Petroleum Traps

February 17, 2015

Two types of petroleum traps are; structural and stratigraphic. Structural traps are formed by deformation of reservoir rock, such as by folding or faulting. Stratigraphic traps are formed by deposition of reservoir rock, such as river channel or reef, or by erosion of reservoir rock, such as an angular unconformity

Structural Trap

Structural trap is a type of geological trap that forms as a result of changes in the structure of the subsurface, due to tectonic, diapiric, gravitational and compactional processes. These changes block the upward migration of hydrocarbons and can lead to the formation of a petroleum reservoir.

Structural traps are the most important type of trap as they represent the majority of the world’s discovered petroleum resources. The three basic forms of structural traps are the anticline trap, the fault trap and the salt dome trap.

Anticlinal trap Photo Copyright © MagentaGreen

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Anticlinal (fold) Trap

An anticline is an area of the subsurface where the strata have been pushed into forming a domed shape. If there is a layer of impermeable rock present in this dome shape, then hydrocarbons can accumulate at the crest until the anticline is filled to the spill point – the highest point where hydrocarbons can escape the anticline. This type of trap is by far the most significant to the hydrocarbon industry. Anticline traps are usually long oval domes of land that can often be seen by looking at a geological map or by flying over the land.

Fault Trap

This trap is formed by the movement of permeable and impermeable layers of rock along a fault line. The permeable reservoir rock faults such that it is now adjacent to an impermeable rock, preventing hydrocarbons from further migration. In some cases, there can be an impermeable substance smeared along the fault line (such as clay) that also acts to prevent migration. This is known as clay smear.

Salt dome Trap

Masses of salt are pushed up through clastic rocks due to their greater buoyancy, eventually breaking through and rising towards the surface (see salt dome). This salt is impermeable and when it crosses a layer of permeable rock, in which hydrocarbons are migrating, it blocks the pathway in much the same manner as a fault trap. This is one of the reasons why there is significant focus on subsalt imaging, despite the many technical challenges that accompany it.

Stratigraphic Traps

Stratigraphic traps are formed as a result of lateral and vertical variations in the thickness, texture, porosity or lithology of the reservoir rock. Examples of this type of trap are an unconformity trap, a lens trap and a reef trap.

Two main groups can be recognized :

Primary
stratigraphic traps result from variations in facies that developed during sedimentation. These include features such as lenses, pinch-outs, and appropriate facies changes.

Secondary
stratigraphic traps result from variations that developed after sedimentation, mainly because of diagenesis. These include variations due to porosity enhancement by dissolution or loss by cementation.

Paleogeomorphic traps are controlled by buried landscape. Some are associated with prominences (hills); others with depressions (valleys). Many are also partly controlled by unconformities so are also termed unconformity traps .

Video:

Formation of Hydrocarbon Trap

Reference:
Petroleum Traps , KING ABDULAZIZ UNIVERSITY : GEOL 463.3—RWR-5
Traps , West Virginia University : Structure traps.pdf
Structural trap : From Wikipedia
Stratigraphic Traps : Paleontological Research Institution and its Museum of the Earth
Schlumberger : Structural trap , Stratigraphic trap

Ancient rocks show life could have flourished on Earth 3.2 billion years ago

February 17, 2015

The oldest samples are sedimentary rocks that formed 3.2 billion years ago in northwestern Australia. They contain chemical evidence for nitrogen fixation by microbes. Credit: R. Buick / UW

A spark from a lightning bolt, interstellar dust, or a subsea volcano could have triggered the very first life on Earth. But what happened next? Life can exist without oxygen, but without plentiful nitrogen to build genes — essential to viruses, bacteria and all other organisms — life on the early Earth would have been scarce.
The ability to use atmospheric nitrogen to support more widespread life was thought to have appeared roughly 2 billion years ago. Now research from the University of Washington looking at some of the planet’s oldest rocks finds evidence that 3.2 billion years ago, life was already pulling nitrogen out of the air and converting it into a form that could support larger communities.

“People always had the idea that the really ancient biosphere was just tenuously clinging on to this inhospitable planet, and it wasn’t until the emergence of nitrogen fixation that suddenly the biosphere become large and robust and diverse,” said co-author Roger Buick, a UW professor of Earth and space sciences. “Our work shows that there was no nitrogen crisis on the early Earth, and therefore it could have supported a fairly large and diverse biosphere.”

The results were published Feb. 16 in Nature.

The authors analyzed 52 samples ranging in age from 2.75 to 3.2 billion years old, collected in South Africa and northwestern Australia. These are some of the oldest and best-preserved rocks on the planet. The rocks were formed from sediment deposited on continental margins, so are free of chemical irregularities that would occur near a subsea volcano. They also formed before the atmosphere gained oxygen, roughly 2.3 to 2.4 billion years ago, and so preserve chemical clues that have disappeared in modern rocks.

Even the oldest samples, 3.2 billion years old — three-quarters of the way back to the birth of the planet — showed chemical evidence that life was pulling nitrogen out of the air. The ratio of heavier to lighter nitrogen atoms fits the pattern of nitrogen-fixing enzymes contained in single-celled organisms, and does not match any chemical reactions that occur in the absence of life.

“Imagining that this really complicated process is so old, and has operated in the same way for 3.2 billion years, I think is fascinating,” said lead author Eva Stüeken, who did the work as part of her UW doctoral research. “It suggests that these really complicated enzymes apparently formed really early, so maybe it’s not so difficult for these enzymes to evolve.”

Genetic analysis of nitrogen-fixing enzymes have placed their origin at between 1.5 and 2.2 billion years ago.

“This is hard evidence that pushes it back a further billion years,” Buick said. Fixing nitrogen means breaking a tenacious triple bond that holds nitrogen atoms in pairs in the atmosphere and joining a single nitrogen to a molecule that is easier for living things to use. The chemical signature of the rocks suggests that nitrogen was being broken by an enzyme based on molybdenum, the most common of the three types of nitrogen-fixing enzymes that exist now. Molybdenum is now abundant because oxygen reacts with rocks to wash it into the ocean, but its source on the ancient Earth — before the atmosphere contained oxygen to weather rocks — is more mysterious.

The authors hypothesize that this may be further evidence that some early life may have existed in single-celled layers on land, exhaling small amounts of oxygen that reacted with the rock to release molybdenum to the water.

“We’ll never find any direct evidence of land scum one cell thick, but this might be giving us indirect evidence that the land was inhabited,” Buick said. “Microbes could have crawled out of the ocean and lived in a slime layer on the rocks on land, even before 3.2 billion years ago.”

Future work will look at what else could have limited the growth of life on the early Earth. Stüeken has begun a UW postdoctoral position funded by NASA to look at trace metals such as zinc, copper and cobalt to see if one of them controlled the growth of ancient life.

Reference:
Eva E. Stüeken, Roger Buick, Bradley M. Guy, Matthew C. Koehler. Isotopic evidence for biological nitrogen fixation by molybdenum-nitrogenase from 3.2 Gyr. Nature, 2015; DOI: 10.1038/nature14180

Note : The above story is based on materials provided by University of Washington. The original article was written by Hannah Hickey.

Earthquakes in Australia are a rare but real hazard

February 17, 2015

Buckled railway lines caused by the 1968 earthquake near Meckering in Western Australia. Credit: Alice Snooke/Geosciences Australia

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Australia is generally regarded as a flat and seismically inert continent that is safe from any serious earthquake hazard. While this is generally true, we do occasionally experience moderate earthquakes, with a magnitude greater than 5.

This fact was witnessed first hand by the residents in Bundaberg and Brisbane, who at 2am (AEDT) yesterday morning felt a magnitude 5.2 earthquake and several smaller aftershocks.
While this earthquake was thankfully small, the world has witnessed several destructive earthquakes in the recent past. This highlights the fact that natural disasters are indiscriminate to political boundaries, while emergency responses are now globally coordinated.

In 2004, the magnitude 9.2 Great Sumatra earthquake – the second largest in recorded history – resulted in a tsunami that killed over 200,000 people.

In 2011, around 230,000 people died following a magnitude 7.0 earthquake in Haiti.

In the same year, magnitude 9.0 Tōhoku earthquake off the east coast of Japan spawned a tsunami, which resulted in around 19,000 deaths and massive infrastructure damage.

A magnitude 8.8 earthquake in Chile in 2010 was fortunate to account for only 500 lives. However, in 2008, the magnitude 8.0 Sichuan earthquake in China killed as many as 87,000 people, leaving up to five million homeless.

The stark variation in casualties reflect not only the magnitude, location and depth of the earthquake, but the population density and strength of infrastructure foundations.

Many people also don’t realise that the moment magnitude scale, or “Richter scale”, is a logarithmic measure of shaking amplitude. This means a magnitude 5 earthquake has a shaking amplitude ten times that of a magnitude 4. This converts to 32 times more energy released for a one-fold increase in moment magnitude, and approximately a 1,000-fold increase for a difference of 2.

To put this in perspective, the 7.2 event in Meereberrie was 1,000 times more powerful than the 5.2 event experienced in Bundaberg yesterday, while the 9.2 Great Sumatran earthquake was 1 million times more powerful.

Beneath terra Australis

The earthquake could have caused damage up to 15km away, and could have been felt by people up to 187km away from the epicentre near Eidsvold. Credit: Geosciences Australia

Earthquakes in Australia have also resulted in significant damage and loss of life. This was certainly the case with the magnitude 5.6 Newcastle earthquake in 1989, which killed 13 people and resulted in a $4 billion damage bill.

Adelaide is the most earthquake prone capital in Australia. It experienced a magnitude 5.4 earthquake in 1954 that caused over A$1 billion of damage in today’s money.

The largest earthquake recorded in Australia was a magnitude 7.2 in Meeberrie in 1941, some 500 km away from Perth. Apart from cracking all the walls of the Meeberrie homestead and some minor damage in Perth, there was no significant damage from this event simply due to the lack of any nearby population centre.

The earthquakes in Australia are a particularly mysterious type, referred to as “intra-plate” earthquakes. These occur within the interior of tectonic plates rather than at plate boundaries – such as Japan, Indonesia, New Zealand, Chile and the Himalaya – where most of the worlds earthquakes occur.

Unlike earthquakes at plate boundaries, the mechanisms driving intraplate earthquakes are poorly understood. Plate boundaries are either convergent (colliding), divergent (separating) or transform (sliding past one another), and together these account for about 90% of the worlds seismicity.

The question of what drives intraplate deformation far from the influence of plate boundaries has global significance, as they often occur in regions that are not well prepared for such events.

To understand intraplate deformation we must have accurate data relating to the current orientation of the Australian stress field. This can only be determined by monitoring borehole breakouts or from earthquakes larger than magnitude 5. Until recently there has been very little detailed mapping of neotectonic features in Australia.

Earthquake activity in our region since 1973, showing small clusters of seismically active regions near Perth, Adelaide and the east coast. Credit: Solomon Buckman, Author provided

Geoscience Australia initiated a trenching program several years ago, which revealed several young fault systems 100 km north of Adelaide. These indicate that the area may well have experienced earthquakes larger than the 1954 earthquake in the not so distant past.

Very little is known about the nature and recurrence intervals of these faults. This is largely due to the fact that the fault traces are usually covered by a thin veneer of soil and sediment that effectively conceals them from view.

New optically stimulated luminescence (OSL) dating techniques applied to the buried sediment that accumulates at the toe of a fault scarp are shedding light on the timing of pre-historic earthquakes and revealing that the Mount Lofty and Flinders ranges in South Australia are quite young geomorphic features and not necessarily the denuded core of an ancient mountain range as once thought.

Plate margins near Australia. The black dots are earthquake epicentres and the red triangles are volcanoes. Credit: USGS

Hit predictions

Although we will never be able to “predict” when an earthquake will occur with enough precision to practically evacuate cities or towns, the study of ancient earthquakes (paleoseismology) is an essential tool in extending our knowledge of pre-historic (1973) earthquakes in areas where recurrence intervals along major faults may be in the order of tens of thousands of years.

The issue of uncertainty in earthquake predictions was brought to the fore recently when six Italian seismologists were convicted of manslaughter for giving inaccurate advice before an earthquake that struck the town of L’Aquila in April 2009, killing more than 300 people.

Much to the relief of the world’s geological community, they were acquitted in November 2014 after an appeal, but it highlights the importance of communicating complex natural phenomena to the general public.

While the earthquake in Queensland this week thankfully caused little damage, we still need a longer term perspective in terms of earthquake mitigation, and also in terms of determining the fundamental driving mechanisms of intra-plate tectonism.

We need to talk to communities about the risk of earthquake activities, even in apparently stable regions like Australia. This is because even we are not immune to the tectonic forces that are driving our continent northward at the incredible velocity of about 6 cm per year – making Australia the fastest moving continent.

Emergency earthquake responses are also now a globally coordinated activity involving numerous countries and organisations. That means we all have an important role to play.

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

Carbonates make diamonds grow in the Earth’s mantle

February 16, 2015

Short-lived splendour: Diamonds are caught up in a cycle of growth and decay in the Earth’s interior. (Photo: paloetic/flickr)

Table of Contents

Lava that is almost as free-flowing as water and, when it cools down, as pale as limestone: the Ol Doinyo Lengai in northern Tanzania is the only active volcano in the world that produces so-called carbonatite lava. Unlike conventional lava, the majority of this lava consists not of molten silicates but of molten carbonates. Volcanoes of this kind are found along rift valleys where the continental plates gradually break apart and new oceans are formed.

Diamond from lime and iron

These carbonate melts, among other things, form when limestones enter the Earth’s mantle. This occurs as a result of subduction, when old oceanic crust plunges down below an adjoining crustal plate. By means of high-pressure experiments in the laboratory, postdoc Arno Rohrbach and ETH Zurich Professor Max Schmidt from the Institute of Geochemistry and Petrology of ETH Zurich studied how the oxidised carbon contained in the carbonates behaves in the Earth’s mantle, and in so doing they made an exciting discovery: at a depth of more than 200 kilometres, the submerged carbonates of the oceanic crust reach their melting point, which is 300 to 400 degrees lower than that of silicates. A carbonatite melt is formed and migrates from the subducted oceanic crust into the surrounding mantle, where it causes partial melting therein. However, because the Earth’s mantle is strongly chemically reducing and contains elemental metallic iron, the CO2 in the carbonatite melt reacts with the elemental iron. This causes diamonds to form.

Earlier studies have already shown that carbonates in the Earth’s mantle cause the surrounding mantle to melt at relatively lower temperatures at pressure in excess of 2.5 gigapascals, but these studies focused exclusively on the oxidised state of the carbonates. However, the ETH Zurich researchers write in their study, which was recently published on-line in “Nature”, that in order to understand what happens in the significantly reduced deeper mantle of the Earth it is necessary to consider the redox equilibrium between oxidised carbonates and the reduced metal-containing deeper mantle.

“Minerals in the Earth’s mantle such as garnet and perovskite preferentially incorporate trivalent iron during their formation”, says Max Schmidt. Part of the otherwise doubly positively charged iron is oxidised for this purpose, while another part that is half the amount of the trivalent iron is simultaneously reduced to elemental iron. Because metallic iron and carbon dioxide are incompatible, the iron metal is oxidised and the carbon dioxide is reduced to pure carbon. Thus, diamonds crystallise out of the carbonate melt at a pressure of more than 10 gigapascals and temperatures of 1400 to 1700 degrees Celsius, consequently the carbonate melt solidifies. Thereafter only triply and doubly positively charged iron together with the diamonds remain in these mantle domains in the transition zone between the upper and lower mantle at a depth between about 410 and 660 kilometres.

The carbon cycle in the Earth’s interior is more complex

However, as a result of convection in the Earth’s mantle over hundreds of millions of years, the “agglomerates” of diamonds, which cover a distance of between one and ten centimetres per year, can be transported into the lower mantle down to a depth well in excess of 2000 kilometres, and can rise up again from there. During the uprise, the diamonds remain stable until they pass back through the transition zone from the lower to the upper mantle of the Earth, in which both the chemical equilibrium and the pressure and temperature conditions change again: here the minerals containing trivalent iron – perovskite and garnet – become unstable and release trivalent iron which then reacts with the diamonds. The carbon is re-oxidised in this process, the diamonds are destroyed and the trivalent iron is reduced to divalent iron. Carbonate melts can form again due to the presence of carbon dioxide, and the divalent iron is incorporated into the minerals olivine and pyroxene, which make up the majority of the upper mantle.

This enabled the researchers to show not only how and where carbonatite melts are formed in the Earth’s mantle. They also demonstrated how the carbon cycle from the Earth’s surface down to its interior functions: from carbon dioxide transported with carbonates into the interior, reduced to pure carbon and finally oxidised back to carbon dioxide as it rises. The resulting carbonatite melt, most of which is normally dissolved in a silicate melt at crustal pressures, ultimately brings the carbon dioxide back to the surface of the Earth through active volcanoes such as the Ol Doinyo Lengai.

Reference:
Rohrbach A &Schmidt M: Redox freezing and melting in the Earth’s deep mantle, Nature (2011), DOI:10.1038/nature09899, published online 23 March 2011

Note : The above story is based on materials provided by ETH Zurich.

Archaeocyatha

February 16, 2015

Archeocyathids from the Poleta formation, eastern California

Table of Contents

Archaeocyatha or archaeocyathids (“ancient cups”) are extinct, sessile, reef-building marine organisms of warm tropical and subtropical waters that lived during the early (lower) Cambrian period. It is believed that the centre of the Archaeocyatha origin is in East Siberia, where they are first known from the beginning of the Tommotian Age of the Cambrian, 525 million years ago (mya). In other regions of the world, they appeared much later, during the Atdabanian, and quickly diversified into over a hundred families. They became the planet’s very first reef-building animals and are an index fossil for the Lower Cambrian worldwide.

Preservation

The remains of Archaeocyatha are mostly preserved as carbonate structures in a limestone matrix. This means that the fossils cannot be chemically or mechanically isolated, save for some specimens that have already eroded out of their matrices, and their morphology has to be determined from thin cuts of the stone in which they were preserved.

Geological history

Today, the archaeocyathan families are recognizable by small but consistent differences in their fossilized structures: Some archaeocyathans were built like nested bowls, while others were as long as 300mm. Some archaeocyaths were solitary organisms, while others formed colonies. In the beginning of the Toyonian Age around 516 mya, the archaeocyaths went into a sharp decline. Almost all species became extinct by the Middle Cambrian, with the final-known species, Antarcticocyathus webberi, disappearing just prior to the end of the Cambrian period. Their rapid decline and disappearance coincided with a rapid diversification of the Demosponges.

The archaeocyathids were important reef-builders in the early to middle Cambrian, with reefs (and indeed any accumulation of carbonates) becoming very rare after the group’s extinction until the diversification of new taxa of coral reef-builders in the Ordovician.

Morphology

The typical archaeocyathid resembled a hollow horn coral. Each had a conical or vase-shaped porous skeleton of calcite similar to that of a sponge. The structure appeared like a pair of perforated, nested ice cream cones. Their skeletons consisted of either a single porous wall (Monocyathida), or more commonly as two concentric porous walls, an inner and outer wall separated by a space. Inside the inner wall was a cavity (like the inside of an empty ice cream cone). At the base, these pleosponges were held to the substrate by a holdfast. The body presumably occupied the space between the inner and outer shells (the intervallum).

Ecology

Flow tank experiments suggest that archaeocyathan morphology allowed them to exploit flow gradients, either by passively pumping water through the skeleton, or, as in present-day, extant sponges, by drawing water through the pores, removing nutrients, and expelling spent water and wastes through the pores into the central space.

Distribution

The archaeocyathans inhabited coastal areas of shallow seas. Their widespread distribution over almost the entire Cambrian world, as well as the taxonomic diversity of the species, might be explained by surmising that that they were planktonic during their larval stage.

Their phylogenetic affiliation has been subject to changing interpretations, yet the consensus is growing that the archaeocyath was indeed a kind of sponge, thus sometimes called a pleosponge. But some invertebrate paleontologists have placed them in an extinct, separate phylum, known appropriately as the Archaeocyatha. However, one cladistic analysis suggests that Archaeocyatha is a clade nested within the phylum Porifera (better known as the true sponges).

Note : The above story is based on materials provided by Wikipedia.

How carbonates behave in the Earth’s interior

February 16, 2015

Carbonates are the most important carbon reservoirs on the planet. But what role do they play in the Earth’s interior? How do they react to conditions in the Earth’s mantle? These are the questions being asked by a group of scientific researchers from Frankfurt, Bayreuth, Berlin/Potsdam, Freiberg and Hamburg, in a project funded by the DFG. The Research Unit brings together experts from various geoscience disciplines and cutting edge technology.

The Earth has an average radius of around 6,400 kilometers. However, the deepest borehole thus far drilled has only reached a depth of twelve kilometers. And even with huge technical advances, it is unthinkable that we will ever be able to carry out empirical research on the deepest layers, according to Björn Winkler, Professor of Crystallography at the Goethe University Frankfurt and coordinator of the new Research Unit. “We can only get an idea of the conditions in the Earth’s interior by combining experiments and model calculations”, he explains. While we already have detailed knowledge of silicates, which are a key component of the earth’s mantle, very little research on carbonates has been done to date. “The composition of the earth can be explained without carbonates – but the question is, how well?”, continues Winkler.

“Structures, Properties and Reactions of Carbonates at High Temperatures and Pressures” is the title of the project being funded by the DFG as of mid-February. “We want to understand how the Earth works,” is the way Winkler describes the primary research goal of the approximately 30 scientists and their teams. What possibilities our planet has for storing carbon, how much carbon there actually is on the earth – the entire carbon cycle is still a complete mystery.

The research group, which combines seven individual projects, is focusing its attention on the Earth’s mantle: the 2,850 kilometer thick middle layer in the internal structure of the earth. The aim is to come to a better understanding of the phase relationships, crystal chemistry and physical properties of carbonates. To that end, the plan is to simulate the conditions of the mantle transition zone and the lower earth mantle below it – namely very high temperatures and very high pressure. Each of the seven projects examines a different aspect; for example the carbonate calcite, or the combination of carbonates with iron or silicates, or the behavior of carbonates under shock.

Winkler and his team have been dealing with this issue for six years already. His colleague, Dr. Lkhamsuren Bayarjargal has already been awarded the Max-von-Laue Prize from the German Association of Crystallography for his work with high-power lasers, and has received funding from the Focus Program of the Goethe University. The nationwide collaboration among the researchers is not an entirely new phenomenon either. The DFG funding will enable them to build special equipment to simulate the conditions in the Earth’s mantle. This research apparatus includes diamond anvil cells, capable of producing pressures a million times greater than atmospheric pressure, and high-power lasers that can generate temperatures of up to 5,000 degrees Celsius. Calculations have shown that these are the conditions that prevail in the Earth’s mantle.

The tiniest amounts of a carbonate are enough for an experiment. During the experiment, the substance is exposed to the respective conditions while the researchers examine it for any changes. A variety of techniques are used for this, such as Raman spectroscopy in Frankfurt, and infrared spectroscopy in Potsdam. “If we come to the same conclusions using different methods, we will know that we have got it right,” says Prof. Winkler.

Note : The above story is based on materials provided by Goethe University.

Historic tide gauge data to shed light on ancient tsunamis

February 16, 2015

Chart from Valetta, Malta, 2nd April 1872, after undergoing conservation, showing the ‘seiching’

By restoring historic tide gauge data from Malta and making it available to the public, researchers at the National Oceanography Centre (NOC) and the UKHO hope to shed new light on past tsunamis and climate change in the Mediterranean.
A tide gauge, installed in the Maltese port of Valetta in 1871, offers the only continuous record of the sea level in the Southern Mediterranean that goes back further than fifty years. However, some of the paper records it produced have deteriorated.

The project coordinator, NOC’s Elizabeth Bradshaw said, “there are a limited number of long-term records of climate data in the world, so rescuing and recovering data is vital for answering questions on climate change and oceanography.”

This project is being run from the British Oceanographic Data Centre (BODC) which is a National Facility, within the NOC, that maintains and distributes marine data.

The Department for Business, Innovation and Skills (BIS) have provided £32,000 from its’ ‘Breakthrough Fund’1 to NOC and the UKHO in order to restore these records and make them available to the public. They hope to digitise the data via a citizen science activity, once this project is complete. Once digitised, scientists will be able to use the data to look for evidence of past tsunamis and climate change.

Professor Kevin Horsburgh, from the NOC, said “Preserving long term data records like these is essential for our understanding of sea level change. The data allows scientists to identify the mechanisms that contribute to long term variability of sea level, as well as to measure the impact of each process. These variations range from long term tidal changes through to century scale change due to climate change”

While modern tide gauges typically only calculate the sea level once every fifteen minutes, this historic analogue gauge made a continuous recording. It worked using a float on the water that, via a system of pulleys and cogs, moved a pen up and down a paper-wrapped drum in a way that reflected the changing sea level.

The British Navy installed the gauge to ensure ships got safely in and out of the harbour. In 1877 the Astronomer Royal George Airy2 used the data from this gauge to write about the particularly interesting tidal signal at Valetta. This signal is caused by the ocean water sloshing back and forth across the Mediterranean basin much as it does in a bath. The gauge remained operational until 1926.

Note : The above story is based on materials provided by National Oceanography Centre.

Meteorite may represent ‘bulk background’ of Mars’ battered crust

February 16, 2015

Designated Northwest Africa (NWA) 7034, and nicknamed “Black Beauty,” the Martian meteorite weighs approximately 11 ounces (320 grams). Credit: NASA

NWA 7034, a meteorite found a few years ago in the Moroccan desert, is like no other rock ever found on Earth. It’s been shown to be a 4.4 billion-year-old chunk of the Martian crust, and according to a new analysis, rocks just like it may cover vast swaths of Mars.
In a new paper, scientists report that spectroscopic measurements of the meteorite are a spot-on match with orbital measurements of the Martian dark plains, areas where the planet’s coating of red dust is thin and the rocks beneath are exposed. The findings suggest that the meteorite, nicknamed Black Beauty, is representative of the “bulk background” of rocks on the Martian surface, says Kevin Cannon, a Brown University graduate student and lead author of the new paper.

The research, co-authored by Jack Mustard from Brown and Carl Agee from the University of New Mexico, is in press in the journal Icarus.

When scientists started analyzing Black Beauty in 2011, they knew they had something special. Its chemical makeup confirmed that it was a castaway from Mars, but it was unlike any Martian meteorite ever found. Before Black Beauty, all the Martian rocks found on Earth were classified as SNC meteorites (shergottites, nakhlites, or chassignites). They’re mainly igneous rocks made of cooled volcanic material. But Black Beauty is a breccia, a mashup of different rock types welded together in a basaltic matrix. It contains sedimentary components that match the chemical makeup of rocks analyzed by the Mars rovers. Scientists concluded that it is a piece of Martian crust — the first such sample to make it to Earth.

Cannon and Mustard thought Black Beauty might help to clear up a longstanding enigma: the spectral signal from SNC meteorites never quite match with remotely sensed specra from the Martian surface. “Most samples from Mars are somewhat similar to spacecraft measurements,” Mustard said, “but annoyingly different.”

Not red: A piece of Mars A chip from “Black Beauty,” a meteorite from Mars, contains different rock types welded together. It helps explain the Martian “dark plains,” large areas of the planet’s surface that have only a thin layer of red dust.

So after acquiring a chip of Black Beauty from Agee, Cannon and Mustard used a variety of spectroscopic techniques to analyze it. The work included use of a hyperspectral imaging system developed by Headwall photonics, a Massachusetts-based company. The device enabled detailed spectral imaging of the entire sample.

“Other techniques give us measurements of a dime-sized spot,” Cannon said. “What we wanted to do was get an average for the entire sample. That overall measurement was what ended up matching the orbital data.”

The researchers say the spectral match helps put a face on the dark plains, suggesting that the regions are dominated by brecciated rocks similar to Black Beauty. Because the dark plains are dust-poor regions, they’re thought to be representative of what hides beneath the red dust on much of the rest of the planet.

“This is showing that if you went to Mars and picked up a chunk of crust, you’d expect it to be heavily beat up, battered, broken apart and put back together,” Cannon said.

That the surface of Mars would be rich in Black Beauty-like breccias makes a lot of sense, given what we know about Mars, the researchers say.

“Mars is punctured by over 400,000 impact craters greater than 1 km in diameter …,” they write. “Because brecciation is a natural consequence of impacts, it is expected that material similar to NWA 7034 has accumulated on Mars over time.”

In other words, Mustard says, the bulk of rocks on the surface of Mars probably look a lot like Black Beauty: “dark, messy and beautiful.”

Reference:
Kevin M. Cannon, John F. Mustard, Carl B. Agee. Evidence for a Widespread Basaltic Breccia Component in the Martian Low-Albedo Regions from the Reflectance Spectrum of Northwest Africa 7034. Icarus, 2015; DOI: 10.1016/j.icarus.2015.01.016

Note: The above story is based on materials provided by Brown University.

Rivers Are Draining Greenland Quickly

February 16, 2015

A river of meltwater flowing across Greenland’s ice sheet. Image Credit: UCLA/Laurence C. Smith.

Rivers of glacial meltwater flowing over Greenland’s frozen surface may be contributing as much to global sea level rise as all other processes that drain water from the melting ice sheet combined, according to researchers at the University of California, Los Angeles, and NASA.
The new finding is published in the journal Proceedings of the National Academy of Sciences. The research is dedicated to the memory of coauthor Alberto Behar of NASA’s Jet Propulsion Laboratory, Pasadena, California, who died in a small-plane crash in Los Angeles on Jan. 9.

Eighty percent of Greenland, which is about the size of the United States west of the Rocky Mountains, is covered by ice, which has the potential to make a significant contribution to sea level rise as it melts.

Because Greenland’s ice sheet is vast and difficult to study from ground level, scientists are still learning about the many processes by which its melting water reaches the ocean. This is the first study of the drainage system of rivers and streams that forms atop the ice sheet in summer.

The new paper is based on research that took place on the ice sheet itself, carried out by lead author Laurence Smith of UCLA, JPL’s Behar and nine other researchers in July 2012, and on remote sensing data from the same period. The researchers traveled by helicopter to map the network of rivers and streams over about 2,000 square miles (5,600 square kilometers) of Greenland. They were especially interested in learning how much of the meltwater remained within the ice sheet and how much drained to the ocean.

Virtually all of the flowing water drains directly to the ocean through sinkholes, the researchers found.

Behar designed two types of remotely controlled boats to collect data from the surface water. One was a drone boat that measured the depth of the water and how much light it reflected, allowing the researchers to create a scale with which to calibrate the depth of the surface water from satellite images. This boat was used on lakes and slow-flowing rivers. For dangerous, swift-flowing rivers, Behar developed disposable robotic river drifters that measured streamflow velocity, depth and temperature as they swept downstream.

“The measurements we collected would not have been possible without the truly innovative instruments designed by Alberto Behar, and his steady hand during some very trying conditions in the field. The scientific outcomes of this study can be traced directly to him,” said lead author Smith, professor and chair of the geography department at UCLA.

Behar, who was also a research professor at Arizona State University in Tempe, produced many other innovative technologies in a 23-year career at JPL that specialized in robotics for exploring extreme environments in our solar system. To measure ice sheets in Antarctica as well as Greenland, he also developed robotic submarines and ice rovers. Behar was an investigation scientist for instruments on NASA’s Mars Curiosity rover and Mars Odyssey orbiter.

Reference:
The full paper is available , Doi: 10.1073/pnas.1413024112

Note : The above story is based on materials provided by NASA. The original article was written by Dr. Tony Phillips.

Paradoxides

February 15, 2015

Table of Contents

Paradoxides is a genus of large to very large trilobites found throughout the world during the Mid Cambrian period. One record-breaking specimen of Paradoxides davidis is 37 centimetres (15 in). It has a semicircular head, free cheeks each ending with a long, narrow, recurved spine, and sickle-shaped eyes, providing almost 360° view, but only in the horizontal plane. Its elongated trunk was composed of 19-21 segments and was adorned with longish, recurved lateral spines. Its pygidium (caudal shield) was comparatively small.

Paradoxides is a characteristic Middle Cambrian trilobite of the ‘Atlantic’ (Avalonian) fauna. Avalonian rocks were deposited near a small continent called Avalonia in the Paleozoic Iapetus Ocean. Avalonian beds are now in a narrow strip along the East Coast of North America, and in Europe.

Description

The exoskeleton of Paradoxides is large to very large, relatively flat, oval to inverted egg-shaped, and about 1⅓× longer than wide, with the greatest width across the genal spines. The headshield (or cephalon) is close to semicircular with long spines developing from the corners of the cephalon. As usual in trilobites, the dorsal suture runs along the top of the eye. As in all Redlichiina this suture runs from the back of the eye slightly outward to the rear margin of the cephalon (a state called opisthoparian) opposite the base of the pleural spines. From the front of the eye the suture describes a slight S-curve forward cutting the front margin in front of the eye. The central raised area of the cephalon (or glabella) is divided in the occipital ring furthest to the back, followed by the first lobe that is like the occipital ring defined by a furrow across the midline and two more lobes that have furrows that do not connect across the midline. The frontal lobe is the widest and shaped like a segment of a circular band. It almost reaches the frontal edge of the cephalon. The eyelobe is short, opposite the first to third glabelar lobes. Paradoxides has a palate (or hypostome) with its front aligned with the front of the glabella and connected to the doublure (a condition science calls conterminant). Exceptionally, the hypostome is even fused with the frontal part of the doublure (called rostral plate), a character that distinguishes it from all other trilobites, except some Cambrian Corynexochida such as Oryctocephalus, and Fieldaspis.

Paradoxides. Cambrian era. Credit: Washington State University

The articulate midpart of the exoskeleton (or thorax) consists of 19-21 segments. The axis is about as wide as each of the ribs (or pleurae) to its sides, not counting the spines at their tips, which gradually arch further back while slightly increasing in length, while the spines on the rear thorax segment are much longer, about twice as long as the associated pleurae, are directly entirely backwards, and extend convincingly beyond the pygidium.

The tailshield (or pygidium) is small and shows the axis with one or two rings and may be partially or completely fused to the last thoracic segment. The axis does not reach the rear margin of the pygidium and defines a U-shaped pleural field.

Ontogeny

The larval development (or ontogeny) of Paradoxides was already described by Barrande (in 1852). The earliest stage (or protaspis) is a disc with three pairs of spines on the margin. Genal spines are placed at halflength directed at about 45° outward and backward, curving slightly further backwards and almost ⅓ of the diameter of the protaspis long. Sharply pointed intergenal spines about 50% of the disc diameter long, are positioned at the back of the future cephalon, are straight and pointing backwards and 15° outward. These spines will have disappeared in adult specimens. The first of future thoracic spines are placed immediately next to the intergenal spines and curve to a parallel with the midline. The front of the glabella almost reaches the front and consists of four sets of lobes divided by a furrow on the midline in the frontal ⅔, and furrows between them. The most backward set consisting of two central and two lateral lobes. Further backwards is the final element of the glabella, one central occipital lobe that carries a small node, and two lateral occipital lobes. The axis is terminated with three rings of somewhat decreasing width. Midlength of the side of the most glabellar lobes run semicircular eyelobes parallel to the margin of the exoskeleton, ending near the base of the intergenal spine.

Behaviour

Like in many early trilobites, the thorax of Paradoxides consists of so-called nonfulcrate segments, that allow for rolling like a pancake, providing protection from front, rear, top and bottom, while leaving access to the soft ventral side of the animal from each of the sides.

Trilobite (Paradoxides sp.). Acadoparadoxides, possibly A. briareus, a large trilobite from about 500 million years ago from Morocco, North Africa (Middle Cambrian). Credit : Mike Peel

Complete specimens of Paradoxides have been found with the free cheeks (or librigenae) and the fused palate (hypostome) and lip (or rostral plate) upside down and front to back beneath the remainder of the exoskeleton (consisting of the so-called cranidium, thorax and pygidium). This suggests that in moulting the body was arched above substrate, with the anterior border at the front and pleural spines of rear thoracic segments dug into sediment. Stretching the body would then result in rupturing the sutures in the cephalon and flipping of the librigenae plus hypostome-rostral plate. After these parts had broken away the animal would exit moving forward from its old exoskeleton, that would also have consisted of a chitinous ventral part, including that of the legs.

Specimens of Paradoxides have been found containing intact Peronopsis trilobites between glabella and hypostome and where the gut would have been and it is assumed these were not food items of the large trilobite but instead either scavenged on its digestive track, or found shelter.

Note : The above story is based on materials provided by Wikipedia.

New Species Discovered Beneath Ocean Crust

February 15, 2015

Image: C-DEBI researchers deply the ROV Jason to collect samples. Alberto Robador / USC

Two miles below the surface of the ocean, researchers have discovered new microbes that “breathe” sulfate.

The microbes, which have yet to be classified and named, exist in massive undersea aquifers — networks of channels in porous rock beneath the ocean where water continually churns. About one-third of the Earth’s biomass is thought to exist in this largely uncharted environment.
“It was surprising to find new bugs, but when we go to warmer, relatively old and isolated fluids, we find a unique microbial community,” said Alberto Robador, postdoctoral researcher at the USC Dornsife College of Letters, Arts and Sciences and lead author of a paper on the new findings that will be published by the open-access journal Frontiers in Microbiology on Jan. 14.

Sulfate is a compound of sulfur and oxygen that occurs naturally in seawater. It is used commercially in everything from car batteries to bath salts and can be aerosolized by the burning of fossil fuels, increasing the acidity of the atmosphere.

Microbes that breathe sulfate — that is, gain energy by reacting sulfate with organic (carbon-containing) compounds — are thought to be some of the oldest types of organisms on Earth. Other species of sulfate-breathing microbes can be found in marshes and hydrothermal vents.

Microbes beneath the ocean’s crust, however, are incredibly tricky to sample.

Researchers from USC and the University of Hawaii took their samples from the Juan de Fuca Ridge (off the coast of Washington state), where previous teams had placed underwater laboratories, drilled into the ocean floor. To place the labs, they lowered a drill through two miles of ocean and bored through several hundred feet of ocean sediment and into the rock where the aquifer flows.

“Trying to take a sample of aquifer water without contaminating it with regular ocean water presented a huge challenge,” said Jan Amend, professor at USC Dornsife and director of the Center for Dark Energy Biosphere Investigations (C-DEBI), which helped fund the research.

To solve this problem, C-DEBI created Circulation Obviation Retrofit Kit (CORK) observatories. The moniker was basically dreamed up to fit the term “CORK” because these devices create a seal at the seafloor, like a cork in a bottle, allowing scientists to deploy instruments and sampling devices down a borehole while keeping ocean water out.

Samples were then shuttled to the surface by remote-controlled undersea vehicles or “elevators” — balloons that drop ballast and float samples gently up to the waiting scientists.

Like the microbes on the forest floor that break down leaf litter and dead organisms, the microbes in the ocean also break down organic — that is, carbon-based — material like dead fish and algae. Unlike their counterparts, however, the microbes beneath the ocean crust often lack the oxygen that is used on land to effect the necessary chemical reaction.

Instead, these microbes can use sulfate to break down carbon from decaying biological material that sinks to the sea bottom and makes its way into the crustal aquifer, producing carbon dioxide.

Learning how these new microbes function will be important to getting a more accurate, quantified understanding of the overall global carbon cycle — a natural cycling of carbon through the environment in which it is consumed by plants, exhaled by animals and enters the ocean via the atmosphere. This cycle is currently being disrupted by man-made carbon dioxide emissions.

“This is the first direct account of microbial activity in these type of environments,” Robador said, “and shows the potential of these organisms to respire organic carbon.”

The research was funded by the National Science Foundation (C-DEBI award OCE0939564, MCB0604014, 1207880 and 1207874) and the NASA Astrobiology Institute.

Video:

Reference:
Activity and phylogenetic diversity of sulfate-reducing microorganisms in low-temperature subsurface fluids within the upper oceanic crust. Doi: 10.3389/fmicb.2014.00748

Note : The above story is based on materials provided by University of Southern California.

Padma River

February 15, 2015

A map showing the major rivers that flow into the Bay of Bengal, including Padma.

Table of Contents

Padma is a major river in Bangladesh. It is the main distributary of the Ganges, flowing generally southeast for 120 kilometres (75 mi) to its confluence with the Meghna River near the Bay of Bengal. The city of Rajshahi is situated on the banks of the river.

History

Etymology

The Padma, Sanskrit for lotus flower, is mentioned in Hindu mythology as a byname for the Goddess Lakshmi.

The name Padma is given to the lower part of the course of the Ganges (Ganga) below the point of the off-take of the Bhagirathi River (India), another Ganges River distributary also known as the Hooghly River. Padma had, most probably, flowed through a number of channels at different times. Some authors contend that each distributary of the Ganges in its deltaic part is a remnant of an old principal channel, and that starting from the western-most one, the Bhagirathi (in West Bengal, India), each distributary to the east marks a position of a newer channel than the one to the west of it.

Geographic effects

Eighteenth-century geographer James Rennell referred to a former course of the Ganges north of its present channel, as follows:

Appearances favour very strongly that the Ganges had its former bed in the tract now occupied by the lakes and morasses between Natore and Jaffiergunge, striking out of the present course by Bauleah to a junction of Burrrampooter or Megna near Fringybazar, where accumulation of two such mighty streams probably scooped out the present amazing bed of the Megna.

The places mentioned by Rennell proceeding from west to east are Rampur Boali, the headquarters of Rajshahi district, Puthia and Natore in the same district and Jaffarganj in the district of Dhaka. The place last named were shown in a map of the Mymensingh district dated 1861, as a subdistrict (thana) headquarters, about 10 kilometres (6 mi) south-east of Bera Upazila police station. It is now known as Payla Jaffarganj and is close to Elachipur opposite Goalunda. According to Rennell’s theory, therefore, the probable former course of the Ganges would correspond with that of the present channel of the Baral River.

Authorities agree that the Ganges has changed its course and that at different times, each of the distributaries might have been the carrier of its main stream.

The bed of the Padma is wide, and the river is split up into several channels flowing between constantly shifting sand banks and islands. During the rains the current is very strong and even steamers may find difficulty in making headway against it. It is navigable at all seasons of the year by steamers and country boats of all sizes and until recently ranked as one of the most frequented waterways in the world. It is spanned near Paksey by the great Hardinge Bridge over which runs one of the main lines of the Bangladesh Railway.

Geography

The Padma enters Bangladesh from India near Chapai Nababganj and meets the Jamuna (Bengali: যমুনা Jomuna) near Aricha and retains its name, but finally meets with the Meghna (Bengali: মেঘনা) near Chandpur and adopts the name “Meghna” before flowing into the Bay of Bengal.

Rajshahi, a major city in western Bangladesh, is situated on the north bank of the Padma.

The Ganges originates in the Gangotri Glacier of the Himalaya, and runs through India and Bangladesh to the Bay of Bengal. The Ganges enters Bangladesh at Shibganj in the district of Chapai Nababganj. West of Shibganj, the Ganges branches into two distributaries, the Bhagirathi and the Padma rivers. The Bhagirathi River, which flows southwards, is also known as the Ganga and was named the Hoogly or Hooghly by the British.

Further downstream, in Goalando, 2,200 kilometres (1,400 mi) from the source, the Padma is joined by the Jamuna (Lower Brahmaputra) and the resulting combination flows with the name Padma further east, to Chandpur. Here, the widest river in Bangladesh, the Meghna joins the Padma, continuing as the Meghna almost in a straight line to the south, ending in the Bay of Bengal.

Pabna District

The Padma forms the whole of the southern boundary of the Pabna District for a distance of about 120 kilometres (75 mi).

Kushtia District

The Jalangi River is thrown off at the point where the mighty Padma touches the district at its most northernly corner, and flows along the northern border in a direction slightly southeast, until it leaves the district some miles to the east of Kushtia. It carries immense volumes of water and is very wide at places, constantly shifting its main channel, eroding vast areas on one bank, throwing chars on the other, giving rise to many disputes as to the possession of the chars and islands which are thrown up.

Note : The above story is based on materials provided by Wikipedia.

Earliest-known arboreal and subterranean ancestral mammals discovered

February 12, 2015

Photos of the fossils of Docofossor (left) and Agilodocodon (right). Credit: Zhe-Xi Luo, University of Chicago

The fossils of two interrelated ancestral mammals, newly discovered in China, suggest that the wide-ranging ecological diversity of modern mammals had a precedent more than 160 million years ago.
With claws for climbing and teeth adapted for a tree sap diet, Agilodocodon scansorius is the earliest-known tree-dwelling mammaliaform (long-extinct relatives of modern mammals). The other fossil, Docofossor brachydactylus, is the earliest-known subterranean mammaliaform, possessing multiple adaptations similar to African golden moles such as shovel-like paws. Docofossor also has distinct skeletal features that resemble patterns shaped by genes identified in living mammals, suggesting these genetic mechanisms operated long before the rise of modern mammals.

These discoveries are reported by international teams of scientists from the University of Chicago and Beijing Museum of Natural History in two separate papers published Feb. 13 in Science.

“We consistently find with every new fossil that the earliest mammals were just as diverse in both feeding and locomotor adaptations as modern mammals,” said Zhe-Xi Luo, PhD, professor of organismal biology and anatomy at the University of Chicago and an author on both papers. “The groundwork for mammalian success today appears to have been laid long ago.”

Agilodocodon and Docofossor provide strong evidence that arboreal and subterranean lifestyles evolved early in mammalian evolution, convergent to those of true mammals. These two shrew-sized creatures — members of the mammaliaform order Docodonta — have unique adaptations tailored for their respective ecological habitats.

Agilodocodon, which lived roughly 165 million years ago, had hands and feet with curved horny claws and limb proportions that are typical for mammals that live in trees or bushes. It is adapted for feeding on the gum or sap of trees, with spade-like front teeth to gnaw into bark. This adaptation is similar to the teeth of some modern New World monkeys, and is the earliest-known evidence of gumnivorous feeding in mammaliaforms. Agilodocodon also had well-developed, flexible elbows and wrist and ankle joints that allowed for much greater mobility, all characteristics of climbing mammals.

“The finger and limb bone dimensions of Agilodocodon match up with those of modern tree-dwellers, and its incisors are evidence it fed on plant sap,” said study co-author David Grossnickle, graduate student at the University of Chicago. “It’s amazing that these arboreal adaptions occurred so early in the history of mammals and shows that at least some extinct mammalian relatives exploited evolutionarily significant herbivorous niches, long before true mammals.”

Docofossor, which lived around 160 million years ago, had a skeletal structure and body proportions strikingly similar to the modern day African golden mole. It had shovel-like fingers for digging, short and wide upper molars typical of mammals that forage underground, and a sprawling posture indicative of subterranean movement.

Docofossor had reduced bone segments in its fingers, leading to shortened but wide digits. African golden moles possess almost the exact same adaptation, which provides an evolutionary advantage for digging mammals. This characteristic is due to the fusion of bone joints during development — a process influenced by the genes BMP and GDF-5. Because of the many anatomical similarities, the researchers hypothesize that this genetic mechanism may have played a comparable role in early mammal evolution, as in the case of Docofossor.

The spines and ribs of both Agilodocodon and Docofossor also show evidence for the influence of genes seen in modern mammals. Agilodocodon has a sharp boundary between the thoracic ribcage to lumbar vertebrae that have no ribs. However, Docofossor shows a gradual thoracic to lumber transition. These shifting patterns of thoracic-lumbar transition have been seen in modern mammals and are known to be regulated by the genes Hox 9-10 and Myf 5-6. That these ancient mammaliaforms had similar developmental patterns is an evidence that these gene networks could have functioned in a similar way long before true mammals evolved.

“We believe the shortened digits of Docofossor, which is a dead ringer for modern golden moles, could very well have been caused by BMP and GDF,” Luo said. “We can now provide fossil evidence that gene patterning that causes variation in modern mammalian skeletal development also operated in basal mammals all the way back in the Jurassic.”

Early mammals were once thought to have limited ecological opportunities to diversify during the dinosaur-dominated Mesozoic era. However, Agilodocodon, Docofossor and numerous other fossils — including Castorocauda, a swimming, fish-eating mammaliaform described by Luo and colleagues in 2006 — provide strong evidence that ancestral mammals adapted to wide-ranging environments despite competition from dinosaurs.

“We know that modern mammals are spectacularly diverse, but it was unknown whether early mammals managed to diversify in the same way,” Luo said. “These new fossils help demonstrate that early mammals did indeed have a wide range of ecological diversity. It appears dinosaurs did not dominate the Mesozoic landscape as much as previously thought.”

References:

Q.-J. Meng, Q. Ji, Y.-G. Zhang, D. Liu, D. M. Grossnickle, Z.-X. Luo. An arboreal docodont from the Jurassic and mammaliaform ecological diversification. Science, 2015; 347 (6223): 764 DOI: 10.1126/science.1260879
Z.-X. Luo, Q.-J. Meng, Q. Ji, D. Liu, Y.-G. Zhang, A. I. Neander. Evolutionary development in basal mammaliaforms as revealed by a docodontan. Science, 2015; 347 (6223): 760 DOI: 10.1126/science.1260880

Note : The above story is based on materials provided by University of Chicago.

Scientists search for new ways to deal with U. S. uranium ore processing legacy

February 12, 2015

A new field project, led by SLAC researchers and the DOE Office of Legacy Management, is using X-ray techniques to target long-lived groundwater contamination (large dark brown area) at former uranium ore processing sites in the floodplains of the upper Colorado River basin. The visible signs of ore processing, tailings piles and contaminated buildings, were cleaned up in the 1990s, and scientists expected that remaining uranium in the ground should have been flushed out into nearby rivers by now (yellow arrow). However, recent estimates predict that contamination will persist for a long period of time, in some cases longer than 100 years. The goal of this new study is to determine why uranium persists in groundwater; scientists will test the hypothesis that buried zones of organic material (dark brown horizontal stripes) store uranium and release it into the water. Samples are being collected in drilling operations and will be analyzed at SLAC’s X-ray facility SSRL. Credit: SLAC National Accelerator Laboratory

Table of Contents

Researchers at the Department of Energy’s SLAC National Accelerator Laboratory are trying to find out why uranium persists in groundwater at former uranium ore processing sites despite remediation of contaminated surface materials two decades ago. They think buried organic material may be at fault, storing toxic uranium at levels that continue to pose risks to human health and the environment, and hope their study will pave the way for better long-term site management and protection of the public and environment.

The contaminated sites, on floodplains in the upper Colorado River basin, operated from the 1940s to the 1970s to produce “yellowcake,” a precursor of uranium fuel used in nuclear power plants and weapons. In the 1990s, site surfaces were cleaned up, and remaining uranium in the ground was expected to flush out over time due to natural groundwater flow across the sites.

“Uranium dissolved in groundwater flows slowly into nearby rivers, where it becomes diluted below the uranium concentrations naturally present in river water,” says John Bargar, SLAC’s project lead and researcher at the lab’s Stanford Synchrotron Radiation Lightsource (SSRL), a DOE Office of Science User Facility. “However, studies have shown that the groundwater contamination is unexpectedly long-lived.”

Buried Organic Material Stores Uranium

But why is this pollution so persistent? To find out, Bargar’s research group recently joined forces with the DOE Office of Legacy Management, which is in charge of the contaminated sites. “Our collaboration is motivated by the need to better understand the geochemical and biological factors influencing uranium mobility and transport,” says William Dam, a hydrologist and site manager at the Office of Legacy Management. “We want to understand the way uranium gets from the ground into the groundwater, creating a plume of contamination in which uranium concentrations stay above regulatory safety requirements.”

Previous field research by Bargar’s team and collaborators at Lawrence Berkeley National Laboratory (LBNL) at the site of a former uranium mill in Rifle, Colorado, has provided a possible explanation for the longevity of the uranium contamination. It revealed that up to 95 percent of the subsurface uranium is concentrated in zones of organic-rich sediment — the buried remains of plants and other organisms along former Colorado River stream banks — generally located 10 to 30 feet underground. These organic substances appear to store large amounts of uranium, restricting its mobility and releasing it very slowly into the surrounding water over many years. Current estimates predict that the contamination will not flush away for at least another 100 years at several sites.

Collaboration Enables Region-wide Testing

“Our model for Rifle predicts that organic-rich zones may generally influence uranium mobility throughout the upper Colorado River basin and therefore could also play an important role at other sites,” says Bargar. As highlighted in the latest Office of Legacy Management Quarterly Report, the new project will include five additional sites in Colorado, Wyoming and New Mexico. The field work started from August to October last year at four sites, and more sample-collecting expeditions will follow this spring.

For Bargar, the collaboration with the Office of Legacy Management is a key factor in the success of the project. “Access to those sites is regulated, and some of them are in very remote locations,” he says. “Our partners from the Office of Legacy Management, as well as LBNL, provide us with site access and logistical support. They also carry out the drilling operations required to take sediment and water samples.”

X-ray Studies of Chemical and Biological Factors

Samples from the field work are shipped to SSRL, where Bargar’s team will analyze them with a variety of X-ray techniques. Scheduled to begin in late January, these experiments will determine the chemical form of uranium in samples from various depths. Some forms of uranium dissolve better in water than others, and the study can reveal how the presence of particular chemical forms in organic-rich zones affects overall uranium mobility at the contaminated sites. The study will also investigate the types of organic carbon present in the ground to help understand how it influences uranium behavior.

The researchers will combine the X-ray data with studies of how bacteria affect uranium chemistry. “We know that microbes strongly influence the chemical form of uranium and, hence, its mobility,” Bargar says. “By collecting information about microbial populations present in the sediments, we hope to gain information about how and when bacteria do that, and how bacteria couple subsurface carbon chemistry to uranium behavior.”

A deeper understanding of the various factors controlling uranium mobility could potentially lead to better ways of cleaning up the nation’s legacy of contamination from uranium mining and processing, and may help researchers devise new remediation strategies for contaminated sites in the upper Colorado River basin and elsewhere.

Note : The above story is based on materials provided by SLAC National Accelerator Laboratory.

New study reveals competition and replacement between two miocene shovel-tuskers

February 12, 2015

Fig. 1, Mandible and lower tusks of Protanancus tobieni. Credit: WANG Shiqi

Dr. Wang Shiqi from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciences and his colleagues recently studied two relatively primitive species of Protanancus, Protanancus tobieni and Protanancus brevirostris. The former discovered from Tongxin of Ningxia Province and Qin’an of Gansu Province, about 16 000 000 years ago and the latter from Guanghe of Gansu Province, about 18 000 000 years ago.
This study published online in the Journal of Vertebrate Paleontology reveals the intensive competition between Protanancus and Platybelodon based on similarities in their mandibular morphologies and dental microwear patterns, with the former genus disappearing from East Asia by the late middle Miocene.

Protanancus is a shovel-tusked proboscidean with elongated mandibular symphysis and flattened lower tusks, similar to the well-known Platybelodon in morphology. Both of them belong to the subfamily Amebeldontinae. Fossil records indicate that the two genera are symbiotic in East Asia for at least 2 000 000 years. Protanancus was extinct in East Asia at about 16 000 000 years ago; however, Platybelodon was flourish, and tended to extinct in East Asia at about 11 000 000 years ago. For example, in the Dingjiaergou section, Protanancus was discovered only from the 3rd layer; whereas Platybelodon was discovered from the 6th, 17th, and 20th layers, with a large abundance. On the contrary, in the Siwalik area of the south Himalayas, lacking the presence of Platybelodon, Protanancus was not extinct until 11 000 000 years ago.

Fig. 2, Cranium and mandible of Protanancus brevirostris. Credit: WANG Shiqi

Microwear study shows that the differences of morphology and distribution of microwear on the cheek teeth of the two genera are statistically insignificant. This result, combined with the similar morphology of the mandible, indicates the two genera had similar feeding behaviors in the similar living environment. If they are indeed living in the same space, strong competition for existence should occurred between Platybelodon and Protanancus.

What is the reason that distinct fates were eventually upon the two similar taxa? The investigation of the inner structure of the lower tusks of the two genera reveals the answer of the question. The inner structure of the lower tusks in Protanancus is concentric laminations as usual proboscideans; whereas that of Platybelodon is specialized as tubular structures. Very simple biomechanical models of finite element have been used to imitate the lower tusks in the two genera. The result indicates that tubular structure shows the greater resistance to the adverse effects of both a heavy load and abrasion than those with concentric laminations. Because the lower tusks are the major feeding apparatus of the two genera. Platybelodon with mechanical advantages of the lower tusk may gradually held ecological space of Protanancus, and eventually led to extinction of the Protanancus, the competitor of Platybelodon.

Fig. 3, Finite element models of lower tusks of Protanancus (A) and Platybelodon (B). Credit: WANG Shiqi

Reference:
“Evolution of Protanancus (Proboscidea, Mammalia) in East Asia” Journal of Vertebrate Paleontology, DOI: 10.1080/02724634.2014.881830

Note : The above story is based on materials provided by Chinese Academy of Sciences.

Oldest fur seal identified, ending 5-million-year ‘ghost lineage’

February 12, 2015

The two seals on the right are a life restoration of the tiny species, whose adult size was only slightly larger than a sea otter. The pinniped depicted above them is the larger-bodied seal Allodesmus, which also existed at the time. Credit: Robert Boessenecker

The oldest known fur seal has been discovered by a Geology PhD student at New Zealand’s University of Otago, providing a missing link that helps to resolve a more than 5-million-year gap in fur seal and sea lion evolutionary history.

Otago’s Robert Boessenecker and colleague Morgan Churchill from the University of Wyoming have named this new genus and species of fur seal Eotaria crypta. The genus name Eotaria means ‘dawn sea lion’.

The discovery of the seal is newly published in UK Royal Society journal Biology Letters.

The species was tiny, with adults being only slightly larger than a sea otter and around the size of a juvenile New Zealand fur seal, says Mr Boessenecker.

Its fossilized partial jaw, with several well-preserved teeth, was recovered from a 15-17 million-year-old rock formation in Southern California in the early 1980s, but until now had been misidentified as belonging to a walrus species.

The fossil was deposited in what is now the John D. Cooper Archaeological and Paleontological Center, where Mr Boessenecker found it while searching through its collections.

He says he instantly realized that it was not the small walrus Neotherium but a tiny, early fur seal.

“This was very exciting as fur seals and sea lions–the family Otariidae–have a limited fossil record that, up until now, extended back to about 10-12 million years ago. Yet we know that their fossil record must go back to around 16-17 million years ago or so, because walruses–the closest modern relative of the otariids–have a record reaching back that far,” he says.

In palaeontology, a gap like this is known as a ‘ghost lineage’, and the new research has now eliminated it. “Until now we had no fossil evidence for the first five million years of fur seal and sea lion evolution. It’s extremely satisfying to have remedied that,” he says.

Mr Boessenecker says Eotaria crypta’s status as a critical transitional fossil is revealed through its teeth which are intermediate between the simplified teeth of modern sea lions and the complex bear-like teeth of the earliest known pinnipeds.

“The mystery remains of why there has only been one of these fur seals ever found given that there have been extensive fossil excavations of similarly aged rocks in California,” he says.

A Japanese palaeontologist, Dr Naoki Kohno, has previously proposed that the earliest fur seals lived in the open ocean and only rarely strayed into continental shelf areas where they would be more likely to be preserved as fossils.

“This hypothesis is supported by this fossil having been collected from rock formed by sediments deposited in what was then continental shelf, rather than extensively studied inland fossil sites, such as Sharktooth Hill, that formed in bays.

Reference:
R. W. Boessenecker, M. Churchill. The oldest known fur seal. Biology Letters, 2015; 11 (2): 20140835 DOI: 10.1098/rsbl.2014.0835

Note: The above story is based on materials provided by University of Otago.

Earthquake early warning begins testing in Pacific Northwest

February 12, 2015

The software opens a program on users’ computers that shows the earthquake epicenter, its magnitude, and the time before shaking. Credit: USGS

The next time a significant earthquake hits in Washington or Oregon, a handful of computers in offices around the region will emit a blaring siren, then a robotic voice will pronounce: “Earthquake. Earthquake. Shaking to begin in… 15 seconds.”
The software, implemented by the University of Washington-based Pacific Northwest Seismic Network based on a California tool, is the region’s first warning system for incoming earthquakes. A prototype was shared this week with a group of people from outside the research community.

The trial group includes Boeing, Microsoft, Sound Transit, Providence Hospital and other hospitals, transportation agencies, utilities and emergency managers. Members will meet Tuesday, Feb. 17, on the UW campus for a workshop to introduce the system and discuss its potential for emergency planning and response in the region, which spans the coastal area from Northern California to southern British Columbia.

“We have found capable partners that will give us good feedback, but we also value diversity,” said John Vidale, a UW professor of Earth and space sciences and director of the seismic network, which includes the UW and the University of Oregon and is overseen by the U.S. Geological Survey.

“The test group is a cross-section of our region’s economy so we can find the best ways of reducing losses from the next earthquake.”

In Japan, similar earthquake alerts have been used to slow bullet trains to prevent derailment, trigger automated earthquake and tsunami alarms in schools, and shut down expensive manufacturing equipment to avoid damage due to shaking.

Here, some 240 seismometers installed throughout Washington and Oregon currently detect vibrations and send readings to a computer at the UW, where the regional seismic network creates an automated report within about 10 minutes after any seismic event.

The seismometers sense the early P waves, and send warning of the more destructive S waves.

The new early warning system being tested will create an automated alert as quickly as four seconds after a quake’s fast-moving but harmless P wave is first detected. Depending on the geography, earthquake size and distance to the user, that could mean a few seconds to more than a minute’s warning before people would start to feel the ground-shaking S waves.

Over the coming months, the researchers expect they will run into problems with missed events or having a single event trigger multiple alerts. They hope to work out these kinks for the next year or so, while institutions begin to think about how they might integrate the alerts into their emergency planning.

“The reason we’re working with this limited group is because they have a tolerance for the errors that we know might crop up,” said Paul Bodin, a UW research professor of Earth and space sciences who is tuning the regional tool.

The UW is collaborating on West Coast early earthquake warnings with the University of California, Berkeley and Caltech, the two groups that developed the software. The UW joined the existing California collaboration after the 2011 Tohoku earthquake and got initial funding from the Gordon and Betty Moore Foundation and the USGS to develop a system similar to the one that saved lives in Japan.

The California and Pacific Northwest regions collaborate, but currently focus on their own equipment, user groups and distinct types of seismic risks.

California has been testing its version with institutional users for more than a year with the support of the state’s emergency management office. The Bay Area Rapid Transit system, or BART, recently began using the alerts to slow its trains to prevent crashes.

The new Pacific Northwest tool will by default issue an alert for any earthquakes above magnitude 3, which are generally harmless and occur somewhere in the region about every two to three weeks. Users can move that minimum threshold upward. Magnitude-4 earthquakes generally happen in this region about twice a year, and magnitude-5 earthquakes, which generate noticeable shaking, occur roughly once a year. A magnitude-9 earthquake last happened here in 1700, but a repeat could come at any time.

The software works on Windows, Apple and Linux desktop computers. Future work will include providing alert messages for mobile devices and other means.

The University of Oregon has, until recently, primarily provided technical assistance for the seismic network, but that role is expanding thanks to federal and state support, said Douglas Toomey, a professor of geophysics. A $670,000 request in the Oregon governor’s proposed budget will allow the UO to add additional sensors in the state.

The federal budget proposed this month by President Obama includes $5 million per year of long-term funding for a West Coast earthquake warning system. That helps reach the $16 million annually that USGS estimates it would cost to implement and maintain a West Coast warning system for the public. A reliable system, Vidale said, would require roughly doubling the current number of seismometers to fill in gaps, replacing older seismometers, updating some telecom equipment to minimize delays in the data transfer, and hiring a larger staff to maintain the equipment.

With funding, alerts could be available to the public within a few years, Vidale said. The goal is to get the technology and the users ready in the two regions, and eventually to merge the two into a single earthquake-alert system that spans the whole West Coast, and perhaps someday other earthquake-prone regions such as Hawaii, Nevada, Utah and Alaska.

“Eventually, we want to provide simple, fast and uniform coverage to protect the citizens and infrastructure,” Vidale said. “This is an exciting first step in that direction.”

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Note : The above story is based on materials provided by University of Washington.

Carbon release from ocean helped end the Ice Ageoc

February 12, 2015

Joides Resolution, Bay of Bengal (Indian Ocean), IODP Expeditions 353. Credit: Photo by William Crawford, IODP/TAMU

A release of carbon dioxide (CO₂) from the deep ocean helped bring an end to the last Ice Age, according to new collaborative research by the University of Southampton, Universitat Autònoma de Barcelona (UAB), the Australian National University (ANU), and international colleagues.
Published today in Nature, the study shows that carbon stored in an isolated reservoir deep in the Southern Ocean re-connected with the atmosphere, driving a rise in atmospheric CO₂ and an increase in global temperatures. The finding gives scientists an insight into how the ocean affects the carbon cycle and climate change.

Atmospheric CO₂levels fluctuate from about 185 parts-per-million (ppm), during ice ages, to around 280 ppm, during warmer periods like today (termed interglacials). The oceans currently contain approximately sixty times more carbon than the atmosphere and that carbon can exchange rapidly (from a geological perspective) between these two systems (atmosphere-ocean).

Joint lead author Dr. Miguel Martínez-Botí from the University of Southampton adds: “The magnitude and rapidity of the swings in atmospheric CO₂ across the ice age cycles suggests that changes in ocean carbon storage are important drivers of natural atmospheric CO₂ variations.

Joint lead author Dr. Gianluca Marino, from ANU and previously at the ICTA, UAB, says: “We found that very high concentrations of dissolved CO₂ in surface waters of the Southern Atlantic Ocean and the eastern equatorial Pacific coincided with the rises in atmospheric CO₂ at the end of the last ice age, suggesting that these regions acted as sources of CO₂ to the atmosphere”.

“Our findings support the theory that a series of processes operating in the southernmost sector of the Atlantic, Pacific and Indian Oceans, a region known as the ‘Southern Ocean’, changed the amount of carbon stored in the deep-sea. While a reduction in communication between the deep-sea and the atmosphere in this region potentially locks carbon away from the atmosphere into the abyss during ice ages, the opposite occurs during warm interglacial periods.”

The international team studied the composition of the calcium carbonate shells of ancient marine organisms that inhabited the surface of the ocean thousands of years ago in order to trace its carbon content.

Co-author Dr. Gavin Foster from the University of Southampton commented: “Just like the way the oceans have stored around 30 per cent of humanity’s fossil fuel emissions over the last 100 years or so, our new data confirms that natural variations in atmospheric CO₂ between ice ages and warm interglacials are driven largely by changes in the amount of carbon stored in our oceans.

“These results will help to better understanding the dynamics of human-induced CO₂ accumulation in the atmosphere since the ocean is an important carbon sink and the largest reservoir of carbon on our planet’ commented co-author Patrizia Ziveri, ICREA professor at the ICTA, UAB.

While these new results support a primary role for the Southern Ocean processes in these natural cycles, we don’t yet know the full story and other processes operating in other parts of the ocean, such as the North Pacific, may have an additional role to play.

Reference:
M. A. Martínez-Botí, G. Marino, G. L. Foster, P. Ziveri, M. J. Henehan, J. W. B. Rae, P. G. Mortyn, D. Vance. Boron isotope evidence for oceanic carbon dioxide leakage during the last deglaciation. Nature, 2015; 518 (7538): 219 DOI: 10.1038/nature14155

Note: The above story is based on materials provided by Universitat Autònoma de Barcelona.

What makes the feather soar

February 12, 2015

Birds have adapted to so many ecological niches in large part because of the variety of ways feathers lend them a competitive advantage. One key to the feather’s manifold manifestations is a family of proteins that evolved some 150 million years ago: the beta-keratins. Credit : Scott Liddell

Table of Contents

Dinosaurs may have gone extinct some 66 million years ago, but that’s hardly the end of their story. One group of their modern-day progeny, the class Avia — namely, birds — is a spectacular evolutionary success story. With more than 10,000 extant species, birds occupy every manner of ecological habitat worldwide.
A unique source of avian adaptability is the feather. Not only are feathers the basis of one of the “killer apps” of evolution, powered flight, they can also provide camouflage, attract mates, protect from the elements and serve as a means of regulating body temperature.

And as Matthew Greenwold, a postdoctoral associate in the department of biological sciences at the University of South Carolina, showed in a recent paper, a key to the feather’s success appears to be the variety and adaptability of the interlocking protein building blocks that feathers are made of.

Feathers and dinosaurs

It’s now largely (but not entirely) accepted among biologists that dinosaurs are the forerunners of birds, Greenwold says, and that certain species of dinosaurs began to evolve feathers about 150 million years ago. The idea has taken some time to take root, in part because most early dinosaur fossils lacked accompanying evidence of feathers.

A lack of feathers in the fossil record was not necessarily an indication that the two didn’t go together, however. Perhaps feathers don’t fossilize as well as bone. More recent discoveries, particularly in China over the past 15 years, provided a wealth of evidence of feathered dinosaurs that convinced many skeptics.

But how did that original feather come about? And how did it result in such diversity among our feathered friends? As it turns out, there’s a major family of protein building blocks largely responsible, beta-keratin.

Beta-keratin is found in just two existing groups of animals: reptiles and birds. It’s the stuff of claws, scales, beaks and feathers. It’s what makes these epidermal appendages strong, tough and, in the case of feathers, also flexible and elastic.

Greenwold’s co-author and postdoctoral adviser, professor Roger Sawyer, has spent over 30 years working with beta-keratin, and his work has helped differentiate among what has turned out to be many variations, some very subtle, on a main theme in beta-keratin.

Beta-keratin or beta-keratins?

“When I first started out, I really thought that feathers of all birds would have pretty similar beta-keratins,” Sawyer says. “If I extracted feather protein from a chicken and then from a zebra finch, they’d be the same. Well it is far, far from that.”

In the 1980s, Sawyer and colleagues showed that there is a core region, 34 amino acids long, that is highly conserved among all beta-keratins and forms a structural filament. His work was also instrumental in helping scientists understand the diversity of several major subtypes of the protein, typically named after the anatomical part from which it was first isolated. These include scale beta-keratin, claw beta-keratin and feather beta-keratin.

They’re very similar — all have the common filament core of 34 amino acids, for example — but the proteins are distinct as well. Feather beta-keratin is about 100 amino acids long, with scale and claw being longer still. The amino acids on either side of the filament core are similar, but serve different roles and are not as highly conserved as the central 34 amino acids.

Despite the monikers, the scale, claw and feather beta-keratins are all mixed in varying amounts in all of the avian epidermal appendages. And at this point, it might have appeared that the broad strokes of the feather structure had been defined: There are a handful of basic types of protein that go into it, and it’s just a question of amounts and how they’re arranged.

But the truth turned out to be much more complicated still. As was shown in 2004 when the chicken genome was published, chickens have numerous copies of the scale, claw, and particularly the feather beta-keratin sequences in their genome. And the “copies” are not really identical, either. On just one of the chicken chromosomes, for example, there are more than 60 feather beta-keratin genes, each very similar to each other but not quite the same. These genes make up the second-largest gene family in the chicken genome.

A flock of genomes

And as part of the international team that recently published full genomes of 48 birds in Science magazine, Greenwold and Sawyer showed that the number of scale, claw and feather beta-keratin genes is highly variable among all birds. So depending on the regulation of protein expression, the feathers that the proteins constitute must be made up of a very complex mixture of building blocks.

Instead of just one brick, beta-keratin, it turned out that there were several types of brick, including scale, claw and feather beta-keratin. And instead of just several types of brick, it turned out that there were dozens of smaller variations within each type of brick, represented by the many slightly differing copy numbers in the gene.

Greenwold, graduate student Weier Bao and Sawyer analyzed the avian genomes and published an accompanying paper in BMC Evolutionary Biology that shows correlations between the number of beta-keratin gene copies and the birds’ lifestyles. Birds of prey, for example, have larger proportions of claw beta-keratins than the average for the entire group of birds.

Feather beta-keratin and a unique avian advantage

The unifying theme, though, is the abundance of feather beta-keratin genes, which make up more than 50 percent of the copies of the several beta-keratin subtypes in all the birds studied. Sawyer and Greenwold made the case in an earlier paper that the expansion and elaboration of the feather beta-keratin gene coincides with the evolution of the feather itself, from a simple body covering to a sophisticated assembly of interconnected working parts that make powered flight, among other competitive advantages, possible.

Feather beta-keratin distinguishes birds from all other living creatures. Birds are the only organisms that have it, they have it in abundance, and together with the other keratins it gives them an edge that makes them nearly ubiquitous in a highly competitive world.

“Feathers are strong, they’re flexible, they’re durable,” Sawyer says. “They can go through a 200-mph dive and sudden recovery without fracturing, such as seen for the peregrine falcon, the fastest member of the animal kingdom. Perhaps we can mimic these amazing properties in new materials.”

Note: The above story is based on materials provided by University of South Carolina.

Controls on Fluvial Evacuation of Sediment from Earthquake-triggered Landslides

February 12, 2015

Major rivers (Min Jiang, Fu Jiang, and Tuo Jiang) impacted by the C.E. 2008 Mw 7.9 Wenchuan earthquake in the Longmen Shan, China. River gauging stations used in this study are shown as circles. Names of nested gauging stations shown in Figures 2B and 2C are highlighted in yellow. Catchment color reflects ratio of mean annual suspended sediment discharge (Qss, Mt yr–1) after the earthquake to that prior to the earthquake. Contours show landslide areal density ρls (%) calculated as proportion of total area mapped as landslides (Li et al., 2014). Columns show pre-earthquake Qss (white) and post-earthquake Qss (red).

Earthquakes can cause huge devastation in mountains by triggering landslides. But what happens when the shaking stops? In the months to years following large earthquakes, rocks and sediment moved by earthquake-triggered landslides still cause serious issues, filling rivers and causing flooding during rainfall. The sediment can also affect water resources and hydro-electric power generation. Loose sediment can also cause more damage if new landslides occur. Despite this, the lifespan over which landslide-produced sediment stays in mountain river catchments following large earthquakes is poorly understood.

Recently, the impacts of the 2008 Wenchuan earthquake (Mw 7.9) on the river catchments of the Longmen Shan mountains were examined by Prof. JIN Zhangdong of Institute of Earth Environment, Chinese Academy of Sciences, Prof. Joshua West of University of Southern California and Dr. Robert Hilton and Prof. Alexander Densmore of Durham University, and involved other PhD students at Xi’an and California.

The devastating 2008 Wenchuan earthquake triggered more than 57,150 landslides in the Longmen Shan mountains in Sichuan in China. JIN Zhangdong et al. used detailed, daily measurements from rivers of the amount of water (water discharge) and the amount of mud and sand (suspended sediment discharge) at 16 gauging stations in the Longmen Shan mountains. These river catchments cover an area of 68,000 km2. The research is able to use data from 2006 (two years before the Wenchuan earthquake) until 2013 (five years after the earthquake) collected by the Chinese Bureau of Hydrology. The data is extremely detailed, and is able to be used to track the immediate changes to river loads after the earthquake. The research also mapped landslides triggered by the earthquake using satellite imagery. These landslide maps were used to calculate the volume of mud and sand delivered by earthquake-triggered landslides to the rivers.

The research suggested that it will take decades to centuries for rivers to remove fine sediment (mud and sand) from earthquake-triggered landslides. It demonstrated for the first time that the memory of rivers to earthquakes is longest where the area of landsliding is high, and where the climate results in lower-intensity rainfall and river flows that are less efficient at removing the excess sediment. The research is essential for better management of the secondary geohazard following large earthquakes.
The research was funded by the Royal Society, the National Science Foundation of China, the Chinese Academy of Sciences and the US National Science Foundation. The research is published in Geology , and the article was highlighted in Geology’s press release.

Reference:
Controls on fluvial evacuation of sediment from earthquake-triggered landslides Geology, February 2015, v. 43, p. 115-118, First published on January 5, 2015, doi: 10.1130/G36157.1

Note : The above story is based on materials provided by Chinese Academy of Sciences.

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