Predictions of where planes can safely fly following volcanic eruptions could be improved, thanks to fresh discoveries about ash clouds.
To study the size of ash grains and how far they can travel, scientists at the Met Office and the Universities of Leeds, Edinburgh and Iceland, compared grains recovered from recent Icelandic eruptions – including samples recovered in Yorkshire – with satellite measurements of ash clouds.
Their findings, published today in Atmospheric Measurement Techniques, will help to improve methods of mapping ash concentration in order to identify zones where it is safe to fly during future eruptions.
Hundreds of flights were cancelled in 2010 and 2011 following volcanic activity in Iceland because of the danger that volcanic ash posed to aircraft and their engines.
In the new study, researchers studied volcanic ash recovered in the UK from the recent Eyjafjallajökull and Grímsvötn eruptions, as well as prehistoric samples from peat bogs in Yorkshire, Scotland and Ireland. Another sample, from an 1875 eruption, had been in a museum for 140 years.
The researchers found that grains were much larger than what had been typically estimated by satellite measurements of ash clouds – even moderately-sized eruptions could disperse large grains as far as the UK.
Study co-author Dr Graeme Swindles, from the School of Geography at the University of Leeds, said: “Microscopic volcanic ash layers preserved in Yorkshire peat bogs and mud at the bottom of lakes, far from volcanoes, are providing much needed information on the characteristics of ash clouds. These records show us that Europe was hit by volcanic ash clouds very frequently in the past.”
The group also used computer models to simulate how clouds of various ash particle sizes would appear to satellite sensors. They found that sensors can underestimate the size of larger particles.
Dr John Stevenson, from the University of Edinburgh, who led the study, said: “Mapping volcanic ash clouds and their risk to aircraft is hard. Large regions of airspace can be contaminated by particles that are invisible to the naked eye. Combining the expertise of volcanologists and atmospheric scientists should help improve forecasts.”
Reference:
“Big grains go far: understanding the discrepancy between tephrochronology and satellite infrared measurements of volcanic ash.” Atmos. Meas. Tech., 8, 2069-2091, 2015 DOI: 10.5194/amt-8-2069-2015
“Discovering the Deep” is now available for pre-order.
A University of Washington oceanographer has helped create the first full-color photographic atlas of the ocean floor. “Discovering the Deep: A Photographic Atlas of the Seafloor and Ocean Crust” (Cambridge University Press, 2015) was almost a decade in the making and contains more than 500 original illustrations and color photos, and access to online educational resources and high-definition videos.
Its pages contain a history of deep-sea science and a global tour of the volcanoes, hot springs, rocks and animals that exist in extreme environments in the ocean depths.
“This book lets people see parts of the Earth that most of them have never seen or thought about before, and the processes that form fundamental parts of our planet—and it does it in a very illustrative way,” said co-lead author Deborah Kelley, a professor in the UW School of Oceanography.
The book comes with endorsements from ocean explorer Robert Ballard; Kathy Sullivan, the head administrator of the National Oceanic and Atmospheric Administration; and filmmaker James Cameron.
“This is the book I wish I’d had on my eight deep-ocean expeditions, to better understand the wonders I was gazing upon,” Cameron writes. He calls it “a must-own for anyone in the ocean sciences, and for those simply curious about what lies down there in the most remote realm on our planet.”
The book covers the history of exploration of the deep sea, and the geology and biology of the roughly 40,000-mile mountain chain of underwater volcanoes that cross the world’s oceans.
Kelley was lead author of the chapter on hydrothermal vents, including the black smokers venting metal-rich fluids of more than 700 F that she has studied for decades. Local examples include the Endeavour vent fields and Axial Seamount, off the Pacific Northwest coast.
Also described is the Lost City vent field, a completely distinct type of hot spring environment in the Atlantic Ocean that Kelley helped discover in 2000. There, limestone chimneys tower 180 feet above the seafloor hosting bizarre lifeforms she and her students have since studied.
“The life in these systems is very diverse, and in many ways we’ve just touched the tip of what’s down there,” Kelley said.
Other authors are Jeffrey Karson of Syracuse University, Michael Perfit of the University of Florida, and Daniel Fornari and Timothy Shank of Woods Hole Oceanographic Institution.
A veteran of the deep sea, Kelley has traveled to the seafloor more than 50 times to depths of more than 2 miles (4 kilometers) in the specialized submersible called Alvin, built to protect passengers from the bone-crushing pressures and near-freezing temperatures of the abyss.
She has seen ocean imaging technology evolve from grainy images to the high-definition photos contained in the book, and the HD video available on an accompanying website.
“When I was first going to sea, we were still using 35 mm cameras, and one of my first jobs at sea was processing film on a rolling ship,” Kelley said. “Where we are now, the technology is exponentially increasing.”
Kelley is part of a current National Science Foundation project that recently wired the largest underwater volcano off Washington’s coast and surrounding areas of the seafloor. More than 100 instruments will use Internet and high-voltage power to observe these dynamic environments in real time.
The entire ocean circulates through the seafloor every 8 to 10 million years, and so the seafloor composition is closely connected to the waters above.
It is not yet known how volcanic eruptions on the seafloor affect the life and chemistry of the oceans, and how the biological communities of the deep sea originate and evolve. The unexpected discovery of life on seafloor volcanoes, that survive off toxic gases instead of sunlight, has raised questions that have yet to be answered.
“These systems have really changed how we think about the oceans, and life on Earth and on other planets,” Kelley said.
This shows the scheme of Crazy Crater. Credit: ETH Zurich / based on Reusch et al. 2015
Anna Reusch, a doctoral student at ETH’s Geological Institute, was utterly amazed one morning: during a routine measuring run with her research vessel on Lake Neuchâtel, she suddenly saw an unusual shape on the control panel screen. Beneath the boat, at a depth of over 100 metres, had to be something no one had ever seen before. She immediately informed her professor, Michael Strasser: “We’ve found something that you absolutely have to see.”
An initial rough data analysis on board indicated that Reusch and her colleagues were looking at a scientific sensation: an enormous crater, measuring 10 metres deep and 160 metres in diameter. “I’ll remember this day for a long time – I never expected anything like this,” recalls Reusch, adding: “It just goes to show that even in the 21st century, there are still thrilling and exciting discoveries to be made in Switzerland!”
Reusch made this discovery as part of “Dynamite,” a project sponsored by the Swiss National Science Foundation. The objective of her subproject is to investigate the sediment in the lakes on the western Swiss Plateau for traces of past earthquakes. Her work involves taking high-resolution measurements of the floor of Lake Neuchâtel to find evidence of tectonically active zones that could trigger major earthquakes. The period Reusch is looking at is geologically speaking very recent: sometime in the past 12,000 years.
But the discovery of the enormous crater and subsequently of other similar structures has turned her doctoral dissertation almost completely upside down. “The craters were so interesting that we simply had to take a closer look at this phenomenon,” she explained.
Four lake craters
All in all, the research team located four craters on the lake bed. All are off the northwest shore at a depth of over 100 metres, with most of them in an area extending from known tectonic fault zones. The researchers have described the four craters in a paper that was recently published in Geophysical Research Letters.
The craters measure 80 to 160 metres in diameter and between 5.5 and 30 metres in depth. Researchers nicknamed the largest of them “Crazy Crater”, not just because of its uncommonly generous proportions, but also because of its unusual shape: whereas comparable structures on the ocean floor usually lose their shape through the action of currents, this one is perfectly round.
Filled with mud
At the foot of the 10-metre-deep Crazy Crater, the researchers were able to make out a mud covering. Beneath it lies a 60-metre-deep vent, filled with a thick suspension of water and sediment. The team was unable to take core samples because the material was too fluid, due to water welling up into the vent from below. This keeps the sediments in the vent in motion, ensuring that they can’t settle into a solid state as normal lake sediment does.
By measuring the isotope fingerprint plus the temperature of the water, suspension and sediment, the scientists were able to show that it was water flowing up into these craters as opposed to, say, gas. Whilst the suspension had a temperature of 8.4 degrees Celsius, both the deep water and the sediment surrounding the crater measured just 5.8 degrees. This corresponds to the normal temperature of the water at that depth in these lakes. By contrast, the temperature of the suspension is comparable to that of the surface water in the bordering karst area.
The suspension inside the vent also contains a smaller proportion of the heavy oxygen-18 isotope than does the surrounding lake water. “The difference in these oxygen signals indicates that we’re talking about two distinct bodies of water here,” says Reusch.
Gigantic spring
For this reason, Reusch believes it is most likely that the craters are linked to the karst systems of the neighbouring Jura Mountains. Water there seeps underground, flows beneath the bed of Lake Neuchâtel and seeks out the path of least resistance up to the surface. That takes the water up through sediment layers over several tens of metres thick that have been deposited on the lake bed over the millennia. “In other words, these craters are in fact springs,” explains Reusch.
Furthermore, the researchers were able to use sediment core samples taken from the area directly surrounding the craters to show that the suspension spills over the lip of the crater from time to time, similar to a volcanic eruption. This has happened at least four times over the past 12,000 years – and yet despite today’s active water flow, it has been more than 1,600 years since Crazy Crater discharged any sediment on the crater levee. Exactly what triggers these eruptions still needs to be investigated. “Researching the dynamics of the craters requires long-term monitoring to keep an eye on the water level of the suspension in the crater,” says Reusch.
Explorer fever
All of the craters explored so far lie 100 metres or more beneath the lake’s surface. Reusch cannot say whether or not there are similar “pockmarks” in the shallows, as she has used sonar to sound only the deep parts of Lake Neuchâtel (30 metres and deeper). The shallow zones have not yet been mapped.
When taking measurements in the lakes, the researchers use a sophisticated multibeam echo sounder, a device used primarily for surveying the ocean floor. Depending on the water depth and the angle of the beams, the device achieves a resolution of up to 20×20 centimetres. At the moment, the sounder has plenty to do: the floor of Switzerland’s lakes remains relatively poorly researched in comparison to the terrain on land. Researchers began examining the bottom of many Swiss lakes with high-resolution methods only a few years ago, and have discovered phenomena in their depths that no one suspected even existed.
Reference:
Reusch A, Loher M, Bouffard D, Moernaut J, Hellmich F, Anselmetti FS, Bernasconi SM, Hilbe M, Kopf A, Lilley MD, Meinecke G, Strasser M: Giant lacustrine pockmarks with subaqueous groundwater discharge and subsurface sediment mobilization, Geophysical Research Letters, 13 May 2015. DOI:10.1002/2015GL064179
Deep-earthquake expert Harry W. Green II is a distinguished professor of the Graduate Division in UC Riverside’s Department of Earth Sciences. Credit: I. Pittalwala, UC Riverside.
Earthquakes are labeled “shallow” if they occur at less than 50 kilometers depth. They are labeled “deep” if they occur at 300-700 kilometers depth. When slippage occurs during these earthquakes, the faults weaken. How this fault weakening takes place is central to understanding earthquake sliding.
A new study published online in Nature Geoscience today by a research team led by University of California, Riverside geologists now reports that a universal sliding mechanism operates for earthquakes of all depths — from the deep ones all the way up to the crustal ones.
“Although shallow earthquakes — the kind that threaten California — must initiate differently from the very deep ones, our new work shows that, once started, they both slide by the same physics,” said deep-earthquake expert Harry W. Green II, a distinguished professor of the Graduate Division in UC Riverside’s Department of Earth Sciences, who led the research project. “Our research paper presents a new, unifying model of how earthquakes work. Our results provide a more accurate understanding of what happens during earthquake sliding that can lead to better computer models and could lead to better predictions of seismic shaking danger.”
The physics of the sliding is the self-lubrication of the earthquake fault by flow of a new material consisting of tiny new crystals, the study reports. Both shallow earthquakes and deep ones involve phase transformations of rocks that produce tiny crystals of new phases on which sliding occurs.
“Other researchers have suggested that fluids are present in the fault zones or generated there,” Green said. “Our study shows fluids are not necessary for fault weakening. As earthquakes get started, local extreme heating takes place in the fault zone. The result of that heating in shallow earthquakes is to initiate reactions like the ones that take place in deep earthquakes so they both end up lubricated in the same way.”
Green explained that at 300-700 kilometers depth, the pressure and temperature are so high that rocks in this deep interior of the planet cannot break by the brittle processes seen on Earth’s surface. In the case of shallow earthquakes, stresses on the fault increase slowly in response to slow movement of tectonic plates, with sliding beginning when these stresses exceed static friction. While deep earthquakes also get started in response to increasing stresses, the rocks there flow rather than break, except under special conditions.
“Those special conditions of temperature and pressure induce minerals in the rock to break down to other minerals, and in the process of this phase transformation a fault can form and suddenly move, radiating the shaking — just like at shallow depths,” Green said.
The research explains why large faults like the San Andreas Fault in California do not have a heat-flow anomaly around them. Were shallow earthquakes to slide by the grinding and crunching of rock, as geologists once imagined, the process would generate enough heat so that major faults like the San Andreas would be a little warmer along their length than they would be otherwise.
“But such a predicted warm region along such faults has never been found,” Green said. “The logical conclusion is that the fault must move more easily than we thought. Extreme heating in a very thin zone along the fault produces the very weak lubricant. The volume of material that is heated is very small and survives for a very short time — seconds, perhaps — followed by very little heat generation during sliding because the lubricant is very weak.”
The new research also explains why faults with glass on them (reflecting the fact that during the earthquake the fault zone melted) are rare. As shallow earthquakes start, the temperature rises locally until it is hot enough to start a chemical reaction — usually the breakdown of clays or carbonates or other hydrous phases in the fault zone. The reactions that break down the clays or carbonates stop the temperature from climbing higher, with heat being used up in the reactions that produce the nanocrystalline lubricant.
If the fault zone does not have hydrous phases or carbonates, the sudden heating that begins when sliding starts raises the local temperature on the fault all the way to the melting temperature of the rock. In such cases, the melt behaves like a lubricant and the sliding surface ends up covered with melt (that would quench to a glass) instead of the nanocrystalline lubricant.
“The reason this does not happen often, that is, the reason we do not see lots of faults with glass on them, is that the Earth’s crust is made up to a large degree of hydrous and carbonate phases, and even the rocks that don’t have such phases usually have feldspars that get crushed up in the fault zone,” Green explained. “The feldspars will ‘rot’ to clays during the hundred years or so between earthquakes as water moves along the fault zone. In that case, when the next earthquake comes, the fault zone is ready with clays and other phases that can break down, and the process repeats itself.”
The research involved the study of laboratory earthquakes — high-pressure earthquakes as well as high-speed ones — using electron microscopy in friction and faulting experiments. It was Green’s laboratory that first conducted a serendipitous series of experiments, in 1989, on the right kind of mantle rocks that give geologists insight into how deep earthquakes work. In the new work, Green and his team also investigated the Punchbowl Fault, an ancestral branch of the San Andreas Fault that has been exhumed by erosion from several kilometers depth, and found nanometric materials within the fault — as predicted by their model.
Video
Reference:
H. W. Green Ii, F. Shi, K. Bozhilov, G. Xia & Z. Reches. Phase transformation and nanometric flow cause extreme weakening during fault slip. Nature Geoscience, 2015 DOI: 10.1038/ngeo2436
The “eternal flame” at the Zoroastrian Ateshgah “Fire Temple” near Baku, Azerbaijan. The temple was built over natural burning seeps that are today extinct. The flame in the photo is now artificially fed via a gas pipe. Active natural flames are instead found at Yanardag, located approximately 9 km NE. Credit: Guisepe Etiope
Gas and oil seeps have been part of religious and cultural practices for thousands of years.
Seeps from which gas and oil escape were formative to many ancient cultures and societies. They gave rise to legends surrounding the Delphi Oracle, Chimaera fires and “eternal flames” that were central to ancient religious practices – from Indonesia and Iran to Italy and Azerbaijan. Modern geologists and oil and gas explorers can learn much by delving into the geomythological stories about the religious and social practices of the Ancient World, writes Guiseppe Etiope of the National Institute of Geophysics and Volcanology in Italy. His research is published in the new Springer book Natural Gas Seepage.
“Knowing present-day gas fluxes from a seep and knowing that a seep was active and vigorous two thousand years ago, we can estimate the total amount of gas that has been released to the atmosphere thus far. What can be measured today is probably also valid, at least in terms of orders of magnitude, for the past,” writes Etiope. “Such information may not only be relevant for atmospheric methane budget studies but may also be important for understanding the leaking potential of petroleum systems, whether they are commercial or not.”
Gas-oil seeps have been the source of mythological tales, and many a Biblical and historic event. The observations of ancient naturalists and historians such as Pliny the Elder, who lived two millennia ago, helped to chronicle many of these occurrences, especially in the Mediterranean area. For example, he wrote about Chimaera, a large burning gas seep in modern day Turkey.. In ancient times, the temple of Hephaestus, the Greek god of fire, was built next to it.
Similar “eternal fires” integrated gas and flame emissions into ancient religious practices in many cultures. For instance, the Zoroastrians worshiped the “Pillars of Fire” near modern Baku in Azerbaijan. In Iraq, the Baba Gurgur seep was probably the “burning fiery furnace” into which King Nebuchadnezzar cast the Jews. A legend of ancient Rome reports a stream of crude oil issuing from the ground around 38 BC. It became a meeting spot for the first Roman converts to Christianity, and is now the site for the Basilica of Santa Maria in Trastevere. The sacred Manggarmas flame in Indonesia, which has been active at least since the 15th century, is still used in an annual Buddhist ceremony.
“Knowing that a certain ‘eternal fire’ observed today was already active in Biblical times indicates that it was not triggered by the recent drilling and production of petroleum,” adds Etiope.
Etiope writes that hydrocarbon seeps also influenced the social and technological development of many ancient populations. It not only contributed to global civilization, but was often the source of wars. The first evidence for petroleum usage comes from Syria, where the Neanderthal used natural bitumen on stone tools some 40,000 years ago.
Reference:
Giuseppe Etiope. Seeps in the Ancient World: Myths, Religions, and Social Development. Natural Gas Seepage, 2015 DOI: 10.1007/978-3-319-14601-0_9
María Elena South: Mars on Earth in the Atacama Desert, Chile. Credit: Armando Azua-Bustos
Researchers have pinpointed the driest location on Earth in the Atacama Desert, a region in Chile already recognised as the most arid in the world. They have also found evidence of life at the site, a discovery that could have far-reaching implications for the search for life on Mars.
For more than a decade, the Yungay region has been established as the driest area of the hyper-arid Atacama desert, with conditions close to the so-called “dry limit” for life on Earth. Several academic papers have been published reporting on the extraordinary characteristics of the site and its relevance to astrobiologists as an analogue of conditions on Mars. However, following a more systematic search of the desert, a Chilean research team has now found a new site, María Elena South (MES), which it describes as “much drier” than Yungay.
Lead author Armando Azua-Bustos, an environmental biologist and research scientist at the Blue Marble Space Institute of Science in Seattle, says the team discovered that MES has a mean atmospheric relative humidity (RH) of 17.3 percent and a soil RH of a constant 14 percent at a depth of one meter. This soil value matches the lowest RH measurements taken by the Mars Science Laboratory at Gale Crater on Mars, establishing the fact that conditions at the site are as dry as those found recently on the Martian surface.
“Remarkably, we found a number of viable bacterial species in the soil profile at MES using a combination of molecular dependent and independent methods, unveiling the presence of life in the driest place on the Atacama Desert reported to date,” Azua-Bustos says.
The team used microsensors, including atmospheric temperature and relative humidity loggers, to take detailed measurements of the microenvironmental conditions at the MES site. It also characterized the geochemical composition of the soils at the site to unveil the presence and type of microbial species able to survive under these conditions. The results are presented in the paper, “Discovery and microbial content of the driest site of the hyperarid Atacama Desert, Chile,” published in March in the journal Environmental Microbiology Reports.
Azua-Bustos has spent the last 12 years studying the Atacama Desert and developing the field of astrobiology in Chile, and in so doing earned the nickname “astrobiologist of the desert.” He first became interested in the region after reading what he describes as a “pivotal paper” published in the journal Science in 2003 by a research team led by Chris McKay, a planetary scientist at NASA Ames Research Center.
The paper proposed the Yungay region in the Atacama as a “pertinent Mars analogue model,” mainly due to its extreme dryness, the characteristics of its soils, the presence of organic species at trace levels and extremely low levels of culturable bacteria.
However, based on his experience as a native of the Atacama who was born and raised in the desert, Azua-Bustos was convinced that there were drier places than Yungay, so he decided to set RH sensors in several places that were potentially drier.
“We found at least three such places, the driest of which we describe in this paper,” he says.
Implications for Astrobiology
For Azua-Bustos, the fact that the conditions at MES site, in terms of dryness, are the closest to Mars as it is possible to get means that it is one of the best analogue models on Earth to understand and investigate the potential existence, and type of, microbial life in the Martian subsurface.
“This also implies that if you want to test the next generation of robots, instruments and other detection techniques and technologies in a Mars-like environment, this is one of the best you can find as it possesses many of the key characteristics that you will find on the Red Planet,” he says.
The site could also be used to conduct experiments that might inform future work carried out by the Mars Science Laboratory (MSL) at Gale Crater in its search for extant life on Mars. In Azua-Bustos’ view, one interesting experiment would be to test the same instruments being used by MSL at the MES site to compare results with the Martian data and to “further detail how similar both sites may be in terms of habitability, having the advantage of this new site in the Atacama as a positive control.”
For Azua-Bustos, the fact that we already know that there is life in the soil at María Elena South means that it would also be interesting to test if the sample analysis at Mars (SAM) instrument (a suite of three instruments, including a mass spectrometer, gas chromatograph, and tuneable laser spectrometer carried onboard the MSL rover), as well as similar detection instruments scheduled to be sent to Mars, are also able to detect life at a similarly dry terrestrial site.
“[K]nowing the amount, location in the subsoil and type of microbial life present in María Elena South, it would be of interest to test the SAM instruments here, in order to test its sensitivity in a site which you know is inhabited. In other words, if SAM or any other instrument were not able to detect life in Maria Elena soils, one could argue that SAM would not be sensitive enough to detect life on Mars,” he adds.
Reference:
“Mars-like soils in the Atacama Desert, Chile, and the dry limit of microbial life.” Science. 2003 Nov 7;302(5647):1018-21. www.ncbi.nlm.nih.gov/pubmed/14605363
“Discovery and microbial content of the driest site of the hyperarid Atacama Desert, Chile.” Environmental Microbiology Reports, 7: 388–394. DOI: 10.1111/1758-2229.12261
Note : The above story is based on materials provided by Astrobio.net. This story is republished courtesy of NASA’s Astrobiology Magazine. Explore the Earth and beyond at www.astrobio.net.
Researchers have uncovered the first geologic evidence that New Zealand’s southern Hikurangi margin can rupture during large earthquakes. The two earthquakes took place within the last 1000 years, and one was accompanied by a tsunami, according to the study published in the Bulletin of the Seimological Society of America (BSSA).
The earthquakes took place roughly 350 years apart, according to the analysis by Kate Clark of GNS Science and colleagues. This may mean that the time between large earthquakes in this region is shorter than scientists have thought. The current seismic models account for these types of earthquakes every 500 to 1000 years.
A worst-case, M8.9 Hikurangi earthquake could cause about 3350 deaths and 7000 injuries, and lead to $13 billion in costs in New Zealand’s capital Wellington alone, according to a calculation made in 2013 by a different set of scientists. The Hikurangi margin marks the area where the Pacific and Australian tectonic plates collide to the east of New Zealand. The margin is one of the few places around the Pacific where a major subduction interface earthquake—which occurs deep in the crust where one plate is thrust under another—has not occurred in historic times.
However, “subduction earthquakes are not a ‘new’ risk for New Zealand, as we have always assumed they can occur, and they are accounted for in our seismic hazard models,” Clark said. “This study is significant in that it confirms that risk.
“We have a record of three to five past earthquakes on most of the major upper plate faults in the [New Zealand] lower North Island and upper South Island, but there was previously no evidence of past subduction earthquakes on the southern Hikurangi margin,” Clark explained. “Subduction earthquakes have the potential to be significantly larger in magnitude than upper plate fault ruptures, affect a much larger spatial area and are much more likely to trigger tsunami.”
To look for evidence of past earthquakes on the margin, the researchers performed a painstaking examination of the geologic layers contained within a salt marsh at Big Lagoon in the southeastern Wairau River valley on South Island. They analyzed cores drilled from the marsh to look at differences in the kinds of sediment and the shells from tiny marine animals called foraminifera, deposited throughout a stretch of the lagoon’s history.
These data revealed that the lagoon sank relatively suddenly twice during the past 1000 years, suggesting that the land was subsiding as a result of significant earthquakes. The more recent earthquake occurred between 520 and 470 years ago.
Another earlier earthquake probably took place between 880 and 800 years ago. Judging by the sedimentary debris found at that time, this earthquake was accompanied by a tsunami that swept more than 360 meters inland at the study site.
Clark said the findings will help researchers better understand the risks posed by large subduction interface earthquakes in the region. Studies have shown, for example, that there have been subduction earthquakes on the central Hikurangi margin, “and we wanted to understand if the central and southern Hikurangi margins are likely to rupture in the same earthquake,” said Clark.
“We can see that the [southern Hikurangi margin] subduction earthquake at about 500 years before present possibly correlates with a central Hikurangi margin earthquake, implying both segments may have ruptured in the same earthquake,” she continued, “but the radiocarbon dating is not yet precise enough to be certain—possibly there were two earthquake closely spaced in time.”
Clark said that she and other scientists are looking at other locations in the lower North Island to find evidence of the same paleoearthquakes, which could help provide a better picture of how big these quakes might have been and how they impacted the region.
“In addition we would like to go further back in time and find evidence of older subduction earthquakes,” Clark said.”With a longer record of past subduction earthquakes we can get a better constraint on the recurrence of such earthquakes, which will help to forecast future subduction earthquakes.”
Figure 3: Fault in Mg2GeO4 olivine (1.3 GPa, 1,200 K).
A University of Oklahoma structural geologist and collaborators are studying earthquake instability and the mechanisms associated with fault weakening during slip. The mechanism of this weakening is central to understanding earthquake sliding.
Ze’ev Reches, professor in the OU School of Geology and Geophysics, is using electron microscopy to examine velocity and temperature in two key observations: (1) a high-speed friction experiment on carbonate at conditions of shallow earthquakes, and (2) a high-pressure/high-temperature faulting experiment at conditions of very deep earthquakes.
Reches and his collaborators have shown phase transformation and the formation of nano-size (millionth of a millimeter) grains are associated with profound weakening and that fluid is not necessary for such weakening. If this mechanism operates in major earthquakes, it resolves two major conflicts between laboratory results and natural faulting–lack of a thermal zone around major faults and the rarity of glassy rocks along faults.
Image Caption (Fig3):
a, Backscatter SEM image of polished section shows the sense of shear, displacement and location of FIB-cut foil. White, MgGeO3 pyroxene (px); mottled regions, (ol+sp) partially transformed before faulting. b, TEM image of FIB cross-section. Fault zone (dashed lines) ~70 nm thick, grain size ≤15 nm. Wall rock both sides of the fault (black) is single large, deformed olivine crystal oriented for strong diffraction. c, Detail of b tilted to a slightly different orientation, showing fault boundaries. Diffraction pattern (inset) shows olivine from the fault wall (arrow) and rings of spinel. Asterisks in b,c identify the same location.
Reference:
Reches co-authored the study with H.W. Green II, University of California, Riverside; F. Shi, China University of Geosciences; K. Bozhilov, University of California, Riverside; and G. Xia, University of Queensland. A paper on this study, “Phase transformation and nanometric flow cause extreme weakening during fault slip,”. DOI: 10.1038/ngeo2436
The newly-created Nishinoshima island at the Ogasawara island chain, 1,000 kilometres south of Tokyo, pictured on March 25, 2015
A brand new island emerging off the coast of Japan offers scientists a rare opportunity to study how life begins to colonise barren land—helped by rotting bird poo and hatchling vomit.
Researchers say bird waste will be the secret ingredient to kickstart Mother Nature’s grand experiment on what is a still active volcano that only poked its head above the waves in November 2013.
That speck of land, some 1,000 kilometres (620 miles) south of Tokyo, has grown to engulf its once larger neighbour, Nishinoshima, a part of Japan’s Ogasawara island chain known for the wealth and variety of its ecosystem.
The new Nishinoshima, a respectable 2.46 square kilometres (0.95 square miles), the Japan Coast Guard said in February—roughly the size of 345 football pitches—is currently almost all bare rock, formed from cooling lava.
But scientists say it will one day be humming with plant—and possibly animal—life, as nature moves in to what is being called a “natural laboratory” on one of the latest bits of real estate in the Pacific Ocean.
“We biologists are very much focusing on the new island because we’ll be able to observe the starting point of evolutionary processes,” said Naoki Kachi, professor and leader of Tokyo Metropolitan University’s Ogasawara Research Committee.
After the volcanic activity calms down, “what will probably happen first will be the arrival of plants brought by ocean currents and attached to birds’ feet,” he said.
Those seabirds, who could use the remote rock as a temporary resting place, could eventually set up home there.
Their excreta—along with their dropped feathers, regurgitated bits of food and rotting corpses—will eventually form a nutrient-rich soil that offers fertile ground for seeds carried by the wind, or brought in the digestive systems of overflying birds.
“I am most interested in the effects of birds on the plants’ ecosystem—how their bodily wastes-turned-organic fertilisers enrich the vegetation and how their activities disturb it,” Kachi told AFP.
The old Nishinoshima, measuring just 0.22 square kilometres, was home to bird colonies until the eruptions scared the creatures away.
A small number have clung on to the only patch of the old island that is still visible, making their nests among ash-covered plants.
Pristine
Japan, which sits at the junction of several tectonic plates, is home to more than 100 active volcanoes.
Scientists have no idea when Nishinoshima will stop spewing lava, but its expansion is being offset by erosion around the edges.
The island is expected to follow a route laid out by Surtsey, an island that emerged from the sea in 1963, around 30 kilometres from the coast of Iceland.
The UN Educational, Scientific and Cultural Organization (UNESCO) World Heritage spot is known globally as an outstanding example of a pristine natural laboratory where researchers have been able to trace the evolution of a habitat.
“Since they began studying the island in 1964, scientists have observed the arrival of seeds carried by ocean currents, the appearance of moulds, bacteria and fungi, followed in 1965 by the first vascular plant,” UNESCO says on its website.
“By 2004, (vascular plants) numbered 60, together with 75 bryophytes, 71 lichens and 24 fungi. Eighty-nine species of birds have been recorded on Surtsey, 57 of which breed elsewhere in Iceland. The 141 hectare island is also home to 335 species of invertebrates.”
Not bad for somewhere that has only existed for half a century.
Nishinoshima might not be quite as quick as Surtsey to establish itself as a teeming wildlife haven—it is a long way from mainland Japan and not too close to its neighbours in the Ogasawara island chain, which limits the number of species of birds and seeds that will make it that far.
Nonetheless, it is an exciting blank canvas, said Kachi, and needs to be treated with respect—which means keeping out foreign invaders that would not naturally drift or fly in.
“I’d like to call on anyone who lands on the island to pay special attention to keeping it the way it is—not to take external species there,” he warned.
He said when he conducted a field study on another island in the chain in 2007, his team prepared a fumigated clean room where they packed all research equipment, after making sure everything they had was either brand new or scrupulously clean.
While Nishinoshima is currently only being monitored from the air, the first field researchers will need to take similar precautions.
“Biologists know the business, but probably the first batch of scientists who will land on the island will be geologists and vulcanologists—who may not be familiar with the problems,” he said.
“I’d be pleased to offer advice on this to scientists in other fields.”
Note : The above story is based on materials provided by AFP.
Gale crater, Mars. Flowing water appears to have carved channels in both the mound and the crater wall. (The Curiosity rover landed at the foot of a layered mountain within this massive crater.) Credit: Courtesy NASA/JPL-Caltech
Data collected on Mars by NASA’s Curiosity rover and analyzed by University of Arkansas researchers indicate that water, in the form of brine, may exist under certain conditions on the planet’s surface.
The finding, published in the May 2015 issue of the journal Nature Geoscience, is based on almost two years of weather data collected from an impact crater near the planet’s equatorial region. Vincent Chevrier, an assistant professor at the University of Arkansas Center for Space and Planetary Sciences, and Edgard G. Rivera-Valentin, a former Doctoral Academy Fellow at the center who is now a scientist at the Arecibo Observatory in Puerto Rico, were members of the team that analyzed the data as part of a grant from NASA.
“What we demonstrated is that under specific circumstances, for a few hours per day, you can have the right conditions to form liquid brines on the surface of Mars,” Chevrier said.
The existence of briny water may explain a phenomenon observed by Mars orbiters called “recurring slope lineae,” which are dark streaks on slopes that appear and grow during the planet’s warm season.
Water is also necessary for the existence of life as we know it, and on Earth, organisms adapt and thrive in extremely briny conditions. Chevrier, however, believes that conditions on Mars are too harsh to support life.
“If we combine observations with the thermodynamics of brine formation and the current knowledge about terrestrial organisms, is it possible to find a way for organisms to survive in Martian brines? My answer is no,” he said.
Mars is cold, extremely dry, and has 200 times lower atmospheric pressure than Earth. Any pure water on the surface would freeze or boil away in minutes. If it sounds alien for water to both freeze and boil, that’s because it is alien to Earth, but not so much for Mars because of the planet’s very low atmospheric pressure.
However, in 2008, NASA’s Phoenix lander identified perchlorate salts in polar soil samples. Perchlorates are rare on Earth, but they are known to absorb moisture from the atmosphere and lower the freezing temperature of water. The widespread existence of perchlorates makes liquid water possible on Mars.
The Curiosity rover confirmed the existence of perchlorates in equatorial soil, and provided detailed observations of relative humidity and ground temperature in all Martian seasons. With that data in hand, Chevrier and Rivera-Valentin were able to conclude that liquid brines can exist today on Mars. Future Mars missions could sample for the brines directly.
Though the briny water on Mars may not support life, it does have implications for future manned missions that would need to create life-sustaining resources such as water and oxygen on the planet, Chevrier said. There is also the possibility that life once existed on ancient Mars.
“We need to understand the earliest environment,” he added. “What was happening 4 billion years ago?”
Reference:
F. Javier Martín-Torres, María-Paz Zorzano, Patricia Valentín-Serrano, Ari-Matti Harri, Maria Genzer, Osku Kemppinen, Edgard G. Rivera-Valentin, Insoo Jun, James Wray, Morten Bo Madsen, Walter Goetz, Alfred S. McEwen, Craig Hardgrove, Nilton Renno, Vincent F. Chevrier, Michael Mischna, Rafael Navarro-González, Jesús Martínez-Frías, Pamela Conrad, Tim McConnochie, Charles Cockell, Gilles Berger, Ashwin R. Vasavada, Dawn Sumner, David Vaniman. Transient liquid water and water activity at Gale crater on Mars. Nature Geoscience, 2015; 8 (5): 357 DOI: 10.1038/ngeo2412
In this Saturday, May 9, 2015 photo, molten rock lights up the night as it spews into a lake of lava near the summit of Kilauea volcano on Hawaii’s Big Island. The lava lake had reached a record high level on May 8 and then began descending, making scientists wonder where the molten rock will go next. Credit: AP Photo/Cathy Bussewitz
A series of earthquakes and shifting ground on the slopes of Kilauea have scientists wondering what will happen next at one of the world’s most active volcanos.
A lake of lava near the summit of Kilauea on Hawaii’s Big Island had risen to a record-high level after a recent explosion. But in the past few days, the pool of molten rock began sinking, and the surface of the lava lake fell nearly 500 feet.
Meanwhile, a rash of earthquakes rattled the volcano with as many as 20 to 25 quakes per hour, and scientists’ tilt meters detected that the ground was deforming.
“Clearly the lava, by dropping out of sight, it has to be going somewhere,” said Steven Brantley, deputy scientist in charge of Hawaiian Volcano Observatory of the U.S. Geological Survey.
One possibility is that a new lava eruption could break through the surface of the mountain, Brantley said.
Right now, there are two active eruptions on Kilauea. One is the eruption spewing into the lava lake in the Halemaumau Crater, which is visible in Hawaii Volcanoes National Park. The other is Puu Oo vent, in Kilauea’s east rift zone, which sent fingers of lava toward the town of Pahoa before stopping outside a shopping center last year.
The flurry of earthquakes that peaked in intensity Friday have been rattling Kilauea’s southwest rift zone, so it’s possible that a new eruption could occur southwest of the Halemaumau Crater, or even in the crater itself, Brentley said. Or, the tilting, shifting ground could lead to nothing.
“We don’t know what the outcome of this activity might be,” Brantley said. “That is the challenge, is trying to interpret what this activity really means in terms of the next step for Kilauea.”
An eruption on the southwest side wouldn’t pose a threat to the population, because the area is generally closed to the public and there aren’t any structures.
The earthquake activity had slowed Saturday morning, and scientists were continuing to watch the volcano closely, Brantley said.
Illustration of the possible location of carbonate spin transition in the lower mantle, courtesy of Sergey Lobanov. Credit: Sergey Lobanov
Carbonates are a group of minerals that contain the carbonate ion (CO32-) and a metal, such as iron or magnesium. Carbonates are important constituents of marine sediments and are heavily involved in the planet’s deep carbon cycle, primarily due to oceanic crust sinking into the mantle, a process called subduction. During subduction, carbonates interact with other minerals, which alter their chemical compositions. The concentrations of the metals gained by carbonate ions during these interactions are of interest to those who study deep earth chemistry cycles.
Carbonates were known to exist in the upper mantle due to their role in the deep carbon cycle. But it was thought that they could not withstand the more-extreme conditions of the lower mantle. Laboratory experiments and the discovery of tiny bits of carbonate impurities in lower mantle diamonds indicated that carbonates could withstand the extreme pressures and temperatures of not only the upper mantle, but the lower mantle as well.
Previous research had shown that upper mantle carbonates are magnesium-rich and iron-poor. Under lower mantle conditions, it is thought that the arrangement of electrons in carbonate minerals changes under the pressure stress in such a way that iron may be significantly redistributed. However, accurate observations of lower mantle carbonates’ chemical composition are not possible yet.
A research team–Carnegie’s Sergey Lobanov and Alexander Goncharov, along with Konstantin Litasov of the Russian Academy of Science and Novosibirsk State University in Russia–focused on the high-pressure chemistry of a carbonate mineral called siderite, which is an iron carbonate, FeCO3, commonly found in hydrothermal vents. Their findings help resolve questions about the presence of iron-containing lower mantle carbonates, and are published by American Mineralogist.
Rearrangement of the electrons in iron upon pressure-induced spin transition in carbonates, courtesy of Sergey Lobanov. Credit: Sergey Lobanov
Until recently the electron-arrangement change responsible for iron redistribution in the lower mantle had not been measured in the lab. It was previously discovered that this change, a phenomenon called a spin transition, took place between about 424,000 and 484,000 times normal atmospheric pressure (43 to 49 gigapascals).The team was able to pinpoint that spin transition was occurring in iron carbonates under about 434,000 times normal atmospheric pressure (44 gigapascals), typical of the lower mantle.
A spin transition is a rearrangement of electrons in a molecule or a mineral (figure 1 below). Electrons hold a compound’s atoms together by bonding. Certain fundamental rules of chemistry govern this bonding process, which have to do with the energy it takes to form the bonds. Pressure-induced spin transitions rearrange electrons and change the energy of the chemical bonds. If the change in chemical bond energy is high enough, the spin transition may trigger iron redistribution between coexisting minerals.
To quantify the energy change, siderite’s spin transition was examined using highly sensitive spectroscopic techniques at pressures ranging from zero to about 711,000 times normal atmospheric pressure (72 gigapascals), and also revealed by a visible color change after the transition, indicating rearrangement of electrons. The obtained spectroscopic data provided the key ingredient to estimating the carbonate composition at pressures exceeding the spin transition-pressure. It turned out that lower mantle carbonates should be iron-rich, unlike upper mantle carbonates (figure 2 below). Similar effects may exist in other lower mantle minerals, if they also undergo spin transitions.
“As we learn more about how the spin transition affects chemical composition in carbonates, we improve our understanding of all iron-bearing minerals, enhancing our knowledge about lower mantle chemistry,” said Lobanov.
Storage tanks for produced water from natural gas drilling in the Marcellus Shale gas play of western Pennsylvania. Credit: USGS photo, Doug Duncan.
In a study of 13 hydraulically fractured shale gas wells in north-central Pennsylvania, USGS researchers found that the microbiology and organic chemistry of the produced waters varied widely from well to well.
The variations in these aspects of the wells followed no discernible spatial or geological pattern but may be linked to the time a well was in production. Further, the study highlighted the presence of some organic compounds (e.g. benzene) in produced waters that could present potential risks to human health, if the waters are not properly managed.
Produced water is the term specialists use to describe the water brought to the land surface during oil, gas, and coalbed methane production. This water is a mixture of naturally occurring water and fluid injected into the formation deep underground to enhance production. A USGS Fact Sheet on produced water provides more background information and terminology definitions.
Although the USGS investigators found that the inorganic (noncarbon-based) chemistry of produced waters from the shale gas wells tested in the Marcellus region was fairly consistent from well to well and meshed with comparable results of previous studies (see USGS Energy Produced Waters Project), the large differences in the organic geochemistry (carbon-based, including petroleum products) and microbiology (e.g. bacteria) of the produced waters were striking findings of the study.
“Some wells appeared to be hotspots for microbial activity,” observed Denise Akob, a USGS microbiologist and lead author of the study, “but this was not predicted by well location, depth, or salinity. The presence of microbes seemed to be associated with concentrations of specific organic compounds — for example, benzene or acetate — and the length of time that the well was in production.”
The connection between the presence of organic compounds and the detection of microbes was not, in itself, surprising. Many organic compounds used as hydraulic fracturing fluid additives are biodegradable and thus could have supported microbial activity at depth during shale gas production.
The notable differences in volatile organic compounds (VOCs) from the produced waters of the tested wells could play a role in the management of produced waters, particularly since VOCs, such as benzene, may be a health concern around the well or holding pond. In wells without VOCs, on the other hand, disposal strategies could concentrate on issues related to the handling of other hazardous compounds.
Microbial activity detected in these samples could turn out to be an advantage by contributing to the degradation of organic compounds present in the produced waters. Potentially, microbes could also serve to help mitigate the effects of organic contaminants during the disposal or accidental release of produced waters. Additional research is needed to fully assess how microbial activity can best be utilized to biodegrade organic compounds found in produced waters.
Reference:
Denise M. Akoba, Isabelle M. Cozzarellia, Darren S. Dunlapa, Elisabeth L. Rowanb, Michelle M. Lorahc. Organic and inorganic composition and microbiology of produced waters from Pennsylvania shale gas wells. DOI:10.1016/j.apgeochem.2015.04.011
Santa Clara Valley, California, USA. Credit: NASA’s Earth Observatory
California and other parts of the western U.S. are experiencing extended severe drought conditions. Varying groundwater levels in valleys throughout the state, balanced by water imported, for instance, via the State Water Project and the federal Central Valley Project make understanding the state’s underlying hydrologic framework all the more important. This paper by R.T. (Randy) Hanson of the U.S. Geological Survey focuses on California’s Santa Clara Valley.
In the introduction to his paper, Hanson provides a succinct history of the area, as paraphrased here: Santa Clara Valley is a long, narrow (240 square miles), trough-like coastal watershed that borders the southern end of San Francisco Bay, extending about 35 miles southeast from there. The watershed principally drains parts of Santa Clara and San Mateo counties. Santa Clara Valley has experienced the typical evolution of land- and water-use development in the western United States, with a transition from an agricultural and ranching economy to one based on urban services and industry. In the first half of the twentieth century, the valley was intensively cultivated for fruit and truck crops, but subsequent development has included urbanization and industrialization, so that the area is now commonly known as “Silicon Valley.”
Hanson says that the valley underwent extensive groundwater development from the early 1900s through the mid-1960s. This development caused groundwater level declines of more than 200 feet and induced regional subsidence of as much as 12.7 feet from the early 1900s to the mid-1960s. As with other coastal aquifer systems, Hanson notes, “the possibility exists that the combined effects of land subsidence and seawater intrusion will result in large water-level declines.”
The San Francisco Water Department started delivering imported water to several north county cities in the early 1950s. In the 1960s, the Santa Clara Valley Water District (SCVWD) began importing surface water into the valley to help meet growing demands and to reduce the area’s dependence on groundwater. The combination of reduced groundwater pumping and this artificial recharge has caused groundwater levels to recover to near their predevelopment levels, and this, in turn, has arrested the land subsidence, says Hanson, noting, “Currently, the water purveyors in the Santa Clara Valley, in conjunction with SCVWD, would like to meet the water demand in the basin while limiting any potential for additional land subsidence.”
Even though extensive studies have been completed in the Santa Clara Valley, there were no comprehensive three-dimensional hydrologic, geologic, and geochemical data that would allow the delineation of the hydrologic framework that controls the distribution and movement of the water resources in the Santa Clara Valley. Hanson’s article summarizes the hydrologic framework of the valley using data obtained from nine new monitoring-well sites and various supply wells in combination with a detailed groundwater-surface-water model.
The synthesis of this framework is based on a sequence of interdisciplinary studies between the U.S. Geological Survey and the Santa Clara Valley Water District. The framework components, as summarized in Hanson’s article, include the hydrogeologic structure of the valley, groundwater budgets, the role of climate cycles, the nature of stream-aquifer interactions, distribution and nature of groundwater pumpage, effects of land subsidence, the distribution of artificial recharge, geochemical characteristics of the aquifers and wells, and the overall water-resource management issues relevant to the sustainable and conjunctive use of the groundwater and surface water resources of the Santa Clara Valley.
Reference:
R. T. Hanson. Hydrologic framework of the Santa Clara Valley, California. Geosphere, 2015; DOI: 10.1130/GES01104.1
A Strombolian type explosion at Stromboli. (9th of October 2006, Stromboli, Photo T. Pfeiffer).
Scientists have made an important step towards understanding how volcanic eruptions happen, after identifying a previously unrecognised potential trigger.
An international team of researchers from the University of Liverpool, Monash University and the University of Newcastle (Australia) think their findings could lead to new ways of interpreting signs of volcanic unrest measured by satellites and surface observations.
Dr Janine Kavanagh, from the University of Liverpool’s School of Environmental Sciences and lead author of the research paper, said: “Understanding the triggers for volcanic eruptions is vital for forecasting efforts, hazard assessment and risk mitigation.
“With more than 600 million people worldwide living near a volcano at risk of eruptive activity, it is more important than ever that our understanding of these complex systems and their triggering mechanisms is improved.
“There is also a strong economic incentive to understand the causes of volcanic activity — as demonstrated in 2010 by the eruption of Eyjafjallajökull, Iceland, which caused air-traffic disruption across Europe for more than one month, with an estimated US$1.8 billion loss in revenue to the airline industry.”
Studying volcanic processes in nature can be challenging because of the remoteness of many volcanoes, the dangers to scientists wanting to study destructive eruptions up close, and the fact that they are often obscured from direct observation by volcanic ash or rock.
To get around this difficulty, the researchers recreated a scaled down version in labs at Monash University.
They studied the plumbing systems of volcanoes by modelling how magma ascends from great depths to the surface through a series of connected fractures (called dykes and sills).
The scientists used a tank filled with gelatine (jelly) into which coloured water was injected to mimic ascending magma. A high-speed camera and a synchronised laser was used to observe what was going on inside the tank as the ascending magma moved upwards.
Professor Sandy Cruden, from the School of Earth, Atmosphere and Environment at Monash University, said: “It was at this point that we discovered a significant and previously unknown drop in pressure when the ascending vertical dyke stalled to form a horizontal sill.”
“Sills often form in nature as part of a developing volcanic plumbing system, and a pressure drop can drive the release of dissolved gasses, potentially causing the magma to explode and erupt.”
“It’s similar to removing a cap from a bottle of shaken fizzy drink — the pressure drop causes bubbles to form and the associated increase in volume results in a fountain of foam erupting from the bottle.”
Volcano-monitoring systems around the world rely on the interpretation of signals of Earth’s surface and subsurface measured by satellites, ground deformation devices and seismometers. These record when and how magma moves at depth and they are used to help determine the likelihood of an eruption occurring.
The new results will aid this effort by adding a previously unknown potential eruption triggering mechanism and by helping to improve understanding of the dynamics of magma ascent, which leads to eruptions.
Reference:
J.L. Kavanagh, D. Boutelier, A.R. Cruden. The mechanics of sill inception, propagation and growth: Experimental evidence for rapid reduction in magmatic overpressure. Earth and Planetary Science Letters, 2015; 421: 117 DOI: 10.1016/j.epsl.2015.03.038
Three-dimensional high velocity structures beneath East Asia from 50 km to 1000 km depth viewed from the southeast. Surface topography with vertical exaggeration is superimposed for geographic references. Isosurfaces of high velocity anomalies in percent referenced to a one-dimensional earth model (STW105) at each depth are plotted from 1% to 4% with 1% interval. Three cut planes show shear wave velocity maps at 410 km, 660 km, and 1000 km depths. The highest elevations represent the Himalayas and the Tibetan Plateau. Credit: Min Chen, Rice University.
A new work based on 3-D supercomputer simulations of earthquake data has found hidden rock structures deep under East Asia. Researchers from China, Canada, and the U.S. worked together to publish their results in March 2015 in the American Geophysical Union Journal of Geophysical Research, Solid Earth.
The scientists used seismic data from 227 East Asia earthquakes during 2007-2011, which they used to image depths to about 900 kilometers, or about 560 miles below ground.
Notable structures include a high velocity colossus beneath the Tibetan plateau, and a deep mantle upwelling beneath the Hangai Dome in Mongolia. The researchers say their line of work could potentially help find hidden hydrocarbon resources, and more broadly it could help explore the Earth under East Asia and the rest of the world.
“With the help of supercomputing, it becomes possible to render crystal-clear images of Earth’s complex interior,” principal investigator and lead author Min Chen said of the study. Chen is a postdoctoral research associate in the department of Earth Sciences at Rice University.
Chen and her colleagues ran simulations on the Stampede and Lonestar4 supercomputers of the Texas Advanced Computing Center through an allocation by XSEDE, the eXtreme Science and Engineering Discovery Environment funded by the National Science Foundation.
“We are combining different kinds of seismic waves to render a more coherent image of the Earth,” Chen said. “This process has been helped by supercomputing power that is provided by XSEDE.”
“What is really new here is that this is an application of what is sometimes referred to as full waveform inversion in exploration geophysics,” study co-author Jeroen Tromp said. Tromp is a professor of Geosciences and Applied and Computational Mathematics, and the Blair Professor of Geology at Princeton University.
In essence the application combined seismic records from thousands of stations for each earthquake to produce scientifically accurate, high-res 3-D tomographic images of the subsurface beneath immense geological formations.
XSEDE provided more than just time on supercomputers for the science team. Through the Campus Champions program, researchers worked directly with Rice XSEDE champion Qiyou Jiang of Rice’s Center for Research Computing and with former Rice staffer Roger Moye, who used Rice’s DAVinCI supercomputer to help Chen with different issues she had with high performance computing.” “They are the contacts I had with XSEDE,” Chen said.
“These collaborations are really important,” said Tromp of XSEDE. “They cannot be done without the help and advice of the computational science experts at these supercomputing centers. Without access to these computational resources, we would not be able to do this kind of work.”
Like a thrown pebble generates ripples in a pond, earthquakes make waves that can travel thousands of miles through the Earth. A seismic wave slows down or speeds up a small percentage as it travels through changes in rock composition and temperature. The scientists mapped these wave speed changes to model the physical properties of rock hidden below ground.
Tromp explained that the goal for his team was to match the observed ground-shaking information at seismographic stations to fully numerical simulations run on supercomputers.
“In the computer, we set off these earthquakes,” says Tromp. “The waves ripple across southeast Asia. We simulate what the ground motion should look like at these stations. Then we compare that to the actual observations.
The differences between our simulations and the observations are used to improve our models of the Earth’s interior,” Tromp said. “What’s astonishing is how well those images correlate with what we know about the tectonics, in this case, of East Asia from surface observations.”
The Tibetan Plateau, known as ‘the roof of the world,’ rises about three miles, or five kilometers above sea level. The details of how it formed remain hidden to scientists today.
The leading theory holds that the plateau formed and is maintained by the northward motion of the India plate, which forces the plateau to shorten horizontally and move upward simultaneously.
Scientists can’t yet totally account for the speed of the movement of ground below the surface at the Tibetan Plateau or what happened to the Tethys Ocean that once separated the India and Eurasia plates. But a piece of the puzzle might have been found.
“We found that beneath the Tibetan plateau, the world’s largest and highest plateau, there is a sub-vertical high velocity structure that extends down to the bottom of the mantle transition zone,” Chen said.
High-resolution 360 degree rotating view of high velocity structures beneath East Asia. Credit: Min Chen, Rice University.
The bottom of the transition zone goes to depths of 660 kilometers, she said. “Three-dimensional geometry of the high velocity structure depicts the lithosphere beneath the plateau, which gives clues of the fate of the subducted oceanic and the continental parts of the Indian plate under the Eurasian plate,” Chen said.
The collision of plates at the Tibetan Plateau has caused devastating earthquakes, such as the recent 2015 Nepal earthquake at the southern edge of where the two plates meet. Scientists hope to use earthquakes to model the substructure and better understand the origins of these earthquakes.
To reach any kind of understanding, the scientists first grappled with some big data, 1.7 million frequency-dependent traveltime measurements from seismic waveforms. “We applied this very sophisticated imaging technique called adjoint tomography with a key component that is a numerical code package called SPECFEM3D_GLOBE,” Chen said.
Specifically, they used SPECFEM3D GLOBE, open source software maintained by the UC Davis Computational Infrastructure for Geodynamics. “It uses parallel computing to simulate the very complex seismic waves through the Earth,” Chen said.
Even with the tools in place, the study was still costly. “The cost is in the simulations of the wave propagation,” says Tromp. “That takes hundreds of cores for tens of minutes at a time per earthquake.
High-resolution 360 degree rotating view of low velocity structures beneath East Asia. Credit: Min Chen, Rice University.
As you can imagine, that’s a very expensive proposition just for one iteration simulating all these 227 earthquakes.” In all, the study used about eight million CPU hours on the Stampede and Lonestar4 supercomputers.
“The big computing power of supercomputers really helped a lot in terms of shortening the simulation time and in getting an image of the Earth within a reasonable timeframe,” said Chen. “It’s still very challenging. It took us two years to develop this current model beneath East Asia. Hopefully, in the future it’s going to be even faster.”
Three-D imaging inside the Earth can help society find new resources, said Tromp. The iterative inversion methods they used to model structures deep below are the same ones used in exploration seismology to look for hidden hydrocarbons.
“There’s a wonderful synergy at the moment,” Tromp said. “The kinds of things we’re doing here with earthquakes to try and image the Earth’s crust and upper mantle and what people are doing in exploration geophysics to try and image hydrocarbon reservoirs.”
“In my point of view, it’s the era of big seismic data,” Chen said. She said their ultimate goal is to make everything about seismic imaging methods automatic and accessible by anyone to better understand the Earth.
It sounded something like a Google Earth for inside the Earth itself. “Right, exactly. Assisted by the supercomputing systems of XSEDE, you can have a tour inside the Earth and possibly make some new discoveries.” Chen said.
A University of Dayton geologist is helping a NASA-U.S. Geological Survey volunteer group detect severe hazards developing as a result of the April 25 and May 12 earthquakes in Nepal.
Umesh Haritashya, an assistant geology professor, leads a group reviewing satellite photos of the Nepalese peak section of Manaslu, the world’s eighth-highest mountain, for “secondary and tertiary hazards like landslides and river blockages.”
This effort is part of the 50-member international volunteer group formed after the Gorkha quake under the umbrella of the NASA international Global Land Ice Measurements from Space project led by Jeff Kargel from the University of Arizona.
“Hopefully, our work will help direct resources to the right place or avert potential future problems due to large mass movements,” Haritashya said.
Haritashya said landslides have blocked rivers and formed lakes at many river basins in the mountainous region. With continuous aftershocks and a second major earthquake such as one on May 12, along with the fast-approaching monsoon season, Haritashya said these lakes are in danger of spilling water into remote villages.
“It is important to understand that no such major threat has been observed at this point, but it is a continuously developing story and we are keeping an eye on a daily basis,” Haritashya said.
Haritashya joined the University of Dayton’s geology department after completing a post-doctoral research appointment in NASA’s international Global Land Ice Measurements from Space project at the University of Nebraska-Omaha.
His research interests include hydropower, water resources, glaciers, climate change and the Himalayas. He is an editorial board member of the Journal of Hydrologic Engineering, The Open Hydrology Journal and Himalayan Geology. Haritashya also helped edit Encyclopedia of Snow, Ice and Glaciers.
For centuries, people have imagined the possibility of life on Mars. But long-held dreams that Martians could be invaders of Earth, or little green men, or civilized superbeings, all have been undercut by missions to our neighboring planet that have, so far, uncovered no life at all.
Yet visits to the Red Planet by unmanned probes from NASA and the European Space Agency have found evidence that a prime condition for life once may have existed: water.”There has been a tremendous amount of very exciting findings this year that Mars once contained actively flowing, low-saline, near-neutral-pH water — pretty much the type of water where you find life on Earth today,” said Alison Olcott Marshall, assistant professor of geology at the University of Kansas. “This has made people think that it’s possible that life could have existed on Mars, although most researchers agree it’s unlikely to exist today — at least on the surface — as conditions on the surface of Mars are incredibly harsh.”
Olcott Marshall is working with her colleague and husband, Craig Marshall, associate professor of geology at KU, to improve the way scientists detect condensed aromatic carbon, thought to be a chemical signature of astrobiology.
“If we’re going to identify life on Mars, it will likely be the fossil remnants of the chemicals once synthesized by life, and we hope our research helps strengthen the ability to evaluate the evidence collected on Mars,” Craig Marshall said.
Craig Marshall is an expert in using Raman spectroscopy to look for carbonaceous materials, while Alison Olcott Marshall is a paleontologist interested in how the record of life gets preserved on Earth, especially when there is no bone or shell or tooth or other hard part to fossilize.
The pair is known recently for overturning the idea that 3.5 billion-year-old specks found in rocks in Australia were the oldest examples of life on Earth. (Rather than ancient bacteria fossils, the researchers showed the shapes were nothing more than tiny gaps in the rock that are packed with minerals.)
If traces if ancient biology are detected in Mars, the KU researchers want to make sure the evidence is more conclusive.
According to a recent paper by the Marshalls in the peer-reviewed Philosophical Transactions of the Royal Society, by itself Raman spectroscopy is able to screen for carbonaceous material, but it can’t determine its source — thus the technology needs to be supplemented in order to determine if life exists on Mars.
“Raman spectroscopy works by impinging a laser on a sample so the molecules within that sample vibrate at diagnostic frequencies,” Craig Marshall said. “Measuring those frequencies allows the identification of inorganic and organic materials. It’s insufficient because however the carbonaceous material is made, it will be the same chemically and structurally, and thus Raman spectroscopy cannot determine the origin.”
The Marshalls call for the use of gas chromatography/mass spectroscopy to supplement Raman spectroscopy and develop more conclusive evidence of ancient extraterrestrial life.
“Much like the search for ancient life on Earth, though, one strand of evidence is not, and should not be, conclusive,” said Alison Olcott Marshall. “This is a vast puzzle, and we want to make sure we are examining as many different pieces as we can.”
Currently, the KU researchers are extending this line of investigation by using Raman spectroscopy to analyze rocks from Earth that are similar to those on Mars. They hope to publish their findings in the near future.
“If you were to pick up a typical rock on Mars it would look quite different, chemically, from a typical rock here on Earth, not to mention the fact that it would be covered in rusty dust,” Alison Olcott Marshall said. “Previous research into how Raman spectroscopy would fare on Mars was mainly done on pure salts and minerals, often ones synthesized in a lab. We identified field sites on the Kansas-Oklahoma border with a chemical content more like what could be found on Mars, right down to the rusty dust, and we’ve been exploring how Raman spectroscopy fares in such an environment.”
Stereonet 9 brings location and date tagging of individual measurements as well as a free form notes field. Points with location data can be plotted on a Google satellite (or terrain or roadmap) image right in the program. This version of Stereonet is compatible with all modern operating systems and has a modern user interface which has been modeled after OSXStereonet for Mac by Nestor Cardozo and me. It can read and write older Stereonet text files but has a new binary format for its native file.
Stereonet 9 for Macintosh uses the modern Mac OS X “Cocoa” architecture. The Macintosh version is being made available here for those users who need binary file compatibility with the Windows version. Stereonet 9 for Macintosh does not have the nifty 3D viewing of OSXStereonet, but does have Google satellite visualization. Stereonet 9 requires Mac OS X 10.7 (Lion) or higher.
For those hardy souls using Linux, you too can download a copy of Stereonet 9, though I have never seen it run on a Linux box and don’t know if there are any compatibility issues!
For long term viability of your data, however, you should still export any work as text files which will always be readable by a large number of programs.
A comprehensive manual is included with the zip archive. For Mac Users still on Mac OS X 10.5 and lower (Leopard, Tiger, etc.), you can download a Carbon version of Stereonet. Note that this version will not be kept up to date with the above Cocoa version.
Major improvements to the Rose diagram functionality, including:
Scale the petals by either length or area (new). Only length was possible before
Calculation of the mean direction for axial data (i.e., data with no directional significance). this is sometimes referred to as Krumbein’s (1939) mean
Half circle rose diagrams always show Krumbein’s mean; full circle diagrams can either depict vector azimuths or, if “treat data as axes” is checked in the Inspector, the full circle diagrams will be symmetric (this has been a highly requested feature that I’ve resisted until now!)
Addition of a Von Mises Distribution option to the Calculations menu which displays the same 2D azimuthal statistics as the Rose diagram displays. The program now calculates the circular variance, kappa, and 1 sigma standard error for azimuthal data.
Plots wil polar grids can now be saved as .pdf and .svg files
Fixed a bug that occurred when planes were being entered in “DD” format and the data details window was opened.
Plants convert carbon dioxide from the atmosphere into organic carbon via photosynthesis. Most of this carbon eventually returns to the atmosphere when plant material (or animals that eat plants) decompose. A small fraction of this material, however, ends up in rivers. They carry it out to sea, where some settles to the seafloor and is buried and disconnected from the atmosphere for millions of years and eventually makes its way back to the surface in the form of rocks. At the same time, rivers also erode carbon-containing rocks into particles carried downstream. The process exposes carbon to air, oxidizing the previously locked-up carbon into carbon dioxide that can leak back out to the atmosphere. Credit: Illustration by Eric Taylor, Woods Hole Oceanographic Institutio
Humans concerned about climate change are working to find ways of capturing excess carbon dioxide (CO2) from the atmosphere and sequestering it in the Earth. But Nature has its own methods for the removal and long-term storage of carbon, including the world’s river systems, which transport decaying organic material and eroded rock from land to the ocean.
While river transport of carbon to the ocean is not on a scale that will bail humans out of our CO2 problem, we don’t actually know how much carbon the world’s rivers routinely flush into the ocean — an important piece of the global carbon cycle.
But in a study published May 14 in the journal Nature, scientists from Woods Hole Oceanographic Institution (WHOI) calculated the first direct estimate of how much and in what form organic carbon is exported to the ocean by rivers. The estimate will help modelers predict how the carbon export from global rivers may shift as Earth’s climate changes.
“The world’s rivers act as Earth’s circulatory system, flushing carbon from land to the ocean and helping reduce the amount that returns to the atmosphere in the form of heat-trapping carbon dioxide,” said lead author and geochemist Valier Galy. “Some of that carbon–‘new’ carbon–is from decomposed plant and soil material that is washed into the river and then out to sea. But some of it comes from carbon that has long been stored in the environment in the form of rocks– ‘old’ carbon–that have been eroded by weather and the force of the river.”
The scientists, who included Bernhard Peucker-Ehrenbrink, and Timothy Eglinton (now at ETH Zürich), amassed data on sediments flowing out of 43 river systems all over the world, which cumulatively account for 20 percent of the total sediments discharged by rivers. The representative rivers also encompassed a broad range of climates, vegetation, geological conditions, and levels of disturbance by people.
From these river sediment flow measurements, the research team calculated amounts of particles of carbon-containing plant and rock debris that each river exported. They estimated that the world’s rivers annually transport 200 megatons (200 million tons) of carbon to the ocean. The total equals about .02 percent of the total mass of carbon in the atmosphere. That may not seem like a lot, but over 1000 to 10,000 years, it continues to add up to significant amounts of carbon (20 and 200 percent) extracted from the atmosphere.
Generally, plants convert CO2 from the atmosphere into organic carbon via photosynthesis. But most of this carbon eventually returns to the atmosphere when plant material (or animals that eat plants) decompose. A small fraction of this material, however, ends up in rivers. They carry it out to sea, where some settles to the seafloor and is buried and disconnected from the atmosphere for millions of years and eventually makes its way back to the surface in the form of rocks.
At the same time, rivers also erode carbon-containing rocks into particles carried downstream. The process exposes carbon to air, oxidizing the previously locked-up carbon into carbon dioxide that can leak back out to the atmosphere. Until now, scientists had no way to distinguish how much of the carbon whisked away by rivers comes from either the biospheric or petrogenic (rock) sources. Without this information, scientists’ ability to model or quantitatively predict carbon sequestration under different scenarios was limited.
To solve this dilemma, the scientists found a novel way to distinguish for the first time the sources of that carbon–either from eroded rocks or from decomposed plant and soil material. They analyzed the amounts of carbon-14, a radioactive isotope, in the river particles. Carbon-14 decays away within about 60,000 years, so it is present only in material that came from living things, and not rocks. Subtracting the portion of particles that did not contain carbon-14, the scientists calculated the percentage that was derived from the terrestrial biosphere: about 80 percent.
But even though biospheric carbon is the major source of carbon exported by rivers, the scientists also discovered that rivers surrounded by greater amounts of vegetation didn’t necessarily transport more carbon to the ocean. Instead, the export was “primarily controlled by the capacity of rivers to mobilize and transport” particles. Erosion is the key factor–the more erosion occurs along the river, the more carbon it transfers to sea and sequesters from the air.
“The atmosphere is a small reservoir of carbon compared to rocks, soils, the biosphere, and the ocean,” the scientists wrote in Nature. “As such, its size is sensitive to small imbalances in the exchange with and between these larger reservoirs.”
The new study gives scientists a firmer handle on measuring the important, and heretofore elusive, role of global rivers in the planetary carbon cycle and enhances their ability to predict how riverine carbon export may shift as Earth’s climate changes.
“This study will provide geochemical modelers with new insights on an important link between the global carbon and water cycles,” says Don Rice, program director in the National Science Foundation’s Division of Ocean Sciences, a major funder of the research.
Reference:
Valier Galy, Bernhard Peucker-Ehrenbrink, Timothy Eglinton. Global carbon export from the terrestrial biosphere controlled by erosion. Nature, 2015; 521 (7551): 204 DOI: 10.1038/nature14400
