This is a life restoration of adult Protoceratops andrewsi in the foreground engaging in speculative display postures. Non-mature animals can be seen in the background. Credit: Rebecca Gelernter / QMUL
Large ornamental structures in dinosaurs, such as horns and head crests are likely to have been used in sexual displays and to assert social dominance, according to a new analysis of Protoceratops carried out by scientists at Queen Mary University of London (QMUL).
This is the first time scientists have linked the function of anatomy to sexual selection in dinosaurs.
Protoceratops had a large bony frill that extended from the back of the head over the neck. Study of fossils aged from babies to adults revealed the adults to have disproportionately larger frills in relation to their size. The research, published in the journal Palaeontologia Electronica, shows that the frill was absent in juveniles and suddenly increased in size as the animals reached maturity suggesting that its function is linked to sexual selection.
This suggests the frill might have been used to attract suitable mates by showing off their best attributes or helping them assert the most dominant position in social interactions.
Dr David Hone, lecturer in Zoology from QMUL’s School of Biological and Chemical Sciences, said: “Palaeontologists have long suspected that many of the strange features we see in dinosaurs were linked to sexual display and social dominance but this is very hard to show. The growth pattern we see in Protoceratops matches that seen for signalling structures in numerous different living species and forms a coherent pattern from very young animals right through to large adults.”
The researchers assessed the change in length and width of the frill over four life stages: hatchling babies, young animals, near-adults, and adults. Not only did the frill change in size but it also changed in shape, becoming proportionally wider as the dinosaur became older.
Dr Rob Knell, Reader in Evolutionary Ecology, also from QMUL’s School of Biological and Chemical Sciences, said: “Biologists are increasingly realising that sexual selection is a massively important force in shaping biodiversity both now and in the past. Not only does sexual selection account for most of the stranger, prettier and more impressive features that we see in the animal kingdom, it also seems to play a part in determining how new species arise, and there is increasing evidence that it also has effects on extinction rates and on the ways by which animals are able to adapt to changing environments.”
The research formed part of current postgraduate student and QMUL graduate Dylan Wood’s undergraduate thesis, which looked at sexual selection in extinct species.
There are numerous, well-preserved specimens of ceratopisian dinosaurs of various sizes and ages making them a good groups to analyse. The researchers analysed 37 specimens of Protoceratops from fossils found in the Djadochta Formation in the Gobi desert and from previous published research. Protoceratops was a small-horned dinosaur that was similar in size to a sheep and was around 2m in total length from snout to tail tip.
Reference:
David W. E. Hone, Dylan Wood, and Robert J. Knell. Positive allometry for exaggerated structures in the ceratopsian dinosaur Protoceratops andrewsi supports socio-sexual signaling. Palaeontologia Electronica, 2016, palaeo-electronica.org/content/2016/1369-sexual-selection-in-ceratopsia
Credit: NASA Earth Observatory maps by Joshua Stevens, using data from Sandwell, D. et al. (2014)
An international scientific team recently published a new map of the ocean floor based on Earth’s gravity field, and it is a particularly useful tool. Such seafloor maps can aid submariners and ship captains with navigation, particularly in previously uncharted areas. They are helpful to prospectors scouting for oil, gas, and mineral resources. And the maps comprise nearly 80 percent of the seafloor that you see when you scroll through Google Earth.
But where the seafloor gravity maps may be most useful, according to Dietmar Müller, is in deciphering the evolution of Earth’s continents and tectonic plates. “Detailed maps of the seafloor are a powerful tool for scientists to investigate how and why the underwater features are formed,” said Müller, a geophysicist at the University of Sydney. “Ocean basins are created by motions of the tectonic plates over tens of millions of years. When continents break apart, the story of their separation is recorded in the ocean floor that forms between them.”
The map above shows seafloor gravity anomalies in the western Indian Ocean, as assembled by David Sandwell of the Scripps Institution of Oceanography, Walter Smith of the National Oceanic and Atmospheric Administration, and colleagues. Shades of orange and red represent areas where seafloor gravity is stronger (in milligals) than the global average, a phenomenon that mostly coincides with the location of underwater ridges, seamounts, and the edges of Earth’s tectonic plates. The darkest shades of blue represent areas with the lowest gravity, corresponding to the deepest troughs and trenches in the ocean.
The maps were created through computer analysis and modeling of new satellite data from the European Space Agency’s CryoSat-2 and from the NASA-CNES Jason-1, as well as older data from missions flown in the 1980s and 90s. Sandwell and his team derived the shape of the seafloor and its gravity field from altimetry measurements of the height of the sea surface; mountains and other seafloor features have a lot of mass, so they exert a gravitational pull on the water above pulling more water toward their center of mass. The new map portrays seafloor features as narrow as 5 kilometers (3 miles).
The maps have been a boon to Müller’s research. His team announced in November 2015 that it had used the gravity maps to discover a new oceanic microplate—a small piece of ocean crust that had broken off from larger tectonic plates. The Mammerickx Microplate, named for a pioneer in seafloor mapping (Jacqueline Mammerickx) is the first to be discovered in the Indian Ocean. Its existence helped Kara Matthews (University of Sydney), Müller, and Sandwell establish that the collision between the Indian plate and Eurasia—which has led to the creation of the Himalayas—began about 47 million years ago.
The map below, created by combining sparse ship soundings (which cover just 17 percent of the ocean) with predicted depths from the Sandwell-Smith marine gravity data, shows the complex seafloor topography and tectonic patterns of the southwest Indian Ocean. About 50 million years ago, the Indian plate was moving 15 centimeters per year, about as fast as a plate can move. When it rammed into Eurasia, it caused the entire plate to slow down and change direction; this affected active seafloor spreading along a ridge thousands of kilometers to the south, where the Indian plate meets the Antarctic plate. Matthews and Müller analyzed the seafloor ripples and ridges in this region and recreated the stresses and motions that eventually ripped a small piece off of the Antarctic plate and spun it like a ball-bearing between two larger plates. The Mammerickx Microplate is roughly the size of West Virginia or Tasmania.
“Normal seafloor spreading does not produce microplates, but if you have a collision of one continent with another continent, it causes the whole plate to change direction,” said Sandwell, a co-author of the paper. “As it changes direction, it creates things like microplates.”
The discovery is an example of new research possible because of the new global seafloor maps. Müller and his research group have been actively combing through the data to map fracture zones and better understand the motions of Earth’s plates over tens of millions of years. They have built a new model of the breakup of Pangaea, and reconstructed the formation of the Pacific Ocean Basin. He noted: “The maps from Sandwell and Smith will enable more accurate mapping of the past movements of tectonic plates and may allow better predictions of giant earthquakes, which occur at subduction zones, where plates are converging.”
The world’s largest canyon may lie under the Antarctic ice sheet, according to analysis of satellite data by a team of scientists, led by Durham University.
Although the discovery needs to be confirmed by direct measurements, the previously unknown canyon system is thought to be over 1,000km long and in places as much as 1km deep, comparable in depth to the Grand Canyon in USA, but many times longer.
The canyon system is made up of a chain of winding and linear features buried under several kilometres of ice in one of the last unexplored regions of the Earth’s land surface: Princess Elizabeth Land (PEL) in East Antarctica. Very few measurements of the ice thickness have been carried out in this particular area of the Antarctic, which has led to scientists dubbing it one of Antarctica’s two ‘Poles of Ignorance’.
The researchers believe that the landscape beneath the ice sheet has probably been carved out by water and is either so ancient that it was there before the ice sheet grew or it was created by water flowing and eroding beneath the ice.
Although not visible to the naked eye, the subglacial landscape can be identified in the surface of the ice sheet.
Faint traces of the canyons were observed using satellite imagery and small sections of the canyons were then found using radio-echo sounding data, whereby radio waves are sent through the ice to map the shape of the rock beneath it. These are very large features which appear to reach from the interior of Princess Elizabeth Land to the coast around the Vestfold Hills and the West Ice Shelf.
The canyons may be connected to a previously undiscovered subglacial lake as the ice surface above the lake shares characteristics with those of large subglacial lakes previously identified. The data suggests the area of the lake could cover up to 1250km², more than 80 times as big as Lake Windermere in the English Lake District.
An airborne survey taking targeted radio-echo sounding measurements over the whole buried landscape is now underway with the aim of unambiguously confirming the existence and size of the canyon and lake system, with results due later in 2016.
Lead researcher, Dr Stewart Jamieson, from the Department of Geography at Durham University in the UK, said: “Our analysis provides the first evidence that a huge canyon and a possible lake are present beneath the ice in Princess Elizabeth Land. It’s astonishing to think that such large features could have avoided detection for so long.
“This is a region of the Earth that is bigger than the UK and yet we still know little about what lies beneath the ice. In fact, the bed of Antarctica is less well known than the surface of Mars. If we can gain better knowledge of the buried landscape we will be better equipped to understand how the ice sheet responds to changes in climate.”
Co-Author Dr Neil Ross from Newcastle University in the UK, said: “Antarctic scientists have long recognised that because the way ice flows, the landscape beneath the ice sheet was subtly reflected in the topography of the ice sheet surface. Despite this, these vast deep canyons and potential large lake had been overlooked entirely.
“Our identification of this landscape has only been possible through the recent acquisition, compilation and open availability of satellite data by many different organisations (e.g. NASA, ESA and the US National Snow and Ice Data Center), to whom we are very grateful, and because of some serendipitous reconnaissance radio-echo sounding data acquired over the canyons by the ICECAP project during past Antarctic field seasons.”
Co-Author Professor Martin Siegert, from the Grantham Institute at Imperial College London, UK, said: “Discovering a gigantic new chasm that dwarfs the Grand Canyon is a tantalising prospect. Geoscientists on Antarctica are carrying out experiments to confirm what we think we are seeing from the initial data, and we hope to announce our findings at a meeting of the ICECAP2 collaboration, at Imperial, later in 2016.
“Our international collaboration of US, UK, Indian, Australian and Chinese scientists are pushing back the frontiers of discovery on Antarctica like nowhere else on earth. But the stability of this understudied continent is threatened by global warming, so all the countries of the world now must rapidly reduce their greenhouse gas emissions and limit the damaging effects of climate change.”
The research is published in Geology.
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Reference:
Stewart S.R. Jamieson et al. An extensive subglacial lake and canyon system in Princess Elizabeth Land, East Antarctica, Geology (2015). DOI: 10.1130/G37220.1
This picture received on January 13, 2016 from the journal “Nature” shows stone artefacts that were found lying scattered on a gravelly surface near Talepu on the Indonesian Island of Sulawesi during the first deep excavations at the site in 2009
Scientists have discovered stone-age tools at least 118,000-years-old on an Indonesian island but no trace of the early humans that made them, according to a study released Wednesday.
The research, published in the journal Nature, also points to a possible link with the first peoples to arrive in Australia.
Unearthed at four separate sites on Sulawesi, the trove of several hundred implements is likely to fuel a long-simmering debate about the identity of now-extinct human species that first came to the island chain.
In 2003, fossil remains from a diminutive species of hominin—a terms that groups extinct lineages of early man and modern humans—was discovered in the neighbouring island of Flores.
Dubbed the “Hobbit”, Homo floresiensis had arrived there at least a million years earlier, dating tests revealed.
The new find shows “that Flores was not the only island once inhabited by archaic humans before Homo sapiens”—a.k.a. modern man—”got there around 50,000 years ago,” lead author Gerrit van den Bergh, a researcher at the University of Wollongong in Australia, told AFP.
The Hobbit, many scientists say, is a descendant of the extinct species Homo erectus that became smaller across hundreds of generations, a process called “insular dwarfing” whereby animals—after migrating across land bridges during periods of low sea level—wind up marooned on islands as oceans rise.
“The fossil fauna associated with the Hobbit and the stone artefacts clearly indicate isolated island conditions,” van den Bergh explained.
Other scientists had argued that Flores man, as it is sometimes called, might have had distinct origins, and a few had even suggested it was a tribe of modern humans suffering a genetic disorder resulting in an abnormally small skull. But both of these notions have been largely dismissed.
Genetic commingling
Whether the makers of the Sulawesi tools are also derived from H. erectus—which lived in nearby Java at least 1.5 million years ago—is impossible to know without fossil evidence.
But the new discovery, van den Bergh said, raises the intriguing possibility of a link with the earliest humans to populate what is today Australia.
“We know from genetic evidence that the first people coming to Australia, and their descendants, have a tiny proportion of their DNA inherited from an enigmatic group of humans called the Denisovans,” he said.
Related to both human and Neanderthal lineages, Denisovans are thought to have split off from the former about 600,000 years ago, and the latter some 400,000 years later. They survived until at least 40,000 years ago.
Fossil records are so meagre—a few teeth and a pinkie bone excavated from a cave in Siberia—that scientists don’t even know what they might have looked like.
But the DNA link with Australia’s original inhabitants strongly suggests that some made their way deep into Asia.
“The genetic exchange between the ancestors of the modern Australians and Denisovans probably took place somewhere in Southeast Asia,” van den Bergh said.
“It could well be that the makers of the recently dated stone tools from Sulawesi could have been these Denisovans.”
Unfortunately, DNA does not survive nearly as well in tropical climes as in frigid Siberia, so the chances of finding genetic clues are diminished.
One thing that is certain, the study said, is that the tools were not made by Homo sapiens. “They are just too old for that,” van den Bergh said.
The sharp-edged tools—single- or double-faced—were made by chipping flakes away from a piece of limestone.
Reference:
Gerrit D. van den Bergh et al. Earliest hominin occupation of Sulawesi, Indonesia, Nature (2016). DOI: 10.1038/nature16448
Note: The above post is reprinted from materials provided by AFP.
Pockmarks are scars on the ocean floor, an evidence of gas release. These likely appeared as the ice sheet retreated from the western part of Svalbard, and the area began to submerge in seawater again. They prove that release of methane followed the retreat of the ice sheet. Credit: Illustration:Alexey Portnov/CAGE
The study indicates that under the frigid weight of Barents Sea Ice sheet, which covered northern Eurasia some 22 000 years ago, significant amounts of methane may have been stored as hydrates in the ground. As the ice sheet retreated, the methane rich hydrates melted, releasing the climate gas into the ocean and atmosphere for millennia.
This finding was published last week in Nature Communications in the paper “Ice-sheet-driven methane storage and release in the Arctic”.
“Creation of gas hydrates requires high pressure; water; gas – mainly methane – and low temperatures. Nowadays we basically consider two environments suitable for this process to occur: subseabed along the world’s continental margins, and permafrost areas on land and off shore. ” Says principal author of the study, Dr. Alexey Portnov of CAGE – Centre for Arctic Gas Hydrate, Environment and Climate at UiT The Arctic University of Norway.
Ice sheets – a third process
But this is the first comprehensive study that shows that there is a third process that can create, contain and maintain large amounts of gas hydrates: ice sheets.
” They are heavy, can exert enormous pressure on the ground below. And they are cold, of course. With enough supply of gas and water from below and favorable geological setting you will likely have enormous amounts of gas hydrates contained under modern ice sheets as well”.
500-meter thick methane reservoir
The theory that this may be happening beneath the Antarctic ice sheet has been published previously in Nature. CAGE-study is a more comprehensive take on that idea, and shows same processes taking place in the Arctic.
Scientists from CAGE have over time collected wide-ranging observational data offshore western Svalbard in the Arctic Ocean. This made it possible to create robust models for a scenario of subglacial evolution of gas hydrate reservoirs during and after Last Glacial Maximum, or last ice age in layman´s terms.
The results of the study indicate that even under conservative estimates of ice thickness a 500-meter thick gas hydrate stability zone existed beneath the ice sheet in the study area. This zone could have served as a methane sink-a reservoir containing immense amounts of the natural greenhouse gas. 1 m3 of gas hydrate contains almost 170 m3 of the greenhouse gas methane.
Rapid melt caused release of methane
During the last ice age the continental margin offshore western Svalbard, was land covered with ice, much as Greenland and Antarctica of today. But as the climate changed, the ice melted over a period of thousands of years, a rapid melt in geological terms.
The scientists have mapped over 1900 pockmarks – gas escape features – on what now is the seafloor in the study area. The age of these pockmarks has in previous studies been estimated as post-glacial, meaning that they appeared after the ice sheet had retreated.
” Pockmarks are evidence of gas release from the ground. We infer that the gas hydrate zone was stable as long as the climate was cold and the ice sheet was stable. Abrupt climate warming caused sheets to melt, decreasing the pressure on the ground and increasing the temperature. This destabilized the hydrates. Methane was released into rising seawater and possibly the atmosphere.” says Portnov.
As the ice sheet retreated, the pressure lifted, steadily widening the corridor for major methane release.
Accelerating climate change
Rapid melting of the ice sheets due to global warming, and subsequent sea level rise has long been a concern to scientists.
Methane, being at least 20 times more potent greenhouse gas than CO2, can accelerate the global warming. If the same process of methane storage is occurring under the current ice sheets, there may be a new threat to take into the account when we are discussing ice sheet retreat in the future.
Modern ice sheets will not need thousands of years to melt., The Greenland ice sheet has been losing an estimated 287 billion metric tons per year, states NASA. The continent of Antarctica has been losing about 134 billion metric tons of ice per year since 2002, albeit its ice sheet tells a more complicated story.
“It is difficult to study this processes in modern polar environments. The ice sheets of Greenland and Antarctica are several kilometers thick and examining the ground beneath them is challenging and expensive, nonetheless. But the circumstances that were present in formation of gas hydrate zones in the past are also present today. We need to take that into the account when we are considering the impacts that the rapid melt of the modern ice sheets will have on our future climate” says Portnov.
Reference:
Alexey Portnov, Sunil Vadakkepuliyambatta, Jürgen Mienert & Alun Hubbard. Ice-sheet-driven methane storage and release in the Arctic. DOI:10.1038/ncomms10314
A team of University of Oregon scientists is home after a month-long cruise in the eastern Mediterranean, but this was no vacation. The focus was the plumbing system of magma underneath the island of Santorini, formed by the largest supervolcanic eruption in the past 10,000 years.
The expedition — led by UO geologists Emilie Hooft and Doug Toomey under a National Science Foundation grant — included British, Greek and U.S. researchers on board the U.S. Research Vessel Marcus G. Langseth. Five UO graduate students and one undergraduate student were on board, and another UO graduate student helped install seismometers on the nearby island of Anafi.
Data collected with seismometers will now be analyzed using large parallel computers to build maps and understand the structure of the magma plumbing system that lies 10 to 20 kilometers, or six to 12 miles, under the seafloor. Little is known about magmatic systems at deep depths.
Photo of two UO grad students prepping a seismometer for deployment”The goal is to understand the deep roots, or magma plumbing system, of an arc volcano,” Hooft said. “We have some idea of how shallow magma bodies are shaped, but the magmatic system that lies in the deep crust remains poorly understood and difficult to study. It is in this region that magmas from the mantle undergo chemical processes to form the rock compositions that presumably dominate the continental lower crust.”
Santorini, besides being an idyllic vacation spot, is perfect for tackling the problem of imaging the deeper roots of a volcano, Hooft said. The island recently has experienced significant unrest linked to magma recharge, including inflation of the ground and intense earthquake swarms.
Since Santorini is a semi-submerged volcanic system, the scientific team was able to collect a very large 3D marine-land seismic dataset using seismic-sound detecting equipment towed behind the R/V Marcus G. Langseth, which is the most-sophisticated seismic vessel in the world’s academic fleet. The equipment generates bubbles of compressed air to produce pressure waves. At the seafloor, the waves enter rocks and return a clean seismic signal as they proceed under the seabed to the roots of the volcanic system.
If successful, the data will provide the structure of the deep magma system and its surroundings in 10 times more detail than any other volcano on Earth. Researchers dropped 91 specially designed seismometers to the seafloor and installed another 65 land seismometers on Santorini and nearby islands. The entire onshore-offshore network recorded the seismic signaling more than 14,000 times.
The scientists mapped new regions of the seafloor, revealing the structure of faults and landslides between the islands of Santorini and Amorgos. These measurements may help resolve questions related to the largest 20th century earthquake in Greece, which occurred in 1956, and its accompanying tsunami.
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Note: The above post is reprinted from materials provided by University of Oregon. The original item was written by Jim Barlow.
Three geologists scramble down a hillside on Sedanka Island that overlooks Stardust Bay. The geologists documented driftlogs stranded at elevations up to 60 m (196 feet) above sea level and over 804 m (.5 mile) inland. The driftlogs, one visible in the lower right of the photo, were probably carried inland and deposited in 1957 by a tsunami generated by the magnitude 8.6 Andreanof Islands earthquake. Credit: Robert Witter, USGS
New data for frequent large tsunamis at a remote island near Dutch Harbor, Alaska provides geological evidence to aid tsunami hazard preparedness efforts around the Pacific Rim. Recent fieldwork in Alaska’s Aleutian Islands suggests that a presently “creeping” section of the Aleutian Subduction Zone fault could potentially generate an earthquake great enough to send a large tsunami across the Pacific to Hawaii.
These findings, published by a team of scientists led by U.S. Geological Survey geologist Rob Witter in Geophysical Research Letters, a journal of the American Geophysical Union, present strong evidence for prehistoric tsunamis in the Aleutian Islands, and call for a reevaluation of earthquake and tsunami hazards along this part of the eastern Aleutian Subduction Zone.
Creeping faults exhibit slow, continuous motion along them. Because the two tectonic plates are not fully locked by friction, it is unclear whether or not creeping faults can host large earthquakes. Geological observations at Stardust Bay, Alaska point toward previously unrecognized tsunami sources along a presently creeping part of the Aleutian Subduction Zone.
Prevailing scientific models about earthquake generation are challenged when it comes to forecasting earthquake probabilities where observations indicate a creeping megathrust (the gently-dipping fault between converging tectonic plates, where one plate is thrust below the other). Usually, scientific models forecast the highest seismic hazard where the tectonic plates are locked together. The study site, Stardust Bay, faces a creeping part of the eastern Aleutian Subduction Zone, which is sandwiched between the rupture areas of historical earthquakes in 1946 and 1957 that generated tsunamis with devastating consequences to coastal communities around the Pacific Ocean. This study is the first to identify geological evidence for repeated prehistoric tsunamis along a creeping part of the eastern Aleutian subduction zone located between the 1946 and 1957 earthquakes.
The new evidence includes six sand sheets deposited up to 15 meters (or 50 feet) above sea level by past large tsunamis that probably were generated by great Aleutian earthquakes, and indicate a previously unknown tsunami source that poses a new hazard to the Pacific basin.
Using hand-driven cores, augers, and shovels to reveal the sediments blanketing a lowland facing the Pacific Ocean, and using radiocarbon dating to estimate the times of sand sheet deposition, scientists established a geologic history of past large tsunamis. The youngest sand sheet and modern drift logs stranded as far as 805 meters, or half a mile, inland and 18 meters (or 60 feet) above sea level record a large tsunami triggered by the magnitude 8.6 Andreanof Islands earthquake in 1957. Older sand sheets resulted from tsunamis that may have been even larger than the 1957 tsunami. The oldest tsunami sand layer was deposited approximately 1700 years ago, and the average interval between tsunami deposits is 300-340 years.
These geological observations indicate large tsunamis in the eastern Aleutians have recurred every 300-340 years on average, and provide additional field-based information that is relevant to new tsunami evacuation zone maps for Hawaii.
Reference:
Robert C. Witter, Gary A. Carver, Richard W. Briggs, Guy Gelfenbaum, Richard D. Koehler, SeanPaul La Selle, Adrian M. Bender, Simon E. Engelhart, Eileen Hemphill-Haley, Troy D. Hill. Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust. Geophysical Research Letters, 2015; DOI: 10.1002/2015GL066083
CU-Boulder researchers are seeing a loss of ice in the high mountains west of Boulder as the climate warms. Credit: University of Colorado
New research led by the University of Colorado Boulder indicates an ongoing loss of ice on Niwot Ridge and the adjacent Green Lakes Valley in the high mountains west of Boulder is likely to progress as the climate continues to warm.
The study area encompasses the Niwot Ridge Long-Term Ecological Research (LTER) site, thousands of acres of alpine tundra, subalpine forest, talus slopes, glacial lakes and wetlands stretching to the top of the Continental Divide in the Rocky Mountains. The Niwot Ridge LTER site, which includes Green Lakes Valley and CU-Boulder’s Mountain Research Station (MRS), is one of 26 North American LTER sites created and funded by the National Science Foundation (NSF) and one of the initial five LTER sites designated by the federal agency in 1980.
The decline of ice at the Niwot Ridge LTER site appears to be associated with rising temperatures each summer and autumn in recent years, said CU-Boulder Professor Mark Williams of the Institute of Arctic and Alpine Research, lead study author. The decline is especially evident on the Arikaree glacier — the only glacier on Niwot Ridge — which has been thinning by about 1 meter per year for the last 15 years.
“Things don’t look good up there,” said Williams. “While there was no significant change in the volume of the Arikaree glacier from 1955 to 2000, severe drought years in Colorado in 2000 to 2002 caused it to thin considerably. Even after heavy snow years in 2011 and again in 2014, we believe the glacier is on course to disappear in about 20 years given the current climate trend.”
The new study looked at changes in the cryosphere — places that are frozen for at least one month of the year– at the Niwot Ridge LTER site going back to the 1960s. In addition to the changes occurring on the Arikaree glacier, the researchers also have seen decreases in ice associated with three rock glaciers (large mounds of ice, dirt and rock) as well as subsurface areas of permafrost — frozen soil containing ice crystals.
The team used several methods to measure surface and subsurface ice on Niwot Ridge: ground-penetrating radar, which measures ice and snow thickness; resistivity, which measures the conductivity of electrical signals through ice; and seismometers to measure signals bounced through subsurface ice. “We found that a combination of all three methods provided the best picture of changing snow and ice conditions on Niwot Ridge,” said Williams.
The researchers also discovered an increased discharge of water from the Green Lakes Valley in late summer and fall after the annual snowpack had melted, a counterintuitive trend that began in the early 1980s, said Williams. The increased discharge appears to be due to higher summer temperatures melting “fossil” ice present for centuries or millennia in glaciers, rock glaciers, permafrost and other subsurface ice.
“We are taking the capital out of our hydrological bank account and melting that stored ice,” he said. “While some may think this late summer water discharge is the new normal, it is really a limited resource that will eventually disappear.”
Scientists have been gathering information on the snow, ice and plant and animal abundance and diversity on Niwot Ridge going back to the 1940s, when CU-Boulder Professor John Marr and colleagues began studies. The two highest climate stations on Niwot Ridge, one at 10,025 feet and the other 12,300 feet, have been monitoring data continuously since 1952.
“This study demonstrates declines in ice — glaciers, permafrost, subsurface ice and lake ice in the Niwot Ridge area over the past 30 years,” said Saran Twombly, LTER program director in NSF’s Division of Environmental Biology, which funded the research. “Long-term research at Niwot Ridge offers a rare opportunity to document the continuous, progressive effects of climate change on high alpine ecosystems, from ice and nutrients to plant and animal communities.”
A special issue of the journal Plant Ecology and Diversity that includes several research papers involving CU-Boulder faculty and students is being published this month. Study co-authors on the Niwot Ridge snow and ice paper, part of the special issue, include emeritus Professor Nel Caine of CU-Boulder, Professor Matthew Leopold of the University of West Australia and professors Gabriel Lewis and David Dethier of Williams College in Williamstown, Massachusetts.
From an ecological standpoint, Niwot Ridge has seen a significant increase in alpine shrubs above treeline in recent decades, said Williams. At one research site known as “The Saddle” at about at 11,600 feet in elevation and 3.5 miles from the Continental Divide, the ecosystem has gone from all tundra grasses and no shrubbery in the early 1990s to about 40 percent shrubs today.
“Places that once harbored magnificent wildflowers in this area are being replaced by shrubs, particularly willows,” he said. “The areas dominated by shrubs are increasing because of a positive feedback — patches of these shrubs act as snow fences, causing the accumulation of more water and nutrients and the growth of more shrubs.”
One nutrient, nitrogen — produced primarily by vehicle emissions and agricultural and industrial operations on the Front Range and elsewhere in the West — is being swept into the atmosphere and deposited on the tundra in increasing amounts, said Williams. Nitrogen deposition also is an issue in nearby Rocky Mountain National Park.
Niwot Ridge is part of the Roosevelt National Forest and has been designated a United Nations Educational, Scientific and Cultural Organization (UNESCO) Biosphere Reserve. The Green Lakes Valley is part of the City of Boulder Watershed and CU-Boulder’s MRS is devoted to the advancement of mountain ecosystems, providing research and educational opportunities for scientists, students and the general public.
Reference:
Matthias Leopold, Gabriel Lewis, David Dethier, Nel Caine, Mark W. Williams. Cryosphere: ice on Niwot Ridge and in the Green Lakes Valley, Colorado Front Range. Plant Ecology & Diversity, 2015; 1 DOI: 10.1080/17550874.2014.992489
Prior to ice on, meteorological instruments are brought to the shore of Toolik Lake in Alaska. Credit: Sally Macintyre
Not all sources of methane emissions are man-made. A new study shows that northern freshwaters are critical emitters of this greenhouse gas.
The findings from the Permafrost Carbon Network, an international organization that includes UC Santa Barbara’s Sally MacIntyre, also underscore the urgency of combatting human-induced global warming. The results appear in the journal Nature Geoscience.
“Climate-sensitive regions in the north are home to most of the world’s lakes,” said co-author MacIntyre, a professor in UCSB’s Department of Ecology, Evolution, and Marine Biology. “Lakes at high northern latitudes are an important—and often overlooked—source of methane, a potent greenhouse gas.”
According to the scientists, climate warming, particularly at high northern latitudes, and longer ice-free seasons in combination with permafrost thaw, are likely to fuel methane release from lakes, potentially causing methane emissions to increase 20 to 50 percent before the end of this century. Such a change, MacIntyre noted, would likely generate a positive feedback on future warming, causing emissions to increase even further.
“This means that efforts to reduce human-induced warming are even more urgent to minimize this type of feedback of natural greenhouse gas emissions,” said co-author David Bastviken, a professor at Linköping University in Sweden, who is currently visiting UCSB. “In a sense, every reduction in emissions from fossil fuels is a double victory.”
By compiling previously reported measurements made at a total of 700 northern water bodies the researchers have been able to more accurately estimate emissions over large scales. They found that methane emissions from lakes and ponds alone are equivalent to roughly two-thirds of all natural methane sources in the northern region.
“The release of methane from northern lakes and ponds needs to be taken seriously,” said lead author Martin Wik, a graduate student at Stockholm University. “These waters are significant, contemporary sources because they cover large parts of the landscape. They are also likely to emit even more methane in the future.”
Reference:
Martin Wik et al. Climate-sensitive northern lakes and ponds are critical components of methane release, Nature Geoscience (2016). DOI: 10.1038/ngeo2578
Complete and well preserved fossil cichlid excavated from the fossil Lagerstätte in Kenya’s Tugen Hills. Credit: LMU/B. Reichenbacher
The question of what conditions were like in the Rift Valley of East Africa 12 million years ago (Mya) has been the subject of intense debate. Now new research just published by a team led by LMU paleontologist Professor Bettina Reichenbacher strongly suggest that extensive grassland habitats were already established in the region by that time. The study’s findings appear in the Geological Magazine, one of the most respected journals in the Earth Sciences.
In 2013 Bettina Reichenbacher and her colleagues discovered a Middle to Late Miocene fossil Lagerstätte in Kenya’s Tugen Hills, which harbors one of the few diverse and well preserved collections of fish fossils yet found anywhere in the world. “Almost all of these specimens belong to the cichlid family (Cichlidae), which still represents a major component of the fauna of East Africa’s Great Lakes today, and they provide a unique glimpse of the evolutionary history of this group,” says Reichenbacher. Her graduate students Melanie Altner and Stefanie Penk have devoted the past several months to the analysis of a fraction of the material so far recovered from the Tugen Hills. Meanwhile, her former Master’s student Cornelia Rasmussen (now at the University of Utah in Salt Lake City) has been studying the sedimentology of the site and her LMU colleague Dr. Jerome Prieto has analyzed the mammalian fossils found in the locality. Dr. Olaf Lenz of the Institute for Applied Geosciences at the Technical University (TU) in Darmstadt brought his expertise to bear on the pollen samples found in the sediments, while Dennis Brüsch (TU Darmstadt) investigated the mineralogy of the clay samples recovered.
Taken together, the results of these analyses provide a rich source of data that will enliven the debate relating to the nature of the climate and the range of environments available in this part of Africa in the Late and Middle Miocene (11-16 Mya). The issue is of considerable interest, because the Rift Valley in Kenya has yielded a rich trove of hominid fossils over the past 80 years or so. Knowledge relating to the climate, ecology and habitats of the region therefore provides insight into the conditions under which the lineage that gave rise to Homo sapiens evolved.
Shaped by catastrophic events
The data derived from the paleontological investigations are incompatible with several previous assumptions. The analyses reveal that some of the fish species identified in the area lived in bodies of water that were quite deep, and were located in semiarid settings. These findings imply that, during the period concerned, tropical woodlands were in decline, and were being replaced by grasslands that were poor in tree species. “The vegetation may have looked rather like that of the grasslands set with acacia trees that are found in modern Somalia,” says Reichenbacher. Based on the pollen found in the sediments, the researchers deduce that the climate was getting drier.
The fish fossils from the area that had been studied up to now all belonged to a single size class, but the LMU team recovered a trove of specimens ranging in size from 1.2 to 15 cm in length. This wide size variation among fossils recovered from the same sedimentary level suggests that all the individuals died over a very short space of time. This in turn implies the occurrence of a sudden and catastrophic event, which wiped out whole populations. This interpretation is supported by the presence of a layer of ash at the same level. “It is very likely that mass die-offs of fish are linked to outbursts of volcanic activity during this period,” says Bettina Reichenbacher.
The impact of tectonic activity
A detailed study of the sediments in which the fish fossils were discovered indicated that, during the period between 9 and 12 Mya, several instances of abrupt change in water levels must have occurred in the lakes and rivers around the Tugen Hills. Most previous studies had assumed that fluctuations in the local climate were responsible for the variations in water levels, but Bettina Reichenbacher maintains that “abrupt changes in the nature of the sediment, in the mineral composition of the parent rock, such as we have discovered, cannot be attributed to fluctuations in climate. We therefore believe that they were caused by tectonic activity.”
Among the fossil material excavated, Reichenbacher’s team has already identified several new species of cichlid. In further studies, they hope to clarify the relationships between the fossil specimens and the cichlids found in the Rift Valley today. “We hope to learn from the evolutionary history of the cichlids whether or not a single drainage system existed in the area in the Later Miocene. The alternative possibility is that the modern drainage networks, whose course is determined by the mountains that define the Rift Valley and which are now characterized by uniquely diversified fish faunas, may have already formed by that time,” Reichenbacher explains.
Reference:
CORNELIA RASMUSSEN et al. Middle–late Miocene palaeoenvironments, palynological data and a fossil fish Lagerstätte from the Central Kenya Rift (East Africa), Geological Magazine (2015). DOI: 10.1017/S0016756815000849
The massive subduction zone earthquake that hit Nepal in 2015 also caused thousands of landslides. Credit: U.S. Geological Survey
Research teams have evaluated the major 7.8 magnitude subduction zone earthquake in Gorkha, Nepal, in April 2015, and identified characteristics that may be of special relevance to the future of the Pacific Northwest.
Most striking was the enormous number and severity of landslides.
Many people understand the damage that can be caused to structures, roads, bridges and utilities by ground shaking in these long-lasting types of earthquakes, such as the one that’s anticipated on the Cascadia Subduction Zone between northern California and British Columbia.
But following the Nepal earthquake – even during the dry season when soils were the most stable – there were also tens of thousands of landslides in the region, according to reconnaissance team estimates. In their recent report published in Seismological Research Letters, experts said that these landslides caused pervasive damage as they buried towns and people, blocked rivers and closed roads.
Other estimates, based on the broader relationship between landslides and earthquake magnitude, suggest the Nepal earthquake might have caused between 25,000 and 60,000 landslides.
The subduction zone earthquake expected in the future of the Pacific Northwest is expected to be larger than the event in Nepal.
Ben Mason, a geotechnical engineer and assistant professor in the College of Engineering at Oregon State University, was a member of the Geotechnical Extreme Event Reconnaissance team that explored the Nepal terrain. He said that event made clear that structural damage is only one of the serious threats raised by subduction zone earthquakes.
“In the Coast Range and other hilly areas of Oregon and Washington, we should expect a huge number of landslides associated with the earthquake we face,” Mason said. “And in this region our soils are wet almost all year long, sometimes more than others. Each situation is different, but soils that are heavily saturated can have their strength cut in half.”
Wet soils will also increase the risk of soil liquefaction, Mason said, which could be pervasive in the Willamette Valley and many areas of Puget Sound, Seattle, Tacoma, and Portland, especially along the Columbia River.
Scientists have discovered that the last subduction zone earthquake to hit the Pacific Northwest was in January 1700, when – like now – soils probably would have been soggy from winter rains and most vulnerable to landslides.
The scientific study of slope stability is still a work in progress, Mason said, and often easier to explain after a landslide event has occurred than before it happens. But continued research on earthquake events such as those in Nepal may help improve the ability to identify areas most vulnerable to landslides, he said. Models can be improved and projections made more accurate.
“If you look just at the terrain in some parts of Nepal and remove the buildings and people, you could think you were looking at the Willamette Valley,” Mason said. “There’s a lot we can learn there.”
In Nepal, the damage was devastating.
Landslides triggered by ground shaking were the dominant geotechnical effect of the April earthquake, the researchers wrote in their report, as slopes weakened and finally gave way. Landslides caused by the main shock or aftershocks blocked roads, dammed rivers, damaged or destroyed villages, and caused hundreds of fatalities.
The largest and most destructive event, the Langtang debris avalanche, began as a snow and ice avalanche and gathered debris that became an airborne landslide surging off a 500-meter-tall cliff. An air blast from the event flattened the forest in the valley below, moved 2 million cubic meters of material and killed about 200 people.
Surveying the damages after the event, Mason said one of his most compelling impressions was the way people helped each other.
“Nepal is one of the poorest places, in terms of gross domestic product, that I’ve ever visited,” he said. “People are used to adversity, but they are culturally rich. After this event it was amazing how their communities bounced back, people helped treat each other’s injuries and saved lives. As we make our disaster plans in the Pacific Northwest, there are things we could learn from them, both about the needs for individual initiative and community response.”
Aside from landslides, many lives were lost in collapsing structures in Nepal, often in homes constructed of rock, brick or concrete, and frequently built without adequate enforcement of building codes, the report suggested. Overall, thousands of structures were destroyed. There are estimates that about 9,000 people died, and more than 23,000 were injured. The earthquake even triggered an avalanche on Mount Everest that killed at least 19 people.
The reconnaissance effort in Nepal was made possible by support from the National Science Foundation, the U.S. Geological Survey, the U.S. Agency for International Development, the OSU College of Engineering, and other agencies and universities around the world.
A magnified photograph of a cross-section through a 3 mm-thick pedothem soil deposit from Wyoming. The line of dots are laser ablation sampling spots that are 0.1 mm in diameter. The innermost mineral material is about 150,000 years old, and becomes progressively younger towards the outside. Credit: Erik Oerter
Scientists have found a new way to tease out signals about Earth’s climatic past from soil deposits on gravel and pebbles, adding an unprecedented level of detail to the existing paleoclimate record and revealing a time in North America’s past when summers were wetter than normal.
A research team led by soil scientists at the University of California obtained data about precipitation and temperature in North America spanning the past 120,000 years, which covers glacial and interglacial periods during the Pleistocene Epoch. They did this at thousand-year resolutions—a blink of an eye in geologic terms—through a microanalysis of the carbonate deposits that formed growth rings around rocks, some measuring just 3 millimeters thick.
“The cool thing that this study reveals is that within soil—an unlikely reservoir given how ‘messy’ most people think it is—there is a mineral that accumulates steadily and creates some of the most detailed information to date on the Earth’s past climates,” said senior author Ronald Amundson, a UC Berkeley professor of environmental science, policy and management.
The study, to be published Monday, Jan. 11, in the Proceedings of the National Academy of Sciences, shows the rich potential held within soil deposits known as pedothems, which form growth rings on rocks. The samples used in the study came from Wyoming’s Wind River Basin.
Because these soil deposits are commonly found in drylands all over the world, they can provide a rich source of data for paleoclimatologists, the authors said.
“We can now begin to develop records of how local and regional climate boundaries have shifted through time and in response to worldwide warming or cooling,” said study lead author Erik Oerter, who conducted the research as part of his UC Berkeley Ph.D. dissertation.
120,000 years of history in 3 millimeters of rock
Pedothems are a powerful complement to existing geological records of past climate, including ice cores, lake and ocean sediments, and stalactites and stalagmites in caves. They have the advantage of being fairly ubiquitous in regions now populated by humans, unlike the polar regions where ice cores are often obtained.
Key advances in the ability to precisely analyze micro-samples of soil deposits enabled researchers to extract telltale signs of climate change.
“By using micro-analytical measurements on spots as small as 0.01 mm in diameter, we can develop time series of past climate conditions in a way that no one has done before,” said Oerter. “It is evident that the carbonate coatings formed in concentric bands around the rocks, much like the annual growth rings in a tree, except that these laminations form over timescales of several hundred years.”
The researchers used laser ablation and an ion microprobe, much like a tiny dental drill, to obtain microscopic samples for analysis. Uranium isotopes were used to date the deposits, while oxygen and carbon isotopes revealed clues about the precipitation, temperature and soil respiration at the time the mineral was formed.
A map of the predominant weather patterns in mid-latitude North American from 70,000 to 55,000 years ago. The large ice sheet covering the northeastern portion of the continent caused a strong high pressure system to persist above it, which drew Gulf of Mexico-sourced precipitation (red arrows) into the mid-continent and Wyoming (white star). The result was rainy summers during this time, and possibly drier winters. Credit: Erik Oerter
For instance, warmer rain from the Gulf of Mexico will result in higher levels of oxygen 18 compared with the cold precipitation from snowstorms blowing eastward across the Rockies. The ratio of carbon 13 and carbon 12 isotopes reflect levels of soil respiration, which is a proxy for plant productivity.
Uranium isotopes were used for dating the sample, but they can also be used to calculate how much rain the soil receives, serving as a type of “paleo rain gauge,” said Oerter, who is now a postdoctoral researcher at the University of Utah.
Finding what other records couldn’t
The new data revealed that 70,000 to 55,000 years ago, in the midst of a minor ice age, the pattern of precipitation in North America shifted from one dominated by a west-to-east flow of storms from the north Pacific to a south-to-north flow from the Gulf of Mexico. The researchers attributed that to a stable, high-pressure system that parked itself over massive ice sheets that covered eastern Canada and northeastern United States, which helped bring up more air from the south.
That atmospheric circulation translated into wetter summers and drier winters in central North America, a reverse of the usual pattern in which more precipitation falls in the winter.
“This is a new insight from geologic sources of paleoclimate data,” said Oerter. “The techniques that we developed can now be applied to similar soil deposits to fill in key gaps in the paleoclimate record. The information will be useful to improve the accuracy of climate models by providing known conditions to calibrate them to.”
Reference:
Pedothem carbonates reveal anomalous North American atmospheric circulation 70,000–55,000 years ago, Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1515478113
Fig 1. Photograph (A), drawing (B) and reconstruction of Ischioceratops zhuchengensis (C). Credit: HE Yiming
The leptoceratopsids are a group of small, quadrupedal horned dinosaurs that have so far been found exclusively in the Upper Cretaceous of Asia and western North America. With a typical body length of about two meters, they are much smaller than the contemporary ceratopsids.
HE Yiming, a Ph. D. student of Institute of Vertebrate Palaeontology and Paleoanthropology, Chinese Academy of Sciences, and his collaborators reported a new leptoceratopsid dinosaur, Ischioceratops zhuchengensis, from the bone-beds of the Upper Cretaceous Wangshi Group of Zhucheng, Shandong Province, China. This fossil represents the second leptoceratopsid dinosaur specimen recovered from the Kugou locality, a highly productive site in Zhucheng. This finding published on December 23 in PLoS ONE 10(12) increases the known taxonomic diversity and morphological disparity of the Leptoceratopsidae and has significant implications for interpretations of neoceratopsian biogeography.
The new species is based on an incomplete, partially articulated specimen including the entire sacrum, a few ossified tendons, both halves of the pelvis, the anterior-most 15 caudal vertebrae in an articulated series, and the right femur, tibia and fibula.
Leptoceratopsids are characterized by robust jaws equipped with highly specialized large teeth and, unlike ceratopsids, lack horns and have extremely short frills. They share some of the advanced features seen in ceratopsids and are closely related to the latter group. Three taxa have been described from the Upper Cretaceous of Asia: Asiaceratops salsopaludalis from Uzbekistan, Udanoceratops tschizhovi from Udan-Sayr, Mongolia, and Zhuchengceratops inexpectus from the Kugou locality, Zhucheng, China.
Fig 2. Photograph (left) and drawing (right) of Ischioceratops zhuchengensis in dorsal view. Credit: HE Yiming
The ischium of Ischioceratops zhuchengensis is morphologically unique among known Dinosauria, flaring gradually to form an obturator process in its middle portion and resembling the shaft of a recurve bow. An elliptical fenestra perforates the obturator process, and the distal end of the shaft forms an axehead-shaped expansion.
The new specimen, like Zhuchengceratops, comes from the Kugou locality. This locality, together with Longgujian (just 600 m north of Kugou) and Zangjiazhuang (5 km away from Kugou), has yielded numerous hadrosaurid bones. The Zangjiazhuang locality has also produced several tyrannosaurid elements and some material atrributable to Sinoceratops zhuchengensis, the only undisputed ceratopsid from outside of North America. “Though lacking cranial elements, the newly collected specimen possesses some morphological features that identify it as a new leptoceratopsid”, said He Yiming, lead author of the study.
“The holotype of Ischioceratops was found at approximately the same stratigraphic level within the Kugou quarry as the holotype specimen of Zhuchengceratops, but there are no overlapping skeletal elements between the two specimens. Our phylogenetic analysis shows that Zhuchengceratops has a close relationship with Ischioceratops in Leptoceratopsidae. Therefore, we provisionally consider Ischioceratops and Zhuchengceratops to be distinct taxa”, said XU Xing, study coauthor and project leader, Institute of Vertebrate Palaeontology and Paleoanthropology in Beijing.
Reference:
Yiming He et al. A New Leptoceratopsid (Ornithischia, Ceratopsia) with a Unique Ischium from the Upper Cretaceous of Shandong Province, China, PLOS ONE (2015). DOI: 10.1371/journal.pone.0144148
Scientists have shed new light on last April’s devastating Himalayan earthquake. Credit: Shutterstock
An international team of scientists has shed new light on the earthquake that devastated Nepal in April 2015, killing more than 8,000 people.
A study published in the journal Nature Geoscience shows that a kink in the regional fault line below Nepal explains why the highest mountains in the Himalayas are seen to grow between earthquakes. This kink has created a ramp 20km below the surface, with material constantly being pushed up and raising the height of the mountains.
The researchers, from the UK’s Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET), as well as academics from the USA and France, also demonstrate that the rupture on the fault stopped 11km below Kathmandu. This indicates that another major earthquake could take place within a shorter timeframe than the centuries that might be expected for the area.
Lead author Dr John Elliott of Oxford University, a member of the COMET team, said: ‘Nepal has some of the highest mountain ranges in the world that have been built up over millions of years because of the collision of India with Asia. But the way in which mountains grow and when this occurs is still debated.
‘We have shown that the fault beneath Nepal has a kink in it, creating a ramp 20km underground. Material is continually being pushed up this ramp, which explains why the mountains were seen to be growing in the decades before the earthquake.
‘The earthquake itself then reversed this, dropping the mountains back down again when the pressure was released as the crust suddenly snapped in April 2015.
‘Using the latest satellite technology, we have been able to precisely measure the land height changes across the entire eastern half of Nepal. The highest peaks dropped by up to 60cm in the first seconds of the earthquake.’
Mount Everest, at more than 50km east of the earthquake zone, was too far away to be affected by the subsidence seen in this event.
Dr Pablo Gonzalez of the University of Leeds, a member of the COMET team, said: ‘We successfully mapped the earthquake motion using satellite technology on a very difficult mountainous terrain. We developed newly processing algorithms to obtain clearer displacement maps, which revealed the most likely fault geometry at depth. Such geometry makes sense of the puzzling geological observations.’
Another key finding of the study shows that the rupture in the fault stopped 11km below Kathmandu, leaving an upper portion that remains unbroken.
Dr Elliott said: ‘Using the high-resolution satellite images, we have shown that only a small amount of the earthquake reached the surface. This is surprising for such a big earthquake, which we would normally expect to leave a major fault trace in the landscape. This makes it a challenge when trying to find past earthquake ruptures, as they could be hidden.
‘We found that the rupture from April’s earthquake stopped 11km beneath Kathmandu, and that this sudden break is because of damage to the fault from interactions with older faults in the region. This is important because the upper half of the fault has not yet ruptured, but is continuously building up more pressure over time as India continues to collide into Nepal.
‘As this part of the fault is nearer the surface, the future rupture of this upper portion has the potential for a much greater impact on Kathmandu if it were to break in one go in a similar sized event to that of April 2015.
‘Work on other earthquakes has suggested that when a rupture stops like this, it can be years or decades before it resumes, rather than the centuries that might usually be expected.
‘Unfortunately, there is no way of predicting precisely when another earthquake will take place. It’s simply a case of countries and cities making sure they are well prepared for when it does happen.’
Reference:
Himalayan megathrust geometry and relation to topography revealed by the Gorkha earthquake, Nature Geoscience , DOI: 10.1038/ngeo2623
Figure 1. The holotype of Bellulornis rectusunguis.
A new species of Early Cretaceous bird was reported on January 6th in Zoological Journal of the Linnean Society by Min Wang, Zhonghe Zhou and Shuang Zhou from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciences. The new discovery provides new information regarding the evolution of morphology of primitive ornithuromorphs, particularly of pectoral girdle, sternum and limb proportion pertaining to powered flight.
Ornithuromorpha is the most derived avian group in the Early Cretaceous, advanced members of which encompass all living birds (Neornithes). The first known appearance datum of this clade is from the Yixian Formation—the middle phase of the Jehol Biota (e.g., Archaeorhynchus and Yixianornis), whereas the younger Jiufotang Formation has produced more than half the named Jehol ornithuromorphs (e.g., Jianchangornis, Schizooura and Piscivoravis), which together recorded over five million years of early evolution of this avian group.
The new fossil bird is represented by a nearly complete skeleton, collected from the Early Cretaceous Jehol Biota in northeastern China. The specimen is housed at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP; Beijing) under collection number IVPP V17970. The new bird is preserved with its wings and legs fully outstretched, mimicking a dancer; and its manual claws are barely recurved; therefore, the new species is named Bellulornis rectusunguis to convey these features. A comprehensive phylogenetic analysis resolved the new taxon in a basal position that is only more derived than Archaeorhynchus and Jianchangornis among ornithuromorphs, increasing the morphological diversity of basal ornithuromorphs. The new specimen has a V-shaped furcula with a short hypocleidium, a feature otherwise known only in Schizooura among Cretaceous ornithuromorphs. We discuss the implications of the new taxon on the evolution of morphology of primitive ornithuromorphs, particularly of pectoral girdle, sternum and limb proportion pertaining to powered flight. The preserved gastroliths and pedal morphology indicate herbivory and lakeshore adaption for this new species.
Figure 2. Sternal morphology of Bellulornis rectusunguis.Figure 3. Cladogram showing the systematic position of Bellulornis rectusunguis among Mesozoic birds
Researchers at the University of Bristol have discovered new insights into previously hidden parts of the earth’s carbon cycle. The team found that carbon recycling extends into the deep mantle by plate subduction, but is still primarily constrained to upper mantle depths, above 700km. The researchers made the discovery that certain rare diamonds are formed when carbon that was sequestered from seawater into the Earth’s shifting tectonic plates reacts with the mantle after the plate is subducted – a process by which it moves under another tectonic plate and sinks into the mantle as the plates converge.
Their research, ‘Slab melting as a barrier to deep carbon subduction’ is published in this week’s edition of Nature.
Professor Mike Walter from the School of Earth Sciences said: ‘Understanding the carbon cycle is of particular interest, as carbon is a crucial building block for life, while in the form of atmospheric CO2 it strongly contributes to the greenhouse effect.
‘Despite the widespread understanding that carbon recycling into the Earth’s interior during subduction has altered the Earth’s surface carbon budget over geological time, the ultimate fate of recycled carbon remains a conundrum, but one which experimental petrologists can address in the laboratory by simulating the different environments inside our planet.’
The researchers experimented on very small samples of synthetic ocean floor rock at high pressures and temperatures. This allowed them to determine the conditions at which subducting slabs would undergo melting as they pass through the upper mantle. By comparing the measured melting behaviour with models of subducting slab temperatures, they showed that almost all slabs are expected to release the majority of their carbon in a melt between about 300 and 700 km depth.
In addition, by experimentally reacting the released melts with ambient mantle, they reproduced the unique mineral makeup that is observed as inclusions in natural ‘superdeep’ diamonds, which originate from depths beyond 250km. This provides not only a plausible explanation for the formation of these unique samples, but also demonstrates that superdeep diamonds are a snapshot of the deepest portions of the Earth’s carbon cycle, making them an invaluable tool for better understanding the interior of our planet.
Dr Andrew Thomson said “One of the most amazing ideas that comes from this work is that superdeep diamonds are like marathon runners that have just crossed the finish line. The difference in this case is the diamonds have just completed one of the most mind baffling journeys possible, from the ocean floor to around 700 km depth and back to the surface. Fortunately for scientists, their mineral inclusions are like stopwatches recording the entire journey, and with further work we will hopefully reveal many more remarkable secrets about their epic journey.’
Dr Simon Kohn said: ‘Superdeep diamonds hold great potential for future research on the Earth’s volatile cycles, and we now know much more about the fundamental process that forms them. We will be able to use the wealth of information that is trapped inside the diamonds to build a detailed picture of processes occurring hundreds of kilometres beneath our feet.”
Dr Richard Brooker said: ‘The thin crust that makes up the dynamic tectonic plates covering the Earth’s surface is relatively exotic compared to the bulk planet composition, and represents a high concentration of many elements important to life on earth, but it continually recycles back into the vast mantle where it become re-diluted to varying degrees over time. However, mixing is not perfect and isolated traces of the subducted crust components remain like fingerprints, which have long been recognised in the magmas (and indeed diamonds) that arrive back at the Earth’s surface. The carbonate-rich melts discovered in this study may potentially be responsible for a specific chemical fingerprints that is repeatedly seen in multiple unrelated global locations.’
Reference:
Andrew R. Thomson et al. Slab melting as a barrier to deep carbon subduction, Nature (2016). DOI: 10.1038/nature16174
Graphic showing how the geoelectric vectors (black) can vary with location during a magnetic storm. Locations with cool colors (blue and green) and long lines represent relatively higher hazards for impacts on Earth’s surface from a magnetic storm. Locations with warm colors (red and orange) and short vectors represent relatively lower hazards for impacts from a magnetic storm, while long vectors represent higher hazard. Credit: Paul Bedrosian, USGS
Magnetic storms can interfere with the operation of electric power grids and damage grid infrastructure. They can also disrupt directional drilling for oil and gas, radio communications, communication satellites and GPS systems.
While magnetic storms are caused by variable conditions in the space weather above our heads, an accurate evaluation of the resulting hazards requires a detailed understanding of the electrical conductivity of the Earth beneath our feet.
A new USGS article examines the feasibility of mapping ground-level hazards from magnetic storms by using magnetotelluric (MT) survey data. The article was recently published in Geophysical Research Letters.
What is a Magnetic Storm?
The Sun is constantly emitting a wind of electrically charged particles. However, when a large sunspot emerges on the face of the Sun, there is an increased chance for an abrupt ejection of concentrated solar wind. A magnetic storm can result from the interaction of these concentrated bursts of solar wind with the Earth’s surrounding magnetosphere. During a magnetic storm, geoelectric fields are induced in the Earth’s interior.
Need for MT Surveys
MT surveys are made by deploying sensors on the ground that measure magnetic and electric field variation over time. Data from such surveys allow scientists to construct three-dimensional models of the Earth’s interior electrical conductivity structure. These models, in turn, enable scientists to estimate electric fields that can be generated in the Earth during magnetic storms.
With support from the National Science Foundation EarthScope project and management from Oregon State University, MT surveys have been made across several geographic regions of the United States.
The data and results from this work will help the Federal Energy Regulatory Commission and the North American Electric Reliability Corporation develop standards to ensure that the nation’s power grids are resilient to geomagnetic storm hazards. This USGS research was motivated by the recent release of the U.S. National Space Weather Strategy, which identifies priorities and needed actions for the benefit of the nation.
Simulation showing how geoelectric vectors (black) would vary across the midwestern United States for hypothetical magnetic variation (green). Geographic differences in geoelectric vectors are the result of complex conductivity within the Earth. Credit: USGS
The Earth is an Electrical Conductor?
Yes, and it is very complex. The conductivity of Earth varies with geographic location and depth below the surface as a result of our planet’s geological and tectonic history.
For a given rock type, electrical conductivity depends on mineralogy, temperature and water content. Seawater is also electrically conductive. Therefore, a complete description of Earth conductivity also depends on the geometry and depth of the oceans.
Basis for Conclusions
USGS scientists studied EarthScope MT survey data from across the midwestern United States to determine whether or not geoelectric fields induced in the Earth during a magnetic storm could be mapped. Their analysis showed that the geoelectric fields can be mapped, and that Earth’s three-dimensional electrical conductivity has a significant effect on these fields during magnetic storms.
Next Steps
Geoelectric mapping is challenging due to the complex structure of the Earth’s interior. Monitoring equipment and surveying sites are sparsely distributed over the United States. The nation needs to improve magnetic monitoring and complete MT surveys in order to accurately estimate magnetic-storm hazards across the country.
USGS Science
The pursuit of understanding space weather and its impacts is a collaborative effort by government, academic and private sector agencies. The White House Office of Science and Technology Policy coordinates the space-weather related work of the several federal agencies, including the USGS.
The USGS Geomagnetism Program monitors variations in the Earth’s magnetic field through a network of 14 ground-based observatories around the United States and its territories. This network enables USGS scientists monitor the geomagnetic field every single second throughout the country. The USGS observatory data are then used to calculate magnetic storm intensity. USGS scientists not only conduct research into the physical causes and effects of magnetic storms, but they develop methods to improve our real-time situational awareness and assess the hazardous effects of magnetic storms.
The USGS is involved with making maps of magnetic activity, which are derived from data we acquire from ground-based observatories. In addition, USGS scientists are mapping the nature of the Earth’s lithosphere to construct maps needed for the evaluation of geomagnetic hazards.
Reference:
Paul A. Bedrosian et al. Mapping geoelectric fields during magnetic storms: Synthetic analysis of empirical United States impedances, Geophysical Research Letters (2015). DOI: 10.1002/2015GL066636
Undersea mountains near the Hawaiian Islands, from the Marine Geoscience Data System. Images of the mountains and nearby seafloor are derived from sonar readings taken along the paths sailed by research ships.
The bottom of the ocean just keeps getting better. Or at least more interesting to look at.
In an ongoing project, mappers at Lamont-Doherty Earth Observatory have been gathering data from hundreds of research cruises and turning it all into accessible maps of the ocean floor with resolutions down to 25 meters.
You can see some of the results here, at a mapping site that allows scientists—and you—to zero in on a particular location, zoom in and download topographical maps of the ocean floor. The Lamont data has also contributed to the latest version of Google ocean map, which now offers its own more closely resolved view of the ocean floor globally. (You can take a quick tour of the updated Google map here.)
“I love looking at everything,” said Vicki Ferrini, a scientist at Lamont who oversees the team that synthesizes the data and creates the maps. Ferrini may have absorbed more data about the ocean floor than anyone; a self-professed map and data geek, she says she has her own map of the oceans in her head.
“I really like these sinuous channels in the deep sea, they’re very cool to me. … There [are] clearly concentrated areas of energy that are able to scour these river-like features through the seafloor. And the [mid-ocean] ridges are all pretty cool.”
The new data from Lamont covers about 8 percent of the ocean floor, a fraction of the oceans, but a sizable piece overall of the earth’s surface. The data mostly comes as a byproduct of scientific expeditions that send research vessels criss-crossing the seas, explained Suzanne Carbotte, a professor of marine geology and geophysics at Lamont. The cruises may not be focused on ocean topography at all; but as the ships sail, they keep their measuring instruments humming and collect sonar data.
The sonar sends a pulse of sound down through the water column, and uses the speed of the sound’s return to calculate depth. Data from U.S. expeditions is archived by the National Oceanic and Atmospheric Administration. Lamont processes that data, gathers more from scientists around the world, and turns it into maps.
The Google ocean map, covering the entire ocean floor, relies mostly on data collected by satellite that is curated by the Scripps Institution of Oceanography, in partnership with NOAA, the U.S. Navy and the National Geospatial Intelligence Agency, with contributions from the Japan Agency for Marine-Earth Science and Technology and Australia Geosciences-AGSO. It also incorporates the more precise data from Lamont. (A video produced by Scripps at this site offers an interesting global tour of mid-ocean ridges.)
The satellite data details small changes in sea surface height which, through gravity, reflect the underlying topography of the sea floor. The latest version of the Scripps-NOAA ocean map offers a resolution of roughly 500 meters—an improvement over the earlier, 1 kilometer resolution. That means one data point for every 500-meter-square grid of the seafloor. Even that rough picture is valuable, Carbotte said. “The coarse data does a beautiful job revealing the detailed boundaries of earth’s tectonic plates and other large-scale seafloor structures, and the map covers the entire ocean,” she said.
Those measurements allowed researchers to discover a new “microplate” in the Indian Ocean—a remnant from the crustal shifts that sent the Indian subcontinent crashing into Eurasia, creating (and still forming) the Himalaya mountains. Researchers studying that plate have come up with a more precise date for when that collision began, 47.3 million years ago.
But the finer resolution mapping processed by Lamont opens up other avenues for scientists. “It allows you to study the active modern processes that shape the seafloor,” Carbotte said, like earthquakes and undersea landslides that can flush sediments across long distances.
Scientists can dive into the maps and data and use various tools at the Marine Geoscience Data System site, created to provide free public access to marine geoscience data. Lamont-Doherty serves as the host laboratory; funding comes from the National Science Foundation, and from Google. The mapping page, here, has a “masking” tool (at the upper right) that allows the viewer to see the tracks of research vessels and contrast the sonar data results with the broader ocean map. Some of the more interesting features include the deep ocean trenches, the zigs and zags of fault lines where earth’s crust is forming and deforming, and massive oceanic plateaus and undersea volcanoes that reflect volcanic outpourings away from the mid-ocean ridges. There are “fabulous canyons that carve the continental margins and channels that extend out into the deeper oceans,” Carbotte said.
Scientists expect to see plenty of activity along the edges of tectonic plates including at the mid-oceanic ridges, where new crust is formed from upwelling and melting of the mantle below, and at subduction zones, where enormous slabs of earth’s crust collide and one plate sinks beneath another. But the new mapping has helped scientists see that there’s also geologic activity in the broad interior spaces of the oceanic plates, Carbotte says, such as fields of volcanic seamounts of many sizes, and far-reaching channels of sediments transported into the deep ocean.
The finer resolution helps scientists study how the crust forms at mid-ocean ridges and then deforms before descending into earth’s mantle, bending and faulting along subduction zones. “With the new detailed data from many subduction zones, we can conduct comparative studies of this bend faulting and relationships to the rate of subduction, the age of the plate and sediment cover, and [that] helps us in … understanding the subduction process,” Carbotte says.
The process of mapping the ocean floor in detail continues; there’s enough data already available to keep Carbotte, Ferrini and the staff busy for a long time. Covering just 8 percent of the oceans has involved hundreds of cruises over millions of miles. The oceans are so large that a thorough mapping would involve an estimated 125 to 200 ship-years of cruises (mapping on land, even on distant planets, can happen far more quickly using satellites). The Lamont crew updates their maps every six months.
Lamont has been collecting measurements and other data about the oceans for more than half a century. The first comprehensive map of the global ocean floor was created by Lamont oceanographers Marie Tharp and Bruce Heezen and published in 1977. In the 1980s, another Lamont scientist, William Haxby, used satellite measurements to compose the first “gravity field” map of the oceans. Now, the same database contributing to Google Earth feeds Lamont’s EarthObserver, a global scientific mapping application for iPads and other mobile devices.
When we step onto an airliner, “We have map displays at our seats that show the flight paths, and it used to be the ocean was just a single flat, featureless blue,” Carbotte said. “Now they make use of these new ocean floor maps, so when you’re flying across the middle of the Atlantic, you can see the mid-ocean ridge right from your airplane seat.”
When calcium carbonate crystallizes into hard shells, it incorporates soft bits of proteins to add strength. Research done in the lab shows how this might happen, and why it works. Credit: Wikipedia Public Domain
Seashells and lobster claws are hard to break, but chalk is soft enough to draw on sidewalks. Though all three are made of calcium carbonate crystals, the hard materials include clumps of soft biological matter that make them much stronger. A study today in Nature Communications reveals how soft clumps get into crystals and endow them with remarkable strength.
The results show that such clumps become incorporated via chemical interactions with atoms in the crystals, an unexpected mechanism based on previous understanding. By providing insight into the formation of natural minerals that are a composite of both soft and hard components, the work will help scientists develop new materials for a sustainable energy future, based on this principle.
“This work helps us to sort out how rather weak crystals can form composite materials with remarkable mechanical properties,” said materials scientist Jim De Yoreo of the Department of Energy’s Pacific Northwest National Laboratory. “It also provides us with ideas for trapping carbon dioxide in useful materials to deal with the excess greenhouse gases we’re putting in the atmosphere, or for incorporating light-responsive nanoparticles into highly ordered crystalline matrices for solar energy applications.”
Beautiful and functional
Calcium carbonate is one of the most important materials on earth, crystallizing into chalk, shells, and rocks. Animals from mollusks to people use calcium carbonate to make biominerals such as pearls, seashells, exoskeletons, or the tiny organs in ears that maintain balance. These biominerals include proteins or other organic matter in the crystalline matrix to convert the weak calcium carbonate to hard, durable materials.
Scientists have been exploring how organisms produce these biominerals in the hopes of determining the basic geochemical principles of how they form, and also how to build synthetic materials with unique properties in any desired shape or size.
The strength of a material depends on how easy it is to disrupt its underlying crystal matrix. If a material is compressed, then it becomes harder to break the matrix apart. Proteins trapped in calcium carbonate crystals create a compressive force — or strain — within the crystal structure.
Unlike the strain that makes muscles sore, this compressive strain is helpful in materials, because it makes it harder to disrupt the underlying crystal structure, thereby adding strength. Scientists understand how forces, stress and strain combine to make strong materials, but they understand less about how to create the materials in the first place.
Pearls of wisdom
The leading explanation for how growing crystals incorporate proteins and other particles is by simple mechanics. Particles land on the flat surface of calcium carbonate as it is crystallizing, and units of calcium carbonate attach over and around the particles, trapping them.
“The standard view is that the crystal front moves too fast for the inclusions to move out of the way, like a wave washing over a rock,” said De Yoreo.
That idea’s drawback is that it lacks the details needed to explain where the strain within the material comes from. The new results from De Yoreo and colleagues do, however.
“We’ve found a completely different mechanism,” he said.
To find out how calcium carbonate incorporates proteins or other strength-building components, the team turned to atomic force microscopy, also known as AFM, at the Molecular Foundry, a DOE Office of Science User Facility at Lawrence Berkeley National Laboratory. In AFM, the microscope tip delicately runs over the surface of a sample like a needle running over the grooves in a vinyl record. This creates a three-dimensional image of a specimen under the scope.
The team used a high concentration of calcium carbonate that naturally forms a crystalline mineral known as calcite. The calcite builds up in layers, creating uneven surfaces during growth, like steps and terraces on a mountainside. Or, imagine a staircase. A terrace is the flat landing at the bottom; the stair steps have vertical edges from which calcite grows out, eventually turning into terraces too.
For their inclusions, the team created spheres out of organic molecules and added them to the mix. These spheres called micelles are molecules that roll up like roly-poly bugs based on the chemistry along their bodies — pointing outwards are the parts of their molecules that play well chemically with both the surrounding water and the calcite, while tucked inside are the parts that don’t get along with the watery environment.
Better composites through chemistry
The first thing the team noticed under the microscope is that the micelles do not randomly land on the flat terraces. Instead they only stick to the edges of the steps.
“The step edge has chemistry that the terrace doesn’t,” said De Yoreo. “There are these extra dangling bonds that the micelles can interact with.”
The edges hold onto the micelles as the calcium carbonate steps close around them, one after another. The team watched as the growing steps squeezed the micelles. As the step closed around the top of the micelle, first a cavity formed and then it disappeared altogether under the surface of the growing crystal.
To verify that the micelles were in fact buried within the crystals, the team dissolved the crystal and looked again. Like running a movie backwards, the team saw micelles appear as the layers of crystal disappeared.
Finally, the team recreated the process in a mathematical simulation. This showed them that the micelles — or any spherical inclusions — are compressed like springs as the steps close around them. These compressed springs then create strain in the crystal lattice between the micelles, leading to enhanced mechanical strength. This strain likely accounts for the added strength seen in seashells, pearls and similar biominerals.
“The steps capture the micelles for a chemical reason, not a mechanical one, and the resulting compression of the micelles by the steps then leads to forces that explain where the strength comes from,” said De Yoreo.
Reference:
Kang Rae Cho, Yi-Yeoun Kim, Pengcheng Yang, Wei Cai, Haihua Pan, Alexander N. Kulak, Jolene L. Lau, Prashant Kulshreshtha, Steven P. Armes, Fiona C. Meldrum & James J. De Yoreo. Direct observation of mineral-organic composite formation reveals occlusion mechanism, Nature Communications January 6, 2016, DOI:10.1038/NCOMMS10187.
This is a reconstruction of dinosaurs engaged in sexual display activity: artwork by Lida Xing and Yujiang Han. Credit: University of Colorado Denver
Dinosaurs engaged in mating behavior similar to modern birds, leaving the fossil evidence behind in 100 million year old rocks, according to new research by Martin Lockley, professor of geology at the University of Colorado Denver.
Lockley, a paleontologist, led an international research team that discovered large ‘scrapes’ in the prehistoric Dakota sandstone of western Colorado. These ancient scrapes are similar to a behavior known as ‘nest scrape display’ or ‘scrape ceremonies’ among modern birds, where males show off their ability to provide by excavating pseudo nests for potential mates.
“These are the first sites with evidence of dinosaur mating display rituals ever discovered, and the first physical evidence of courtship behavior,” Lockley said. “These huge scrape displays fill in a missing gap in our understanding of dinosaur behavior.”
The study will be published in the journal Scientific Reports (Nature Publishing Group) on January 7.
Lockley, an expert on dinosaur footprints, found evidence of more than 50 dinosaur scrapes, some as large as bathtubs, in an area where tracks of carnivorous and herbivorous dinosaurs have also been confirmed. The display arenas, also called ‘leks’ were found in two National Conservation Areas (Dominguez-Escalante and Gunnison Gorge) on property permitted by the Bureau of Land Management near Delta, Colorado.
Lockley also discovered evidence of mating areas at Dinosaur Ridge, a National Natural Landmark, just west of Denver.
This new fossil evidence supports theories about the nature of dinosaur mating displays and the evolutionary driver known as `sexual selection.’ Since prehistoric times, males looking for mates, have driven off weaker rivals. Females, meanwhile, have chosen the most impressive male performers as consorts.
Similar sexual selection behaviors are common in mammals and birds. But until now scientists could only speculate about dinosaur mating behavior, assuming it might be similar to that of their modern relatives, the birds.
“The scrape evidence has significant implications,” said Lockley. “This is physical evidence of pre-historic foreplay that is very similar to birds today. Modern birds using scrape ceremony courtship usually do so near their final nesting sites. So the fossil scrape evidence offers a tantalizing clue that dinosaurs in ‘heat’ may have gathered here millions of years ago to breed and then nest nearby.”
Lockley and his team were unable to remove the scrape marks from the gigantic slabs of rock without damaging them. Instead, they created 3-D images of the scrapes using a technique of layering photographs called photogrammetry. They also made rubber molds and fiberglass copies of the scrapes that are being stored at the Denver Museum of Nature & Science.
Reference:
Martin G. Lockley, Richard T. McCrea, Lisa G. Buckley, Jong Deock Lim, Neffra A. Matthews, Brent H. Breithaupt, Karen J. Houck, Gerard D. Gierliński, Dawid Surmik, Kyung Soo Kim, Lida Xing, Dal Yong Kong, Ken Cart, Jason Martin, Glade Hadden. Theropod courtship: large scale physical evidence of display arenas and avian-like scrape ceremony behaviour by Cretaceous dinosaurs. Scientific Reports, 2016; 6: 18952 DOI: 10.1038/srep18952
