Maps of GPS points in the western United States, with blue indicating a drop and yellow-red reflecting a rise. Credit: Image courtesy of University of California – San Diego
The severe drought gripping the western United States in recent years is changing the landscape well beyond localized effects of water restrictions and browning lawns. Scientists at Scripps Institution of Oceanography at UC San Diego have now discovered that the growing, broad-scale loss of water is causing the entire western U.S. to rise up like an uncoiled spring.
Investigating ground positioning data from GPS stations throughout the west, Scripps researchers Adrian Borsa, Duncan Agnew, and Dan Cayan found that the water shortage is causing an “uplift” effect up to 15 millimeters (more than half an inch) in California’s mountains and on average four millimeters (0.15 of an inch) across the west. From the GPS data, they estimate the water deficit at nearly 240 gigatons (62 trillion gallons of water), equivalent to a six-inch layer of water spread out over the entire western U.S.
Adrian Borsa, an assistant research geophysicist at Scripps Institution of Oceanography, UC San Diego.
Results of the study, which was supported by the U.S. Geological Survey (USGS), appear in the August 21 online edition of the journal Science.
While poring through various sets of data of ground positions from highly precise GPS stations within the National Science Foundation’s Plate Boundary Observatory and other networks, Borsa, a Scripps assistant research geophysicist, kept noticing the same pattern over the 2003-2014 period: All of the stations moved upwards in the most recent years, coinciding with the timing of the current drought.
Agnew, a Scripps Oceanography geophysics professor who specializes in studying earthquakes and their impact on shaping Earth’s crust, says the GPS data can only be explained by rapid uplift of the tectonic plate upon which the western U.S. rests (Agnew cautions that the uplift has virtually no effect on the San Andreas fault and therefore does not increase the risk of earthquakes).
For Cayan, a research meteorologist with Scripps and USGS, the results paint a new picture of the dire hydrological state of the west.
“These results quantify the amount of water mass lost in the past few years,” said Cayan. “It also represents a powerful new way to track water resources over a very large landscape. We can home in on the Sierra Nevada mountains and critical California snowpack. These results demonstrate that this technique can be used to study changes in fresh water stocks in other regions around the world, if they have a network of GPS sensors.”
The study was supported by USGS National Earthquake Hazards Reduction Program.
Journal Reference:
Adrian Antal Borsa, Duncan Carr Agnew, and Daniel R. Cayan. Ongoing drought-induced uplift in the western United States. Science, 21 August 2014 DOI: 10.1126/science.1260279
Note : The above story is based on materials provided by University of California – San Diego.
Jurassic thylacocephalan Clausocaris lithographica. Credit: Haug et al. 2014
A new species of carnivorous crustacean has been identified, which roamed the seas 435 million years ago, grasping its prey with spiny limbs before devouring it. The fossil is described and details of its lifestyle are published in the open access journal BMC Evolutionary Biology.
The fossils were discovered near Waukesha, Wisconsin, with the new species, Thylacares brandonesis, named after the Brandon Bridge Formation where it was found. It is the oldest known example of the Thylacocephala group — shrimp-like creatures, mostly from the Jurassic period, known for their bulbous eyes and multiple limbs. The muscle structure and leg morphology of the new species suggests that it used its long, claw-like appendages to catch prey in a similar way to modern remipedes, blind crustaceans still found in salt water-filled caves.
Derek Briggs, Yale University, says: “This new research extends the range of this enigmatic group of fossil arthropods back to the Silurian, some 435 million years ago, and provides evidence that they belong among the crustaceans, the modern group that includes lobsters, shrimps and crabs.”
Carolin Haug, LMU Munich, said: “T. brandonensis was probably an actively hunting predator, which caught the prey with its front claws and crushed it into smaller pieces with the protrusions nearer its mouthparts.”
“This early, Silurian, example of Thylacocephala is in many ways much less extreme than the more recent Jurassic species. It still has normal-sized eyes in contrast to the very enlarged ones that came later, and shorter front claws in T. brandonensis compared to the extremely elongated ones in more recent Jurassic representatives.”
The description of the new Silurian species was part of a wider investigation into this group of fossils, including several new Jurassic specimens. Modern imaging techniques allowed the scientists to visualise new features, such as the tiny details of the T. brandonensis muscle structure. Based on these images, they created 3D models of the new species, which help us to understand the creature’s life habits.
Journal Reference:
Carolin Haug, Derek E G Briggs, Donald G Mikulic, Joanne Kluessendorf, Joachim T Haug. The implications of a Silurian and other thylacocephalan crustaceans for the functional morphology and systematic affinities of the group. BMC Evolutionary Biology, 2014; 14 (1): 159 DOI: 10.1186/s12862-014-0159-2
Note : The above story is based on materials provided by BioMed Central.
The San Andreas Fault is a continental transform fault that runs a length of roughly 810 miles (1,300 km) through California in the United States. The fault’s motion is right-lateral strike-slip (horizontal motion). It forms the tectonic boundary between the Pacific Plate and the North American Plate
The fault was first identified in Northern California by UC Berkeley geology professor Andrew Lawson in 1895 and named by him after a small lake which lies in a linear valley formed by the fault just south of San Francisco, the Laguna de San Andreas. After the 1906 San Francisco Earthquake, Lawson also discovered that the San Andreas Fault stretched southward into southern California. Large-scale (hundreds of miles) lateral movement along the fault was first proposed in a 1953 paper by geologists Mason Hill and Thomas Dibblee
Morganucodon and Kuehneotherium. Credit: Pamela Gill
New analyses of tiny fossil mammals from Glamorgan, South Wales are shedding light on the function and diets of our earliest ancestors, a team including researchers from the University of Southampton report today in the journal Nature. Mammals and their immediate ancestors from the Jurassic period (201-145 million years ago) developed new characteristics — such as better hearing and teeth capable of precise chewing.
By analysing jaw mechanics and fossil teeth, the team were able to determine that two of the earliest shrew-sized mammals, Morganucodon and Kuehneotherium, were not generalised insectivores but had already evolved specialised diets, feeding on distinct types of insects.
Lead author, Dr Pamela Gill of the University of Bristol, said: “None of the fossils of the earliest mammals have the sort of exceptional preservation that includes stomach contents to infer diet, so instead we used a range of new techniques which we applied to our fossil finds of broken jaws and isolated teeth. Our results confirm that the diversification of mammalian species at the time was linked with differences in diet and ecology.”
The team used synchrotron X-rays and CT scanning to reveal in unprecedented detail the internal anatomy of these tiny jaws, which are only 2cm in length. As the jaws are in many pieces, the scans were ‘stitched together’ to make a complete digital reconstruction. Finite element modelling, the same technique used to design hip joints and bridges, was used to perform a computational analysis of the strength of the jaws. This showed that Kuehneotherium and Morganucodon had very different abilities for catching and chewing prey.
Study co-author, Dr Neil Gostling from the University of Southampton, said: “The improvement in CT scanning, both in the instrumentation, at Light Source at the Paul Scherrer Institute in Switzerland where we scanned or even the µ-VIS Centre at Southampton, along with access for research of this kind, allows us to make inroads into understanding the biology and the ecology of animals long dead. The questions asked of the technology do not produce ‘speculation’, rather the results show a clearly defined answer based on direct comparison to living mammals. This would not be possible without the computational techniques we have used here.”
Using an analysis previously carried out on the teeth of present-day, insect-eating bats, the researchers found that the teeth of Morganucodon and Kuehneotherium had very different patterns of microscopic pits and scratches, known as ‘microwear’. This indicated they were eating different things with Morganucodon favouring harder, crunchier food items such as beetles while Kuehneotherium selected softer foods such as scorpion flies which were common at the time.
Team leader, Professor Emily Rayfield from the University of Bristol, added: “This study is important as it shows for the first time that the features that make us unique as mammals, such as having only one set of replacement teeth and a specialised jaw joint and hearing apparatus, were associated with the very earliest mammals beginning to specialise their teeth and jaws to eat different things.”
Note : New analyses of tiny fossil mammals from Glamorgan, South Wales are shedding light on the function and diets of our earliest ancestors, a team including researchers from the University of Southampton report today in the journal Nature. Mammals and their immediate ancestors from the Jurassic period (201-145 million years ago) developed new characteristics — such as better hearing and teeth capable of precise chewing.
By analysing jaw mechanics and fossil teeth, the team were able to determine that two of the earliest shrew-sized mammals, Morganucodon and Kuehneotherium, were not generalised insectivores but had already evolved specialised diets, feeding on distinct types of insects.
Lead author, Dr Pamela Gill of the University of Bristol, said: “None of the fossils of the earliest mammals have the sort of exceptional preservation that includes stomach contents to infer diet, so instead we used a range of new techniques which we applied to our fossil finds of broken jaws and isolated teeth. Our results confirm that the diversification of mammalian species at the time was linked with differences in diet and ecology.”
The team used synchrotron X-rays and CT scanning to reveal in unprecedented detail the internal anatomy of these tiny jaws, which are only 2cm in length. As the jaws are in many pieces, the scans were ‘stitched together’ to make a complete digital reconstruction. Finite element modelling, the same technique used to design hip joints and bridges, was used to perform a computational analysis of the strength of the jaws. This showed that Kuehneotherium and Morganucodon had very different abilities for catching and chewing prey.
Study co-author, Dr Neil Gostling from the University of Southampton, said: “The improvement in CT scanning, both in the instrumentation, at Light Source at the Paul Scherrer Institute in Switzerland where we scanned or even the µ-VIS Centre at Southampton, along with access for research of this kind, allows us to make inroads into understanding the biology and the ecology of animals long dead. The questions asked of the technology do not produce ‘speculation’, rather the results show a clearly defined answer based on direct comparison to living mammals. This would not be possible without the computational techniques we have used here.”
Using an analysis previously carried out on the teeth of present-day, insect-eating bats, the researchers found that the teeth of Morganucodon and Kuehneotherium had very different patterns of microscopic pits and scratches, known as ‘microwear’. This indicated they were eating different things with Morganucodon favouring harder, crunchier food items such as beetles while Kuehneotherium selected softer foods such as scorpion flies which were common at the time.
Team leader, Professor Emily Rayfield from the University of Bristol, added: “This study is important as it shows for the first time that the features that make us unique as mammals, such as having only one set of replacement teeth and a specialised jaw joint and hearing apparatus, were associated with the very earliest mammals beginning to specialise their teeth and jaws to eat different things.”
Note : The above story is based on materials provided by University of Southampton.
A new ovoid structure discovered in the Nakhla Martian meteorite is made of nanocrystalline iron-rich clay, contains a variety of minerals, and shows evidence of undergoing a past shock event from impact, with resulting melting of the permafrost and mixing of surface and subsurface fluids.
Based on the results of a broad range of analytical studies to determine the origin of this new structure, scientists present the competing hypotheses for how this ovoid formed, point to the most likely conclusion, and discuss how these findings impact the field of astrobiology in a fascinating article published in Astrobiology, a peer-reviewed journal from Mary Ann Liebert, Inc., publishers.
In the article, “A Conspicuous Clay Ovoid in Nakhla: Evidence for Subsurface Hydrothermal Alteration on Mars with Implications for Astrobiology,” Elias Chatzitheodoridis, National Technical University of Athens, Greece, and Sarah Haigh and Ian Lyon, the University of Manchester, UK, describe the use of tools including electron microscopy, x-ray, and spectroscopy to analyze the ovoid structure. While the authors do not believe the formation of this structure involved biological materials, that is a possible hypothesis, and they note that evidence exists supporting the presence of niche environments in the Martian subsurface that could support life.
“This study illustrates the importance of correlating different types of datasets when attempting to discern whether something in rock is a biosignature indicative of life,” says Sherry L. Cady, PhD, Editor-in-Chief of Astrobiology and Chief Scientist at the Pacific Northwest National Laboratory. “Though the authors couldn’t prove definitively that the object of focus was evidence of life, their research strategy revealed a significant amount of information about the potential for life to inhabit the subsurface of Mars.”
Journal Reference:
Elias Chatzitheodoridis, Sarah Haigh, Ian Lyon. A Conspicuous Clay Ovoid in Nakhla: Evidence for Subsurface Hydrothermal Alteration on Mars with Implications for Astrobiology. Astrobiology, 2014; 14 (8): 651 DOI: 10.1089/ast.2013.1069
Note : The above story is based on materials provided by Mary Ann Liebert, Inc., Publishers.
A new study provides an exciting insight into the Late Cretaceous and the diversity and distribution of the toothless ‘dragon’ pterosaurs from the Azhdarchidae family. The research was published in the open access journal ZooKeys.
The Azhdarchidan pterosaurs derive their name from the Persian word for dragon — Aždarha. Interestingly, this derived and rather successful group of pterosaurs included some of the largest known flying animals of all times, with a wingspan reaching between 10 and 12 m.
‘Dragon’ pterosaurs had a worldwide distribution once and were the last of their kind to survive on the planet, until some 60 mya. They dominated the skies during the Late Cretaceus and unlike their predecessors, were characteristically toothless.
“This shift in dominance from toothed to toothless pterodactyloids apparently reflects some fundamental changes in Cretaceous ecosystems, which we still poorly understand,” comments the author of the study Dr Alexander Averianov, Zoological Institute of the Russian Academy of Sciences.
Generally fossil record of pterosaurs is patchy and confined mostly to sedimentary deposits known as Konservat-Lagerstätten where exceptional depositional conditions facilitated preservation of fragile pterosaur bones. Unfortunately, such Lagerstätten are very rare for the Late Cretaceous when most of the evolutionary history of Azhdarchidae took place, which makes these exciting creatures exceptionally hard to study.
“Azhdarchidae currently represent a real nightmare for paleontologists: most taxa are known from few fragmentary bones, which often do not overlap between named taxa, the few articulated skeletons are poorly preserved, and some of the best available material has remained undescribed for forty years.” explains Dr Averianov about the difficulties studying the group.
Despite these difficulties, the number of localities were azhdarchidan pterosaurs were found is impressive and undoubtedly reflect the important role they played in the Cretaceous ecosystems. These flying giants likely inhabited a large variety of environments, but seem to have been abundant near large lakes and rivers and most common in nearshore marine environments. Note : The above story is based on materials provided by Pensoft Publishers. The original story is licensed under a Creative Commons License.
The microorganisms that came out of Subglacial Lake Whillans were “incredibly diverse,” and the microbial cells came in a variety of shapes. The yellow arrow points to a rod-shaped cell as seen through a scanning electron microscope. Credit: Image courtesy of WISSARD
The first breakthrough paper to come out of a massive U.S. expedition to one of Earth’s final frontiers shows that there’s life and an active ecosystem one-half mile below the surface of the West Antarctic Ice Sheet, specifically in a lake that hasn’t seen sunlight or felt a breath of wind for millions of years.
The life is in the form of microorganisms that live beneath the enormous Antarctic ice sheet and convert ammonium and methane into the energy required for growth. Many of the microbes are single-celled organisms known as Archaea, said Montana State University professor John Priscu, the chief scientist of the U.S. project called WISSARD that sampled the sub-ice environment. He is also co-author of the MSU author-dominated paper in the Aug. 21 issue of Nature.
“We were able to prove unequivocally to the world that Antarctica is not a dead continent,” Priscu said, adding that data in the Nature paper is the first direct evidence that life is present in the subglacial environment beneath the Antarctic ice sheet.
Lead author Brent Christner said, “It’s the first definitive evidence that there’s not only life, but active ecosystems underneath the Antarctic ice sheet, something that we have been guessing about for decades. With this paper, we pound the table and say, ‘Yes, we were right.'”
Priscu said he wasn’t entirely surprised that the team found life after drilling through half a mile of ice to reach Subglacial Lake Whillans in January 2013. An internationally renowned polar biologist, Priscu researches both the South and North Poles. This fall will be his 30th field season in Antarctica, and he has long predicted the discovery.
More than a decade ago, he published two manuscripts in the journal Science describing for the first time that microbial life can thrive in and under Antarctic ice. Five years ago, he published a manuscript where he predicted that the Antarctic subglacial environment would be the planet’s largest wetland, one not dominated by the red-winged blackbirds and cattails of typical wetland regions in North America, but by microorganisms that mine minerals in rocks at subzero temperatures to obtain the energy that fuels their growth.
Following more than a decade of traveling the world presenting lectures describing what may lie beneath Antarctic ice, Priscu was instrumental in convincing U.S. national funding agencies that this research would transform the way we view the fifth largest continent on the planet.
Although he was not really surprised about the discovery, Priscu said he was excited by some of the details of the Antarctic find, particularly how the microbes function without sunlight at subzero temperatures and the fact that evidence from DNA sequencing revealed that the dominant organisms are archaea. Archaea is one of three domains of life, with the others being Bacteria and Eukaryote.
Many of the subglacial archaea use the energy in the chemical bonds of ammonium to fix carbon dioxide and drive other metabolic processes. Another group of microorganisms uses the energy and carbon in methane to make a living. According to Priscu, the source of the ammonium and methane is most likely from the breakdown of organic matter that was deposited in the area hundreds of thousands of years ago when Antarctica was warmer and the sea inundated West Antarctica. He also noted that, as Antarctica continues to warm, vast amounts of methane, a potent greenhouse gas, will be liberated into the atmosphere enhancing climate warming.
The U.S. team also proved that the microorganisms originated in Lake Whillans and weren’t introduced by contaminated equipment, Priscu said. Skeptics of his previous studies of Antarctic ice have suggested that his group didn’t actually discover microorganisms, but recovered microbes they brought in themselves.
“We went to great extremes to ensure that we did not contaminate one of the most pristine environments on our planet while at the same time ensuring that our samples were of the highest integrity,” Priscu said.
Extensive tests were conducted at MSU two years ago on WISSARD’s borehole decontamination system to ensure that it worked, and Priscu led a publication in an international journal presenting results of these tests. This decontamination system was mated to a one-of-a-kind hot water drill that was used to melt a borehole through the ice sheet, which provided a conduit to the subglacial environment for sampling.
Every day in Antarctica, he would tell his team to keep it simple, Priscu said. To prove that an ecosystem existed below the West Antarctic Ice Sheet, he wanted at least three lines of evidence. They had to see microorganisms under the microscope that came from Lake Whillans and not contaminated equipment. They then had to show that the microorganisms were alive and growing. They had to be identifiable by their DNA.
When the team found those things, he knew they had succeeded, Priscu said.
The Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project officially began in 2009 with a $10 million grant from the National Science Foundation. Now involving 13 principal investigators at eight U.S. institutions, the researchers drilled down to Subglacial Lake Whillans in January 2013. The microorganisms they discovered are still being analyzed at MSU and other collaborating institutions.
Christner said species are hard to determine in microbiology, but “We are looking at a water column that probably has about 4,000 things we call species. It’s incredibly diverse.”
Planning to drill again this austral summer in a new Antarctic location, Priscu said WISSARD was the first large-scale multidisciplinary effort to directly examine the biology of an Antarctic subglacial environment. The Antarctic Ice Sheet covers an area 1 ½ times the size of the United States and contains 70 percent of Earth’s freshwater, and any significant melting can drastically increase sea level. Lake Whillans, one of more than 200 known lakes beneath the Antarctic Ice Sheet and the primary lake in the WISSARD study, fills and drains about every three years. The river that drains Lake Whillans flows under the Ross Ice Shelf, which is the size of France, and feeds the Southern Ocean, where it can provide nutrients for life and influence water circulation patterns.
The opportunity to explore the world under the West Antarctic Ice Sheet is an unparalleled opportunity for the U.S. team, as well as for several MSU-affiliated researchers who are part of that team and wrote or co-authored the Nature paper, Priscu said.
Christner, for one, was a postdoctoral researcher with Priscu and Mark Skidmore at MSU from 2002 through 2006. He is now associate professor of biological sciences at Louisiana State University. Jill Mikucki, now an assistant professor at the University of Tennessee in Knoxville, was one of Priscu’s doctoral students. Skidmore is a glacial geochemist in MSU’s Department of Earth Sciences. Andrew Mitchell, now at Aberystwyth University in the United Kingdom, was a postdoctoral researcher with MSU’s Center for Biofilm Engineering. Alex Michaud and Trista Vick-Majors are currently earning their doctorates in Priscu’s research group at MSU. Other MSU people on the team were Education and Outreach Coordinator Susan Kelly and Project Manager John Sherve.
The fact that MSU was so involved reflects the fact that it is pioneering a new field of science, Priscu said. MSU is the common ancestor of many scientists who study life in and under ice.
“I always tell my students when they come into the lab that ‘We are inventing this field of science. It’s working on life in ice and under ice. This field has never existed before. We thought it up. You are pioneers,'” Priscu said.
Appreciative of the opportunity to participate in WISSARD, Vick-Majors said she saw bacteria under the microscope within an hour after the first sample of water was pulled out of Subglacial Lake Whillans. Within days, she saw proof that the bacteria were active.
“It was very exciting. It will be hard to top,” she said.
She added that, “If you want to do microbial ecology in Antarctic subglacial environments, John is probably the person you want to work with. I feel very lucky to have gotten the opportunity.”
Agreeing, Michaud said, “Some of the graduate students joke, ‘How do we top this?’ We can’t.”
But the students can build on their WISSARD experience and gain a deeper understanding of Subglacial Lake Whillans and other subglacial habitats, he said. It’s not about going out and finding more novel habitats.
Christner said the team that wrote the paper in Nature is the dream team of polar biology. Besides the MSU-affiliated scientists, the co-authors include Amanda Achberger, a graduate student at Louisiana State University; Carlo Barbante, a geochemist at the University of Venice in Italy; Sasha Carter, a postdoctoral researcher at the University of California in San Diego; and Knut Christianson a postdoctoral researcher from St. Olaf College in Minnesota and New York University.
“I hope this exciting discovery will touch the lives (both young and old) of people throughout the world and inspire the next generation of polar scientists,” Priscu said.
Note : The above story is based on materials provided by Montana State University. The original article was written by Evelyn Boswell.
This is a marine crocodilian, here a dyrosaurid, swimming in the warm surface waters during the end of the Cretaceous period. Credit: Guillaume Suan
The ancestors of today’s crocodiles colonised the seas during warm phases and became extinct during cold phases, according to a new Anglo-French study which establishes a link between marine crocodilian diversity and the evolution of sea temperature over a period of more than 140 million years.
The research, led by Dr Jeremy Martin from the Université de Lyon, France and formerly from the University of Bristol, UK is published this week in Nature Communications.
Today, crocodiles are ‘cold-blooded’ animals that mainly live in fresh waters but two notable exceptions, Crocodylus porosus and Crocodylus acutus venture occasionally into the sea. Crocodiles occur in tropical climates, and they are frequently used as markers of warm conditions when they are found as fossils.
While only 23 species of crocodiles exist today, there were hundreds of species in the past. On four occasions in the past 200 million years, major crocodile groups entered the seas, and then became extinct. It is a mystery why they made these moves, and equally why they all eventually went extinct. This new study suggests that crocodiles repeatedly colonized the oceans at times of global warming.
Lead author of the report, Dr Jeremy Martin said: “We thought each of these evolutionary events might have had a different cause. However, there seems to be a common pattern.”
Dr Martin, with a team of paleontologists and geochemists from the Université de Lyon and the University of Bristol, compared the evolution of the number of marine crocodilian fossil species to the sea temperature curve during the past 200 million years. This temperature curve, established using an isotopic thermometer, is widely applied for reconstruction of past environmental conditions and in this case, is based on the isotopic composition of the oxygen contained in the fossilised remains of fossil marine fish (bone, teeth, scales).
Co-author, Christophe Lécuyer explained: “According to this method, it is possible to calculate the temperature of the water in which these fish lived by applying an equation linking the isotopic composition of the fossilised remains to the temperature of mineralisation of their skeleton. The seawater temperatures derived from the composition of fish skeleton thus corresponds to the temperature of water in which the marine crocodiles also lived.”
The results show that colonisation of the marine environment about 180 million years ago was accompanied by a period of global warming of the oceans. These first marine crocodilians became extinct about 25 million years later, during a period of global freezing. Then, another crocodilian lineage appeared and colonised the marine environment during another period of global warming.
The evolution of marine crocodilians is therefore closely tied to the temperature of their medium, and shows that their evolution and their lifestyle, as in modern crocodilians, are constrained by environmental temperatures.
Nevertheless, one fossil lineage does not appear to follow this trend. Jurassic metriorhynchoids did not go extinct during the cold spells of the early Cretaceous, unlike the teleosaurids, another group of marine crocodilians. Quite surprisingly, metriorhynchoids only disappeared a few million years later. This exception will certainly provide grounds for new research, particularly into how the biology of this group adapted to life in the pelagic environment.
Professor Michael Benton from the University of Bristol, another co-author of the study, said: “This work illustrates a case of the impact of climate change on the evolution of animal biodiversity, and shows that for crocodilians, warming phases of our earth’s history constitute ideal opportunities to colonise new environments.”
Note : The above story is based on materials provided by University of Bristol.
Schematic illustration of Earth’s magnetic field. Credit: Courtesy of NASA, Credit/Copyright: Peter Reid, The University of Edinburgh
Earth’s magnetic field, a familiar directional indicator over long distances, is routinely probed in applications ranging from geology to archaeology. Now it has provided the basis for a technique which might, one day, be used to characterize the chemical composition of fluid mixtures in their native environments.
Researchers from the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) conducted a proof-of-concept NMR experiment in which a mixture of hydrocarbons and water was analyzed using a high-sensitivity magnetometer and a magnetic field comparable to that of Earth.
The work was conducted in the NMR laboratory of Alexander Pines, one of the world’s foremost NMR authorities, as part of a long-standing collaboration with physicist Dmitry Budker at the University of California, Berkeley, along with colleagues at the National Institute of Standards and Technology (NIST). The work will be featured on the cover of Angewandte Chemie and is published in a paper titled “Ultra-Low-Field NMR Relaxation and Diffusion Measurements Using an Optical Magnetometer.” The corresponding author is Paul Ganssle, who was a PhD student in Pines’ lab at the time of the work.
“This fundamental research program seeks to answer a broad question: how can we sense the interior chemical and physical attributes of an object at a distance, without sampling it or encapsulating it?” says Vikram Bajaj, a principal investigator in Pines’ group. “A particularly beautiful aspect of magnetic resonance is its ability to gently peer within intact objects, but it’s tough to do that from far away.”
The exquisite sensitivity of NMR for detecting chemical composition, and the spatial resolution which it can provide in medical applications, requires large and precise superconducting magnets. These magnets are expensive and immobile. Further, the sample of interest must be placed inside the magnet, such that the entire sample is exposed to a homogeneous magnetic field. This well-developed method is called high-field NMR. The sensitivity of high-field NMR is proportional to magnetic field strength.
But chemical characterization of objects that cannot be placed inside a magnet requires a different approach. In ex situ NMR measurements, the geometry of a typical high-field experiment is reversed such that the detector probes the sample surface, and the magnetic field is projected into the object. A main challenge with this situation is generating a homogeneous magnetic field over a sufficiently large sample area: it is not feasible to generate field strengths necessary to make conventional high-resolution NMR measurements.
Instead of a superconducting magnet, low-field NMR measurements may rely on Earth’s magnetic field, given a sufficiently sensitive magnetometer.
“One nice thing about Earth’s magnetic field is that it’s very homogeneous,” explains Ganssle. “The problem with its use in inductively-detected MRI [MRI — magnetic resonance imaging — is NMR’s technological sibling] is that you need a magnetic field that’s both strong and homogeneous, so you need to surround the whole subject with superconducting coils, which is not something that’s possible in an application like oil-well logging.”
“Sensitivity of magnetic resonance depends profoundly on the magnetic field, because the field causes the detected spins to align slightly,” adds Bajaj. “The stronger the applied field, the stronger the signal, and the higher its frequency, which also contributes to the detection sensitivity.”
Paul Ganssle is the corresponding author of a paper in Angewandte Chemie describing ultra-low-field NMR using an optical magnetometer. (Photo by Roy Kaltschmidt)
Earth’s magnetic field is indeed very weak, but optical magnetometers can serve as detectors for ultra-low-field NMR measurements in the ambient field alone without any permanent magnets. This means that ex-situ measurements lose chemical sensitivity due to field strength alone. But this method offers other advantages.
Relaxation and diffusion
In high-field NMR, the chemical properties of a sample are determined from their resonance spectrum, but this is not possible without either extremely high fields or extremely long-lived coherent signals (neither of which are possible with permanent magnets). In contrast, relaxation and diffusion measurements in low-field NMR are more than sufficient to determine bulk materials properties.
“The approach at low-field, which you can achieve using permanent magnets or Earth’s magnetic field, is to measure spin relaxation,” explains Ganssle. Relaxation refers to the rate at which polarized spin returns to equilibrium, based on chemical and physical characteristics of the system. Additionally, NMR experiments resolve chemical compounds based on their different diffusion coefficients, which depend on the size and shape of the molecule.
A key difference between this and conventional experiments is that the relaxation and diffusion properties are resolved through optically-detected NMR, which operates sensitively even in low magnetic fields.
“A previous achievement of our collaboration has been the development of magnetometers for the detection of NMR,” says Bajaj. “This experiment represents the first time magnetometers have been used to make combined relaxation and diffusion measurements of multicomponent mixtures.”
Relaxation and/or diffusion measurements are already commonly used in the oil industry for underground NMR measurements, though conventional probes use a permanent magnet to increase the local magnetic field. There were attempts to perform oil well logging starting in the 1950s using the Earth’s ambient field, but insufficient detection sensitivity led to the introduction of magnets, which are now ubiquitous in logging tools.
“What’s novel here is that using magnetometers, we finally have technology that might be sensitive enough for efficient detection in the Earth’s field, perhaps ultimately enabling detection at longer distances,” explains Scott Seltzer, a co-author on the study.
The design was tested in the lab by measuring relaxation coefficients first for various hydrocarbons and water by themselves, then for a heterogeneous mixture, as well as in two-dimensional correlation experiments, using a magnetometer and an applied magnetic field representative of Earth’s.
“This proof of concept might be productively applied in the oil industry,” says Ganssle. “We mixed hydrocarbons and water, pre-polarized them with a magnet, and applied a magnetic field the same as the Earth’s. Then we made measurements with our magnetometer and determined that we had easily enough sensitivity to separate components of oil and water based on their relaxation spectra.”
This technology could help the oil industry to characterize fluids in rocks, because water relaxes at a different rate from oil. Other applications include measuring the content of water and oil flowing in a pipeline by measuring chemical composition with time, and inspecting the quality of foods and any kind of polymer curing process such as cement curing and drying.
The next step involves understanding the depth in a geological formation that could be imaged with this technology.
“Our next study will be tailored to that question,” says Bajaj. “We hope that this technology will eventually peer a meter or more into the formation and elucidate the chemistry within.”
Eventually, probes could be used to characterize entire borehole environments in this way, while current devices can only image inches deep. The combination of terrestrial magnetism and versatile sensing technology again offers an elegant solution.
Other authors on the Angewandte Chemie paper include Hyun Doug Shin, Micah Ledbetter, Dmitry Budker, Svenja Knappe, John Kitching, and Alexander Pines. The current publication presents some of the work for which Berkeley Lab won an R&D 100 award earlierthis year on optically-detected oil well logging by MRI.
This research was supported by the U.S. Department of Energy’s Office of Science.
Note : The above story is based on materials provided by DOE/Lawrence Berkeley National Laboratory. The original article was written by Rachel Berkowitz.
This is a Saturday May 8 2010 file image taken from video of a column of ash rising from Iceland’s Eyjafjallajokul volcano. It was reported Tueday Aug. 19, 2014 that thousands of small intense earthquakes are rocking Iceland amid concerns that one of the country’s volcanoes may be close to erupting. Iceland has raised its aviation alert level for the risk of a possible volcanic eruption to orange _ the second-most severe level. The alert is worrisome because of the chaos that followed the April 2010 eruption of Eyjafjallajokul, when more than 100,000 flights were cancelled because volcanic ash floating in the atmosphere is considered an aviation safety hazard. (AP Photo/ APTN)
Thousands of small intense earthquakes are rocking Iceland amid concerns that one of the country’s volcanoes may be close to erupting.
Iceland has raised its aviation alert level for the risk of a possible volcanic eruption to orange—the second-most severe level. The alert is worrisome because of the chaos that followed the April 2010 eruption of Eyjafjallajokul, when more than 100,000 flights were cancelled because volcanic ash floating in the atmosphere is considered an aviation safety hazard.
Some 3,000 earthquakes have taken place since Saturday in Bardarbunga—a subglacial stratovolcano located under Iceland’s largest glacier. Iceland’s Meteorological Office said that no earthquakes above magnitude 3 have been recorded in the last 24 hours.
Seismologists said Tuesday magma is moving, but it is traveling horizontally.
Figure A: The Northern Hemisphere in a cold (stadial) phase During the cold stadial periods of the last ice age, massive ice sheets covered northern parts of North America and Europe. Strong northwest winds drove the Arctic sea ice southward, even as far as the French coast. Since the extended ice cover over the North Atlantic prevented the exchange of heat between the atmosphere and the ocean, the strong driving forces for the ocean currents that prevail today were lacking. Ocean circulation, which is a powerful “conveyor belt” in the world’s oceans, was thus much weaker than at present, and consequently transported less heat to northern regions. Map: Alfred-Wegener-Institut Figure A: The Northern Hemisphere in a cold (stadial) phase
Over the past one hundred thousand years cold temperatures largely prevailed over the planet in what is known as the last ice age. However, the cold period was repeatedly interrupted by much warmer climate conditions. Scientists have long attempted to find out why these drastic temperature jumps of up to ten degrees took place in the far northern latitudes within just a few decades.
Now, for the first time, a group of researchers at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), have been able to reconstruct these climate changes during the last ice age using a series of model simulations. The surprising finding is that minor variations in the ice sheet size can be sufficient to trigger abrupt climate changes. The new study was published online in the scientific journal Nature last week and will be appearing in the 21 August print issue.
During the last ice age a large part of North America was covered with a massive ice sheet up to 3km thick. The water stored in this ice sheet is part of the reason why the sea level was then about 120 meters lower than today. Young Chinese scientist Xu Zhang, lead author of the study who undertook his PhD at the Alfred Wegener Institute, explains. “The rapid climate changes known in the scientific world as Dansgaard-Oeschger events were limited to a period of time from 110,000 to 23,000 years before present. The abrupt climate changes did not take place at the extreme low sea levels, corresponding to the time of maximum glaciation 20,000 years ago, nor at high sea levels such as those prevailing today – they occurred during periods of intermediate ice volume and intermediate sea levels.” The results presented by the AWI researchers can explain the history of climate changes during glacial periods, comparing simulated model data with that retrieved from ice cores and marine sediments.
During the cold stadial periods of the last ice age, massive ice sheets covered northern parts of North America and Europe. Strong westerly winds drove the Arctic sea ice southward, even as far as the French coast. Since the extended ice cover over the North Atlantic prevented the exchange of heat between the atmosphere and the ocean, the strong driving forces for the ocean currents that prevail today were lacking. Ocean circulation, which is a powerful “conveyor belt” in the world’s oceans, was thus much weaker than at present, and consequently transported less heat to northern regions.
Figure B: The Northern Hemisphere in a warm phase (a brief, warm interstadial phase during glacial climates) During the extended cold phases the ice sheets continued to thicken. When higher ice sheets prevailed over North America, typical in periods of intermediate sea levels, the prevailing northwest winds split into two branches. The major wind field ran to the north of the so-called Laurentide Ice Sheet and ensured that the sea ice boundary off the European coast shifted to the north. Ice-free seas permit heat exchange to take place between the atmosphere and the ocean. At the same time, the southern branch of the northwesterly winds drove warmer water into the ice-free areas of the northeast Atlantic and thus amplified the transportation of heat to the north. The modified conditions stimulated enhanced circulation in the ocean. Consequently, a thicker Laurentide Ice Sheet over North America resulted in increased ocean circulation and therefore greater transportation of heat to the north. The climate in the Northern Hemisphere became dramatically warmer within a few decades until, due to the retreat of the glaciers over North America and the renewed change in wind conditions, it began to cool off again. Map: Alfred-Wegener-Institut
During the extended cold phases the ice sheets continued to thicken. When higher ice sheets prevailed over North America, typical in periods of intermediate sea levels, the prevailing westerly winds split into two branches. The major wind field ran to the north of the so-called Laurentide Ice Sheet and ensured that the sea ice boundary off the European coast shifted to the north. Ice-free seas permit heat exchange to take place between the atmosphere and the ocean. At the same time, the southern branch of the northwesterly winds drove warmer water into the ice-free areas of the northeast Atlantic and thus amplified the transportation of heat to the north. The modified conditions stimulated enhanced circulation in the ocean. Consequently, a thicker Laurentide Ice Sheet over North America resulted in increased ocean circulation and therefore greater transportation of heat to the north. The climate in the Northern Hemisphere became dramatically warmer within a few decades until, due to the retreat of the glaciers over North America and the renewed change in wind conditions, it began to cool off again.
“Using the simulations performed with our climate model, we were able to demonstrate that the climate system can respond to small changes with abrupt climate swings,” explains Professor Gerrit Lohmann, leader of the Paleoclimate Dynamics group at the Alfred Wegener Institute, Germany. In doing so he illustrates the new study’s significance with regards to contemporary climate change. “At medium sea levels, powerful forces, such as the dramatic acceleration of polar ice cap melting, are not necessary to result in abrupt climate shifts and associated drastic temperature changes.”
At present, the extent of Arctic sea ice is far less than during the last glacial period. The Laurentide Ice Sheet, the major driving force for ocean circulation during the glacials, has also disappeared. Climate changes following the pattern of the last ice age are therefore not to be anticipated under today’s conditions.
Figure C: Schematic depiction of current climate conditions in the Northern Hemisphere At present, the extent of the Arctic sea ice is far less than during the last glacial period. The Laurentide Ice Sheet, the major driving force for ocean circulation during the glacials, has also disappeared. Model simulations demonstrate that today’s climate is much more robust in resisting the changes which existed during phases of intermediate ice thickness and intermediate sea levels. It was then, during the last ice age, that the most rapid temperature swings in the Northern Hemisphere took place. Map: Alfred-Wegener-Institut
“There are apparently some situations in which the climate system is more resistant to change while in others the system tends toward strong fluctuations,” summarises Gerrit Lohmann. “In terms of the Earth’s history, we are currently in one of the climate system’s more stable phases. The preconditions, which gave rise to rapid temperature changes during the last ice age do not exist today. But this does not mean that sudden climate changes can be excluded in the future.”
More information:
Xu Zhang, Gerrit Lohmann, Gregor Knorr, Conor Purcell: Abrupt glacial climate shifts controlled by ice sheet changes. Nature, DOI: 10.1038/nature13592
Note : The above story is based on materials provided by Helmholtz Association of German Research Centres
An erupting volcanic island that is expanding off Japan could trigger a tsunami if its freshly-formed lava slopes collapse into the sea, scientists said Tuesday.
The small, but growing, island appeared last year and quickly engulfed the already-existing island of Nishinoshima, around 1,000 kilometres (620 miles) south of Tokyo. It now covers 1.26 square kilometres (0.5 square miles).
The island’s craters are currently spewing out 200,000 cubic metres (7 million cubic feet) of lava every day—enough to fill 80 Olympic swimming pools—which is accumulating in its east, scientists said.
“If lava continues to mount on the eastern area, part of the island’s slopes could collapse and cause a tsunami,” warned Fukashi Maeno, assistant professor of the Earthquake Research Institute at the University of Tokyo.
He said a rockfall of 12 million cubic metres of lava would generate a one metre (three feet) tsunami that could travel faster than a bullet train, hitting the island of Chichijima—130 kilometres away—in around 18 minutes, he said.
Chichijima, home to some 2,000 people, is the largest island in the Ogasawara archipelago, a wild and remote chain that is administratively part of Tokyo.
“The ideal way to monitor and avoid a natural disaster is to set up a new tsunami and earthquake detection system near the island, but it’s impossible for anyone to land on the island in the current situation,” Maeno added.
An official from the Japan Meteorological Agency, which monitors earthquakes and tsunamis, said the agency is watching for any signs of anything untoward.
“We studied the simulation this morning, and we are thinking of consulting with earthquake prediction experts… about the probability of this actually happening, and what kind of measures we would be able to take,” he said.
Japan’s northeast was ravaged by a huge tsunami in March 2011, when a massive undersea earthquake sent a wall of water barrelling into the northeast coast, killing more than 18,000 people and wrecking whole towns.
Fossil Hallucigenia sparsa from the Burgess Shale Credit: M. R. Smith / Smithsonian Institute
One of the most bizarre-looking fossils ever found — a worm-like creature with legs, spikes and a head difficult to distinguish from its tail — has found its place in the evolutionary Tree of Life, definitively linking it with a group of modern animals for the first time.
The animal, known as Hallucigenia due to its otherworldly appearance, had been considered an ‘evolutionary misfit’ as it was not clear how it related to modern animal groups. Researchers from the University of Cambridge have discovered an important link with modern velvet worms, also known as onychophorans, a relatively small group of worm-like animals that live in tropical forests. The results are published in the advance online edition of the journal Nature.
The affinity of Hallucigenia and other contemporary ‘legged worms’, collectively known as lobopodians, has been very controversial, as a lack of clear characteristics linking them to each other or to modern animals has made it difficult to determine their evolutionary home.
What is more, early interpretations of Hallucigenia, which was first identified in the 1970s, placed it both backwards and upside-down. The spines along the creature’s back were originally thought to be legs, its legs were thought to be tentacles along its back, and its head was mistaken for its tail.
Hallucigenia lived approximately 505 million years ago during the Cambrian Explosion, a period of rapid evolution when most major animal groups first appear in the fossil record. These particular fossils come from the Burgess Shale in Canada’s Rocky Mountains, one of the richest Cambrian fossil deposits in the world.
Looking like something from science fiction, Hallucigenia had a row of rigid spines along its back, and seven or eight pairs of legs ending in claws. The animals were between five and 35 millimetres in length, and lived on the floor of the Cambrian oceans.
A new study of the creature’s claws revealed an organisation very close to those of modern velvet worms, where layers of cuticle (a hard substance similar to fingernails) are stacked one inside the other, like Russian nesting dolls. The same nesting structure can also be seen in the jaws of velvet worms, which are no more than legs modified for chewing.
“It’s often thought that modern animal groups arose fully formed during the Cambrian Explosion,” said Dr Martin Smith of the University’s Department of Earth Sciences, the paper’s lead author. “But evolution is a gradual process: today’s complex anatomies emerged step by step, one feature at a time. By deciphering ‘in-between’ fossils like Hallucigenia, we can determine how different animal groups built up their modern body plans.”
While Hallucigenia had been suspected to be an ancestor of velvet worms, definitive characteristics linking them together had been hard to come by, and their claws had never been studied in detail. Through analysing both the prehistoric and living creatures, the researchers found that claws were the connection joining them together. Cambrian fossils continue to produce new information on origins of complex animals, and the use of high-end imaging techniques and data on living organisms further allows researchers to untangle the enigmatic evolution of earliest creatures.
“An exciting outcome of this study is that it turns our current understanding of the evolutionary tree of arthropods — the group including spiders, insects and crustaceans — upside down,” said Dr Javier Ortega-Hernandez, the paper’s co-author. “Most gene-based studies suggest that arthropods and velvet worms are closely related to each other; however, our results indicate that arthropods are actually closer to water bears, or tardigrades, a group of hardy microscopic animals best known for being able to survive the vacuum of space and sub-zero temperatures — leaving velvet worms as distant cousins.”
“The peculiar claws of Hallucigenia are a smoking gun that solve a long and heated debate in evolutionary biology, and may even help to decipher other problematic Cambrian critters,” said Dr Smith.
Note: The above story is based on materials provided by University of Cambridge. The original story is licensed under a Creative Commons Licence.
Tjuv-Ante’s cave seen from the outside looking in. Credit: Image courtesy of University of Southern Denmark
Scientists have found that microscopic organisms can create dripstones in caves. The research illustrates how biological life can influence the formation of Earth’s geology — and the same may be happening right now on other planets.
According to traditional textbooks, dripstones are created by geological or geochemical processes with no influence from living organisms. But now scientists report that formation of dripstones can be a lot more complex than that: Sometimes microbes are responsible for the formation of these geological features.
The researchers from Denmark, Sweden and Spain have investigated dripstone formation in a Swedish cave and conclude that microbes play an active part in their formation.
“If microbes can be responsible for dripstone formation on Earth, the same thing might be happening other places in space,” explains researcher Magnus Ivarsson from Nordic Center for Earth Evolution (NordCEE) at University of Southern Denmark.
The planet Mars is known to be home for a number of caves similar to caves with dripstones created from microbes on Earth. If there are dripstones in these caves, they might have been formed by microbes and thus they are an indication that biological organisms have once lived on Mars.
“If I were a microbe I would definitely live in a cave on Mars,” says Magnus Ivarsson.
He and his colleagues have reported their findings in “International Journal of Speleology.” The colleagues are Therese Sallstedt from NordCEE, University of Southern Denmark, Johannes Lundberg from Swedish Museum of Natural History, Rabbe Sjöberg, retired from Umeå University and Juan Ramon Vidal Romani from University of Coruña in Spain.
The researchers examined dripstones in the Tjuv-Antes cave in Northern Sweden. The cave is 30 meters long and it is home for various kinds of dripstones. When they examined the dripstones the researchers saw distinct layers, mirroring how the dripstones have grown over time and left seasonal layers. Dark layers consist of fossilized microbes and light layers consist of calcite.
The researchers conclude that the microbes were active in the formation of the dripstones.
“Microbes actively contributed to the formation of the dripstones. They didn’t just live on the surface of them,” says Magnus Ivarsson.
Microbes were more active in spring and summer
The layers indicate that the microbes were most active in spring and summer when rain dripped down through the soil and into the cave.
“These drops of water brought nutrients with them, which was consumed by the microbes. As the microbes metabolized they excreted calcium which precipitated and in time helped form the dripstones,” says Magnus Ivarsson.
“Without this microbial activity dripstones would be smaller — or maybe even totally absent,” he adds.
The studying of microbes in caves is not only important for understanding the powers of life on Earth and on other planets. It also has importance for human health:
“Everyday millions of people go into underground caves; metros, train stations, etc. These artificially constructed caves offer some of the same living conditions for microbes as naturally created caves. Health authorities are therefore interested in monitoring and understanding what kind of pathogenic microorganisms can live and grow on the walls of for example metro-stations,” explains Magnus Ivarsson.
Together with Swedish colleagues Magnus Ivarsson is involved in monitoring microbial growth in metro-stations in Stockholm.
Note : The above story is based on materials provided by University of Southern Denmark.
The University of Waterloo has unveiled a new satellite image of Antarctica, and the imagery will help scientists all over the world gain new insight into the effects of climate change.
Thanks to a partnership between the Canadian Space Agency (CSA), MacDonald, Dettwiler and Associates Ltd. (MDA), the prime contractor for the RADARSAT-2 program, and the Canadian Cryospheric Information Network (CCIN) at UWaterloo, the mosaic is free and fully accessible to the academic world and the public.
Using Synthetic Aperture Radar with multiple polarization modes aboard the RADARSAT-2 satellite, the CSA collected more than 3,150 images of the continent in the autumn of 2008, comprising a single pole-to-coast map covering all of Antarctica. This is the first such map of the area since RADARSAT-1 created one in 1997.
“The mosaic provides an update on the ever-changing ice cover in this area that will be of great interest to climatologists, geologists, biologists and oceanographers,” said Professor Ellsworth LeDrew, director of the CCIN and a professor in the Faculty of Environment at Waterloo. “When compared to the previous Antarctic RADARSAT-1 mosaic, we can map changes in the icescape with unprecedented accuracy and confidence. Earth’s polar regions are considered a bellwether for the effects of climate change.”
Professor LeDrew is at the forefront of a cultural shift in the way researchers discover, share and preserve their research data. The CCIN links international researchers around the world with numerous government, university and private organizations to provide data and information management infrastructure for the Canadian cryospheric community. This mosaic map of the Antarctic is the latest addition to the CCIN’s Polar Data Catalogue. It is available on the Polar Data Catalogue website. (https://www.polardata.ca/pdcsearch/)
“The Polar Data Catalogue’s mandate is to make such information freely available to scientists, students and the public to enhance our understanding and stewardship of the polar regions,” said Professor LeDrew. “We are proud to work with the Canadian Space Agency and MDA to bring this outstanding Canadian technology and science to the international community.”
Next up for the partnership is a similar mosaic for Greenland, which will provide further crucial information about our shifting climate in the northern hemisphere. There are also plans to continue creating mosaics of Antarctica every few years to provide more data for researchers.
Note : The above story is based on materials provided by University of Waterloo.
Small fluctuations in the sizes of ice sheets during the last ice age were enough to trigger abrupt climate change, scientists have found.
The team, which included Cardiff University researchers, compared simulated model data with that retrieved from ice cores and marine sediments in a bid to find out why temperature jumps of up to ten degrees took place in far northern latitudes within just a few decades during the last ice age.
The analysis, led by Germany’s Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI), is published Aug. 21, 2014 in the scientific journal Nature.
The research confirms that thicker ice sheets increased ocean circulation and transferred more heat to the north due to a redirection of the prevailing winds. As the north warmed, glaciers retreated, the winds returned to normal conditions, and the north became cooler once again, completing the cycle
Conor Purcell from Cardiff University’s School of Earth and Ocean Sciences, said: “Using the simulations performed with our climate model, we were able to demonstrate that the climate system can respond to small changes with abrupt climate swings. Our study suggests that at medium sea levels, powerful forces, such as the dramatic acceleration of polar ice cap melting, are not necessary to create abrupt climate shifts and temperature changes.”
At present, the extent of Arctic sea ice is far less than during the last glacial period. The Laurentide Ice Sheet, the major driving force for ocean circulation during the glacials, has also disappeared. Climate changes following the pattern of the last ice age are therefore not anticipated under today’s conditions.
Professor Gerrit Lohmann, leader of the Paleoclimate Dynamics group at the AWI said: “In terms of the Earth’s history, we are currently in one of the climate system’s more stable phases. The preconditions which gave rise to rapid temperature changes during the last ice age do not exist today, but sudden climate changes cannot be excluded in future.”
Note : The above story is based on materials provided by Cardiff University.
The program encodes a method for generating facies models based on descriptions of outcrops of sedimentary successions or modern analogs of sedimentary systems. The method uses syntactic pattern recognition to encode facies analogs as grammars and a parser to generate stochastic facies models using the information from the grammar.
Channel
The aim of the program is to improve the reconstruction of complexely shaped sand bodies in petroleum reservoirs, particularly those from channelised environments. The facies models are generated as thin 3D layers which can be stacked to form a 3D volume. The parser is a predictive (generative) parser. It is able to condition the facies models to sparse hard data (such as the results of interpretation of poor quality seismic data).
These programs are distributed in the hope that they will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details or go to www.gnu.org/licenses
Further Information
Hill, E.J. and Griffiths, C.M., 2009. Describing and generating facies models for reservoir characterisation: 2D map view. Marine and Petroleum Geology. 26, 1554-1563.Hill, E.J., in review. Generating conditioned facies models using a parser with randomised backtracking.
Download:
Numbat3D programs, User Manual and Java source code:
Credit: Helmholtz Association of German Research Centres
Local surface uplift can block rivers, particularly in mountainous regions. The impounded water, however, always finds its way downstream, often cutting a narrow gorge into the rocks. Subsequent erosion of the rocks can lead to a complete eradication of this initial incision, until not a trace is left of the original breakthrough. In extreme cases the whole gorge disappears, leaving behind a broad valley with a flat floodplain. Previously, the assumption was that this transition from a narrow gorge to a wide valley was driven by gorge widening and the erosion of the walls of the gorges.
A team of scientists from the GFZ German Research Centre for Geosciences in Potsdam has now revealed a new mechanism that drives this process of fluvial erosion. The geoscientists analyzed the development of a gorge on the Da’an Chi river in Taiwan over a period of almost ten years. There, uplift that was caused by the Jiji earthquake of 1999 (magnitude 7.6), and that runs transverse to the river, had formed a blockage. Earthquakes of that size occur there every 300 to 500 years. “Before the quake there was no sign of a gorge at all in this riverbed, which is one and a half kilometers wide”, explains Kristen Cook of the GFZ. “We have here the world’s first real-time observation of the evolution of gorge width by fluvial erosion over the course of several years.” Currently the gorge is roughly a kilometer long, 25 meters wide and up to 17 meters deep. Initially, the gorge walls were eroded at a rate of five meters per year, and today are still retreating one and a half meters per year.
The scientists identified a hitherto unknown mechanism by which the gorge is destroyed. “Downstream sweep erosion” they termed this process. “A wide braided channel upstream of the gorge is necessary,” explains co-author Jens Turowski (GFZ). “The course of this channel changes regularly and it has to flow in sharp bends to run into the gorge. In these bends, the bed-load material that is transported by the river hits the upper edge of the gorge causing rapid erosion.” This mechanism gradually washes away all of the bedrock surrounding the gorge and, therefore, is the cause for the planation of the riverbed over the complete width of the valley. Assuming the current erosion rate of 17 meters per year, it will take here at the Da’an Chi River only 50 to 100 years until again a flat beveled channel again fills the valley. In contrast, lateral erosion in the gorge would be too slow to eradicate the gorge in the time of one earthquake cycle. The newly discovered downstream sweep erosion is far more effective.
More information:
Kristen L. Cook, Jens M. Turowski and Niels Hovius: “River gorge eradication by downstream sweep erosion”, Nature Geoscience, Advance Online Publication, 17.08.2014, DOI: 10.1038/ngeo2224
Note : The above story is based on materials provided by Helmholtz Association of German Research Centres
Astronaut photograph of the Syr Darya River floodplain
The Syr Darya is a river in Central Asia. The second part of the name (Darya) means river, though “Syr Darya River” is the conventional name. The current name dates only from the 18th century; since roughly the Muslim Conquests of Central Asia the river was known as the Seyhun (سيحون) River, i.e., one of the four rivers of Jannah, or paradise. Prior to the coming of Islam to Central Asia, the river’s name is recorded by several sources, including those relating to Alexander the Great as the Jaxartes River.
The earliest recorded name comes down to us as Jaxartes /ˌdʒæɡˈzɑrtiːz/ or Iaxartes /ˌaɪ.əɡˈzɑrtiːz/ (Ἰαξάρτης) in Ancient Greek. The Greek preserves the Old Persian name Yakhsha Arta (“True Pearl”), perhaps a reference to the color of its glacially-fed water. More evidence for the Persian etymology comes from its Turkic name up to the time of the Arab Conquest, the Yinchu, or Pearl, River.
Following the Conquests, the river appears in the sources uniformly as the Seyhun (سيحون), one of the four rivers flowing from Jannah.
The Turkic and current name of the River, Syr (Sïr), does not appear before the 16th century. In the 17th century, Abu al-Ghazi Bahadur Khan, historian and ruler of Khiva, calls the Aral Sea the “Sea of Sïr,” or Sïr Tengizi.
Geography
Map of the watershed of Syr Darya. Aral Sea boundaries are c. 1960.
The river rises in two headstreams in the Tian Shan Mountains in Kyrgyzstan and eastern Uzbekistan—the Naryn River and the Kara Darya which come together in the Uzbek part of the Fergana Valley—and flows for some 2,212 kilometres (1,374 mi) west and north-west through Uzbekistan and southern Kazakhstan to the remains of the Aral Sea. The Syr Darya drains an area of over 800,000 square kilometres (310,000 sq mi), but no more than 200,000 square kilometres (77,000 sq mi) actually contribute significant flow to the river. Its annual flow is a very modest 37 cubic kilometres (30,000,000 acre·ft) per year—half that of its sister river, the Amu Darya.
Along its course, the Syr Darya irrigates the most productive cotton-growing region in the whole of Central Asia, together with the towns of Kokand, Khujand, Kyzylorda and Turkestan.
Various local governments throughout history have built and maintained an extensive system of canals. These canals are of central importance in this arid region. Many fell into disuse in the 17th and early 18th cnetury, but the Khanate of Kokand rebuilt many in the 19th century, primarily along the Upper and Middle Syr Darya.
Massive expansion of irrigation canals in Middle and Lower Syr Darya during the Soviet period to water cotton and rice fields caused ecological damage to the area. The amount of water taken from the river was such that in some periods of the year, no water at all reaches the Aral Sea, similar to the Amu Darya situation in Uzbekistan and Turkmenistan.
Note : The above story is based on materials provided by Wikipedia
The dinosaurs had it easy (Image: Detlev Van Ravenswaay/SPL)
IT WAS a blitzkrieg with no let-up. Earth may have been pounded by massive asteroids for a billion years longer than we thought, with the impacts only stopping about 3 billion years ago. If that is true, early life had to endure a bombardment that periodically melted Earth’s surface.
The planet formed 4.5 billion years ago, and chunks of rock many kilometres across continued falling onto it for hundreds of millions of years. It seemed there was a final burst of impacts around 3.9 billion years ago – and by 3.8 billion years ago it was all over. The first fossils of life are very slightly younger.
That story is wrong, says Donald Lowe of Stanford University in California. The barrage continued far longer. “Its termination was not an abrupt drop-off but a gradual waning until 3 billion years ago,” he says.
Lowe and his colleagues have spent 40 years studying a patch of ancient rocks in eastern South Africa called the Barberton Belt. Over 25 years ago they found four layers of spherical particles, which seemed to have condensed from clouds of vaporised rock. Lowe says they are the traces of four major meteorite impacts, and date from between 3.5 and 3.2 billion years ago.
Now Lowe’s team have described another four layers of spherules from the same period. That means there were eight major impacts within about 250 million years, bolstering the case that the bombardment was still going on (Geology, doi.org/t48).
The moon also bears scars of major impacts up to 3 billion years ago, says William Bottke of the Southwest Research Institute in Boulder, Colorado. “This makes it unavoidable that the Earth was still getting hit by big things late in the game,” he says.
The impacts were on a scale beyond anything that Earth has experienced since the dawn of complex animals. The asteroid believed to have finished off the dinosaurs left a layer of spherules a few millimetres thick. “Our layers are 30 to 40 centimetres,” says Lowe. That suggests the asteroids were at least 20 kilometres across and possibly more than 70. “They were big boys,” says Lowe.
Each impact would have flung huge amounts of rock and gas into the air and blasted a crater 400 to 800 kilometres across. Lowe recently calculated that one such impact would have caused an earthquake that went on for many minutes and tsunamis that could have circled the entire planet.
Such impacts would wipe out most animals and plants if they happened today, but back then all life was single-celled. “We don’t know if this was apocalyptic for the microbes,” says Lowe. Those on the far side of the planet “would have to ride out some large waves” and a rain of hot rocks, but some would surely have survived.
One major group of microbes would have been at more risk: photosynthetic bacteria, which had to live near the surface of the ocean where there was plenty of light. “A very large impact has the potential to evaporate the top 100 metres of the ocean,” says Lowe. “The atmosphere would have heated up to hundreds of degrees Celsius. That would be apocalyptic. If you evaporate below the photic zone, you would obliterate photosynthesis.”
It’s a definite possibility, says Bottke. Such severe impacts could help explain why the air became rich in oxygen only around 2.4 billion years ago. Oxygen is a waste product of photosynthesis, and photosynthetic bacteria may not have been able to gain a foothold on the early Earth under such heavy bombardment. Bottke says there may have been a “back and forth battle”, with life “fighting sporadic setbacks” from asteroid impacts.
Note : The above story is based on materials provided by Michael Marshall “newscientist”
