and the Klondike goldfields of Canada’s Yukon Territory.

Prior to this study, these thin-limbed, lightly built horses were thought to be related to the Asiatic wild ass or onager, or simply a separate species within the genus Equus, which includes living horses, asses, and zebras. The new results, however, reveal that these horses were not closely related to any living population of horses.

Now named Haringtonhippus francisci, this extinct species of North American horse appears to have diverged from the main trunk of the family tree leading to Equus some 4 to 6 million years ago.

“The horse family, thanks to its rich and deep fossil record, has been a model system for understanding and teaching evolution. Now ancient DNA has rewritten the evolutionary history of this iconic group,” said first author Peter Heintzman, who led the study as a postdoctoral researcher at UC Santa Cruz.

“The evolutionary distance between the extinct stilt-legged horses and all living horses took us by surprise, but it presented us with an exciting opportunity to name a new genus of horse,” said senior author Beth Shapiro, professor of ecology and evolutionary biology at UC Santa Cruz.

The team named the new horse after Richard Harington, emeritus curator of Quaternary Paleontology at the Canadian Museum of Nature in Ottawa. Harington, who was not involved in the study, spent his career studying the ice age fossils of Canada’s North and first described the stilt-legged horses in the early 1970s.

“I had been curious for many years concerning the identity of two horse metatarsal bones I collected, one from Klondike, Yukon, and the other from Lost Chicken Creek, Alaska. They looked like those of modern Asiatic kiangs, but thanks to the research of my esteemed colleagues they are now known to belong to a new genus,” said Harington. “I am delighted to have this new genus named after me. ”

The new findings show that Haringtonhippus francisci was a widespread and successful species throughout much of North America, living alongside populations of Equus but not interbreeding with them. In Canada’s North, Haringtonhippus survived until roughly 17,000 years ago, more than 19,000 years later than previously known from this region.

At the end of the last ice age, both horse groups became extinct in North America, along with other large animals like woolly mammoths and saber-toothed cats. Although Equus survived in Eurasia after the last ice age, eventually leading to domestic horses, the stilt-legged Haringtonhippus was an evolutionary dead end.

“We are very pleased to name this new horse genus after our friend and colleague Dick Harington. There is no other scientist who has had greater impact in the field of ice age paleontology in Canada than Dick,” said coauthor Grant Zazula, a Government of Yukon paleontologist. “Our research on fossils such as these horses would not be possible without Dick’s life-long dedication to working closely with the Klondike gold miners and local First Nations communities in Canada’s North.”

Coauthor Eric Scott, a paleontologist at California State University San Bernardino, said that morphologically, the fossils of Haringtonhippus are not all that different from those of Equus. “But the DNA tells a fascinatingly different story altogether,” he said. “That’s what is so impressive about these findings. It took getting down to the molecular level to discern this new genus.”

Reference:
Peter D Heintzman, Grant D Zazula, Ross DE MacPhee, Eric Scott, James A Cahill, Brianna K McHorse, Joshua D Kapp, Mathias Stiller, Matthew J Wooller, Ludovic Orlando, John Southon, Duane G Froese, Beth Shapiro. A new genus of horse from Pleistocene North America. eLife, 2017; 6 DOI: 10.7554/eLife.29944

Note: The above post is reprinted from materials provided by University of California – Santa Cruz.

Geophysicists uncover new evidence for an alternative style of plate tectonics

Time slices of the computational geodynamic model showing dripping continental root and eventual surface uplift over a 4.5 million year period across Turkey's Central Anatolian Plateau
Time slices of the computational geodynamic model showing dripping continental root and eventual surface uplift over a 4.5 million year period across Turkey’s Central Anatolian Plateau. Credit: University of Toronto

When renowned University of Toronto (U of T) geophysicist J. Tuzo Wilson cemented concepts in the emerging field of plate tectonics in the 1960s, he revolutionized the study of Earth’s physical characteristics and behaviours. Decades later, successor researchers at U of T and Istanbul Technical University have determined that a series of volcanoes and a mountain plateau across central Turkey formed not solely by the collision of tectonic plates, but instead by a massive drip and then detachment of the lower tectonic plate beneath Earth’s surface.

The researchers propose that the reason the Central Anatolian (Turkish) Plateau has risen by as much as one kilometre over the past 10 million years is because the planet’s crust and upper mantle — the lithosphere — has thickened and dripped below the region. As the lithosphere sank into the lower mantle, it first formed a basin at the surface, which later sprang up when the weight below broke off and sank further into the deeper depths of the mantle.

“It seems the heavy base of the tectonic plate has ‘dripped’ off into the mantle, leaving a massive gap in the plate beneath Central Anatolia. Essentially, by dropping this dense lithospheric anchor, there has been an upward bobbing of the entire land mass across hundreds of kilometres,” said Professor Oğuz H. Göğüş of the Eurasia Institute of Earth Sciences at Istanbul Technical University (ITU), lead author of a study reporting the findings published in Nature Communications this month.

It’s a new idea where plate shortening initially squeezed and folded a mountain belt, triggering the thickening and dripping of the deep lithosphere, and then increasing the elevation of most of central Turkey. Puzzled by the presence of such a process at a significant distance away from regular plate tectonic boundaries, the research team set about identifying why, in an area of high heating and high elevation, is the lithosphere below completely gone — something that was recently discovered from seismology.

They tested high-performance computational models against known geological and geophysical observations of the Central Anatolian Plateau, and demonstrated that a drip of lithospheric material below the surface can account for the measured elevation changes across the region.

“It’s a new variation on the fundamental concepts of plate tectonics,” said Professor Russell Pysklywec, chair of the Department of Earth Sciences at U of T and one of the study’s coauthors. “It gives us some insight into the connection between the slow circulation of near-solid rock in Earth’s mantle caused by convection currents carrying heat upwards from the planet’s interior, and observed active plate tectonics at the surface.

“This is part of the holy grail of plate tectonics — linking the two processes to understand how the crust responds to the mantle thermal engine of the planet.”

Pysklywec carried out the study with Göğüş, who received his PhD from U of T in 2010, and fellow researchers at ITU including Professor A. M. C. Şengör, and Erkan Gün of the Eurasia Institute of Earth Sciences at Istanbul Technical Institute. Gün is also now a current graduate student at U of T, supervised by Pysklywec. The research adds to decades of groundbreaking work in plate tectonics at U of T, and builds on Wilson’s seminal work.

“Tuzo Wilson is a towering figure in geophysics internationally and the person most responsible for pioneering the ideas of plate tectonics in the 1960s,” said Pysklywec. “I am pleased that we are continuing his legacy in geophysics with our work.”

While Pysklywec notes there are many locations on Earth missing its lithosphere below, he is quick to reassure that no place is in imminent danger of sinking into the mantle or boosting upwards overnight. “Our results show that the Central Anatolian Plateau rose over a period of millions of years. We’re talking about mantle fluid motions and uplift at the pace at which fingernails grow.”

Göğüş highlights the links of the tectonics with human history saying, “The findings are exciting also because of the link with the remarkable historical human activity of Central Anatolia where some of the earliest known civilizations have existed. For example, Central Anatolia is described as an elevated, dry, cold plain of Lycaonia in Strabo’s Geographika in 7 BC, and even cave paintings in the region dating to approximately 7000 BC record active volcanic eruptions on the plateau.”

Reference:
Oğuz H. Göğüş, Russell N. Pysklywec, A. M. C. Şengör, Erkan Gün. Drip tectonics and the enigmatic uplift of the Central Anatolian Plateau. Nature Communications, 2017; 8 (1) DOI: 10.1038/s41467-017-01611-3

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

Abominable Snowman? Nope. Study ties DNA samples from purported Yetis to Asian bears

A femur bone from the decayed body of a purported Yeti found in a cave in Tibet
A femur bone from the decayed body of a purported Yeti found in a cave in Tibet. Biologist Charlotte Lindqvist tested DNA from the bone for Icon Films’ “YETI OR NOT” TV special, which aired on Animal Planet in 2016. Credit: Icon Films Ltd.

The Yeti or Abominable Snowman — a mysterious, ape-like creature said to inhabit the high mountains of Asia — looms large in the mythology of Nepal and Tibet.

Sightings have been reported for centuries. Footprints have been spotted. Stories have been passed down from generation to generation.

Now, a new DNA study of purported Yeti samples from museums and private collections is providing insight into the origins of this Himalayan legend.

The research, which will be published in Proceedings of the Royal Society B, analyzed nine “Yeti” specimens, including bone, tooth, skin, hair and fecal samples collected in the Himalayas and Tibetan Plateau. Of those, one turned out to be from a dog. The other eight were from Asian black bears, Himalayan brown bears or Tibetan brown bears.

“Our findings strongly suggest that the biological underpinnings of the Yeti legend can be found in local bears, and our study demonstrates that genetics should be able to unravel other, similar mysteries,” says lead scientist Charlotte Lindqvist, PhD, an associate professor of biological sciences in the University at Buffalo College of Arts and Sciences, and a visiting associate professor at Nanyang Technological University, Singapore (NTU Singapore).

Lindqvist’s team is not the first to research “Yeti” DNA, but past projects ran simpler genetic analyses, which left important questions unresolved, she says.

“This study represents the most rigorous analysis to date of samples suspected to derive from anomalous or mythical ‘hominid’-like creatures,” Lindqvist and her co-authors write in their new paper. The team included Tianying Lan and Stephanie Gill from UB; Eva Bellemain from SPYGEN in France; Richard Bischof from the Norwegian University of Life Sciences; and Muhammad Ali Nawaz from Quaid-i-Azam University in Pakistan and the Snow Leopard Trust Pakistan program.

The science behind folklore

Lindqvist says science can be a useful tool in exploring the roots of myths about large and mysterious creatures.

She notes that in Africa, the longstanding Western legend of an “African unicorn” was explained in the early 20th century by British researchers, who found and described the flesh-and-blood okapi, a giraffe relative that looks like a mix between that animal and a zebra and a horse.

And in Australia — where people and oversized animals may have coexisted thousands of years ago — some scholars have speculated that references to enormous animal-like creatures in Australia’s Aboriginal “Dreamtime” mythology may have drawn from ancient encounters with real megafauna or their remains, known today from Australia’s fossil record.

But while such connections remain uncertain, Lindqvist’s work — like the discovery of the okapi — is direct: “Clearly, a big part of the Yeti legend has to do with bears,” she says.

She and colleagues investigated samples such as a scrap of skin from the hand or paw of a “Yeti” — part of a monastic relic — and a fragment of femur bone from a decayed “Yeti” found in a cave on the Tibetan Plateau. The skin sample turned out to be from an Asian black bear, and the bone from a Tibetan brown bear.

The “Yeti” samples that Lindqvist examined were provided to her by British production company Icon Films, which featured her in the 2016 Animal Planet special “YETI OR NOT,” which explored the origins of the fabled being.

Solving a scientific mystery, too: How enigmatic bears evolved

Besides tracing the origins of the Yeti legend, Lindqvist’s work is uncovering information about the evolutionary history of Asian bears.

“Bears in this region are either vulnerable or critically endangered from a conservation perspective, but not much is known about their past history,” she says. “The Himalayan brown bears, for example, are highly endangered. Clarifying population structure and genetic diversity can help in estimating population sizes and crafting management strategies.”

The scientists sequenced the mitochondrial DNA of 23 Asian bears (including the purported Yetis), and compared this genetic data to that of other bears worldwide.

This analysis showed that while Tibetan brown bears share a close common ancestry with their North American and Eurasian kin, Himalayan brown bears belong to a distinct evolutionary lineage that diverged early on from all other brown bears.

The split occurred about 650,000 years ago, during a period of glaciation, according to the scientists. The timing suggests that expanding glaciers and the region’s mountainous geography may have caused the Himalayan bears to become separated from others, leading to a prolonged period of isolation and an independent evolutionary path.

“Further genetic research on these rare and elusive animals may help illuminate the environmental history of the region, as well as bear evolutionary history worldwide — and additional ‘Yeti’ samples could contribute to this work,” Lindqvist says.

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

Atlantic and Pacific Ocean DO NOT MIX

Why do the two oceans not mix?

It’s not two oceans meeting, its glacial melt water meeting the off shore waters of gulf of Alaska. The reason for this strange phenomenon is due to the difference of water density, temperature and salinity of the glacial melt water and off shore waters of gulf of Alaska, making it difficult to mix.

Ken Bruland, professor of ocean sciences at University of California-Santa Cruz, was on that cruise. In fact, he was the one who snapped the pic. He said the purpose of the cruise was to examine how huge eddies — slow moving currents — ranging into the hundreds of kilometers in diameter, swirl out from the Alaska coast into the Gulf of Alaska.

Those eddies often carry with them huge quantities of glacial sediment thanks to rivers like Alaska’s 286-mile-long Copper River, prized for its salmon and originating from the Copper Glacier far inland. It empties out east of Prince William Sound, carrying with it all that heavy clay and sediment. And with that sediment comes iron.

“Glacier rivers in the summertime are like buzzsaws eroding away the mountains there,” Bruland said. “In the process, they lift up all this material — they call it glacial flour — that can be carried out.”

Once these glacial rivers pour out into the larger body of water, they’re picked up by ocean currents, moving east to west, and begin to circulate there. This is one of the primary methods that iron — found in the clay and sediment of the glacial runoff — is transported to iron-deprived regions in the middle of the Gulf of Alaska.

A Series of Fortunate Events: Antarctic Zircons Tell Story of Early Volcanism

Mount Etna in Italy
Mount Etna in Italy is a modern example of alkaline volcanism. Credit: Shawn Appel on Unsplash

Geoscientists from Michigan Technological University, University of Wisconsin Oshkosh and ETH Zurich have traced the age and chemical signatures stored in tiny zircon minerals to examine the recycling of carbon from the mantle to the surface through time.

A better understanding of these changes in carbon recycling help improve models about how the planet’s early processes transitioned from the cold Snowball Earth with near-global ice cover into more temperate swings between ice ages and warming periods. The team’s research will be published in Nature Geoscience next Monday.

“The geochemistry reflects a disequilibrium—and the Earth has to expel all of that to try to get back to equilibrium,” says Chad Deering, one of the co-authors and an assistant professor of geology at Michigan Tech. “What we propose is that a series of events had to coincide to ultimately lead to the optimal conditions required to release an anomalous amount of carbon.”

The chemical change is recorded on the scale of continents, but the details of that continent-building are locked in the layer-by-layer crystal structures of tiny zircons gathered from Antarctica. Some of the minerals are smaller than 100 microns, barely the width of an average human hair.

“We focused on looking at the trace elements in those zircons,” Deering says. “There’s a classification scheme that we use to determine the original rock type that the mineral grew in, which then tells us what kind of magma left that particular chemical signature of trace elements.”

The ETH Zurich lab then used uranium-lead dating to determine how old the samples are. Given the dates and trace elements, what Deering and his team observed is a peak in carbon-emitting magma types that occurred between 500 to 700 million years ago during the Ediacaran period. What that means is that a significant amount of carbon was likely released.

Volcanoes emit a lot of carbon dioxide—some much more so than others. Alkaline volcanoes like Mount Etna in Italy and Mount Erebus in Antarctica dwarf the carbon output of other volcanos by 10 to 50 times. And it’s the same type of volcanism that was identified in the zircons studied by Deering.

“Alkaline magmas are produced by melting just a little bit of the mantle,” he explains, adding that while rare and small in volume, their importance is in the amount of carbon dioxide belted out and the special conditions they form under. “What happens as subduction occurs is that the mantle becomes ‘polluted’ with volatile material from the Earth’s surface—water, carbon, sulfur.”

The changes leading up to this significant event are slow—occurring over hundreds of millions of years—and have major consequences. As the Earth cools through time and the mantle becomes increasingly more polluted, it will eventually generate alkaline magma that can erupt at the surface. The cooler subduction and mantle pollution can produce rocks known as blueschists, well-documented in the rock record during the Ediacaran period, along with alkaline volcanism. Following the pulse of carbon-rich volcanism, atmospheric carbon dioxide spikes, which is also recorded in the carbon isotope record, accompanied by a warming period. All told, this series of events gave rise to the atmosphere and geological cycles that shaped the planet as it is today.

“To create a timeline, we needed to have dates on a significant number of zircons spanning many hundreds of millions of years,” Deering says. “In essence, we discovered that throughout the Earth’s history there was a particularly significant pulse of carbon emitted that immediately preceded the Cambrian explosion, the most important emergence of life that has yet to occur.”

Gleaned from tiny zircons, the team used the chemical signatures of ancient volcanoes to establish that a series of fortunate events occurred as the oldest continents were constructed and materials recycled from the surface to eventually shape our modern carbon cycle.

Reference:
Timothy Paulsen et al, Evidence for a spike in mantle carbon outgassing during the Ediacaran period, Nature Geoscience (2017). DOI: 10.1038/s41561-017-0011-6

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

Less life: Limited phosphorus recycling suppressed early Earth’s biosphere

This is a Wyoming portion of The Phosphoria Formation, a deposit that stretches across several states in the western United States and is the largest source of phosphorus fertilizer in the country
As Earth’s oxygen levels rose to near-modern levels over the last 800 million years, phosphorus levels increased, as well, according to modeling led by the UW’s Michael Kipp and others. Accordingly, Kipp says, large phosphate deposits show up in abundance in the rock record at about this time. This is a Wyoming portion of The Phosphoria Formation, a deposit that stretches across several states in the western United States and is the largest source of phosphorus fertilizer in the country. The photo shows layers of phosphorus that are 10s of meters thick, shales the contain high concentrations of organic carbon and phosphorus. Kipp said many such deposits are documented over time but are rare in the Precambrian era. “Thus, they might represent a conspicuous temporal record of limited phosphorus recycling.” Credit: Michael Kipp / University of Washington

The amount of biomass — life — in Earth’s ancient oceans may have been limited due to low recycling of the key nutrient phosphorus, according to new research by the University of Washington and the University of St. Andrews in Scotland.

The research, published online Nov. 22 in the journal Science Advances, also comments on the role of volcanism in supporting Earth’s early biosphere — and may even apply to the search for life on other worlds.

The paper’s lead author is Michael Kipp, a UW doctoral student in Earth and space sciences; coauthor is Eva Stüeken, a research fellow at the University of St. Andrews and former UW postdoctoral researcher. Roger Buick, UW professor of Earth and space sciences, advised the researchers.

Their aim, Kipp said, was to use theoretical modeling to study how ocean phosphorus levels have changed throughout Earth’s history.

“We were interested in phosphorus because it is thought to be the nutrient that limits the amount of life there is in the ocean, along with carbon and nitrogen,” said Kipp. “You change the relative amount of those and you change, basically, the amount of biological productivity.”

Kipp said their model shows the ability of phosphorus to be recycled in the ancient ocean “was much lower than today, maybe on the order of 10 times less.”

All life needs abundant food to thrive, and the chemical element phosphorus — which washes into the ocean from rivers as phosphate — is a key nutrient. Once in the ocean, phosphorus gets recycled several times as organisms such as plankton or eukaryotic algae that “eat” it are in turn consumed by other organisms.

“As these organisms use the phosphorus, they in turn get grazed upon, or they die and other bacteria decompose their organic matter,” said Kipp, “and they release some of that phosphorus back into the ocean. It actually cycles through several times,” allowing the liberated phosphorus to build up in the ocean. The amount of recycling is a key control on the amount of total phosphorus in the ocean, which in turn supports life.

Buick explained: “Every gardener knows that their plants grow only small and scraggly without phosphate fertilizer. The same applies for photosynthetic life in the oceans, where the phosphate ‘fertilizer’ comes largely from phosphorus liberated by the degradation of dead plankton.”

But all of this requires oxygen. In today’s oxygen-rich oceans, nearly all phosphorus gets recycled in this way and little falls to the ocean floor. Several billion years ago, in the Precambrian era, however, there was little or no oxygen in the environment.

“There are some alternatives to oxygen that certain bacteria could use, said co-author Stüeken. “Some bacteria can digest food using sulfate. Others use iron oxides.” Sulfate, she said, was the most important control on phosphorus recycling in the Precambrian era.

“Our analysis shows that these alternative pathways were the dominant route of phosphorus recycling in the Precambrian, when oxygen was very low,” Stüeken said. “However, they are much less effective than digestion with oxygen, meaning that only a smaller amount of biomass could be digested. As a consequence, much less phosphorus would have been recycled, and therefore total biological productivity would have been suppressed relative to today.”

Kipp likened early Earth’s low-oxygen ocean to a kind of “canned” environment, with oxygen sealed out: “It’s a closed system. If you go back to the early Precambrian oceans, there’s not very much going on in terms of biological activity.”

Stüeken noted that volcanoes were the biggest source of sulfate in the Precambrian, unlike now, and so they were necessary for sustaining a significant biosphere by enabling phosphorus recycling.

In fact, minus such volcanic sulfate, Stüeken said, Earth’s biosphere would have been very small, and may not have survived over billions of years. The findings, then, illustrate “how strongly life is tied to fundamental geological processes such as volcanism on the early Earth,” she said.

Kipp and Stüeken’s modeling may have implications as well for the search for life beyond Earth.

Astronomers will use upcoming ground- and space-based telescopes such as the James Webb Space Telescope, set for launch in 2019, to look for the impact of a marine biosphere, as Earth has, on a planet’s atmosphere. But low phosphorus, the researchers say, could cause an inhabited world to appear uninhabited — making a sort of “false negative.”

Kipp said, “If there is less life — basically, less photosynthetic output — it’s harder to accumulate atmospheric oxygen than if you had modern phosphorus levels and production rates. This could mean that some planets might appear to be uninhabited due to their lack of oxygen, but in reality they have biospheres that are limited in extent due to low phosphorus availability.

“These ‘false negatives’ are one of the biggest challenges facing us in the search for life elsewhere,” said Victoria Meadows, UW astronomy professor and principal investigator for the NASA Astrobiology Institute’s Virtual Planetary Laboratory, based at the UW.

“But research on early Earth’s environments increases our chance of success by revealing processes and planetary properties that guide our search for life on nearby exoplanets.”

Reference:
Michael A. Kipp, Eva E. Stüeken. Biomass recycling and Earth’s early phosphorus cycle. Science Advances, 2017; 3 (11): eaao4795 DOI: 10.1126/sciadv.aao4795

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

Decline in atmospheric carbon dioxide key to ancient climate transition

shell of a fossil planktic foraminifera Globigerinoides ruber.
Reflected light image of the shell of a fossil planktic foraminifera Globigerinoides ruber. The boron isotopic composition of the shells of this species was used to reconstruct atmospheric CO2 1 million years ago in this study. Credit: Tom Chalk

A decline in atmospheric carbon dioxide (CO2) levels led to a fundamental shift in the behaviour of the Earth’s climate system around one million years ago, according to new research led by the University of Southampton.

A team of international scientists used new geochemical measurements, coupled with a model of the ‘Earth system’, to show that the growth and changing nature of continental ice sheets, approximately a million years ago, coincided with a cascade of events that ultimately lowered atmospheric CO2 during glacial intervals — periods when the Earth experienced extreme cold.

The researchers have shown this change was key in triggering what is known as the Mid-Pleistocene Transition (MPT), which lasted around 400,000 years. The MPT had long lasting effects on the frequency at which the Earth transitioned between periods of warm and cold climate, (the ‘ice age cycles’).

Findings of the study are published in the journal Proceedings of the National Academy of Sciences.

For much of the last three million years the Earth’s climate naturally cycled every 40,000 years from frigid glacial intervals, where continental ice covered much of North America and Europe, to warm interglacial climates like the pre-industrial period, when Europe and North America were largely ice free.

These ice age cycles, also known as Milkovitch Cycles after the Serbian mathematician who discovered them, are paced by regular changes in the way the Earth orbits the sun and spins on its axis, caused by the gravitational pull of the other planets in our solar system. Around one million years ago, during the MPT, the period of the cycles abruptly changed to every 100,000 years. However, this transition is not accompanied by a change in the nature of the orbital cycles and so represents a significant challenge to the Milkovitch Theory to explain ice age cycles.

Dr Tom Chalk, a post-doctoral fellow at the University of Southampton, who jointly led the study explains: “We know from bubbles of the ancient atmosphere trapped in Antarctic ice cores that changes in atmospheric CO2 accompanied the more recent ice age cycles. CO2 was low when it was cold during the glacials and it was higher during the warm interglacials — in this way it acted as a key amplifier of the relatively minor climate forcing from the orbital cycles. Unfortunately, the ice core records only stretch back to around 800,000 years ago and so do not go over this key transition interval. In order to better understand the cause of the MPT, we needed a way to reconstruct CO2 further back in time.”

To do this, the team used a technique based on the boron isotopic composition of the shells of ancient marine fossils called ‘foraminifera’. These are tiny marine plankton that live near the sea surface and the chemical make-up of their microscopic shells records the environmental conditions of the time when they lived, millions of years ago.

Professor Gavin Foster, of the University of Southampton, continues: “From these boron isotope measurements we were able to recover a snapshot of the variability in atmospheric CO2 around 1.1 million years ago. We were able to show, for the first time that, just as in the ice core record, CO2 and climate varied in tandem. There were two main differences however: firstly, during the glacials before the MPT, CO2 did not drop as low as it did in the ice core record after the MPT, remaining about 20-40 parts per million (ppm) higher. Secondly, the climate system was also more sensitive to changing CO2 after the MPT than before.”

The Earth’s climate system is very complex and the various interconnections between its numerous processes and feedbacks are best understood within a computational modelling framework. Dr Mathis Hain, a NERC Independent Research Fellow at the University of Southampton, added: “In order to determine why glacial-aged CO2 declined by 20-40 ppm across the MPT we used a biogeochemical model. Our best model fit to the available data suggests that the reduced drawdown of CO2 during glacial periods prior to the MPT was due to a reduced flux of dust to the Southern Ocean at this time. A higher dust flux during more recent glacial intervals brought much needed iron to that region, stimulating primary productivity and phytoplankton growth, locking more CO2 away in the deep ocean. We do not know yet exactly why the climate became dustier after MPT, but it is likely due to the ice sheets getting bigger and changing atmospheric circulation.”

Over the last 20 years or so there have been many different ideas to explain this important climate transition, some have called on changes in the nature of the ice sheets themselves, others on atmospheric CO2 change. What the team’s new data and modelling show is that what happened in reality was a mix of both types of ideas — the climate and the ice sheets became more sensitive, this led to bigger ice sheets, and this in turn led to enhanced CO2 drawdown. As with many facets of the Earth system these changes acted in a vicious circle, feeding on one another, ultimately sustaining longer glacial periods following the MPT.

There is still much that remains to be found out about how the Earth system responds to climate forcing. This study, however, illustrates the exquisite coupling that exists in the Earth System between climate change, ice-sheet mass, and the polar ocean mechanisms that regulate natural CO2 change.

Reference:
Thomas B. Chalk, Mathis P. Hain, Gavin L. Foster, Eelco J. Rohling, Philip F. Sexton, Marcus P. S. Badger, Soraya G. Cherry, Adam P. Hasenfratz, Gerald H. Haug, Samuel L. Jaccard, Alfredo Martínez-García, Heiko Pälike, Richard D. Pancost, Paul A. Wilson. Causes of ice age intensification across the Mid-Pleistocene Transition. Proceedings of the National Academy of Sciences, 2017; 201702143 DOI: 10.1073/pnas.1702143114

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

Unique underwater stalactites

The Hells Bells in the El Zapote cave near Puerto Morelos on the Yucatán Peninsula.
The Hells Bells in the El Zapote cave near Puerto Morelos on the Yucatán Peninsula. Credit: E.A.N./IPA/INAH/MUDE/UNAM/HEIDELBERG

In recent years, researchers have identified a small group of stalactites that appear to have calcified underwater instead of in a dry cave. The Hells Bells in the El Zapote cave near Puerto Morelos on the Yucatán Peninsula are just such formations. A German-Mexican research team led by Prof. Dr Wolfgang Stinnesbeck from the Institute of Earth Sciences at Heidelberg University recently investigated how these bell-shaped, metre-long formations developed, assisted by bacteria and algae. The results of their research have been published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

Hanging speleothems, also called stalactites, result through physicochemical processes in which water high in calcium carbonate dries up. Normally they rejuvenate and form a tip at the lower end from which the drops of water fall to the cave floor. The formations in the El Zapote cave, which are up to two metres long, expand conically downward and are hollow with round, elliptical or horseshoe-shaped cross-sections. Not only are they unique in shape and size, but also their mode of growth, according to Prof. Stinnesbeck. They grow in a lightless environment near the base of a 30 m freshwater unit immediately above a zone of oxygen-depleted and sulfide-rich toxic saltwater. “The local diving community dubbed them Hells Bells, which we think is especially appropriate,” states Wolfgang Stinnesbeck. Uranium-thorium dating of the calcium carbonate verifies that these formations must have actually grown underwater, proving that the Hells Bells must have formed in ancient times. Even then the deep regions of the cave had already been submerged for thousands of years.

According to the Heidelberg geoscientist, this underwater world on the Yucatán Peninsula in Mexico represents an enigmatic ecosystem providing the conditions for the formation of the biggest underwater speleothems worldwide. Previously discovered speleothems of this type are much smaller and less conspicuous than the Hells Bells, adds Prof. Stinnesbeck. The researchers suspect that the growth of these hollow structures is tied to the specific physical and biochemical conditions near the halocline, the layer that separates the freshwater from the underlying saltwater. “Microbes involved in the nitrogen cycle, which are still active today, could have played a major role in calcite precipitation because of their ability to increase the pH,” explains Dr Stinnesbeck.

Reference:
Stinnesbeck, W., Frey, E., Zell, P., Avíles, J., Hering, F., Frank, N., Arps, J., Geenen, A., Gescher, J., Isenbeck-Schröter, M., Ritter, S., Stinnesbeck, S., Aceves Núñez, E., Fito Dahne, V., González González, A.H., Deininger, M. Hells Bells – unique speleothems from the Yucatán Peninsula, Mexico, generated under highly specific subaquatic conditions. Palaeogeography, Palaeoclimatology, Palaeoecology, 2017 DOI: 10.1016/j.palaeo.2017.10.01

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

Research reveals the scale at which Earth’s mantle composition varies

The mantle beneath Earth's mid-oceanic ridges contains heterogeneous blobs of material
The mantle beneath Earth’s mid-oceanic ridges contains heterogeneous blobs of material. A new study puts new constraints on the sizes of those blobs. Credit: Boda Liu

New research by Brown University geochemists provides new insights on the scale at which Earth’s mantle varies in chemical composition. The findings could help scientists better understand the mixing process of mantle convection, the slow churning that drives the movement of Earth’s tectonic plates.

“We know that the mantle is heterogeneous in composition, but it’s been difficult to figure out how large or small those heterogeneities might be,” said Boda Liu, a Ph.D. student in geology at Brown. “What we show here is that there must be heterogeneities of at least a kilometer in size to produce the chemical signature we observe in rocks derived from mantle materials.”

The research, which Liu co-authored with Yan Liang, a professor in Brown’s Department of Earth Environmental and Planetary Sciences, is published in Science Advances.

Earth’s crust is on a constantly moving conveyer belt driven by the convecting mantle. At mid-ocean ridges, the boundaries on the ocean floor where tectonic plates are pulling away from each other, new crust is created by eruption of magmas formed by the rising of the mantle materials from depth. At subductions zones, where one tectonic plate slides beneath another, old crust material, weathered by processes on the surface, is pushed back down into the mantle. This recycling can create mantle materials of different or “enriched” compositions, which geochemists refer to as “heterogeneities.” What happens to that enriched material once it’s recycled isn’t fully understood.

“This is one of the big questions in Earth science,” Liang said. “To what extent does mantle convection mix and homogenize these heterogeneities out? Or how might these heterogeneities be preserved?”

Scientists learn about the composition of the mantle by studying mid-ocean ridge basalts (MORBs), rocks formed by the solidification of magmas erupted on the seafloor. Like fingerprints, isotope compositions of MORBs can be used to trace the mantle source from which they were derived.

Another type of seafloor rock called abyssal peridotites is the leftover mantle after the formation of MORBs. These are chunks of mantle rock that once were the uppermost mantle and later uplifted to the seafloor. Abyssal peridotites have a different isotope composition than MORBs that appear to come from the same mantle region. To explain that difference in isotope compositions, scientists have concluded that the MORBs are capturing the isotope signal from pockets of enriched material—the remnants of subducted crust preserved in the mantle.

The question this new study sought to answer is how large those enriched pockets would need to be for their isotope signature to survive the trip to the surface. As magma rises toward the surface, it interacts with the ambient mantle, which would tend to dampen the signal of enriched material in the melt. For their study, Liu and Liang modeled the melting and magma transport processes. They found that in order to produce the different isotope signals between MORBs and abyssal peridotites, the pockets of enriched material at depth would need to be at least one kilometer in size.

“If the length scale of the heterogeneity is too small, the chemical exchange during magma flow would wipe the heterogeneities out,” Liang said. “So in order to produce the composition difference we see, our model shows that the heterogeneity needs to be a kilometer or more.”

The researchers hope their study will add a new perspective to the fine-scale structure of the mantle produced by mantle convection.

“Our contribution here is to give some sense of how large some of these heterogeneities might be,” Liang said. “So the question to the broader community becomes: What might be the deep mantle processes that can produce this?”

Reference:
Boda Liu et al. The prevalence of kilometer-scale heterogeneity in the source region of MORB upper mantle, Science Advances (2017). DOI: 10.1126/sciadv.1701872

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

Going underground: Cambridge digs into the history of geology with landmark exhibition

‘A Geological Map of England and Wales’, 1819, George Bellas Greenough (1778-1855). Credit: University of Cambridge

A box full of diamonds, volcanic rock from Mount Vesuvius, and the geology guide that Darwin packed for his epic voyage on the Beagle will go on display in Cambridge this week as part of the first major exhibition to celebrate geological map-making.

Uncovering how the ground beneath our feet was mapped for the first time – and revealing some of the controversies and tragedies geology brought to the surface of intellectual debate, Landscapes Below opens to the public on Friday, November 24, at Cambridge University Library.

Featuring the biggest-ever object (1.9mx1.6m) to go on display at the Library: George Bellas Greenough’s 1819 A Geological Map of England and Wales (the first map produced by the Geological Society of London), as well as a visually stunning collection of maps from the earliest days of geology – the exhibition explores how these new subterranean visions of the British landscape influenced our understanding of the Earth. All the maps belonging to the library are going on display for the first time.

“I think the maps are beautiful objects, tell fascinating stories and frame geology in a new light,” said exhibition curator Allison Ksiazkiewicz. “This was a new take on nature and a new way of thinking about the landscape for those interested in nature.

“We show how the early pioneers of this new science wrestled with the ideas of a visual vocabulary – and how for the first time people were encouraged to think about the secretive world beneath their feet.”

As well as maps, Landscapes Below also brings together an extraordinary collection of fossils, artworks and a collection of 154 diamonds, on loan from the Sedgwick Museum of Earth Sciences. Displayed together for the first time, the diamonds were collected, arranged, and produced by Jacques Louis, Comte de Bournon who later became the Keeper of the Royal Mineral Collection for King Louis XVIII.

Another important exhibit on display for the first time is the first edition of George Cuvier and Alexandre Brongniart’s Researches on the Fossil Bones of Quadrupeds (1811), on loan from Trinity College. It examined the geology of the Paris Basin and revolutionised what was considered ‘young’ in geological terms.

Artists were also keen to accurately depict the geological landscape. After surviving Captain Cook’s ill-fated third voyage of discovery, artist, John Webber returned to England and travelled around the country painting landscapes and geological formations, as seen in Landscape of Rocks in Derbyshire. Christopher Packe’s A New Philosophico-Chorographical Chart of East-Kent (1743), on loan from the Geological Society of London, is a remarkable, engraved map that draws on early modern medicine in the interpretation of the surrounding landscape.

“The objects we’re putting on display show the many different applications of geological knowledge,” added Ksiazkiewicz. “Whether it’s a map showing the coal fields of Lancashire in the 1830s – or revealing how this new science was used for economic and military reasons.”

In many ways, the landscapes the earliest geologists worked among became battlegrounds as a scientific old guard – loyal to the established pursuits of mineralogy and chemistry – opposed a new generation of scientists intent on using the fossil record in the study of the Earth’s age and formation.

Exhibitions Officer Chris Burgess said: “Maps were central to the development of geology but disagreement between its leading figures was common. Maps of the period did not just show new knowledge but represented visible arguments about how that knowledge should be recorded.”

The exhibition also includes objects from those with rather tragic histories, including William Smith – whose famous 1815 Geological Map of England has been described as the ‘Magna Carta of geology’. Despite publishing the world’s first geological map (which is still used as the basis of such maps today), Smith was shunned by the scientific community for many years, became a bankrupt, and ended up in debtors’ prison.

John MacCulloch, who produced the Geological Map of Scotland, did not live to see his work published after his honeymoon carriage overturned and killed him at the age of 61. He spent 15 summers surveying Scotland, after convincing the Board of Ordnance to sponsor the project. There was some dispute about how MacCulloch calculated his mileage and spent the funds, and the Ordnance only paid for six summers’ worth of work. Five summers were paid for by the Treasury and four from his own pocket.

Added Ksiazkiewicz: “Not only do these maps and objects represent years of work by individuals looking to develop a new science of the Earth, they stir the imagination. You can imagine yourself walking across the landscape and absorbing all that comes with it – views, antiquities, fossils, and vegetation. And weather, there’s always weather.”

Landscapes Below runs from November 25, 2017 to March 29, 2018 at Cambridge University Library’s Milstein Exhibition Centre. Admission is free. Opening times are Mon-Fri 9am-6pm and Saturday 9am-16.30pm. Closed Sundays.

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

Climate change could increase volcano eruptions

Tephras -- rock fragments and particles ejected by a volcanic eruption.
Tephras — rock fragments and particles ejected by a volcanic eruption. Credit: Image courtesy of University of Leeds

Shrinking glacier cover could lead to increased volcanic activity in Iceland, warn scientists.

A new study, led by the University of Leeds, has found that there was less volcanic activity in Iceland when glacier cover was more extensive and as the glaciers melted volcanic eruptions increased due to subsequent changes in surface pressure.

Dr Graeme Swindles, from the School of Geography at Leeds, said: “Climate change caused by humans is creating rapid ice melt in volcanically active regions. In Iceland, this has put us on a path to more frequent volcanic eruptions.”

The study examined Icelandic volcanic ash preserved in peat deposits and lake sediments and identified a period of significantly reduced volcanic activity between 5,500 and 4,500 years ago. This period came after a major decrease in global temperature, which caused glacier growth in Iceland.

The findings, published in the journal Geology, found there was a time lag of roughly 600 years between the climate event and a noticeable decrease in the number of volcanic eruptions. The study suggests that perhaps a similar time lag can be expected following the more recent shift to warmer temperatures.

Iceland’s volcanic system is in process of recovering from the ‘Little Ice Age’ — a recorded period of colder climate roughly between the years 1500 to 1850. Since the end of the Little Ice Age, a combination of natural and human caused climate warming is causing Icelandic glaciers to melt again.

Dr Swindles said: “The human effect on global warming makes it difficult to predict how long the time lag will be but the trends of the past show us more eruptions in Iceland can be expected in the future.

“These long term consequences of human effect on the climate is why summits like COP are so important. It is vital to understand how actions today can impact future generations in ways that have not been fully realised, such as more ash clouds over Europe, more particles in the atmosphere and problems for aviation. ”

Icelandic volcanism is controlled by complex interactions between rifts in continental plate boundaries, underground gas and magma build-up and pressure on the volcano’s surface from glaciers and ice. Changes in surface pressure can alter the stress on shallow chambers where magma builds up.

Study co-author, Dr Ivan Savov, from the School of Earth & Environment at Leeds, explains: “When glaciers retreat there is less pressure on Earth’s surface. This can increase the amount of mantle melt as well as affect magma flow and how much magma the crust can hold.

“Even small changes in surface pressure can alter the likelihood of eruptions at ice-covered volcanos.”

Reference:
Graeme T. Swindles, Elizabeth J. Watson, Ivan P. Savov, Ian T. Lawson, Anja Schmidt, Andrew Hooper, Claire L. Cooper, Charles B. Connor, Manuel Gloor, Jonathan L. Carrivick. Climatic control on Icelandic volcanic activity during the mid-Holocene. Geology, 2017; DOI: 10.1130/G39633.1

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

Mysterious deep-Earth seismic signature explained

The movement of seismic waves through the material of the mantle allows scientists to image Earth's interior, just as a medical ultrasound allows technicians to look inside a blood vessel
The movement of seismic waves through the material of the mantle allows scientists to image Earth’s interior, just as a medical ultrasound allows technicians to look inside a blood vessel. Image is courtesy of Edward Garnero and Allen McNamara’s 2008 Science paper Structure and Dynamics of Earth’s Lower Mantle, provided with Garnero’s permission. Credit: Edward Garnero and Allen McNamara

New research on oxygen and iron chemistry under the extreme conditions found deep inside the Earth could explain a longstanding seismic mystery called ultralow velocity zones. Published in Nature, the findings could have far-reaching implications on our understanding of Earth’s geologic history, including life-altering events such as the Great Oxygenation Event, which occurred 2.4 billion years ago.

Sitting at the boundary between the lower mantle and the core, 1,800 miles beneath Earth’s surface, ultralow velocity zones (UVZ) are known to scientists because of their unusual seismic signatures. Although this region is far too deep for researchers to ever observe directly, instruments that can measure the propagation of seismic waves caused by earthquakes allow them to visualize changes in Earth’s interior structure; similar to how ultrasound measurements let medical professionals look inside of our bodies.

These seismic measurements enabled scientists to visualize these ultralow velocity zones in some regions along the core-mantle boundary, by observing the slowing down of seismic waves passing through them. But knowing UVZs exist didn’t explain what caused them.

However, recent findings about iron and oxygen chemistry under deep-Earth conditions provide an answer to this longstanding mystery.

It turns out that water contained in some minerals that get pulled down into the Earth due to plate tectonic activity could, under extreme pressures and temperatures, split up—liberating hydrogen and enabling the residual oxygen to combine with iron metal from the core to create a novel high-pressure mineral, iron peroxide.

Led by Carnegie’s Ho-kwang “Dave” Mao, the research team believes that as much as 300 million tons of water could be carried down into Earth’s interior every year and generate deep, massive reservoirs of iron dioxide, which could be the source of the ultralow velocity zones that slow down seismic waves at the core-mantle boundary.

To test this idea, the team used sophisticated tools at Argonne National Laboratory to examine the propagation of seismic waves through samples of iron peroxide that were created under deep-Earth-mimicking pressure and temperature conditions employing a laser-heated diamond anvil cell. They found that a mixture of normal mantle rock with 40 to 50 percent iron peroxide had the same seismic signature as the enigmatic ultralow velocity zones.

For the research team, one of the most-exciting aspects of this finding is the potential of a reservoir of oxygen deep in the planet’s interior, which if periodically released to the Earth’s surface could significantly alter the Earth’s early atmosphere, potentially explaining the dramatic increase in atmospheric oxygen that occurred about 2.4 billion years ago according to the geologic record.

“Finding the existence of a giant internal oxygen reservoir has many far-reaching implications,” Mao explained. “Now we should reconsider the consequences of sporadic oxygen outbursts and their correlations to other major events in the Earth’s history, such as the banded-iron formation, snowball Earth, mass extinctions, flood basalts, and supercontinent rifts.”

Reference:
Hydrogen-bearing iron peroxide and the origin of ultralow-velocity zones, Nature (2017). DOI:10.1038/nature24461

Note: The above post is reprinted from materials provided by Carnegie Institution for Science.

How the Earth stops high-energy neutrinos in their tracks

This image shows a visual representation of one of the highest-energy neutrino detections superimposed on a view of the IceCube Lab at the South Pole
This image shows a visual representation of one of the highest-energy neutrino detections superimposed on a view of the IceCube Lab at the South Pole. Credit: IceCube Collaboration

For the first time, a science experiment has measured Earth’s ability to absorb neutrinos — the smaller-than-an-atom particles that zoom throughout space and through us by the trillions every second at nearly the speed of light. The experiment was achieved with the IceCube detector, an array of 5,160 basketball-sized sensors frozen deep within a cubic kilometer of very clear ice near the South Pole. The results of this experiment by the IceCube collaboration, which includes Penn State physicists, will be published in the online edition of the journal Nature on November 22, 2017.

“This achievement is important because it shows, for the first time, that very-high-energy neutrinos can be absorbed by something — in this case, the Earth,” said Doug Cowen, professor of physics and astronomy & astrophysics at Penn State. The first detections of extremely-high-energy neutrinos were made by IceCube in 2013, but a mystery remained about whether any kind of matter could truly stop a neutrino’s journey through space. “We knew that lower-energy neutrinos pass through just about anything,” Cowen said, “but although we had expected higher-energy neutrinos to be different, no previous experiments had been able to demonstrate convincingly that higher-energy neutrinos could be stopped by anything.”

The results in the Nature paper are based on one year of data from about 10,800 neutrino-related interactions. Cowen and Tyler Anderson, an assistant research professor of physics at Penn State, are members of the IceCube collaboration. They are coauthors of the Nature paper who helped to build the IceCube detector and are contributing to its maintenance and management.

This new discovery with IceCube is an exciting addition to our deepening understanding of how the universe works. It also is a little bit of a disappointment for those who hope for an experiment that will reveal something that cannot be explained by the current Standard Model of Particle Physics. “The results of this Ice Cube study are fully consistent with the Standard Model of Particle Physics — the reigning theory that for the past half century has described all the physical forces in the universe except gravity,” Cowen said.

Neutrinos first were formed at the beginning of the universe, and they continue to be produced by stars throughout space and by nuclear reactors on Earth. “Understanding how neutrinos interact is key to the operation of IceCube,” explained Francis Halzen, principal investigator for the IceCube Neutrino Observatory and a University of Wisconsin-Madison professor of physics. “We were of course hoping for some new physics to appear, but we unfortunately find that the Standard Model, as usual, withstands the test,” Halzen said.

IceCube’s sensors do not directly observe neutrinos, but instead measure flashes of blue light, known as Cherenkov radiation, emitted after a series of interactions involving fast-moving charged particles that are created when neutrinos interact with the ice. By measuring the light patterns from these interactions in or near the detector array, IceCube can estimate the neutrinos’ energies and directions of travel. The scientists found that the neutrinos that had to travel the farthest through Earth were less likely to reach the detector.

Most of the neutrinos selected for this study were more than a million times more energetic than the neutrinos produced by more familiar sources, like the Sun or nuclear power plants. The analysis also included a small number of astrophysical neutrinos, which are produced outside the Earth’s atmosphere, from cosmic accelerators unidentified to date, perhaps associated with supermassive black holes.

“Neutrinos have quite a well-earned reputation of surprising us with their behavior,” says Darren Grant, spokesperson for the IceCube Collaboration, a professor of physics at the University of Alberta in Canada, and a former postdoctoral scholar at Penn State. “It is incredibly exciting to see this first measurement and the potential it holds for future precision tests.”

In addition to providing the first measurement of the Earth’s absorption of neutrinos, the analysis shows that IceCube’s scientific reach extends beyond its core focus on particle physics discoveries and the emerging field of neutrino astronomy into the fields of planetary science and nuclear physics. This analysis also is of interest to geophysicists who would like to use neutrinos to image the Earth’s interior in order to explore the boundary between the Earth’s inner solid core and its liquid outer core.

“IceCube was built to both explore the frontiers of physics and, in doing so, possibly challenge existing perceptions of the nature of universe. This new finding and others yet to come are in that spirt of scientific discovery,” said James Whitmore, program director in the National Science Foundation’s physics division. Physicists now hope to repeat the study using an expanded, multiyear analysis of data from the full 86-string IceCube array, and to look at higher ranges of neutrino energies for any hints of new physics beyond the Standard Model.

Reference:
M. G. Aartsen et al. Measurement of the multi-TeV neutrino interaction cross-section with IceCube using Earth absorption. Nature, 2017; DOI: 10.1038/nature24459

Note: The above post is reprinted from materials provided by Penn State.

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