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Earth not due for a geomagnetic flip in the near future, researchers show

Artistic impression of latitudinally more widespread aurora as an expected consequence of geomagnetic field strength much lower than today’s. Credit: Huapei Wang (with material courtesy of NASA’s Earth Observatory) and edited by MIT News 

The intensity of Earth’s geomagnetic field has been dropping for the past 200 years, at a rate that some scientists suspect may cause the field to bottom out in 2,000 years, temporarily leaving the planet unprotected against damaging charged particles from the sun. This drop in intensity is associated with periodic geomagnetic field reversals, in which the Earth’s North and South magnetic poles flip polarity, and it could last for several thousand years before returning to a stable, shielding intensity.

With a weakened geomagnetic field, increased solar radiation might damage electronics—from individual pacemakers to entire power grids—and could induce genetic mutations. A reversal may also affect the navigation of animals that use Earth’s magnetic field as an internal compass.

But according to a new MIT study in the Proceedings of the National Academy of Sciences, the geomagnetic field is not in danger of flipping anytime soon: The researchers calculated Earth’s average, stable field intensity over the last 5 million years, and found that today’s intensity is about twice that of the historical average.

This indicates that the current field intensity has a long way to fall before reaching an unstable level that would lead to a reversal.

“It makes a huge difference, knowing if today’s field is a long-term average or is way above the long-term average,” says lead author Huapei Wang, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “Now we know we are way above the unstable zone. Even if the [field intensity] is dropping, we still have a long buffer that we can comfortably rely on.”

Flip-flopping through history

Earth has undergone multiple geomagnetic reversals over its lifetime, flip-flopping its polarity at random intervals.

“Sometimes you won’t have a flip for about 40 million years; other times there will be 10 flips in 1 million years,” Wang says. “On average, the duration between two flips is a few hundred thousand years. The last flip was around 780,000 years ago, so we are actually overdue for a flip.”

The most obvious sign of an impending reversal is a geomagnetic field intensity that’s significantly below its historical, long-term average—a sign that the planet is tipping toward an unstable state. While satellites and ground-based observatories have made accurate measurements over the last 200 years of the current field intensity, there are less reliable estimates over the last few million years.

Wang and his colleagues, from Rutgers University and France, sought to measure Earth’s paleomagnetic field using ancient rocks erupted from volcanoes on the Galapagos Islands—an ideal site, since the island chain is on the equator. As Earth’s magnetic field, in its stable configuration, is a dipole, the intensity of the field should be the same at both poles, and half that intensity at the equator.

Wang reasoned that knowing the paleomagnetic field intensity at the equator and the poles would therefore give an accurate estimate of the planet’s average historical intensity.

Rocks from a dipole

Wang obtained samples of ancient volcanic lavas from the Galapagos, while his colleagues from the Scripps Institution of Oceanography at the University of California at San Diego excavated similarly aged rocks from Antarctica. Such volcanic rocks retain information on the geomagnetic field intensity at the time they cooled.

The two teams brought the samples back to their respective labs, and measured the rocks’ natural remanent magnetization, or orientation of ferromagnetic particles. They then heated the rocks, and cooled them in the presence of a known magnetic field, measuring the rocks’ magnetization after cooling.

A rock’s remanent magnetization is proportional to the magnetic field in which it cooled. Therefore, using the data from their experiments, the researchers were able to calculate the peak distribution of the ancient geomagnetic field intensity, both at the equator—about 15 microtesla—and the poles—about 30 microtesla. Today’s field intensities at the same locations are around 30 microtesla and 60 microtesla, respectively—double the historical, long-term values.

“That means today’s value is anomalously high, and even if it’s dropping, it’s dropping to a long-term average, not from an average to zero,” Wang says.

Far from zero

So why have scientists assumed that Earth’s geomagnetic field is dropping to a precipitous low? It turns out this assumption is based on flawed historical data, Wang says.

Scientists have estimated paleomagnetic intensities at various latitudes around the Earth, but Wang’s is the first data from equatorial regions. However, Wang found that scientists were misinterpreting how rocks recorded their magnetic fields, leading to inaccurate estimates of paleomagnetic intensity. Specifically, scientists were assuming that as individual ferromagnetic grains of rocks cooled, their unpaired electron spins assumed a uniform orientation, reflecting the magnetic field intensity.

However, this effect only holds true up to a certain size. In larger grains, unpaired electron spins assume various orientations in different domains of the grain, thereby complicating the field intensity picture.

Wang developed a method to correct for such multidomain effects, and applied the method to his Galapagos lavas. The results, he says, are more reliable than previous estimates of the paleomagnetic field.

As for when Earth may experience its next flip, Wang says the answer is still up in the air.

“What I can say is, if you keep a constant present-day decrease rate, it will take another 1,000 years for the field to drop to its long-term average,” Wang says. “From there, the field intensity may go up again. There’s really no way to predict what will happen after that, given the random nature of the magnetohydrodynamic process of the geodynamo.”

Reference:
Weaker axially dipolar time-averaged paleomagnetic field based on multidomain-corrected paleointensities from Galapagos lavas, PNAS, DOI: 10.1073/pnas.1505450112

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

Mountain ranges evolve and respond to Earth’s climate, study shows

Valley of the Ten Peaks and Moraine Lake, Banff National Park, Canada. Mountains from left to right: Tonsa (3057 m), Mount Perren (3051 m), Mount Allen (3310 m), Mount Tuzo (3246 m), Deltaform Mountain (3424 m), Neptuak Mountain (3233 m) Credit: Gorgo

Ground-breaking new research has shown that erosion caused by glaciation during ice ages can, in the right circumstances, wear down mountains faster than plate tectonics can build them.

The international study, including Dr Ian Bailey from the University of Exeter, has given a fascinating insight into how climate and tectonic forces influence mountain building over a prolonged period of time.

The research team attempted to measure all the material that left and entered the St Elias Mountain range, on the Alaskan coast, over the past five million years, using state-of-the-art seismic imaging equipment and marine coring.

They found that erosion accelerated sharply when global climate cooling triggered stronger and more persistent ice ages about one million years ago.

The pioneering new research, which is the product of the culmination more than a decade of field work, has shown that mountain ranges actively evolve with, and respond to, the Earth’s climate, rather than being static, unyielding parts of the landscape.

The international study, conducted by the Integrated Ocean Drilling Program and led by scientists from The University of Texas at Austin, University of Florida and Oregon State University, is published in the Proceedings of the National Academy of Sciences on Monday, November 23.

Dr Bailey, a Geology Lecturer from the Camborne School of Mines, based at the University of Exeter’s Penryn Campus in Cornwall said: “Understanding precisely how the balance of climate and tectonic forces influences mountain building remains an outstanding unknown in Earth Sciences.

“A tremendous amount of important information has been gained by studying the onshore geology associated with the St Elias Mountain range.

“Our exciting findings, which add new insight to this important debate, could only be made, however, by examining at the adjacent off-shore marine sediment record.”

The study, conducted by a team of scientists from 10 countries, used seismic equipment to image and map a huge fan of sediment in the deep sea in the Gulf of Alaska caused by erosion of the St Elias Mountain range and took short sediment cores to understand the modern system.

They then determined when and how fast the fan accumulated by dating nearly four kilometres of marine cores collected from the gulf and the Alaskan continental shelf.

Sean Gulick, lead author and co-chief scientist from the University of Texas Institute for Geophysics (UTIG), a unit of the Jackson School of Geosciences said: “It turned out most sediments were younger than we anticipated, and most rates of sediment production and thus erosion were higher than we anticipated.

“Since the big climate change during the mid-Pleistocene transition when we switched from short (about 40,000-year) ice ages to super long (about 100,000-year) ice ages, erosion became much greater. In fact, there was more erosion than tectonics has replaced.”

“We were pleasantly surprised by how well we could establish ages of the sediment sequences as we were drilling, and the composition of the sediment gave clear evidence of when the glaciation started and then expanded, in synch with global climate trends over the past several million years,” said co-author Alan Mix of Oregon State University. “Only by drilling the sea floor where the sediment accumulates could we see these details.”

Mountain ranges form when tectonic plates thrust into one another over millions of years and scrunch up the Earth’s outer crust. But even as mountains are built by these titanic forces, other agents—some combination of tectonic and climate processes—work to remove the accumulating crust.

Since the mid-Pleistocene, erosion rates have continued to beat tectonic inputs by 50 to 80 percent, demonstrating that climatic processes, such as the movement of glaciers, can outstrip mountain building over a span of a million years. The findings highlight the pivotal role climate fluctuations play in shaping Earth’s landforms.

Reference:
Mid-Pleistocene climate transition drives net mass loss from rapidly uplifting St. Elias Mountains, Alaska, PNAS, DOI: 10.1073/pnas.1512549112

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

Climate can grind mountains faster than they can be rebuilt, study indicates

Mount Everest as seen from the aircraft of Drukair in Bhutan. Credit: shrimpo1967/flickr 

Researchers for the first time have attempted to measure all the material leaving and entering a mountain range over millions of years and discovered that glacial erosion can, under the right circumstances, wear down mountains faster than plate tectonics can build them.

A study of the St. Elias Mountains on the Alaskan coast by researchers from The University of Texas at Austin, University of Florida, Oregon State University and elsewhere found that erosion accelerated sharply about one million years ago.

The study adds insight into a longstanding debate over the balance of climate and tectonic forces that influence mountain building, which defines how landscapes are shaped by and in turn influence climate. The findings will be published this week in the Proceedings of the National Academy of Sciences.

The international research team, working under the Integrated Ocean Drilling program, included Oregon State University Professors Alan Mix and Joe Stoner and postdoctoral researcher Maureen Walczak as well as other scientists from the U.S., Germany, Brazil, Norway, India, China, Japan, Canada, Australia and the United Kingdom.

The seagoing expedition was the culmination of more than a decade of field work. On a previous expedition, the researchers first mapped a huge submarine sediment fan in the Gulf of Alaska built by sediment eroded from the nearby mountains. Next, they recovered sediment cores to understand the fan environments and recent history. The cores are now archived in the national repository at Oregon State.

Most recently, the researchers collected and dated almost four kilometers of drill cores from the floor of the gulf and the Alaskan continental shelf, revealing millions of years of geologic history.

“It turned out most sediments were younger than we anticipated, implying that erosion was higher than we expected,” said lead author and co-chief scientist Sean Gulick of the University of Texas Institute for Geophysics.

Mountain ranges form when tectonic plates thrust into one another over millions of years and scrunch up the Earth’s outer crust. But even as mountains are built by these titanic forces, other agents work to wear them down.

“About a million years ago, short, 40,000-year climate oscillations jumped into a new mode with stronger, 100,000-year long glacial cycles, and erosion of the mountains accelerated under attack from the ice,” Gulick said. “In fact, more rock was eroded than tectonics has replaced.”

Co-chief scientist John Jaeger of the University of Florida added: “People often see mountain ranges as permanent, but they aren’t really. If more rock is pushed in, they grow, and if more rock is eroded away, they shrink.”

Since the mid-Pleistocene, erosion rates have beaten tectonic inputs by 50 to 80 percent, demonstrating that climatic processes that ultimately drive the glaciers can outstrip mountain building over a span of a million years. The findings highlight the pivotal role climate fluctuations play in shaping Earth’s landforms.

“We were pleasantly surprised by how well we could establish ages of the sediment sequences and the composition of the sediment gave clear evidence of when the glaciation started and then expanded, in sync with global climate trends,” said co-author Mix of OSU’s College of Earth, Ocean, and Atmospheric Sciences.

“Only by drilling the sea floor where the sediment accumulates could we see these details in focus.”

The study was funded by the U.S. National Science Foundation and the Integrated Ocean Drilling Program.

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

Geological relics point to Nullarbor climate shift

“The pocket” and small caves of one of the pocket valleys on the Hampton Scarp. Credit: Matej Lipar

People travelling across the Nullarbor Plain nowadays would be used to the region’s arid nature but it may surprise some to learn that climate conditions along the Nullarbor were exactly the opposite approximately 3-5 million years ago.

La Trobe University researcher Dr Matej Lipar and Anton Melik Geographical Institute researcher Dr Mateja Ferk came to this conclusion after spending three years walking hundreds of kilometres along Nullarbor escarpments searching for clues about the region’s ancient hydrological history.

Their efforts bore fruit in the form of discovering 140 pocket valleys along the Hampton and Wylie scarps of the Nullarbor.

Pocket valleys are small steep-headed valleys formed by ancient underground water flows reaching an escarpment, pouring out of the underground system usually via a cave and then undermining the escarpment edge.

“We discovered the first real proof of pocket valley existence almost by accident” Dr Lipar says.

“We were sitting on an escarpment when we saw what looked like limestone rock but it was composed of big horizontally laminated crystals, showing that the rock had been originally formed in a cave—this was flowstone”.

Flowstone—sedimentary rock deposited by flowing water—at the head of a valley is one of the key indicators for a pocket valley as it shows its relationship to ancient caves and consequently indicate a wetter climate.

They also discovered sediments (alluvial fans) deposited at the base of the valleys by ancient high rainfall events during progressively drier climate as well as a calcrete layer on top of the sediment, suggesting the region became increasingly arid until the present day.

“We can tell by dating the flowstone when the Nullarbor was much more humid than today,” Dr Lipar says.

“The flowstone dating produced an average age of 3.6 million years which correlates well with other studies of stalagmites in the Nullarbor.”

While the sediments found at the base of the valleys were washed out of caves from high rainfall events which happened about one million years ago.

“The wash outs happen in a dryer period in which sporadic high rainfall events occur, so we can see about a million years ago the climate was becoming similar to the current climate, semi-arid with occasional high rainfall events,” Dr Lipar says.

Note: The above post is reprinted from materials provided by Science Network WA.

The world’s biggest volcano is a magnetic mix-up

Tamu Massif rises four kilometers from the seafloor. A 3D image shows various peaks that have formed over 145 million years. Credit: Scripps Oceanographic Institute/John Greene 

Earth’s biggest volcano, its peak nearly two kilometers beneath the Pacific Ocean waves, is beginning to reveal its secrets.

New magnetic data suggest that the gigantic underwater mountain known as Tamu Massif, 1,600 kilometers east of Japan, is a kind of volcanic hybrid—a mash-up of long chains of volcanoes and one enormous eruption. “We’re looking at something that’s in between a mid-ocean ridge and a simple conical volcano,” says William Sager, a marine geophysicist at the University of Houston. Mid-ocean ridges are where fresh lava wells up from deep inside Earth to create newborn ocean crust; they run for thousands of kilometers along the centers of most ocean basins.

Sager and his colleagues collected the new data on a five-week-long cruise that ended on November 10 onboard the R/V Falkor, a research vessel run by the Schmidt Ocean Institute of Palo Alto, Calif. The trip was the latest attempt to unravel the mysteries of this enormous volcano, and showed that its birth was more complex than scientists had suspected.

Covering an area roughly the size of New Mexico, Tamu Massif towers more than four kilometers above the seafloor. “This volcano is a beast,” says Jörg Geldmacher, a marine geophysicist at the GEOMAR Helmholtz Center for Ocean Research Kiel in Germany.

Tamu Massif’s size may trace back to the unusual circumstances of its origin. Around 145 million years ago lava began pouring out on the seafloor where three mid-ocean ridges came together in a geologic “triple junction.” Each ridge spewed out lava that cooled and preserved a record of the Earth’s magnetism at the time. Because the planet’s magnetic field has reversed direction many times over millions of years, the lava over time recorded stripes of alternating magnetic polarity on either side of the ridge where it was born.

Earlier research cruises had mapped hints of these magnetic stripes, by towing magnetic recording instruments behind ships as they sailed back and forth. But the information was spotty. Sager and Masao Nakanishi, a geophysicist at Chiba University in Japan, organized the Falkor cruise to gather the best magnetic data to date. They sailed up and back over Tamu Massif in an enormous grid covering nearly a million square kilometers.

Some 1.7 million magnetic measurements later, the scientists confirmed what they had only suspected earlier: Tamu Massif seems to have coherent magnetic stripes on either side of it, like those seen at seafloor spreading ridges. That suggests at least part of Tamu Massif was born from fresh lava welling up in orderly stripes at the geological triple junction.

The main mountain itself is more of a shapeless magnetic blob, however. That blobbiness suggests something else is also going on—perhaps a plume of hot rock rising from deep within Earth up through the mantle, fueling an eruption on the surface like a welder’s torch blasting upward. If so, then Tamu Massif is one of the few places on the planet where a mantle plume may have interacted with a triple junction, Geldmacher says.

The question is how much lava came from one as opposed to the other. “If you looked at a mid-ocean ridge and sliced it open, you’d find magma underneath,” Sager says. “How do you get a separate volcanic plumbing system at the same spot?”

The researchers still need to work through the Falkor data, but the new information should help unravel the mystery of the volcano’s birth, Nakanishi says. More broadly, Tamu Massif could help scientists better understand the volcanic phenomena that create the three fifths of Earth’s crust that lies beneath the oceans.

During the cruise, the Falkor also mapped Tamu Massif in unprecedented three-dimensional detail. Among other things it revealed a newfound small mountain off the west end. And steep cliffs at the base of Tamu Massif may represent places where it is subsiding into the seafloor or where underwater landslides occurred.

Video

Note: The above post is reprinted from materials provided by Nature. The original article was written by Scientific American.

3D imaging sheds new light on 250 million year old fossil

The University of Valencia leads a study that uses high-resolution imaging techniques to reinterpret fossilised bones first encountered in northeast Italy in 1989.

Fossils have long been a rich source of information on the animal species that inhabited the earth before us. Bones, teeth, prints and even excrement (known as fecal pellets) all form part of the fossil record studied by paleontologists. Exceptionally, the fossilised remains of animal bones regurgitated by other animals (gastric pellets) are also found, as is the case here: the study focuses on a rare gastric pellet found in 1989 near Preone (Udine, Italy) previously thought to contain the bones of a pterosaur reptile. However, 3D rendering techniques have recently revealed an affinity with a different reptile family, the protorosaurs.

Back in 1989 the remains were identified and reported as one of the very few cases of fossilised regurgitated pterosaur bones. Pterosaurs are a group of flying reptiles that lived during most of the Mesozoic Era (some 252 to 66 million years ago). The animal was likely hunted and eaten, albeit partially, by a large fish. Limited by technological capacity, its remains were ascribed to the only pterosaur known to have existed in this region, thePreondactylus buffarinii.

Researchers from the Institut Català de Paleontologia Miquel Crusafont (Miquel Crusafont Catalan Paleontology Institute, ICP) re-studied the remains using a technique called X-ray microtomography or X-ray microCT, which yields high-resolution 3D images. If an ordinary CT scan reveals information not visible from the outside, then here the detail was such that previously undetected anatomical features were identified, transforming the scientists’ interpretation of the contents of this gastric pellet: “The anatomical study of these images not only does not support the hypothesis that the bones belong to a pterosaur reptile, but also reveal a certain likeness with the protorosaur family. More specifically, with the Langobardisaurus pandolfii,” explains Borja Holgado, the main researcher behind this study. “The morphology of the extended vertebrae now identified as cervical and the articular facets (the surface where two bones meet) of the dorsal are the most striking features that led to this new interpretation,” he adds.

The protorosaurs are a group of reptiles with long necks similar to present-day lizards that lived between 260 and 210 million years ago, shortly before dinosaurs dominated all terrestrial ecosystems.

Researcher Fabio M. Dalla Vecchia, who also participated in this study, was one of the researchers who first analysed these remains in the nineties, attributing them to a pterosaur reptile. It was Dalla Vecchia himself who proposed the review. Hypothesising as to the origin of the pellet, he says: “This work confirms that it is a stomach regurgitation possibly produced by a large fish, as we identified in the first study.” The rocks where the fossil was found were confirmed to be of marine origin. However, there is no evidence of marine predator reptiles having inhabited either the immediate geological formation or in contemporary formations in the wider region. “This points to a fish as the best candidate for the regurgitation of these remains,” he concludes.

To clarify, the presence of a presumably terrestrial protorosaurian reptile in marine formations is not unusual. The fossil record in the study region includes abundant remains from land-based organisms, as well as organic matter of terrestrial origin. These flora and fauna would have lived in the vicinity of a water formation and been washed into it by natural phenomena such as tidal currents, storms or hurricanes.

Reference:
Borja Holgado, Fabio Marco Dalla Vecchia, Josep Fortuny, Federico Bernardini, Claudio Tuniz. A Reappraisal of the Purported Gastric Pellet with Pterosaurian Bones from the Upper Triassic of Italy. PLOS ONE, 2015; 10 (11): e0141275 DOI: 10.1371/journal.pone.0141275

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

Methane feeds subsea ice mounds off Siberia

This is the view of the subsea pingo features as the scientists see them. The pingos were discovered during a seismic survey of the area. They range from 70m to 1000m in diameter. Credit: P. Serov

Pingos are spectacular landforms associated with permafrost in the Arctic. They are circular or elliptical formations protruding from the level ground of the tundra, and can be up to 60 meters high. In essence, they are huge lumps of ice covered with soil. Similar structures are now found strewn on the ocean floor in the Arctic shallow seas.

A recent study by Pavel Serov, PhD at Center for Arctic Gas Hydrate, Environment and Climate (CAGE), describes for the first time pingo like features offshore Siberia. The study suggests that they are forming because of the thawing of the subsea permafrost, and was published in Journal of Geophysical Research.

“Pingos are intensively discussed in the scientific community especially in the context of global climate warming scenarios. They may be the step before the methane blows out.” says Serov.

In the area of Yamal peninsula craters

Pingos came to public attention because of the story of the mysterious craters that suddenly appeared in Yamal Peninsula, Siberia. There is a theory that the craters may have been pingos. Beneath them the methane gas accumulated. The pressure built up under the ice lump due to the thawing of the permafrost and reactivated production of methane in the soil. The whole feature then blew up in one event releasing unknown amounts of gas.

Serov and colleagues focused on two subsea pingos that were identified offshore the very same area of the mysterious Yamal peninsula craters. The study shows how important methane accumulation is for the formation of subsea pingos. The study area lies in the shallow South Kara Sea, at approximately 40-meter water depth. Serov and colleagues, present in their paper a range of scenarios for the formation of the mounds, leading to potential blowouts of methane.

“Our question was: Are these mounds submerged terrestrial pingos? Or are they something different forming under marine conditions? One of the South Kara Sea pingos was leaking a lot of methane but where was the methane coming from?”

But as the CAGE study shows these newly discovered subsea pingos may be quite recent. This lends support to another hypotheses, the one that states that mechanisms that form pingos on land and mechanisms that form mounds on the ocean floor are completely different.

“The subsea-pingo like formations are significantly larger than the ones on land. Gas leakage from one of the ocean floor pingos offshore Siberia shows a specific chemical signature that indicates modern generation of methane. We suggest that the mound formed more recently, moving material physically upwards.”

A short glacial history lesson of Arctic shallow seas

During the ice ages of late Pleistocene, which started some 1,8 million years ago, Arctic soil froze. Beneath a thick layer of permafrost deposits of gas hydrate, an icy substance that contains enormous amounts of methane, formed. Because of the growing inclusion of sea water in the ice sheet build up the sea level dropped simultaneously, and these Arctic shallow seas became land. However, when the latest of the ice ages ended, some 19 000 years ago, the glaciers melted. The frozen shelves were flooded and what once were landmasses became the ocean floor.

Several million square kilometers of permafrost submerged. And, when submerged, it started melting. The temperature of the salty ocean water was warm and thus well above the freezing temperatures of terrestrial Siberia that maintain the permafrost. But we still find permafrost on the ocean floor. It acts as an impermeable cap over large deposits of methane beneath the presently warming ocean.

As permafrost extends into the ocean so do the pingos. They even appear in geographical proximities to the ones observed on land. An early study suggested that these pingos formed on land during the glacial period, and are therefore relics from the ice age, just like the Arctic subsea permafrost.

“The average ocean temperature is much warmer than Siberia, initially suggesting that the formation of subsea pingos could not be recent, as anticipated for pingos in cold Siberian environments. “ says CAGE director, prof. Jürgen Mienert, a co-author on the paper.

Thawing of permafrost and pressure from methane

But as the CAGE study shows these newly discovered subsea pingos may be quite recent. This lends support to another hypotheses, the one that states that mechanisms that form pingos on land and mechanisms that form mounds on the ocean floor are completely different.

“The subsea-pingo like formations are significantly larger than the ones on land. Gas leakage from one of the ocean floor pingos offshore Siberia shows a specific chemical signature that indicates modern generation of methane. We suggest that the mound formed more recently, moving material physically upwards.”

Dissociation of methane ice

On land pingos are mainly formed when the water freezes into an ice core under soil, because of the chilling temperatures of permafrost. However, subsea pingos, may be formed because of the thawing of relict subsea permafrost and dissociation of methane rich gas hydrates.

Gas hydrates are ice-like solids composed of among other things methane and water. They form and remain stable under a combination of low temperature and high pressure. In permafrost the temperatures are very low and gas hydrates are stable even under the low pressure, such as on shallow Arctic seas. Thawing of permafrost leads to temperature increases, which in turn leads to melting of gas hydrates, therefore, releasing the formerly trapped gas.

“ The methane creates the necessary force that pushes the remaining frozen sediment layers upward, forming mounds.” says Serov.

Quiet explosions beneath the Arctic shallow seas

Subsea pingos can potentially blow out, without massive attention, as was the case with the highly visible Yamal craters, but with massive expulsions of methane into the ocean. For petroleum companies these areas may pose a geohazard. Drilling a hole into one of these subsea pingos, can be not only expensive but also catastrophic. During a geotechnical drilling in the close by Pechora Sea, an industry vessel unknowingly drilled a hole into one of these mounds. It triggered a massive release of gas that almost sunk the vessel.

“We don´t know if the methane expelled from the subsea pingos reaches the atmosphere, but it is crucial that we observe and understand these processes better, especially in shallow areas, where the distance between the ocean floor and the atmosphere is short.” says Serov.

Video

Russian scientists have explored a newly-formed and mysterious crater in Siberia. Theу hope their research will shed light on the origin of the hole in the land that locals call ‘the end of the world.’

Reference:
Pavel Serov, Alexey Portnov, Jurgen Mienert, Peter Semenov, Polina Ilatovskaya. Methane release from pingo-like features across the South Kara Sea shelf, an area of thawing offshore permafrost. Journal of Geophysical Research: Earth Surface, 2015; 120 (8): 1515 DOI: 10.1002/2015JF003467

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

A whiff from blue-green algae likely responsible for Earth’s oxygen

Photo credit: Mableen/iStock 

Earth’s oxygen-rich atmosphere emerged in whiffs from a kind of blue-green algae in shallow oceans around 2.5 billion years ago, according to new research from Canadian and US scientists.

These whiffs of oxygen likely happened in the following 100 million years, changing the levels of oxygen in Earth’s atmosphere until enough accumulated to create a permanently oxygenated atmosphere around 2.4 billion years ago – a transition widely known as the Great Oxidation Event.

“The onset of Earth’s surface oxygenation was likely a complex process characterized by multiple whiffs of oxygen until a tipping point was crossed,” said Brian Kendall, a professor of Earth and Environmental Sciences at the University of Waterloo. “Until now, we haven’t been able to tell whether oxygen concentrations 2.5 billion years ago were stable or not. These new data provide a much more conclusive answer to that question.”

The findings are presented in a paper published this month in Science Advances from researchers at Waterloo, University of Alberta, Arizona State University, University of California Riverside, and Georgia Institute of Technology. The team presents new isotopic data showing that a burst of oxygen production by photosynthetic cyanobacteria temporarily increased oxygen concentrations in Earth’s atmosphere.

“One of the questions we ask is: ‘did the evolution of photosynthesis lead directly to an oxygen-rich atmosphere? Or did the transition to today’s world happen in fits-and-starts?” said Professor Ariel Anbar of Arizona State University. “How and why Earth developed an oxygenated atmosphere is one of the most profound puzzles in understanding the history of our planet.”

The new data supports a hypothesis proposed by Anbar and his team in 2007. In Western Australia, they found preliminary evidence of these oxygen whiffs in black shales deposited on the seafloor of an ancient ocean.

The black shales contained high concentrations of the elements molybdenum and rhenium, long before the Great Oxidation Event.

These elements are found in land-based sulphide minerals, which are particularly sensitive to the presence of atmospheric oxygen. Once these minerals react with oxygen, the molybdenum and rhenium are released into rivers and eventually end up deposited on the sea floor.

In the new paper, researchers analyzed the same black shales for the relative abundance of an additional element: osmium. Like molybdenum and rhenium, osmium is also present in continental sulfide minerals. The ratio of two osmium isotopes – 187Os to 188Os – can tell us if the source of osmium was continental sulfide minerals or underwater volcanoes in the deep ocean.

The osmium isotope evidence found in black shales correlates with higher continental weathering as a result of oxygen in the atmosphere. By comparison, slightly younger deposits with lower molybdenum and rhenium concentrations had osmium isotope evidence for less continental input, indicating the oxygen in the atmosphere had disappeared.

Reference:
Transient episodes of mild environmental oxygenation and oxidative continental weathering during the late Archean, Science Advances, DOI: 10.1126/sciadv.1500777

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

Ancient fossil forest unearthed in Arctic Norway

Reconstructed drawing of fossil forest in Svalbard. Credit: Image courtesy of Cardiff University

UK researchers have unearthed ancient fossil forests, thought to be partly responsible for one of the most dramatic shifts in Earth’s climate in the past 400 million years.

The fossil forests, with tree stumps preserved in place, were found in Svalbard, a Norwegian archipelago situated in the Arctic Ocean. They were identified and described by Dr Chris Berry of Cardiff University’s School of Earth and Ocean Science.

Prof John Marshall, of Southampton University, has accurately dated the forests to 380 million years.

The forests grew near the equator during the late Devonian period, and could provide an insight into the cause of a 15-fold reduction in levels of carbon dioxide (CO2) in the atmosphere around that time.

Current theories suggest that during the Devonian period (420-360 million years ago) there was a huge drop in the level of CO2 in the atmosphere, thought to be largely caused by a change in vegetation from diminutive plants to the first large forest trees.

Forests pulled CO2 out of the air through photosynthesis — the process by which plants create food and tissues — and the formation of soils.

Although initially the appearance of large trees absorbed more of the sun’s radiation, eventually temperatures on Earth also dropped dramatically to levels very similar to those experienced today because of the reduction in atmospheric CO2.

Because of the high temperatures and large amount of rainfall on the equator, it is likely that equatorial forests contributed most to the drawdown of CO2. Svalbard was located on the equator around this time, before the tectonic plate drifted north by around 80° to its current position in the Arctic Ocean.

“These fossil forests shows us what the vegetation and landscape were like on the equator 380 million years ago, as the first trees were beginning to appear on Earth,” said Dr Berry.

The team found that the forests in Svalbard were formed mainly of lycopod trees, better known for growing millions of years later in coal swamps that eventually turned into coal deposits — such as those in South Wales. They also found that the forests were extremely dense, with very small gaps — around 20cm — between each of the trees, which probably reached about 4m high.

Dr Berry had previously worked with American colleagues to describe another slightly older forest, at Gilboa in upstate New York. The Gilboa forest was located at least 30° south of the equator at that time, and the tree stumps in place belonged to different types of plants.

“This demonstrates that there was already geographical diversity of forest plant types and ecology just as soon as they had evolved,” Dr Berry continued.

“During the Devonian Period, it is widely believed that there was a huge drop in the level of carbon dioxide in the atmosphere, from 15 times the present amount to something approaching current levels.

“The evolution of tree-sized vegetation is the most likely cause of this dramatic drop in carbon dioxide because the plants were absorbing carbon dioxide through photosynthesis to build their tissues, and also through the process of forming soils.”

Svalbard is currently one of the most northernmost inhabited areas in the world with a population of around 2,500.

Svalbard now plays host to the ‘Global Seed Vault’ — a secure, underground frozen seed bank in which a large variety of plant seeds are preserved. The vault functions to provide a safety net against a loss of diversity in a global crisis.

“It’s amazing that we’ve uncovered one of the very first forests in the very place that is now being used to preserve the Earth’s plant diversity,” continued Dr Berry.

The new findings have been published today in the journal Geology.

Reference:
C. M. Berry, J. E. A. Marshall. Lycopsid forests in the early Late Devonian paleoequatorial zone of Svalbard. Geology, 2015; 43 (12): 1043 DOI: 10.1130/G37000.1

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

Fossil fireworm species named after rock musician

The fossil fireworm Rollinschaeta myoplena is from the Cretaceous of Lebanon, preserving muscle tissue, which fluoresce white under UV light. Researchers from the University of Bristol, UK, who discovered this muscly creature named it after the legendary muscular frontman of punk band Black Flag, Henry Rollins Credit: Luke Parry/University of Bristol

A muscly fossil fireworm, discovered by scientists from the University of Bristol and the Natural History Museum, has been named Rollinschaeta myoplena in honour of punk musician and spoken word artist, Henry Rollins.

The fossil worm is a polychaete annelid, a marine relative of earthworms and leeches. Polychaetes are entirely soft bodied and thus seldom occur as fossils. When conditions are right, however, some remarkable and surprising details of such creatures can be preserved, as in the case of Rollinschaeta which is preserved mostly as three dimensional muscle tissue.

Bristol PhD student Luke Parry, one of the researchers who made the discovery, said: “Fossil muscle tissue is rare and usually not described in any detail by palaeontologists, but our discovery highlights that soft tissues preserved in fossils can offer details approaching what we can observe in living organisms. When choosing a name for our muscly beast, we decided to honour Henry Rollins, the legendary, muscular frontman of LA punk band Black Flag.”

The researchers were able to identify different muscle groups in Rollinschaeta as the creature’s muscles were replicated by the mineral apatite soon after its death. Using CT scanning, the scientists investigated the three dimensional arrangement of muscles in living annelids to compare them with Rollinschaeta.

Surprisingly, it was possible to determine, based only on its muscles, that Rollinschaeta is a member of the fireworms (Amphinomidae) whose living representatives are common predators on coral reefs and whose segments bear abundant stinging bristles from which they get their name.

Co-author of the study, Dr Jakob Vinther of Bristol’s School of Earth Sciences said: “While carrying out the research, we informally referred to the creature as ‘the muscle worm’ due to its preservation in almost pure muscle. Part of the reason why it’s preserved so well by muscle is that it was, in real life, a very buff little worm. Fireworms are active during the daytime on coral reefs and other environments with strong currents which makes them much more muscular compared to most other bristle worms.”

The fossil fireworm Rollinschaeta myoplena from the Cretaceous of Lebanon, preserving muscle tissue, which fluoresce white under UV light Credit: Luke Parry/University of Bristol

The study also highlights a major bias in soft tissue preservation. “The Lebanese locality where Rollinschaeta fossils were found yields many other bristle worm species, but they usually don’t preserve any muscle tissue, except for tiny bits,” said co-author Paul Wilson, a recently graduated MSc student from Bristol, now a PhD student at the University of Warwick. “Therefore, we have illustrated a clear variation in the propensity for muscle tissue preservation which shows that not all organisms have the right composition for all sorts of exceptional preservation.”

Greg Edgecombe of the Natural History Museum, co-author of the study, said: “This is the first time that any fossil has been identified by its muscle anatomy. It’s probably more of a curiosity due to the exceptional composition and muscularity of this fireworm rather than something we might expect to turn up in the fossil record a lot. But it does show that when muscles get preserved, we can get a lot of information about extinct animals from them.”

The research is published this week in BMC Evolutionary Biology.

Reference:
‘A new fireworm (Amphinomidae) from the Cretaceous of Lebanon identified from three-dimensionally preserved myoanatomy’ by Parry, L.A., Wilson, P., Sykes, D., Edgecombe, G.D. and Vinther, J. in BMC Evolutionary Biology. DOI:10.1186/s12862-015-0541-8

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

A new look at an old jaw clarifies mammal evolution

Surveying the site: Two decades ago in Greenland, Stephen Gatesy (black shirt), and colleagues Neil Shubin (green) and Farish Jenkins (tan) looked through thousands of limestone slabs in search of fossils. Credit: Mike Shapiro/University of Utah

On an expedition to Greenland in the summer of 1995 — their fifth season of digging in the tundra — a team including Stephen Gatesy, Neil Shubin, and Farish Jenkins had finally found something that might yield a clue about mammal evolution: A pair of one inch long jaws embedded in limestone.

“When I first picked up the cell-phone sized slab of rock containing the two jaws I could tell that it was something important — multi-rooted teeth with complex cusps were obvious, both advanced features,” recalled Gatesy, professor of ecology and evolutionary biology at Brown Unviersity. “But after finding the counter-slab — the matching rock containing more bone — nearby, we spent days looking for more with very little success. It was more than a bit anticlimactic because you can’t do much with a tiny specimen like that in the field; you wrap it up and wait to get it back to the lab.

“Once more details were revealed by manual preparation with fine needles under a microscope,” he said, “we realized that we’d found the first haramiyid fossil that was more than just isolated teeth. Having teeth together in jaws let us interpret their chewing motion and infer diet.”

Haramiyids, it turns out, were early precursors to mammals that lived 210 million years ago. The team’s interpretation, published in Nature in 1997, was that the fossil represented an example of proto-mammal diversification occurring well before the origin of “crown mammals.” Over the next 20 years, the idea proved to be a subject of considerable debate.

Now the team has published a new analysis in the Proceedings of the National Academy of Sciences, using technologies such as high-resolution computer tomography and 3-D computer reconstruction, that weren’t available two decades ago. Shubin’s lab at the University of Chicago led the work.

The analysis revealed complex teeth and chewing motions adapted for an herbivorous diet. This indicates that diverse feeding adaptations were evolving in the Triassic era among these proto-mammals. On the other hand, primitive structures of its jaw provided evidence that the species and its relatives were not “crown mammals,” which emerged later in the Jurassic era after the end-Triassic extinction event.

“Micro-CT scanning allowed extremely detailed 3-D models to be created of each tooth and bone,” Gatesy said. “We then combined evidence from all the material into a composite jaw. I don’t think this would have been possible without digital tools. Our anatomical conclusions largely corroborate the findings of our earlier paper but also increase our confidence in key characters.”

In other words, new technology allowed the team to make the most of the small, hard-earned find made after years of digging near the top of the world.

“It’s always satisfying when better methods come along to offer a fresh glimpse at old evidence,” Gatesy said. “I also found the revival of our old collaboration both nostalgic and bittersweet. Sadly, we lost two of our five co-authors within the last three years and they are sorely missed.”

Gatesy’s work goes on and he continues to be inspired by the team’s other findings in the Arctic.

“The dinosaur footprints we uncovered have changed the path of my career so that now fossil tracks are a major component of my research,” he said. “Although I haven’t been back to the Arctic since 2004, I’m actively looking at old and new sites with dinosaur footprints in the nearby Connecticut River Valley.”

In the classroom, meanwhile, Gatesy uses his basic research on anatomy across many creatures and hundreds of millions of years to help teach the gross anatomy class to first-year medical students.

In addition to Gatesy, Shubin and the late Jenkins, the paper’s other authors are lead author Zhe-Xi Luo, and the late William Amaral, another member of the original team.

Video

3D Reconstruction of the jaw of Haramiyavia, one of the earliest known proto-mammals, clarifies the debate over when mammals evolved. The study, published in the Proceedings of the National Academy of Sciences on Nov 16, 2015, confirms previous suggestions that mammal diversification occurred in the Jurassic around 175 million years ago—more than 30 million years after Haramiyavia and other forerunners to mammals diversified in the Triassic.

Reference:
Zhe-Xi Luo, Stephen M. Gatesy, Farish A. Jenkins, Jr., William W. Amaral, and Neil H. Shubin. Mandibular and dental characteristics of Late Triassic mammaliaform Haramiyavia and their ramifications for basal mammal evolution. DOI: 10.1073/pnas.1519387112

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

New element tracking method a boon for geoscientists

Thea Whitman collects samples from experimental plots at Cornell’s Mount Pleasant research farm. 

Geoscientists track how elements cycle across land, air and water to better understand climate change, ecological food webs and resources, plant nutrient cycling, water use and for forensics purposes.

But until now, they have only been able to parse inputs of such elements as carbon or nitrogen in a system when there are two sources. Yet many natural systems may have three or more interdependent sources, leaving researchers unable to separate inputs from one source to another, and hindering them from understanding how sources may interact with each other to affect overall carbon or nitrogen cycling in that system.

A Cornell study in the Nov. 4 issue of Nature Communications describes a new method that allows geoscientists to tease out the exact inputs from three different sources.

“It is important for understanding greenhouse gas emissions, microbial interactions, sources of leaching of nutrients into a river, when we have three sources where an element can come from,” said Johannes Lehmann, professor of soil and crop sciences, and a co-author of the paper. Thea Whitman, Ph.D. ’14, a former graduate student in Lehmann’s lab, is the paper’s first author.

Whitman and Lehmann developed their method to quantify inputs from three sources by doing experiments on soil carbon dioxide emissions from the interaction of microbial mineralization of soil organic carbon, root respiration and biochar, which they added to the system.

To measure carbon from two sources, for example, researchers look within sources for signatures of two isotopes of carbon, which are species of carbon with different atomic weights. In this way, researchers may run simple equations to derive the carbon inputs from each source. But such equations using two isotopes don’t work with three sources.

With three sources, the researchers created a second plot experiment identical to the original plot, except they altered one of the sources such that compared to the first experiment, it had a different isotope ratio (the ratio between carbon 12 and carbon 13 within the source sample, for example). For instance, in a scenario where the researchers test carbon emissions from soil, compost and a plant, the researchers might add compost in the second plot that has 10 percent of the heavier isotope, compared to 5 percent in the original sample.

With distinct measurements from all three sources, the rest is algebra.

In the study, the researchers used this new method to determine that the presence of plant roots decreased carbon dioxide losses from soil organic carbon when biochar was added to soil. This effect would have remained undetected without the new method. Such interactions between roots, soil organic carbon and organic amendments are important for current efforts to sequester carbon in soils as a way to mitigate climate change, Lehmann said.

Reference:
Thea Whitman et al. A dual-isotope approach to allow conclusive partitioning between three sources, Nature Communications (2015). DOI: 10.1038/ncomms9708

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

‘Trigger debate’ over Indonesian mud volcano sheds light on dynamics of disasters

In May 2006, an underground mud volcano erupted in the East Java province of Indonesia, displacing more than 40,000 people as boiling hot mud swept into their fields and villages.

The Lapindo mudflow became one of Indonesia’s most controversial disasters as a gas exploration company and the Indonesian government debated for years over whether drilling or an earthquake hundreds of kilometers away caused the volcano to overflow.

Meanwhile, thousands of people whose homes and property were destroyed were left in limbo without compensation as this episode of scientific contention played out, said Phillip Drake, University of Kansas assistant professor of English, who studies the intersection of science and rhetoric surrounding environmental disasters.

“It was interesting to learn more about people who were trying to survive in the face of political, economic and social uncertainty without access to some of the tools or support systems that we take for granted here,” said Drake, author of the article “Multiple visions of Indonesia’s mud volcano: Understanding representations of disaster across discursive settings,” which was recently published online in the journal Disasters.

The “trigger debate” of the Lapindo mudflow centered around whether the cause was human error—the unsafe drilling in a gas exploration mine 150 meters from the center of the mudflow—or natural forces—a massive earthquake two days earlier in Yogyakarta about 200 kilometers away. The debate would decide fault and determine who would coverage monetary damages and likely bear the brunt of legal retribution.

The drilling company, Lapindo Brantas, and the government together presented sets of geological experts that interpreted the data in ways that support the company’s interests and differ from interpretations by most international experts.

“One major factor precluding scientific consensus is the influence of stakeholders who are—or at least perceived to be—mobilizing contested science to promote or protect their interests,” Drake said.

The trigger debate over the Lapindo mudflow is important on a broader level, Drake said, especially regarding issues related to global warming and as the use of hydraulic fracturing spreads through the United States and the world, which has forced questions to arise about the contested representations of energy science, pollution, companies, activists and residents.

He said it is important to focus on the human element of disaster and think beyond nature as the primary cause of disaster.

“It’s easy to naturalize it, and once you naturalize it and blame it on nature, the automobile industry is off the hook. Coal mines are off the hook. You have companies involved in deforestation that are off the hook as well,” Drake said. “It’s a useful way to blame nature to mask environmental atrocities that are occurring.”

Oftentimes as well, disasters emerge through “slow violence,” as human decisions and relationships contribute to environmental conditions that can cause a disaster. Frequently, such a disaster disproportionately affects poor people who live close to hazards, like a coast in a seismically active region, a volcano or a nuclear power plant, he said.

“I would like people to think about disasters as not necessarily a single moment or a single event that occurs with a very distinct beginning and end, but it’s something that is always unfolding in time,” Drake said. “We are currently living and creating the conditions under which disaster will be felt or experienced in the future.”

Changing how we approach resolving conflicts about the cause of disasters and how victims are configured could have wide applications behind Indonesia, Drake said.

“This analytical expansion,” he said, “would involve the observation of broader historical, political, economic, cultural and geological factors.”

Reference:
Phillip Drake. Multiple visions of Indonesia’s mud volcano: understanding representations of disaster across discursive settings, Disasters (2015). DOI: 10.1111/disa.12145

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

When did the Andes mountains form?

Torres del Paine from Lake Pehoé, Torres del Paine National Park, Chile. Credit: Miguel Vieira

The Andes have been a mountain chain for much longer than previously thought, new research from the University of Bristol, UK suggests.

The Andes were formed by tectonic activity whereby earth is uplifted as one plate (oceanic crust) subducts under another plate (continental crust). To get such a high mountain chain in a subduction zone setting is unusual which adds to the importance of trying to figure out when and how it happened. However, the timing of when the Andean mountain chain uplift occurred has been a topic of some controversy over the past ten years.

The prevailing view is that the Andes became a mountain range between ten to six million years ago when a huge volume of rock dropped off the base of Earth’s crust in response to over-thickening of the crust in this region. When this large portion of dense material was removed, the remaining portion of the crust underwent rapid uplift.

The timing of such uplift is important in helping scientists to understand how mountains form, how they erode and what impact this may have on global atmospheric circulation patterns and climate.

To investigate the timing of Andean uplift, Dr Laura Evenstar from Bristol’s School of Earth Sciences used a new method based on cosmic rays that create a rare form of helium (cosmogenic He-3) in minerals at Earth’s surface. The abundance of cosmogenic He-3 depends on the altitude of the surface and thus can be used to understand the altitude history of a rock surface.

With collaborators at Scottish Universities Environmental Research Centre and partially funded by BHP Billiton, Dr Evenstar analysed large boulders from 2km high in the western margin of the Andes. She has shown that the Andes were already near their present elevation 14 million years ago.

Dr Evenstar said: “It seems highly likely that the Andes have gone up slowly over at least the last 30 million years, and are the result of gradual thickening of the crust. This means that the uplift of the Andes probable effected large scale atmospheric circulation patterns at least 4 million years before previously thought.”

Reference:
Laura A. Evenstar, Finlay M. Stuart, Adrian J. Hartley, Brain Tattitch. Slow Cenozoic uplift of the western Andean Cordillera indicated by cosmogenic3He in alluvial boulders from the Pacific Planation Surface. Geophysical Research Letters, 2015; 42 (20): 8448 DOI: 10.1002/2015GL065959

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

Largest diamond in over century found in Botswana

A picture from the Lucara Diamond Corporation of the 1,111 carat gem quality, Type IIa diamond

A 1,111 carat “high quality diamond” has been discovered at a mine in Botswana, said to be the biggest find in more than a century, according to the mine company.

The gem, only second in size to the Cullinan diamond which was unearthered in South Africa in 1905, was mined by Lucara Diamond Corp.

“The magnificent stone, which originated from the south lobe of Lucara’s Karowe Mine, is the world second largest gem quality diamond ever recovered and largest ever to be recovered through a modern processing facility,” the Stockholm listed company said a statement.

Shares in Lucara shot up 34 percent to 14.2 kronor in morning Thursday trading in Stockholm.

Botswana is the world’s second biggest diamond producer, and Lucara said the gem was the largest ever to be recovered in the country.

“The significance of the recovery of a gem quality stone larger than 1,000 carats, the largest for more than a century….cannot be overstated,” said William Lamb, the President and chief executive of Lucara.

The 1,111 carat stone is the world’s second largest gem quality diamond ever recovered

The stone is yet to be evaluated, but commodities and mining analyst Kieron Hodgson, said it has “the potential to be one very expensive diamond.”

“Valuation will depend on potential inclusions, how it would behave in cutting, optimal shape as well as final colour,” he told AFP.

“All these things will need to be evaluated prior to bidding.”

The biggest diamond discovered is the 3,106-carat Cullinan, found near Pretoria in South Africa in 1905.

It was cut to form the Great Star of Africa and the Lesser Star of Africa, which are set in the Crown Jewels of Britain.

Lucara indicated on its website that the Karowe Mine had also this week turned up further finds—an 813 carat stone and a 374 carat stone, prompting Lamb to laud “an amazing week” for the company.

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

New theory on Earth’s biggest mystery

The end of the Devonian period around 359 million years ago saw the extinction of major groups like the placoderm fishes.

A new theory suggests depletion of trace elements in the oceans was a factor in three major mass extinction events in the past 600 million years, according to new research led by Flinders University’s Professor John Long.

While some of these events around the five mass extinction events in this timeframe have been well studied, such as the killer asteroid that wiped out the dinosaurs 66 million years ago, others are more enigmatic and entertain a variety of possible causes, according to the Flinders Strategic Professor in Palaeontology.

“Although there are other explanations to be considered, the possibility that the severe depletion of trace elements in the oceans was a factor in these extinctions has never been put forward before. The implications are vital for understanding our planet’s future,” says Professor Long.

“Without adequate supplies of trace element nutrients in our seas, life can go extinct.

“We need to better understand the cycles of oceanic nutrients to make sure such events do not occur in the future.”

The groundbreaking research, published in the journal Gondwana Research this month, shows that three of the major mass extinction events may have been caused by severe depletion of trace elements necessary for life in the Earth’s oceans.

Using a new data set of trace element abundances compiled by the University of Tasmania (UTAS), the research team discovered that selenium and other trace elements reached critical low points at the end of the Ordovician period (c.455 million years ago), at the end of the Devonian period (about 359-370 million years ago) and at the end of the Triassic period (about 200 million years ago).

“This research offers a plausible new scenario for how these devastating mass extinction events might have developed,” Professor Long says.

The research was carried out by developing a new set of analyses using more than 1800 marine rock samples taken from around the globe, spanning the past 3.5 billion years and measuring extremely low levels of trace element abundance with great accuracy.

“Our research team at UTAS have used laser analytical techniques to measure selenium concentrations in marine pyrite, which has grown on the ocean floors over the last 600 million years,” says co-author of the study Professor Ross Large, from the University of Tasmania.

“Trace elements like zinc, selenium, copper, cobalt, manganese and selenium, in particular, are required for life in doses that have a very specific tolerance range. Too much or too little selenium can be toxic,” says Professor Large.

“Today’s oceans contain about 155 ppt of selenium in their surface waters, changing slightly with depth. Tolerance levels of selenium are known for phytoplankton, molluscs, fish, and many land animals and plants.

“Critically low levels of selenium in past oceans would have affected the survival of plankton, eventually leading to collapse of the food chains, and extinctions.”

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

From nanocrystals to earthquakes, solid materials share similar failure characteristics

When solid materials such as nanocrystals, bulk metallic glasses, rocks, or granular materials are slowly deformed by compression or shear, they slip intermittently with slip-avalanches similar to earthquakes. Credit: University of Illinois

Apparently, size doesn’t always matter. An extensive study by an interdisciplinary research group suggests that the deformation properties of nanocrystals are not much different from those of Earth’s crust.

“When solid materials such as nanocrystals, bulk metallic glasses, rocks, or granular materials are slowly deformed by compression or shear, they slip intermittently with slip-avalanches similar to earthquakes,” explained Karin Dahmen, a professor of physics at the University of Illinois at Urbana-Champaign. “Typically these systems are studied separately. But we found that the scaling behavior of their slip statistics agree across a surprisingly wide range of different length scales and material structures.”

“Identifying agreement in aspects of the slip statistics is important, because it enables us to transfer results from one scale to another, from one material to another, from one stress to another, or from one strain rate to another,” stated Shivesh Pathak, a physics undergraduate at Illinois, and a co-author of the paper, “Universal Quake Statistics: From Compressed Nanocrystals to Earthquakes,” appearing in Scientific Reports. “The study shows how to identify and explain commonalities in the deformation mechanisms of different materials on different scales.

“The results provide new tools and methods to use the slip statistics to predict future materials deformation,” added Michael LeBlanc, a physics graduate student and co-author of the paper. “They also clarify which system parameters significantly affect the deformation behavior on long length scales. We expect the results to be useful for applications in materials testing, failure prediction, and hazard prevention.”

Researchers representing a broad a range of disciplines–including physics, geosciences, mechanical engineering, chemical engineering, and materials science–from the United States, Germany, and the Netherlands contributed to the study, comparing five different experimental systems, on several different scales, with model predictions.

As a solid is sheared, each weak spot is stuck until the local shear stress exceeds a random failure threshold. It then slips by a random amount until it re-sticks. The released stress is redistributed to all other weak spots. Thus, a slipping weak spot can trigger other spots to fail in a slip avalanche.

Using tools from the theory of phase transitions, such as the renormalization group, one can show that the slip statistics of the model do not depend on the details of the system.

“Although these systems span 13 decades in length scale, they all show the same scaling behavior for their slip size distributions and other statistical properties,” stated Pathak. “Their size distributions follow the same simple (power law) function, multiplied with the same exponential cutoff.”

The cutoff, which is the largest slip or earthquake size, grows with applied force for materials spanning length scales from nanometers to kilometers. The dependence of the size of the largest slip or quake on stress reflects “tuned critical” behavior, rather than so-called self-organized criticality, which would imply stress-independence.

“The agreement of the scaling properties of the slip statistics across scales does not imply the predictability of individual slips or earthquakes,” LeBlanc said. “Rather, it implies that we can predict the scaling behavior of average properties of the slip statistics and the probability of slips of a certain size, including their dependence on stress and strain-rate.”

Reference:
Jonathan T. Uhl, Shivesh Pathak, Danijel Schorlemmer, Xin Liu, Ryan Swindeman, Braden A. W. Brinkman, Michael LeBlanc, Georgios Tsekenis, Nir Friedman, Robert Behringer, Dmitry Denisov, Peter Schall, Xiaojun Gu, Wendelin J. Wright, Todd Hufnagel, Andrew Jennings, Julia R. Greer, P. K. Liaw, Thorsten Becker, Georg Dresen, Karin A. Dahmen. Universal Quake Statistics: From Compressed Nanocrystals to Earthquakes. Scientific Reports, 2015; 5: 16493 DOI: 10.1038/srep16493

Note: The above post is reprinted from materials provided by University of Illinois College of Engineering.

Melting Scandinavian ice provides missing link in Europe’s final Ice Age story

The site in Sweden where scientists located fossilised midges from a prehistoric lake. Credit: Barbara Wohlfarth, The University of Stockholm

Molecular-based moisture indicators, remains of midges and climate simulations have provided climate scientists with the final piece to one of the most enduring puzzles of the last Ice Age.

For years, researchers have struggled to reconcile climate models of the Earth, 13,000 years ago, with the prevailing theory that a catastrophic freshwater flood from the melting North American ice sheets plunged the planet into a sudden and final cold snap, just before entering the present warm interglacial.

Now, an international team of scientists, led by Swedish researchers from Stockholm University and in partnership with UK researchers from the Natural History Museum (NHM) London, and Plymouth University, has found evidence in the sediments of an ancient Swedish lake that it was the melting of the Scandinavian ice sheet that provides the missing link to what occurred at the end of the last Ice Age. The study, published in Nature Communications, today, examined moisture and temperature records for the region and compared these with climate model simulations.

Francesco Muschitiello, a PhD researcher at Stockholm University and lead author of the study, said: “Moisture-sensitive molecules extracted from the lake’s sediments show that climate conditions in Northern Europe became much drier around 13,000 years ago.”

Steve Brooks, Researcher at the NHM, added: “The remains of midges, contained in the lake sediments, reveal a great deal about the past climate. The assemblage of species, when compared with modern records, enable us to track how, after an initial warming of up to 4° Centigrade at the end of the last Ice Age, summer temperatures plummeted by 5°C over the next 400 years.”

Dr Nicola Whitehouse, Associate Professor in Physical Geography at Plymouth University, explained: “The onset of much drier, cooler summer temperatures, was probably a consequence of drier air masses driven by more persistent summer sea-ice in the Nordic Seas.”

According to Francesco Muschitiello the observed colder and drier climate conditions were likely driven by increasingly stronger melting of the Scandinavian ice sheet in response to warming at the end of the last Ice Age; this led to an expansion of summer sea ice and to changes in sea-ice distribution in the eastern region of the North Atlantic, causing abrupt climate change. Francesco Muschitiello added: “The melting of the Scandinavian ice sheet is the missing link to understanding current inconsistencies between climate models and reconstructions, and our understanding of the response of the North Atlantic system to climate change.”

Dr Francesco Pausata, postdoctoral researcher at Stockholm University, explained: “When forcing climate models with freshwater from the Scandinavian Ice Sheet, the associated climate shifts are consistent with our climate reconstructions.”

The project leader, Professor Barbara Wohlfarth from Stockholm University, concluded: “The Scandinavian ice sheet definitely played a much more significant role in the onset of this final cold period than previously thought. Our teamwork highlights the importance of paleoclimate studies, not least in respect to the ongoing global warming debate.”

Reference:
Muschitiello, F., Pausata, F.S.R., Watson, J.E., Smittenberg, R.H., Salih, A.A.M., Brooks, S.J., Whitehouse, N.J. Karlatou-Charalampopoulou, A., Wohlfarth, B. Fennoscandian freshwater control on Greenland hydroclimate shifts at the onset of the Younger Dryas. Nature Communications, 2015 (in press). DOI:10.1038/ncomms9939

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

The mighty dinosaurs were bugged by other critters

Even Tyrannosaurus rex had to deal with the smaller irritations in life. Credit: Pixabay/AnoviJoe, CC BY

Dinosaurs were the dominant group of terrestrial vertebrate animals for more than a hundred million years. Some of them grew to gargantuan sizes but even these mighty creatures would have fallen prey to parasites.

But when you look back on the geological record, parasite fossils are really rare. This is because fossilisation itself is a rare occurrence and most parasites are tiny, squishy things that don’t get preserved under anything less than the most ideal conditions.

Fortunately, there is growing interest in the study of fossil parasites, and there are some fossils which give us a glimpse at what kind of parasites infected dinosaurs.

One source of fossilised parasites is amber, which is fossilised tree sap. Some bits of amber can contain insects that became entrapped millions of years ago.

Trapped in the amber

In Michael Crichton’s novel Jurassic Park, and Steven Spielberg’s follow-up movie, dinosaurs were cloned from DNA that was extracted from amber-entombed insects that once fed on dinosaur blood.

Unlike in Jurassic Park though, the fossilised biting insects we find today do not contain intact dinosaur DNA, but they do contain fossils of parasites that might have infected dinosaurs.

Some biting midges from the Cretaceous were actually carrying malaria-type parasites in their gut much like the type found in modern birds and reptiles. So perhaps some dinosaurs might have contracted malaria and other such insect-borne diseases from those blood-suckers.

The internal organs of a dinosaur would have also been a cosy home for many internal parasites. In the Jurassic Park movie, Dr Ellie Sattler was up to her elbows in a Triceratops dung pile looking for traces of lilac berries.

If she had the opportunity to examine some of that sample under the microscope, it is likely she might have also found eggs of various parasitic worms.

While there are no Triceratops and other big dinosaurs roaming around today leaving convenient dung piles for us to examine, the next best thing we have is coprolite.

Dinosaur poop

Coprolite is simply the technical term for fossilised poop, and as any parasitologist or veterinarian knows, riffling through poop samples is a routine way for figuring out what parasites are found in an animal.

It was through examining samples of fossilised poop that scientists have found evidence for parasitic flukes and roundworms in dinosaurs.

So how big did these parasite get? Unfortunately, we can’t really tell from their eggs. Both giant tapeworms and tiny flukes start out life as microscopic eggs. It’s tempting to think massive creatures such as dinosaurs must have had massive parasites, but that’s not necessarily the case.

Today’s Great White Sharks are infected by tiny tapeworms, Humpback whales are covered in whale lice (which are actually crustaceans) that measures just a few millimetres long, and blood flukes that infect elephants are skinny worms that measure about a centimetre in length.

Some giant sauropod dinosaurs might have had giant tapeworms, but it is just as likely that their guts and other organs would have had been filled with millions of tiny roundworms and flukes.

Friend or foe

For a large animal, a colony of tiny worms are not much of a burden and in low numbers their impact is relatively low. But not all parasites are so benign.

For example, palaeontologists examining the jaw bones of tyrannosaurid dinosaurs have found pockmarks similar to those found in birds infected with a single-cell parasite call Trichomonas which causes debilitating lesions in their mouth and throat.

So the great Tyrannosaurus rex might have been afflicted with and succumbed to parasites similar to the ones that plague pigeons today.

Fossils allow us to put a minimum age on how long a particular group of parasites have been around, what host they infected, and how they compare with their living relatives.

Tapeworms had been infecting sharks back when the dominant land predators were saber-toothed proto-mammals called Gorgonopsians. Tongue worms (which today live in the respiratory tract of terrestrial vertebrates) were hanging out on the carapace of crustaceans during the Silurian period (about 425 million years ago) when the ocean was filled with giant sea scorpions.

When the dinosaurs came along, they simply presented new opportunities for potential parasites.

Given that parasites can often shape entire ecosystems through the effects they have on their hosts, it is important to keep in mind the roles parasites might have played in the prehistoric world.

There might be a Velociraptor which had been lagging behind in the pack because it had fallen ill from dino-malaria, or a Tyrannosaurus rex chomping on the rump of a Triceratops might have swallowed a whole load of parasitic worm larvae with every mouthful.

A Jurassic World full of dinosaurs is incomplete without its share of prehistoric parasites.

Note: The above post is reprinted from materials provided by The Conversation.
This story is published courtesy of The Conversation (under Creative Commons-Attribution/No derivatives).

High-tech analysis of proto-mammal fossil clarifies the mammalian family tree

This is an illustration of Haramiyavia, the earliest known proto-mammal (top). A 3-D reconstruction of the 210 million-year-old fossil jaw is superimposed (bottom). Credit: April Neander

A new analysis of the jaw of Haramiyavia clemmenseni, one of the earliest known proto-mammals, clarifies the timeline of early mammalian evolution. Through high-resolution computer tomography, scientists from the University of Chicago, Harvard University and Brown University were able to examine the Haramiyavia type specimen in unprecedented detail.

The analysis revealed complex teeth and chewing motions adapted for an herbivorous diet — indicating diverse feeding adaptations evolved early among proto-mammal lineages. But the primitive structures of its jaw, related to a primitive middle ear, suggest that Haramiyavia and its relatives were not mammals, and instead occupied a more ancestral position on the mammalian evolutionary tree.

The findings, published in the Proceedings of the National Academy of Sciences on Nov. 16, 2015, shed light on efforts to accurately date the period when major mammalian groups first evolved. The study confirms previous suggestions that mammal diversification occurred in the Jurassic around 175 million years ago — more than 30 million years after Haramiyavia and other forerunners to mammals diversified in the Triassic.

“This fossil is a unique representative from an incredibly important era in the evolution of mammals; the ecosystem of the whole world changed as the Triassic transitioned into the Jurassic,” said study senior author Neil Shubin, PhD, Robert R. Bensley Distinguished Service Professor of Organismal Biology and Anatomy at the University of Chicago. “When you look at the entirety of the Haramiyavia jaw and its primitive features, it’s clear that this group sat at the very base of the mammalian family tree, much in the same way that Tiktaalik rosea sat at the base of the tetrapod tree.”

Haramiyids are one of the earliest proto-mammal lineages, arising in the Triassic period around 210 million years ago. Known only through isolated teeth, haramiyids were largely mysterious until the discovery of the remarkably well-preserved jaw of Haramiyavia — with intact molars, nearly complete mandibles and postcranial skeletal bones–in Greenland in 1995 by a team including Shubin, Stephen Gatesy, professor of biology at Brown University, and the late Farish Jenkins, former professor of zoology at Harvard University.

“As the earliest known haramiyid, Haramiyavia is the key piece of evidence for inferences about the timeline of early mammalian evolution,” said study co-author Zhe-Xi Luo, PhD, professor of organismal biology and anatomy at the University of Chicago.

A 30-million-year question

The initial analysis of Haramiyavia relied on painstaking manual preparation by the late William Amaral, former fossil preparator at Harvard University, and significant portions of the fossil were not fully described.

This gap in knowledge led to a debate over the shape of the mammalian evolutionary tree: Did haramiyids belong on the crown mammal branch, from which all modern mammals descend, suggesting that mammals began to diversify more than 210 million years ago in the Triassic? Or did haramiyids occupy a separate, more ancestral branch at the base of the family tree, suggesting mammal diversification occurred much later?

To resolve this question, Shubin, Gatesy, and Luo, reexamined the entirety of the Haramiyavia specimen using a suite of modern technological tools, including high-resolution computed tomography (CT) scans and 3D reconstruction. Coupled with exhaustive documentation from the initial fossil preparation, the team was able to describe Haramiyavia in unprecedented detail.

The team found many primitive structures in the jaw, including a postdentary trough that is connected to a primitive middle ear. This was strong evidence that Haramiyavia was unrelated to other crown mammals — in particular, the multituberculates, a group of early mammal that has previously been thought to be closely related to the haramiyids.

This finding places Haramiyavia and all other members of the haramiyid lineage on a more ancestral position in the mammalian evolutionary tree, on a separate branch from mammals. This reaffirms previous arguments that the explosion of modern mammal diversification did not occur in the Triassic period, but many millions of years later in the Jurassic.

“With CT and other new technologies, we can extract anatomical insights that were not possible to obtain in the past, allowing us to more accurately interpret mammalian evolution,” Luo said. “Haramiyavia establishes the ancestral morphology for the haramiyid group, which can now be clearly placed at the base of the mammalian family tree.”

The team also created virtual animations that showed how the teeth of Haramiyavia actually functioned 210 million years ago. Analyses with scanning electron microscopy revealed Haramiyavia possessed complex teeth that indicated an herbivorous diet, including incisors for cutting and complex cheek teeth for grinding plant food. Later herbivorous mammals evolved similar complex teeth, despite not being directly descended from the haramiyids — a striking example of convergent evolution.

The feeding habits made Haramiyavia the earliest known herbivore among mammalian ancestors and placed them apart from other early proto-mammal groups, which had teeth adapted to insect or worm-based diets. This suggests that the early forerunners to mammals diversified in the Triassic, branching out into multiple ecological niches that likely shaped later mammalian evolution.

“When we worked on the Haramiyavia fossil in the 90s, we had to literally scrape at it with a needle under a microscope. It took months to years to come up with sketches and clay models,” Shubin said. “It’s really fun for me to see how it worked back then, and today study the fossil with computer reconstructions and 3D printed models. It’s an amazing demonstration of how new technology can transform an old discovery.”

Reference:
Zhe-Xi Luo, Stephen M. Gatesy, Farish A. Jenkins Jr., William W. Amaral, and Neil H. Shubin. Mandibular and dental characteristics of Late Triassic mammaliaform Haramiyavia and their ramifications for basal mammal evolution. PNAS, November 16, 2015 DOI: 10.1073/pnas.1519387112

Note: The above post is reprinted from materials provided by University of Chicago Medical Center.

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