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Volcanic eruptions: How bubbles lead to disaster

Volcanic eruptions How bubbles-GeologyPage
Tambora on the Indonesian island of Sumbawa: The explosive eruption of this volcano 200 years ago cooled the climate and lead to a year without a summer. Credit: Jialiang Gao / Wikimedia Commons CC BY-SA 3.0

In 1816, summer failed to make an appearance in central Europe and people were starving. Just a year earlier, the Tambora volcano had erupted in Indonesia, spewing huge amounts of ash and sulphur into the atmosphere. As these particles partly blocked sunlight, cooling the climate, it had a serious impact on the land and the people, even in Switzerland.

Since then, volcanologists have developed more precise ideas of why super-volcanoes such as Tambora are not only highly explosive but also why they release so much sulphur into the atmosphere.

Gas bubbles tend to accumulate in the upper layers of magma reservoirs, which are only a few kilometres beneath the earth’s surface, building up pressure that can then be abruptly liberated by eruption. These bubbles mainly contain water vapour but also sulphur.

Sulphur-rich eruptions

“Such volcanic eruptions can be extremely powerful and spew an enormous amount of ash and sulphur to the surface,” says Andrea Parmigiani, a post-doc in the Institute of Geochemistry and Petrology at ETH Zurich. “We’ve known for some time that gas bubbles play a major role in such events, but we had only been able to speculate on how they accumulate in magma reservoirs.”

Together with other scientists from ETH Zurich and Georgia Institute of Technology (Georgia Tech), the researchers studied the behaviour of bubbles with a computer model.

The scientists used theoretical calculations and laboratory experiments to examine in particular how bubbles in crystal-rich and crystal-poor layers of magma reservoirs move buoyantly upward. In many volcanic systems, the magma reservoir consists mainly of two zones: an upper layer consisting of viscous melt with almost no crystals, and a lower layer rich in crystals, but still containing pore space.

Super bubbles meander through a maze

When Andrea Parmigiani, Christian Huber and Olivier Bachmann started this project, they thought that the bubbles, as they moved upwards through crystal-rich areas of the magma reservoirs, would dramatically slow down, while they would go faster in the crystal-poor zones.

“Instead, we found that, under volatile-rich conditions, they would ascend much faster in the crystal-rich zones, and accumulate in the melt-rich portions above” says Parmigiani.

Parmigiani explains this as follows: when the proportion of bubbles in the pore space of the crystal-rich layers increases, small individual bubbles coalesce into finger-like channels, displacing the existing highly viscous melt. These finger-like channels allow for a higher vertical gas velocity. The bubbles, however, have to fill at least 10 to 15 % of the pore space.

“If the vapour phase cannot form these channels, individual bubbles are mechanically trapped,” says the earth scientist. As these finger-like channels reach the boundary of the crystal-poor melt, individual, more spherical bubbles detach, and continue their ascent towards the surface. However, the more bubble, the more reduce their migration velocity is.

This is because each bubble creates a return flow of viscous melt around it. When an adjacent bubble feels this return flow, it is slowed down. This process was demonstrated in a laboratory experiment conducted by Parmigiani’s colleagues Salah Faroughi and Christian Huber at Georgia Tech, using water bubbles in a viscous silicone solution.

“Through this mechanism, a large number of gas bubbles can accumulate in the crystal-poor melt under the roof of the magma reservoir. This eventually leads to overpressurization of the reservoir,” says lead author Parmigiani. And because the bubbles also contain sulphur, this also accumulates, explaining why such a volcano might emit more sulphur than expected based on its composition.

What this means for the explosivity of a given volcano is still unclear. “This study focuses primarily on understanding the basic principles of gas flow in magma reservoirs; a direct application to prediction of volcanic behaviour remains a question for the future,” says the researcher, adding that existing computer models do not depict the entire magma reservoir, but only a tiny part of it: roughly a square of a few cubic centimeter with a clear boundary between the crystal-poor and crystal-rich layers.

To calculate this small volume, Parmigiani used high-performance computers such as the Euler Cluster at ETH Zurich and a supercomputer at the Swiss National Supercomputing Centre in Lugano.

For the software, the researcher had access to the open-source library Palabos, which he continues to develop in collaboration with researchers from University of Geneva. “This software is particularly suitable for this type of simulation,” says the physicist.

Reference:
A. Parmigiani, S. Faroughi, C. Huber, O. Bachmann, Y. Su. Bubble accumulation and its role in the evolution of magma reservoirs in the upper crust. Nature, 2016; DOI: 10.1038/nature17401

Note: The above post is reprinted from materials provided by ETH Zurich. The original item was written by Peter Rüegg.

Prehistoric peepers give vital clue in solving 300-million-year-old ‘Tully Monster’

Prehistoric peepers give vital clue-GeologyPage
This is an image of the ‘Tully Monster’ fossil and ‘meatball’ and ‘sausage’ melanosomes. Credit: University of Leiceste

A 300-million-year-old fossil mystery has been solved by a research team led by the University of Leicester, which has identified that the ancient ‘Tully Monster’ was a vertebrate — due to the unique characteristics of its eyes.

Tullimonstrum gregarium or as it is more commonly known the ‘Tully Monster’, found only in coal quarries in Illinois, Northern America, is known to many Americans because its alien-like image can be seen on the sides of large U-haul™ trailers which ply the freeways.

Despite being an iconic image — a fossil with a striped body, large tail, a pair of stalks terminating in dark, oval-shaped ‘blobs’ and a large elephant trunk-like proboscis at the head end which has a pincer-like claw filled with teeth — it is a complete mystery as to what kind of extinct animal it was.

Professor Sarah Gabbott from the University of Leicester’s Department of Geology said: “Since its discovery over 60 years ago scientists have suggested it is a whole parade of completely different creatures ranging from molluscs to worms — but there was no conclusive evidence and so speculation continued.”

Thomas Clements, a PhD student from the University of Leicester and lead author on the paper, explained: “When a fossil has anatomy this bizarre it’s difficult to know where to start, so we decided to look at the most striking feature — the stalked structures with dark blobs.”

This proved to be the vital clue the team needed to solve the mystery.

In a new study published in Nature, the University of Leicester palaeontologists, along with colleagues at the University of Bristol and the University of Texas in Austin, discovered that the dark ‘blobs’ were actually made up of hundreds of thousands of microscopic dark granules, each 50 times smaller than the width of a human hair.

The shape and chemical composition of these granules is identical to organelles found in cells called melanosomes; these being responsible for creating and storing the pigment melanin.

Dr Jakob Vinther (University of Bristol) said: “We used a new technique called Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) to identify the chemical signature of the fossil granules and compared it to known modern melanin from crows and this proved that we had discovered the oldest fossil pigment currently known.”

Thomas added: “Nearly all animals can produce the pigment melanin. It’s what gives humans the range of skin and hair colours we see today. Melanin is also found in the eyes of many animal groups where it stops light from bouncing around inside the eyeball and allows the formation of a clear visual image.”

Identifying fossil melanosomes containing melanin and a lens is the first time it has been conclusively proved that Tullimonstrum had eyes on stalks.

When the team looked closer at the melanosomes they made another exciting discovery.

Professor Gabbott said: “There were two distinct shapes of melanosomes in Tullimonstrum’s eyes: some look like microscopic ‘sausages’ and others like microscopic ‘meatballs’. This evidence was crucial because only vertebrates have two different shapes of melanosome, meaning that unlike previous researchers that thought that Tullimonstrum was an invertebrate (animal without a backbone), this is the first unequivocal evidence that Tullimonstrum is a member of the same group of animals as us, the vertebrates.”

Thomas added: “This is an exciting study because not have we discovered the oldest fossil pigment, but the structures seen in Tullimonstrum’s eyes suggest it had good vision. The large tail and teeth suggest that the Tully Monster is in fact a type of very weird fish.”

Reference:
Thomas Clements, Andrei Dolocan, Peter Martin, Mark A. Purnell, Jakob Vinther, Sarah E. Gabbott. The eyes of Tullimonstrum reveal a vertebrate affinity. Nature, 2016; DOI: 10.1038/nature17647

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

Ice streams can be slowed down by gas hydrates

Ice streams can be slowed-GeologyPage
Jakobshavn Glacier is one of the fastest moving ice streams in the world contributing massive amount of ice to the oceans. Credit: NASA Earth Observatory

A sticky spot the size of a small island once slowed down a large ice stream. It was comprised of gas hydrates according to a new study in Nature Geoscience.

One of the major questions today is: What are the ice sheets going to do in an ever-warming climate? Ice sheets of Greenland and Antarctica are major contributors to the sea level rise, which can make life difficult for many coastal nations in the near future.

To understand the ice sheets we need to understand their drainage system — a key component of this is ice streams, fast-flowing rivers of ice, that deliver ice from the centre of the ice sheet to the oceans. Many of these ice streams are speeding up, which may be seen as the logical consequence of the warming climate. But some are slowing down, even stopping, examples of this may be found in the Ross ice streams of West Antarctica.

A new study in Nature Geoscience suggests that a 250km2 sticky spot made up of sediments with gas hydrates in them, slowed down an ice stream in the Barents Sea. This happened sometime during the last ice age, 20,000 years ago, when the Barents Sea was covered with an ice sheet.

Slipping on mud

The event left a large footprint on the ocean floor of today. This is the first time that gas hydrates have been inferred to put brakes on an ice stream.

“Many factors influence the flow of the ice, but we know that what happens at the interface between the ice and the ground below is crucial. Our understanding of what is happening under the kilometres of ice remains elusive. ” says principal author behind the study Monica Winsborrow.

Ice flows fast because there is lubrication on the bottom. For instance the stream will slide faster on muddy sediments below.

It’s like slipping in the mud.

“The friction itself creates heat that melts the base of the ice stream. Also geothermal flow and melt water from the surface reaching the bottom can lubricate the stream. The gravity takes care of the rest.” says Winsborrow.

Hook and loop principle

But not all of the bed is equally lubricated. The sticky spots under the ice act almost like hook and loop fasteners. They hook the ice and hold it back until the critical speed and mass is achieved, and the ice stream starts flowing again.

” We know that there are a lot of gas leaks in the Barents Sea today. And we know that there are deeper hydrocarbon reservoirs here. Under the pressure and temperatures of the ice sheet this gas would have created hydrates.” Winsborrow states.

The gas hydrates contain methane molecules trapped in a cage of water molecules. To form they absorb water from the sediments. This makes sediments under the ice stiffer and would have strengthened them.

Gas hydrates are also themselves harder, and stiffer than the sediments. The result is that sediments loose their muddiness, making it harder for the ice to slide. The stagnated streams will eventually restart again, as more ice is fed into the stream.

Gas hydrates under modern ice sheets

Gas hydrate sticky spots under ice streams are a potentially widespread feature also today.

“If there are gas hydrates under today’s ice sheets, they can slow the ice streams. There are studies indicating that there may be vast reservoirs of hydrates under the West Antarctic Ice sheet. Anywhere you have a hydrocarbon reservoir, water, high pressure and low temperature, you will get gas hydrate.” says Winsborrow.

Ice streams of today are extensively monitored with GPS tracking systems, but it is very difficult to gaze beneath three kilometres of ice to see what is going on at the bottom. But scars left by the Barents Sea Ice sheet are visible on the ocean floor today. That makes this ancient ice sheet an important analogue, especially for the modern West Antarctica Ice Sheet, as both are based in marine environments.

“We need these analogies from the past. Understanding what is happening at the base of ice streams is important for modelling and predicting the future of the ice sheets.”

Reference:
Monica Winsborrow, Karin Andreassen, Alun Hubbard, Andreia Plaza-Faverola, Eythor Gudlaugsson, Henry Patton. Regulation of ice stream flow through subglacial formation of gas hydrates. Nature Geoscience, 2016; DOI: 10.1038/ngeo2696

Note: The above post is reprinted from materials provided by University of Tromso (Universitetet i Tromsø – UiT).

Earthquake may have been manmade, but more data needed to assess hazards in Texas

seismogram 3

The most comprehensive analysis to date of a series of earthquakes that included a 4.8 magnitude event in East Texas in 2012 has found it plausible that the earthquakes were caused by wastewater injection. The findings also underscore the difficulty of conclusively tying specific earthquakes to human activity using currently available subsurface data.

The study, conducted by researchers at The University of Texas at Austin Bureau of Economic Geology, was published April 13 in the Journal of Geophysical Research: Solid Earth, a journal of the American Geophysical Union. The study focused on an earthquake sequence near Timpson, Texas, and builds on previous studies that have associated these earthquakes with wastewater injection.

To determine whether the earthquakes could have been caused by the injection of fluid into the underground geological formation, researchers built the first computer model for this site that simulates the effects of fluid injection on the stability of the fault that potentially generated the earthquakes. In their simulations, researchers used a range of likely values for input parameters. Those parameters included physical properties of the reservoir and the orientation of the fault. Earthquakes were generated using a certain range of input parameters, but no earthquakes were generated in simulations using a wider set of equally probable parameters.

The 4.8 magnitude earthquake researchers looked at in this study occurred on May 17, 2012. It was the largest ever recorded in the area and followed a series of smaller earthquakes that started in April 2008, some 17 months after two wastewater injections wells began operating nearby. The wells are used to dispose of saline water that is produced with oil and gas from deep hydrocarbon reservoirs.

The researchers tested a number of likely scenarios to assess if the volume and rate of fluid injected into the disposal wells were high enough to cause nearby faults to slip. Earthquakes occur when faults slip, a process that is aided by the high pressure generated in the porous rock formation during wastewater injection, but also occurs by natural tectonic processes.

Previous studies relied on the timing and proximity of wastewater injection to earthquakes to decide if earthquakes were induced by human activity. This was the first to simulate the mechanics of an earthquake generated by water injection for this site.

“It is part of a continuing research effort by The University of Texas at Austin,” said Peter Eichhubl, a senior research scientist at the Bureau of Economic Geology, which is the State Geological Survey of Texas and a research unit in The University of Texas Jackson School of Geosciences. “We used a more rigorous approach than previous studies, but our analyses are limited by the availability of robust, high-quality data sets that describe the conditions at depth at which water is injected and earthquakes occur. This study demonstrates the need for more and higher quality subsurface data to properly evaluate the hazards associated with wastewater injection in Texas.”

The relationship between seismic events, or earthquakes, and human activity has become more of a concern in recent years. While Oklahoma and Kansas are ranked highest in earthquake activity associated with oil and gas operations, Texas has experienced several earthquakes that have been linked to wastewater injection. The University of Texas at Austin is taking a leading role in the ongoing research. By the end of the year, the bureau will be operating a statewide network of seismographs called TexNet that will monitor, locate and catalog seismic activity with magnitude of 2 and greater.

TexNet, which was authorized and funded by the Texas Legislature and Gov. Greg Abbott last year, will improve the state’s ability to more rapidly and more accurately investigate earthquakes. Eichhubl said the data collected will help understand baseline seismicity and in so doing assist future studies that try to determine possible links between human activity and seismic events.

Note: The above post is reprinted from materials provided by University of Texas at Austin.

Senior Research Engineer explores a new path through the Earth’s crust

Senior Research Engineer explores-Geologypage
Senior research engineer Paul Woskov is exploring a millimeter-wave technology for drilling through rock. Credit: Paul Rivenberg

Paul Woskov is collecting rocks. A growing number of granite and basalt squares perch on cabinet tops and shelves around his office, each a record of his latest experiment in drilling. Some show clean circles that fully penetrate the rock, while others hold glassy craters.

Woskov, a senior research engineer at MIT’s Plasma Science and Fusion Center (PSFC), is using a gyrotron, a specialized radio-frequency (RF) wave generator developed for fusion research, to explore how millimeter RF waves can open holes through hard rock by melting or vaporizing it. Penetrating deep into hard rock is necessary to access virtually limitless geothermal energy resources, to mine precious metals, or explore new options for nuclear waste storage. But it is a difficult and expensive process, and today’s mechanical drilling technology has limitations. Woskov believes that powerful millimeter-wave sources could increase deep hard rock penetration rates by more than ten times at lower cost over current mechanical drilling systems, while providing other practical benefits.

“There is plenty of heat beneath our feet,” he says, “something like 20 billion times the energy that the world uses in one year.” But, Woskov notes, most studies of the accessibility of geothermal energy are based on current mechanical technology and its limitations. They do not consider that a breakthrough advance in drilling technology could make possible deeper, less expensive penetration, opening into what Woskov calls “an enormous reserve of energy, second only to fusion: base energy, available 24/7.”

Current rotary technology is a mechanical grinding process that is limited by rock hardness, deep pressures, and high temperatures. Specially designed “drilling mud,” pumped through the hollow drill pipe interior, is used to enable deep drilling and to remove the excess cuttings, returning them to the surface via the ring-shaped space between the drill pipe and borehole wall. The pressure of the mud also keeps the hole from collapsing, sealing, and strengthening the hole in the process. But there is a limit to the pressures such a borehole can withstand, and typically holes cannot be drilled beyond 30,000 feet (9 km).

Woskov asks, “What if you could drill beyond this limit? What if you could drill over 10 kilometers into the Earth’s crust?” With his proposed gyrotron technology this is theoretically possible.

Woskov laughs when he reveals that drilling engineers have a hard time believing his technology does not use the costly drilling mud they depend on. But, he explains, with a gyrotron, high-temperature physics will replace the mechanical functions of low-temperature mud, allowing drillers to extract rock matter through vaporization or displace the melt through pressurization. Similarly, the high temperature melted rock will seal the walls of the borehole, and the high pressure from the increased temperature will prevent collapse. In principle, because an increase in temperature in a confined volume will always result in an increase in pressure over local pressure, drillers could maintain the stability of a borehole to greater depths than possible with drilling muds.

Woskov observes yet another advantage: “Our beams don’t need to be round. Forces underground are anisotropic—not symmetrical. That is one reason holes collapse. But we can shape our beam to respond to local pressures. You can create an elliptical hole with the major axis corresponding to the anisotropy of the forces, essentially recovering the strength of a round hole in a symmetrical force field.”

Later this spring, the researcher is planning to move his base of operation from the PSFC to the Air Force Research Lab (AFRL) in Kirkland, New Mexico, in order to take advantage of a microwave source that would allow him to perform experiments at a power level a factor of 10 higher than is currently possible in the laboratory at MIT. He would be able to graduate from drilling rocks in the 4-6 inch range to those in the 2-4 feet range. He is especially interested in exploring how well the rock can be vaporized, which would only be possible with the higher power available at AFRL.

Support for this project originally came from MIT Energy Initiative (MITEI), which in 2008 provided seed money and later a follow-up grant. Although Woskov continues to pursue ways his technology can advance geothermal energy research, his current support is from the Department of Energy’s Office of Nuclear Science, through Impact Technologies LLC, which funds him to explore deep bore hole storage of radioactive and nuclear wastes. At 6 km deep, such bore holes would place waste much farther from the biosphere than is possible with near-earth depositories such as Yucca Mountain. The bottom 2 kilometers of the hole would hold waste, capped with a 2-km seal—which is currently considered the “weak link” in the process. Woskov is experimenting with melted basalt and the more viscous granite to learn how he can seal the holes with melted rock, which could provide the most secure entombment of the waste products.

Woskov, who joined MIT’s Francis Bitter Magnet Laboratory in 1976 before becoming a founding member of the Plasma Fusion Center in 1979, is approaching his 40th anniversary at MIT. The first three decades of his tenure focused heavily on high-power far infrared scattering for measuring energy distribution of fast ions, the product of fusion reactions. The exploration took much longer than anyone anticipated, but when it eventually found success in Europe on the TEXTOR tokamak reactor, Woskov was left looking for a new direction.

While still pursuing fusion, he began exploring some spinoff technologies that could be realized in a matter of years rather than decades. He received one R&D 100 Award after another for a series of projects: a thermometer for measuring temperatures in high-temperature furnaces; a hazardous waste emissions monitor for incinerators and power pants; a device to monitor molten metals: all experiments that used developments in fusion research to address shorter-term problems.

“Occasionally you have to do something that has a near-term reward,” Woskov laughs, noting that it can be frustrating when you work on something for 30 years without a final product.

The beauty that long-term fusion research has provided the technology for so many exciting short-term projects is not lost on Woskov. And he notes with amusement that so much fusion research revolves around protecting materials in fusion devices from being damaged by hot plasma, while his current project exploits the high energy of fusion technology to see how effectively it can melt materials.

Woskov foresees a number of other uses for the microwave technology. The high-temperature pressures of microwaves could be used to break apart rocks for mining, or excavate rock to create tunnels and canals. It could also be used for fracking in place of pressurized water, which is controversial due to its limited supply and resulting water contamination.

“Energy trumps matter,” Woskov proclaims, excited by how microwave heat and pressure could literally move mountains, or at least pieces of them. For now he’s going to continue melting his way through the earth’s crust, one rock at a time.

Note: The above post is reprinted from materials provided by Massachusetts Institute of Technology.
This story is republished courtesy of MIT News, a popular site that covers news about MIT research, innovation and teaching.

The fourth dimension

The fourth dimension-GeologyPage
Figure 2 from Francesco Casu1 and Andrea Manconi: (A) Optical image (source Google Earth) of the study area, the Afar rift zone, Ethiopia, with indication of the used ascending (ASC) and descending (DESC) Envisat advanced synthetic aperture radar (ASAR) frames (purple and blue shading, respectively). The areas where pixel offsets have been computed in the ASC and DESC orbits are indicated by the black and white rectangles, respectively. (B) Differential interferogram between 12 June 2006 and 23 September 2009 (ASC orbit, track 300) in radar coordinates, superimposed on a SAR amplitude image of the area. Large displacements caused the high fringe rate as well as the coherence loss in the near field.

Remote sensing techniques facilitate observations and monitoring of ground displacements. In particular, space-borne Differential Synthetic Aperture Radar Interferometry (DInSAR) allows accurate measurements of ground deformation by properly analyzing multi-temporal satellite acquisitions over the region of interest.

However, limitations of DInSAR may arise when large and/or rapid surface deformation occurs, including those caused by active rifting. Understanding the three-dimensional characteristics of the deformation field, as well as its temporal evolution, cannot be accomplished by DInSAR alone.

Accurate spatial and temporal dense information on the displacements is, however, crucial for the correct interpretation of complex geological phenomena. In this paper, Francesco Casu and Andrea Manconi propose an algorithm to retrieve the four-dimensional (i.e., along north, east, up, and time) surface deformation field over zones affected by active rifting.

In the Afar depression system, one of the locations worldwide where active rifting processes can be observed, Casu and Manconi retrieved information in areas where data was not previously recorded. Their method demonstrates its validity in complex situations such as rifting episodes, where the deformation associated to repeated intrusions, faulting, and lithospheric extension might overlap in space and time.

Reference:
Four-dimensional surface evolution of active rifting from spaceborne SAR data
Francesco Casu, 1 IREA (Istituto per il Rilevamento Elettromagnetico dell’Ambiente), National Research Council, Via Diocleziano 328, 80124 Napoli, Italy; and Andrea Manconi and Dept. of Earth Sciences, Swiss Federal Institute of Technology, 8902 Zurich, Switzerland. Themed issue: Anatomy of Rifting: Tectonics and Magmatism in Continental Rifts, Oceanic Spreading Centers, and Transforms.  DOI: 10.1130/GES01225.1

Note: The above post is reprinted from materials provided by Geological Society of America.

Bringing the landslide laboratory to remote regions

Bringing the landslide-GeologyPage
This is a movable lab for field study of gravity erosion on the Loess Plateau of China. Credit: X.-Z. Xu/DLUT

It’d be hard to overstate how landslide-prone China’s Loess Plateau is; thanks to millions of years’ accumulation of the wind-deposited, highly-porous sediment from which the plateau takes its name, the region has been called the most erosion-prone on Earth.

However, despite the prominent geomorphic role gravity erosion plays on the slopes — which affects an area of more than 200,000 square kilometers in the upper and middle reaches of China’s Yellow River — the process isn’t well understood due to the complexity of soil failure occurrence and behavior, according to Xiang-Zhou Xu, a professor of Dalian University of Technology in Dalian, China.

“Areas of the Loess Plateau, especially the Loess Hill Ravine Region and the Loess Mesa Ravine Region, are severely affected by gravity erosion,” Xu said. “How to quantitatively evaluate the roles of various mass failures on the steep slope is significant in controlling failure disasters.”

Xu and his collaborators at Dailan University of Technology, the Yellow River Institute of Hydraulic Research, and Chinese Academy of Sciences and Ministry of Water Resources and present their measurement system this week in the journal Review of Scientific Instruments, from AIP Publishing.

The centerpiece of the researcher’s system is a portable tent that can be assembled in the field, allowing them to conduct site-specific tests, such as simulated rainfall, while providing the same conditions for these simulations and observations as a laboratory setting. Given proper site preparation, Xu estimates, the tent could be quickly assembled within two to three days.

Their experiments involve a MX-2010-G topography meter, a structured-light 3-D surface-measuring instrument which can digitally reconstruct the 3-D geometric shape of a target surface designed by the team to monitor the slope’s behavior under simulated rainfall. The volume of gravity erosion, along with a slew of other erosion data, can then be obtained by comparing the slope geometries in the moments before and after the simulated erosion incident.

The experimental results show that, after six runs of rainfall — each with the amount of 54 millimeters of water on a steep loess slope with slope angle greater than 70° — the total amount of soil eroded by gravity on the side of each landform was about twice that of the total eroded by water. Moreover, the researchers found that the gravity erosion primarily occurs in a short period of time, which is considered to be more dangerous — thus warranting increased attention to the effects of gravity erosion on the steep slope.

“The measurement system was used to complete the survey for over 130 rainfall simulation events, and it confirmed the feasibility and reliability of this technique,” Xu said.

One of the shortcomings of the researcher’s setup, however, is that the procedures for calculating the volume of soil loss involve many separate pieces of software — making a surveyor’s skills for precise measuring for most surveying tasks indispensable.

“Presently, we are developing a new type of topography meter that could be more intelligently steered.” Xu added. “In the near future, an unskilled surveyor could also obtain the required accuracy level as well as proper and efficient data collection or setup, at the same speed as the work done by a skilled surveyor.”

Reference:
Wen-Zhao Guo, Xiang-Zhou Xu, Wen-Long Wang, Ji-Shan Yang, Ya-Kun Liu, Fei-Long Xu. A measurement system applicable for landslide experiments in the field. Review of Scientific Instruments, 2016; 87 (4): 044501 DOI: 10.1063/1.4944805

Note: The above post is reprinted from materials provided by American Institute of Physics.

Oxygen key to containing coal ash contamination

Oxygen key to containing-GeologyPage
This is the TVA Kingston Fossil Plant in Roane County, Tenn. was the site of a 2008 spill of more than 1 billion gallons of coal ash slurry. Credit: Duke University

As energy companies decide what to do with aging coal ash disposal facilities in North Carolina and across the nation, they may be overlooking a fundamental but potentially critical variable — oxygen.

In a new study appearing in the April issue of Applied Geochemistry, researchers from Duke University demonstrate that the level of oxygen in a coal ash disposal site can greatly affect how much toxic selenium and arsenic can be leached from the system.

“The tests that the Environmental Protection Agency relies on consider variables like the pH of the water, but they don’t look at whether the system is aerobic or anaerobic,” said Heileen Hsu-Kim, the Mary Milus Yoh and Harold L. Yoh, Jr. Associate Professor of Civil and Environmental Engineering. “We wanted to demonstrate that oxygenation actually matters a lot, especially for arsenic and selenium.”

In the wake of a 2014 coal ash spill into North Carolina’s Dan River from a ruptured Duke Energy drainage pipe, the question of what to do with other aging coal ash retention ponds and future waste has been a hotly debated topic.

Duke Energy currently plans to dig up 24 of its 36 ponds in the Carolinas. But the 12 remaining ponds without a cleanup plan hold more than 70 percent of the 108 million tons of ash held in North Carolina ponds.

One option is to essentially turn the ponds into a landfill by removing the water, capping the remaining waste with a top liner and covering it all with soil.

“Some of these ponds did not have bottom liners when they were originally constructed, so they’ll be susceptible to leaking to groundwater even if they are covered on top,” said Hsu-Kim, who also holds an appointment in Duke’s Nicholas School of the Environment. “When you cap a site, you’re separating it from air. And if the buried waste goes anaerobic, it could enhance the leaching of some elements, leading to more contamination than expected.”

In the study, Hsu-Kim and her graduate student Grace Schwartz set up a series of microcosms — small-scale laboratory replicas of an environment. They then looked at how much arsenic and selenium leached out of the system both with and without oxygen. Both contaminants are potential problems for aquatic wildlife, and arsenic can be cancerous to humans.

The tests showed that with oxygen, the levels of selenium leaching are much higher than that of arsenic. But that trend flips when the system becomes anaerobic — there is an increase in the leaching of arsenic and a decrease for selenium.

Hsu-Kim points out that this result is not surprising given the chemistry of the two elements, and previous projects not related to coal ash sites have demonstrated these results in the real world. The study points out that this could be happening in coal ash sites as well.

“I’m trying to figure out if anyone is thinking about the fact that they’re changing the oxygen conditions within the ash site by covering it,” said Hsu-Kim. “This research suggests that some of the proposed methods for ash ponds closure in North Carolina may not be a slam dunk solution to the problem.”

Reference:
“Leaching potential and redox transformations of arsenic and selenium in sediment microcosms with fly ash,” Grace E. Schwartz, Nelson Rivera, Sung-Woo Lee, James M. Harrington, James C. Hower, Keith E. Levine, Avner Vengosh, Heileen Hsu-Kim. Applied Geochemistry, 2016. DOI: 10.1016/j.apgeochem.2016.02.013

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

Hi-tech opens up Earth’s secrets

Hi-tech opens up Earth-GeologyPage
Tectonic plates. Credit: Image courtesy of James Cook University

JCU’s Dr Rob Holm applied modern technology to existing geological data. He said the results open up completely new and original interpretations of geological processes.

“This research shows the value of applying new techniques to the extensive database of already existing scientific literature,” he said.

“It can track the motion of tectonic plates to explain the formation of oceans and mountain ranges as these plates break apart and crash into one another, and even holds far-reaching implications for the distribution of animal species and Earth’s climate though time.”

The animation shows the recent (from less than 8 million years ago) geological history of Papua New Guinea and the Solomon Islands. “Geologists can now see the different processes that are active in tectonic plates and mountain building in almost real time,” said Dr Holm.

He said it had revealed different geological relationships for the region, which had not been previously considered.

“This work highlights how the motion of tectonic plates and their related landmasses are intricately linked to the motion of other plates and plate boundaries surrounding them, and those further afield,” he said.

Dr Holm, a lecturer in petrology and mineralogy, said the work had more than theoretical applications. “We can now see the geological settings during the formation of mineral deposits rather than simply at the present day. As a result we gain a better understanding of the geological settings for deposit formation and can better predict worthwhile locations to explore.”

He said the work could also help with understanding and predicting earthquakes or volcanic eruptions. “It allows us to reconstruct and track the boundaries between tectonic plates. A better appreciation of this will give us a greater ability to predict where and when these hazards can occur.”

Dr Holm said the research illustrated the highly dynamic setting of the PNG and Solomon Islands region.

“Over a short geological time the Bismarck Sea has been created where no ocean previously existed, and the Solomon Sea has been reduced to a few 100 km across from what was once a vast ocean basin in excess of 1000 km wide, ” he said.

Dr Holm said the research will be expanded throughout the region to understand the evolution of the southwest Pacific, and also to investigate the long-term geological development of the region.

Reference:
Robert J. Holm, Gideon Rosenbaum, Simon W. Richards. Post 8Ma reconstruction of Papua New Guinea and Solomon Islands: Microplate tectonics in a convergent plate boundary setting. Earth-Science Reviews, 2016; 156: 66 DOI: 10.1016/j.earscirev.2016.03.005

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

Researchers define links within two supercontinents

Researchers define links-GeologyPage
Kevin Chamberlain, a research professor in the UW Department of Geology and Geophysics, is co-author of a paper that appears online in Nature Geoscience today (April 11). The paper highlights a technique that he helped develop to test pre-Pangea continental reconstructions. Here, Chamberlain poses with a mass spectrometer and holds a piece of a mafic dike, or black rock, which cuts through white, or granitic, rock (also pictured) that represents continental crust. Credit: University of Wyoming

A University of Wyoming researcher contributed to a paper that has apparently solved an age-old riddle of how constituent continents were arranged in two Precambrian supercontinents—then known as Nuna-Columbia and Rodinia. It’s a finding that may have future economic implications for mining companies.

Specifically, the article describes a technique Kevin Chamberlain, a UW research professor in the Department of Geology and Geophysics, and other researchers used to test reconstructions of ancient continents. The paper argues that the rocks or crust now exposed in southern Siberia were once connected to northern North America for nearly a quarter of the Earth’s history. Those two continental blocks now form the cores of the modern continents of Asia and North America.

Chamberlain was co-author of the paper, titled “Long-Lived Connection between Southern Siberia and Northern Laurentia in the Proterozoic,” that appeared in today’s (April 11) online issue of Nature Geoscience. The monthly multi-disciplinary journal focuses on bringing together top-quality research across the entire spectrum of the Earth sciences, along with relevant work in related areas. The journal’s content reflects all the disciplines within the geosciences, encompassing field work, modeling and theoretical studies.

“The article highlights a technique that our project has been using to test pre-Pangea or ancient continental reconstructions,” Chamberlain says. “We have been using the ages, orientations and paleo-magnetic characteristics of short-lived (1 million to 10 million years in duration) igneous, mafic dike swarms as piercing points to determine nearest-neighbor continents in the past.”

Mafic dikes are dark-colored rocks or minerals that are in a dike formation, which is a sheet of rock that formed in a fracture in a pre-existing rock body. Chamberlain says mafic dikes, like those studied in the paper, can be found in Wyoming. Mafic dikes in the state include the black vein that can be seen in Mount Moran in the Teton Range; the black, horizontal band on the east face of Medicine Bow Peak; and those that crisscross the Granitic Mountains in central Wyoming.

Using labs at UW and UCLA, Chamberlain says his role in the project was to determine the magmatic ages of numerous mafic dikes through uranium-lead radiometric dating. He was one of four geochronology labs on the team and the only one based in the United States.

The linear dikes from these igneous events (large igneous provinces, or LIPs) are relatively narrow, roughly 100 meters or less, but can be 1,000 to 1,500 kilometers in length. They erupt in a radial pattern.

During later rifting, the continents broke into fragments, which later combined into subsequent new continents, such as our modern-day seven continents.

“There may have been four or five cycles of supercontinent formation,” Chamberlain says.

Each continental fragment preserves a dike swarm record, he explains. By comparing the temporal records called bar codes (since a plot of dike date vs. time looks like a bar code) of older fragments known as cratons (the cores of modern continents), Chamberlain says he was able to test whether the cratons were close enough to share LIP dike swarms. He adds the research team also can determine when the two cratons joined, as well as when they split apart.

“In this new study, we believe that northern Laurentia (North America) and southern Siberia were joined for nearly 1.2 billion years from 1.9 billion years ago to 700 million years ago,” he says. “Geologists are like detectives. It seems like we come to the crime scene after the fact and put together the pieces.”

This finding disproves previous constructions of Nuna-Columbia and Rodinia, and establishes new arrangements of the continental blocks within them, he says.

The project determined the ages of nearly 250 mafic dikes worldwide, a number Chamberlain says is large enough to build a database comparison between all of the older continental fragments from roughly 500 million years ago to 2,700 million years ago. The research group also worked on more recent LIPs—about 400 million to 100 million years ago—which have importance for oil and gas exploration, and hydrocarbon maturation models.

A consortium of mining companies funded the research project for five years. Their reasoning: That the continental reconstructions for times when major, known metal deposits formed would be useful for prospecting new finds on the conjugate continents, Chamberlain says. These new deposits may be buried under hundreds of meters of younger rock. So, by establishing which continents were next to the known deposits when they formed, the hope is that additional minerals may be found in the future.

“A lot of the major metal deposits in the earth formed in the early part of Earth’s history,” Chamberlain says.

A print version of the paper is scheduled to appear in the May issue of Nature Geoscience.

Reference:
R. E. Ernst et al. Long-lived connection between southern Siberia and northern Laurentia in the Proterozoic, Nature Geoscience (2016). DOI: 10.1038/ngeo2700

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

Wealth of unsuspected new microbes expands tree of life

Wealth of unsuspected new-GeologyPage
This is a new and expanded view of the tree of life, with clusters of bacteria (left), uncultivable bacteria called ‘candidate phyla radiation’ (center, purple) and, at lower right, the Archaea and eukaryotes (green), including humans. Credit: Graphic by Zosia Rostomian, Lawrence Berkeley National Laboratory

The tree of life, which depicts how life has evolved and diversified on the planet, is getting a lot more complicated.

Researchers at the University of California, Berkeley, who have discovered more than 1,000 new types of bacteria and Archaea over the past 15 years lurking in Earth’s nooks and crannies, have dramatically rejiggered the tree to account for these microscopic new life forms.

“The tree of life is one of the most important organizing principles in biology,” said Jill Banfield, a UC Berkeley professor of earth and planetary science and environmental science, policy and management. “The new depiction will be of use not only to biologists who study microbial ecology, but also biochemists searching for novel genes and researchers studying evolution and earth history.”

Much of this microbial diversity remained hidden until the genome revolution allowed researchers like Banfield to search directly for their genomes in the environment, rather than trying to culture them in a lab dish. Many of the microbes cannot be isolated and cultured because they cannot live on their own: they must beg, borrow or steal stuff from other animals or microbes, either as parasites, symbiotic organisms or scavengers.

The new tree, to be published online April 11 in the new journal Nature Microbiology, reinforces once again that the life we see around us – plants, animals, humans and other so-called eukaryotes – represent a tiny percentage of the world’s biodiversity.

“Bacteria and Archaea from major lineages completely lacking isolated representatives comprise the majority of life’s diversity,” said Banfield, who also has an appointment at Lawrence Berkeley National Laboratory. “This is the first three-domain genome-based tree to incorporate these uncultivable organisms, and it reveals the vast scope of as yet little-known lineages.”

According to first author Laura Hug, a former UC Berkeley postdoctoral fellow who is now on the biology faculty at the University of Waterloo in Ontario, Canada, the more than 1,000 newly reported organisms appearing on the revised tree are from a range of environments, including a hot spring in Yellowstone National Park, a salt flat in Chile’s Atacama desert, terrestrial and wetland sediments, a sparkling water geyser, meadow soil and the inside of a dolphin’s mouth. All of these newly recognized organisms are known only from their genomes.

“What became really apparent on the tree is that so much of the diversity is coming from lineages for which we really only have genome sequences,” she said. “We don’t have laboratory access to them, we have only their blueprints and their metabolic potential from their genome sequences. This is telling, in terms of how we think about the diversity of life on Earth, and what we think we know about microbiology.”

One striking aspect of the new tree of life is that a group of bacteria described as the “candidate phyla radiation” forms a very major branch. Only recognized recently, and seemingly comprised only of bacteria with symbiotic lifestyles, the candidate phyla radiation now appears to contain around half of all bacterial evolutionary diversity.

While the relationship between Archaea and eukaryotes remains uncertain, it’s clear that “this new rendering of the tree offers a new perspective on the history of life,” Banfield said.

“This incredible diversity means that there are a mind-boggling number of organisms that we are just beginning to explore the inner workings of that could change our understanding of biology,” said co-author Brett Baker, formerly of Banfield’s UC Berkeley lab but now at the University of Texas, Austin, Marine Science Institute.

Tree depicts life we see today

Charles Darwin first sketched a tree of life in 1837 as he sought ways of showing how plants, animals and bacteria are related to one another. The idea took root in the 19th century, with the tips of the twigs representing life on Earth today, while the branches connecting them to the trunk implied evolutionary relationships among these creatures. A branch that divides into two twigs near the tips of the tree implies that these organisms have a recent common ancestor, while a forking branch close to the trunk implies an evolutionary split in the distant past.

Archaea were first added in 1977 after work showing that they are distinctly different from bacteria, though they are single-celled like bacteria. A tree published in 1990 by microbiologist Carl Woese was “a transformative visualization of the tree,” Banfield said. With its three domains, it remains the most recognizable today.

With the increasing ease of DNA sequencing in the 2000s, Banfield and others began sequencing whole communities of organisms at once and picking out the individual groups based on their genes alone. This metagenomic sequencing revealed whole new groups of bacteria and Archaea, many of them from extreme environments, such as the toxic puddles in abandoned mines, the dirt under toxic waste sites and the human gut. Some of these had been detected before, but nothing was known about them because they wouldn’t survive when isolated in a lab dish.

For the new paper, Banfield and Hug teamed up with more than a dozen other researchers who have sequenced new microbial species, gathering 1,011 previously unpublished genomes to add to already known genome sequences of organisms representing the major families of life on Earth.

She and her team constructed a tree based on 16 separate genes that code for proteins in the cellular machine called a ribosome, which translates RNA into proteins. They included a total of 3,083 organisms, one from each genus for which fully or almost fully sequenced genomes were available.

The analysis, representing the total diversity among all sequenced genomes, produced a tree with branches dominated by bacteria, especially by uncultivated bacteria. A second view of the tree grouped organisms by their evolutionary distance from one another rather than current taxonomic definitions, making clear that about one-third of all biodiversity comes from bacteria, one-third from uncultivable bacteria and a bit less than one-third from Archaea and eukaryotes.

“The two main take-home points I see in this tree are the prominence of major lineages that have no cultivable representatives, and the great diversity in the bacterial domain, most importantly, the prominence of candidate phyla radiation,” Banfield said. “The candidate phyla radiation has as much diversity within it as the rest of the bacteria combined.”

Reference:
Laura A. Hug, Brett J. Baker, Karthik Anantharaman, Christopher T. Brown, Alexander J. Probst, Cindy J. Castelle, Cristina N. Butterfield, Alex W. Hernsdorf, Yuki Amano, Kotaro Ise, Yohey Suzuki, Natasha Dudek, David A. Relman, Kari M. Finstad, Ronald Amundson, Brian C. Thomas & Jillian F. Banfield. A new view of the tree of life. DOI:10.1038/nmicrobiol.2016.48

Note: The above post is reprinted from materials provided by University of California – Berkeley.

Sannur Cave, Beni Suef, Egypt

Sannur Cave
Sannur Cave

Sannur Cave Protectorate is located in the Beni-Suef governorate of Egypt and lies at 70 km southeast of the city of Beni Suef and 200 km from Cairo. The place has many geographical formations of stalactites and stalagmites as well. The reserve becomes even more important due to the natural formations present here many of which are rare and hard to find elsewhere. The reserve is filled with a large number of quarries dating back to different eras.

Discovery

The alabaster digging operations which is still continued, led to the discovery of 54 big cavities that opened way to the caves and were present at the bottom of the earth. The reserve has just one chamber or cave in it. The cave here extends to an area of 700 meters and has a depth and width of 15 meters respectively. The caves contain geographical formations which are referred as ups and downs. The most important feature of the natural formations is the quality and also the rare nature of these which are found nowhere else on the globe. The researchers and geologists thus find this reserve very important to learn and do conductive research and studies about the environmental and other conditions that prevailed during the ancient times.

The Sannur Caves were discovered in the 1989s after a blasting in the quarry led to opening of an entrance way to the chamber. The cave is overlaid with alabaster that has been brought by the thermal springs and the chamber is made of limestone. The unique geography and natural formations make this place very popular and have helped the same get recognized as a protectorate by the prime minster decree in 1992.

Formation

Sannur Cave is a classic karst cave created by groundwater percolating through the Eocene limestone of the Galala Plateau. It is the best example of this type of cave in Egypt. As the water percolates downwards, excess calcium carbonates are deposited on the roof and floor of the cave forming spectacular stalactites and stalagmites of various forms. When a light is shone on them, they glitter like a wonderland. Above ground, there are deposits of the red soil (terra rossa) associated with such formations, as well as several swallow-holes (dolines).

Sannur Cave is characterized by the presence of geological formations known as Stalactites and Stalagmites in a perfect beautiful formed over millions of years, about 60 million years ago dates back to the Era of Middle Eocene. Leakage of aqueous solutions of calcium carbonate saturated through the roof of the cave and then evaporated, leaving the mineral salts that accumulated in the form of deposits of stalactites and stalagmites. Sannur cave extends a distance of about 700 m, breadth about 15 m and depth is about 15 m. The cave is important to the scarcity of such natural formations “Egyptian Alabaster” as it is of great importance for researchers, Geologists, and Caving fans.

Photos

Map

Reference:
Beni Suef Governorate: Sannur Valley Cave Protectorate
Egypt State Information Service

The rise of the mammals

The rise of the mammals-GeologyPage
Ectoconus teeth.

An asteroid strike put an end to the dinosaurs 66 million years ago, making way for mammals to thrive – that much we know. But how exactly did our ancestors go about their march to dominance? Stephen Brusatte and Sarah Shelley introduce an unassuming fossil that holds some of the answers.

Edward Drinker Cope named more than 1,000 species and published nearly 1,500 papers during his long career in vertebrate palaeontology. He worked on everything, from fish and frogs to sea-living reptiles and dinosaurs. But in 1881 he announced a discovery that stood above the rest. In the characteristic understatement of a 19th-century gentleman scientist, Cope boasted that the new fossil would be remembered as ‘an important event in the history of palaeontological science’. He wasn’t referring to a charismatic dinosaur of colossal size or an early branch of the human family tree. Instead, he was talking about an unassuming little mammal called Periptychus, just about the size of a dog, found in the dusty badlands of the American Southwest.

Cope’s excitement was prophetic. Periptychus may look like nothing more than a cute pet, but it and a growing number of other mammal fossils are now helping us better understand one of the pivotal moments of Earth history. At the end of the Cretaceous, about 66 million years ago, a 10-kilometre-wide asteroid slammed into what is now Mexico. It rudely interrupted a world in which dinosaurs were dominant, and had been for more than 100 million years. The asteroid hit with the force of several million nuclear bombs, unleashing a torrent of tsunamis and wildfires and sending dust into the stratosphere, blocking out the sun and poisoning the atmosphere. Ecosystems were devastated and many plants and animals went extinct. When things eventually settled down and the Earth recovered, dinosaurs were nowhere to be found and mammals were everywhere.

This is one of the classic stories in Earth science, repeated to every first-year geology student. The asteroid knocked out the dinosaurs making way for mammals, which had been living in the shadows for tens of millions of years, to prosper, eventually leading to primates and, later, to us. But surprisingly we still know little about when and how mammals started their march to dominance. Why did some mammals survive the extinction but not dinosaurs? How quickly did mammals diversify after the asteroid? When did the major groups of living mammals like rodents, elephants and primates originate?

Periptychus and its kin seem to hold the key. These so-called ‘archaic’ mammals thrived during the first few million years after the dinosaurs died out, during a time called the Paleocene (66-56 million years ago). They were the very mammals that took the reins from Tyrannosaurus and Triceratops, establishing a new world in which mammals invaded nearly every conceivable environment across the globe and ascended to the top of the food chain in many ecosystems. But surprisingly, after the initial fossil discoveries by Cope and other 19th- and early-20th-century palaeontologists, research on these archaic Paleocene species nearly died out itself. As dinosaurs and fossil hominids grabbed the headlines and research funds, Periptychus and other Paleocene mammals became an afterthought.

But now a new generation of scientists is returning to these Paleocene fossils because of their obvious importance in understanding a major interval of environmental change. We have been working in New Mexico (USA), one of the best places in the world to find both the latest Cretaceous dinosaurs and the Paleocene mammals that replaced them. We are doing fieldwork with our colleague Thomas Williamson, who for more than two decades has been scouring the San Juan Basin area of north-western New Mexico in the hunt for new fossils. Our joint work in the Paleocene-aged Nacimiento Formation is aimed at finding new Paleocene mammals, tracking the diversity of mammals across this interval, and better understanding the environments they lived in.

Working in New Mexico harkens back to the early days of palaeontology, when explorers would fan out to remote corners of the globe in search of the unknown. Fieldwork in the San Juan Basin probably hasn’t changed much since Cope’s day. Although New Mexico is within the borders of one of the most economically developed countries in the world, a lot of unexplored territory and many undiscovered fossils remain. Most of the state is vast, empty desert: it is a third larger than the UK in land area, but has only 3 per cent of the population. When we’re out prospecting in the barren, candy-striped hills it isn’t uncommon to go entire days without seeing other people.

Our field expeditions over the past five years have produced many new fossils and an emerging picture of what happened to mammals before, during, and after the end-Cretaceous mass extinction. We’ve discovered spectacular new specimens of big plant-eating mammals like Pantolambda and Ectoconus (a close cousin of Periptychus), fast-running species like Tetraclaenodon, weird burrowers like Wortmania, and bizarre rodent-like mammals called multituberculates. Our team has also used radiometric dating to place these fossils in time, analysed sediments and isotopes to reconstruct the environments they lived in, and used diversity analysis to look at broad evolutionary trends during this dynamic period of mammal evolution.

There’s still plenty to do but an evolutionary picture is coming into focus. Mammals did not pass through the mass extinction unscathed; the close relatives of modern marsupials were decimated but the hitherto unspectacular placentals (mammals that give live birth to well-developed young) weathered the storm and radiated in the aftermath. This radiation was rapid: within a few hundred thousand years at most there were complex ecosystems with mammals of many sizes, up to about cow size, filling many niches, eating different types of food, and living in the ground, on the land and in the trees.

So it looks like the end-Cretaceous extinction was a knife-edge moment in evolution. Right up until the asteroid impact dinosaurs prospered, then the environment rapidly changed and very quickly entirely new animals – placental mammals – moved in and took over. There is surely a lesson here: when rapid environmental change occurs, animals and ecosystems that have been successful for millions of years can suddenly disappear and the world changes in an instant. When this happened at the end of the Cretaceous it set in motion a chain of events which led, eventually, to humans. If it happens again, who knows where that unpredictable chain could lead.

Note: The above post is reprinted from materials provided by Natural Environment Research Council.

Ocean-bound scientists drilling for new clues about dinosaur extinction event

Ocean-bound scientists drilling -GeologyPage

On April 14, scientists will begin collecting new samples from the Chicxulub impact crater, remnant of an asteroid that crashed into Earth 66 million years ago and caused the extinctions of 75 percent of the planet’s species, including the dinosaurs. The international team includes two Penn State researchers, Tim Bralower, professor of geosciences, and Heather Jones, Ph.D. candidate in geosciences.

Scientists theorize that a 6-mile-wide asteroid struck the Earth on Mexico’s Yucatan Peninsula, resulting in a chain of events—global darkness, nuclear winter, ocean acidification and rampant wildfires—that wiped out nearly all life. The asteroid struck Earth with more than a billion times the energy of an atomic bomb, researchers estimate, and melted the rock at ground zero.

The International Ocean Discovery Program (IODP) research team hopes to learn new details about how life persisted following the impact. Team members also hope to better understand the mechanics of the crash, such as how rapidly temperature changed after impact, the angle at which the asteroid struck the Earth and how the bedrock behaved under such intense pressure.

Stationed on a drilling rig 25 miles off the coast of Mexico, the team will collect samples from the circle-shaped perimeter, known as the ‘peak ring,’ of the Chicxulub impact crater. The Chicxulub crater is the only known impact crater on Earth with an intact peak ring, and it is the only crater that has been linked to a mass extinction.

“I’m excited to be part of the project because it’s the first time that anyone has collected samples from the crater’s peak ring,” said Bralower. “Deep underneath the peak ring is a geological layer called the melt layer. This layer shows evidence of widespread melting at the time of the crash, and this melting was a critical part of the extinction process because it led to a global rainout of tiny melt droplets that caused wildfires.”

Bralower will be on board the drilling rig to conduct initial analyses of the samples as the IODP team digs. Once the cores have been extracted, the team will transport them to IODP’s Bremen Core Repository in Germany. Jones will travel to Germany in September to help the team conduct a detailed analysis of the cores.

To collect their samples, the team has to dig through layers of sediment that have built up on top of the melt layer. They are looking for signs of life and other geological information from between 55 and 66 million years ago. They will first dig 0.3 miles under the ocean floor to the layer of sediment that was deposited roughly 55 million years ago. From there, they aim to collect cores dating back to 66 million years ago, and this is where Bralower’s expertise comes into play. He will conduct microscopic analyses on each sample collected at 20- to 30-foot intervals to date the time period of the sediment. To access the sediment deposited 66 million years ago, the team will need to drill a total of 0.5 miles under the sea floor.

“This is really my bread and butter,” Bralower said. “Every time we bring a new piece of core up, we’ll take a crumb and look at it under a microscope. Based on the fossils we find, we’ll know how old the sample is.”

Bralower will be looking specifically for phytoplankton fossils because they are easy to prepare and analyze on the ship. Because phytoplankton are at the bottom of the food chain, analyzing their distribution through the 11-million-year interval could help researchers better understand how quickly life recovered after the impact.

The international team includes scientists from Mexico, Japan, Australia, Canada, China and six European countries.

This work is being supported by the International Continental Scientific Drilling Program and the European Consortium for Ocean Research Drilling.

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

When life returned after a volcanic mass extinction

When life returned after-GeologyPage
Representative Image

A worldwide mass extinction 201.5 million years ago wiped out 60 percent of sea life, including coral reefs and shelled marine animals. On land, the dead included many plants as well as giant reptiles that competed with the earliest dinosaurs.

The mass extinction apparently was caused by huge carbon dioxide emissions from gargantuan volcanic eruptions in the center of the supercontinent Pangea, which eventually broke into today’s modern continents. The eruptions were in what is named the Central Atlantic Magmatic Province because the Atlantic Ocean eventually formed there as Pangea broke apart.

In the April 6 issue of the journal Nature Communications, a new study used fossils and mercury isotopes from volcanic gas deposited in ancient proto-Pacific Ocean sediment deposits in Nevada to determine when life recovered following the mass extinction at the end of the Triassic Period. The Proto-Pacific surrounded Pangea.

Kathleen Ritterbush, an assistant professor of geology and geophysics at the University of Utah, co-authored the study. It found a significant recovery of sea life didn’t occur until after the end of the massive volcanic eruptions, which occurred in spurts between 201.6 million and 200.9 million years ago.

While colleagues did the mercury analysis, Ritterbush collected rocks and analyzed ancient sea sponges. Traces of mercury in rock showed the timing of major lava eruptions as Pangea split.

Although squid-like ammonites diversified rapidly when eruptions ceased, seafloor ecology recovered slowly. Sponges carpeted coastal habitats for about 2 million years before mollusks and corals finally re-established ecosystems as complex as before the eruptions.

Reference:
Alyson M. Thibodeau, Kathleen Ritterbush, Joyce A. Yager, A. Joshua West, Yadira Ibarra, David J. Bottjer, William M. Berelson, Bridget A. Bergquist, Frank A. Corsetti. Mercury anomalies and the timing of biotic recovery following the end-Triassic mass extinction. Nature Communications, 2016; 7: 11147 DOI: 10.1038/ncomms11147

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

North Atlantic played pivotal role in last great climate tipping point

North Atlantic played pivotal-GeologyPage
For the past 2.7 million years Earth’s climate has switched more than 50 times between a cold glacial state and warm interglacial state.

North Atlantic played pivotal role in last great climate tipping point, research shows.

The North Atlantic Ocean played a key role in the last great tipping point in Earth’s climate system, pioneering new research has shown.

An international research team has discovered ground-breaking new reasons why large continental ice-sheets first grew in North America and Scandinavia during the late Pliocene Epoch era, 2.7 millions of years ago.

The collaborative team was led by Dr Ian Bailey from the University of Exeter and Prof Paul Wilson from the University of Southampton, and also involved scientists from Woods Hole Oceanographic Institute in the USA and GEOMAR in Germany.

The researchers measured the composition of isotopes of the chemical element neodymium that can be found in fish teeth preserved in a North Atlantic marine core to track the origin of deep waters bathing the bottom of the Atlantic Ocean during this climate transition.

For the past 2.7 million years Earth’s climate has switched more than 50 times between a cold glacial state and warm interglacial state much like today. Contrary to previous assertions, they found that the first of these glacial events in the northern hemisphere were associated with major expansions of carbon-rich southern-sourced deep waters into the northwestern Atlantic abyss, over one million years earlier than previously thought.

The team also found that three of the largest glacial cycles between 2.5 and 2.7 million years ago appear to be associated with southern-sourced water incursions into the deep Atlantic that were as significant as those documented for the last glacial maximum.

The research is published in leading scientific journal, Nature Geoscience, on Monday, 4 April 2016.

Dr Bailey, a Geology Lecturer from the Camborne School of Mines, based at the University of Exeter’s Penryn Campus in Cornwall said: “We could not have made these new findings with confidence using only a classic method for tracing watermass origin such as carbon isotopes.

“But when we combined such data with an alternative novel proxy such as neodymium isotopes, we were able to reveal a dramatically new picture of watermass mixing in the deep North Atlantic during late Pliocene glacial intensification.”

Dr Bailey said that it has long been argued that changes in North Atlantic circulation played a leading role in driving late Pliocene northern hemisphere glaciation because of its capacity to modulate the transfer of heat and moisture from the tropics to the poles.

He added: “Our findings suggest, though, that the North Atlantic Ocean was not a driving factor in this transition, but, through storage of atmospheric carbon dioxide in the deep Atlantic, it operated as a positive feedback that helped to usher in glaciation at this time.

“What we’ve done is document a process which is thought to be special to the largest and longest glacial cycles of the past one million years, but we have shown that it has been occurring ever since large continental ice-sheets formed in the Northern Hemisphere.”

Professor Wilson, who is Head of Palaeoceanography and Palaeoclimate Research Group at the University of Southampton, a unit within the School of Ocean and Earth Science based at the National Oceanography Centre said: “The mechanism driving these expansions of southern sourced water into the deep Atlantic still needs working on. It is thought that North Atlantic Deepwater formation is sensitive to glacial freshwater inputs to the ocean in the north.

“Yet our new data hint that these southern-hemisphere invasions may even predate the onset of major northern hemisphere glaciation. Counter intuitively our findings may therefore suggest that they were driven from the south.”

Reference:
David C. Lang, Ian Bailey, Paul A. Wilson, Thomas B. Chalk, Gavin L. Foster, Marcus Gutjahr. Incursions of southern-sourced water into the deep North Atlantic during late Pliocene glacial intensification. Nature Geoscience, 2016; DOI: 10.1038/ngeo2688

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

Dallol Volcano

Dallol Volcano

Dallol is a volcanic explosion crater (or maar) in the Danakil Depression, northeast of the Erta Ale Range in Ethiopia. It has been formed by the intrusion of basaltic magma in Miocene salt deposits and subsequent hydrothermal activity. Phreatic eruptions took place here in 1926, forming Dallol Volcano, numerous other eruption craters dot the salt flats nearby. These craters are the lowest known subaerial volcanic vents in the world, at over 45 m (150 ft) below sea level. The most recent major activity was in October 2004 when the shallow magma chamber beneath Dallol deflated and fed a magma intrusion southwards beneath the rift.

Numerous hot springs are discharging brine and acidic liquid here. Widespread are small, temporary geysers which are forming cones of salt.

Dallol is nested on top of an at least 1000m thick layer of quaternary evaporates including large potash (potassium salt) reserves, the source of which will be discussed in more detail below.  Dallol mountain is thought to have been formed as the result of intrusion of a basaltic magma body underneath. The circular depression near the center of Dallol mountain is presumably a collapse crater, although neither its age nor the exact process from which it resulted are known. The SW flank of Dallol mountain harbours impressive salt canyons formed by erosion processes.

The 1926 phreatic eruption formed a 30m wide crater and was the last significant event at Dallol.  Currently, activity is in the form of hot brine springs.  Salts washed out of the underlying layers are transported to the surface by geothermally heated water and rapidly crystallize as the water evaporates.  The characteristic white, yellow and red colours are the result of sulphur and potassium salts coloured by various ions. The terminology Dallol is often used to define an even larger area, which may cause confusion as to the location of mining operations in the area.

Reference:
Wikipedia: Dallol (volcano)
photovolcanica: Dallol Volcano

New models predicting where to find fossils

New models predicting-GeologyPage
Approach to identify potential fossil areas with combined models.

An international team of scientists has developed a way to help locate fossils of long-extinct animals.

Using the estimated ages and spatial distribution of Australian megafauna fossils, the team from University of Adelaide in Australia and Kiel University in Germany built a series of mathematical models to determine the areas in the country most likely to contain fossils.

Published in PLOS ONE, the models were developed for Australia but the researchers provide guidelines on how to apply their approach to assist fossil hunting in other continents.

“A chain of ideal conditions must occur for fossils to form, which means they are extremely rare ─ so finding as many as possible can tell us more of what the past was like, and why certain species went extinct,” says project leader Professor Corey Bradshaw, Sir Hubert Wilkins Chair of Climate Change at the University of Adelaide.

“Typically, however, we use haphazard ways to find fossils. Mostly people just go to excavation sites and surrounding areas where fossils have been found before. We hope our models will make it easier for palaeontologists and archaeologists to identify new fossil sites that could yield vast treasures of prehistoric information.”

Research student and lead author Sebastián Block and the team made use of modelling techniques commonly used in ecology. They modelled past distribution of species, the geological suitability of fossil preservation, and the likelihood of fossil discovery in the field. They applied their techniques to a range of Australian megafauna that became extinct over the last 50,000 years, such as the giant terror bird Genyornis, the rhino-sized ‘wombat’ Diprotodon, and the marsupial ‘lion’ Thylacoleo.

To produce the species distribution models of these long-extinct animals, the researchers used ‘hindcasted global circulation models’ to provide predicted temperature and rainfall for the deep past, and matched this with the estimated ages of the fossils.

“What we did was build a probability map for each of these layers – the species distribution, the right sort of geological conditions for fossil formation (for example, sedimentary rocks, or caves and lakes), and the ease of discovery (for example, open areas rather than dense forest),” says Professor Bradshaw. “We combined each of these for an overall ‘suitability for fossil discovery’ map.”

“Our methods predict potential fossil locations across an entire continent, which is useful to identify potential fossil areas far from already known sites,” says Kiel University’s Professor Ingmar Unkel. “It’s a good ‘exploration filter; after which remote-sensing approaches and fine-scale expert knowledge could complement the search.”

The model showed areas south of Lake Eyre and west of Lake Torrens in South Australia and a large area around Shark Bay, Western Australia and other areas in south-western Australia with a high potential to yield new megafauna fossils.

Reference:
Sebastián Block et al. Where to Dig for Fossils: Combining Climate-Envelope, Taphonomy and Discovery Models, PLOS ONE (2016). DOI: 10.1371/journal.pone.0151090

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

Six to 10 million years ago: Ice-free summers at the North Pole

Six to 10 million years ago-GeologyPage
Bathymetric plot of the Lomonossov Ridge‘s western slope, where the unique sediment cores have been taken. Credit: Alfred-Wegener-Institut /Rüdiger Stein

An international team of scientists led by the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) have managed to open a new window into the climate history of the Arctic Ocean. Using unique sediment samples from the Lomonosov Ridge, the researchers found that six to ten million years ago the central Arctic was completely ice-free during summer and sea-surface temperature reached values of 4 to 9 degrees Celsius. In spring, autumn and winter, however, the ocean was covered by sea ice of variable extent, the scientists explain in the current issue of the journal Nature Communications. These new findings from the Arctic region provide new benchmarks for groundtruthing global climate reconstructions and modelling.

The researchers had recovered these unique sediment samples during an expedition with Germany’s research icebreaker RV Polarstern in summer of 2014. “The Arctic sea ice is a very critical and sensitive component in the global climate system. It is therefore important to better understand the processes controlling present and past changes in sea ice. In this context, one of our expedition’s aims was to recover long sediment cores from the central Arctic, that can be used to reconstruct the history of the ocean’s sea ice cover throughout the past 50 million years. Until recently, only a very few cores representing such old sediments were available, and, thus, our knowledge of the Arctic climate and sea ice cover several millions of year ago is still very limited,” Prof. Dr. Ruediger Stein, AWI geologist, expedition leader and lead author of the study, explains.

The scientists found an ideal place for recovering the sediment cores on the western slope of the Lomonosov Ridge, a large undersea mountain range in the central Arctic. “This slope must have experienced gigantic recurring landslides in the past, which resulted in the exhumation of more than 500-metre thick ancient sediment and rock formations. We were also surprised about the wide-spread occurrence of these slide scars, which extend over a length of more than 300 kilometres, almost from the North Pole to the southern end of the ridge on the Siberian side,” Ruediger Stein explains.

Sediment core emerges as a unique climate archive

Within a two-days coring action, he and his team took 18 sediment cores from this narrow area on Lomonosov Ridge on board the Polarstern research vessel. Although the recovered sediment cores were only four to eight metres long, one of them turned out to be precisely one of those climate archives that the scientists had been looking for a long time. “With the help of certain microfossils, so-called dinoflagellates, we were able to unambiguously establish that the lower part of this core consists of approximately six to eight million-year-old sediments, thereby tracing its geological history back to the late Miocene. With the help of so-called ‘climate indicators or proxies’, this gave us the unique opportunity to reconstruct the climate conditions in the central Arctic Ocean for a time period for which only very vague and contradictory information was available,” says Stein.

Some scientists were of the opinion that the central Arctic Ocean was already covered with dense sea ice all year round six to ten million years ago — roughly to the same extent as today. The new research findings contradict this assumption. “Our data clearly indicate that six to ten million years ago, the North Pole and the entire central Arctic Ocean must in fact have been ice-free in the summer,” says Stein.

Biomarkers preserved in the sea floor allow insight into the climate’s past

This statement is based on studies of organic compounds (so-called biomarkers) that were produced by certain organisms that lived in the Arctic Ocean at that time and that have been preserved in the sediment deposits. The researchers were able to extract two of such marker groups from the sediments:

“The first group of biomarkers is derived from carbonaceous algae that live in surface water, i.e. they need open water and, being plants, depend on light. Since in the central Arctic Ocean sunlight is only available during the spring and summer months and is pitch-dark at all other times, the data derived from these carbonaceous algae provide us with information about the surface water conditions during the summer period,” says Stein.

Furthermore, these carbonaceous algae produce different biomarker compounds depending on the water temperature. “These molecules allowed us to estimate that the surface water temperature of the Arctic Ocean was approximately 4 to 9 degrees Celsius in the late Miocene. Because these values are well above zero, this is a clear indication that ice-free conditions existed in the summer,” says the scientist.

However, as the second group of biomarkers shows, the Arctic Ocean was not ice-free all year round. It is formed by specific diatoms that live in the Arctic sea ice. Ruediger Stein: “By combining our data records on surface water temperature and on sea ice, we are now able to prove for the first time that six to ten million years ago, the central Arctic Ocean was ice-free in the summer. In the spring and the preceding winter, on the other hand, the ocean was covered by sea ice. The seasonal ice cover around the North Pole must have been similar to that in the Arctic marginal seas today.”

New climate data help to improve climate models

These new findings of the Arctic Ocean climate history reconstructed from sediment data, are further corroborated by climate simulations, as was shown by the AWI modellers who participated in this study. This only applies, however, if we assume a relatively high carbon dioxide content in the atmosphere of 450 ppm. If the climate models were run using a significantly lower carbon dioxide content of about 280 ppm, as some studies postulate for the late Miocene, then an ice-free Arctic cannot be simulated. Whether the carbon dioxide content in the Miocene was indeed relatively high or whether the sensitivity of the model is too weak to simulate the magnitude of high-latitude warming in a warmer than modern climate, is currently subject to further international research. One of the overarching goals here is to improve the predictive capacity of climate models. Ruediger Stein: “Once our climate models are capable of reliably reproducing surface-water temperature and sea ice cover of earlier periods, we will also be able to further improve the climate models for a better prediction of future climate change and sea ice conditions in the central Arctic Ocean, a major challenge for all of us for the coming years.”

Further scientific drilling planned on the Lomonosov Ridge

Despite the outstanding results and the accompanying euphoria, the participating scientists agree that this was merely the first step and that other important steps must follow. “While our new sediment cores give us an undreamt-of initial insight into the early climate history of the Arctic, these climate records are still very incomplete. In order to fully unravel the great mystery of Arctic climate history over the past 20 to 60 million years, we need much longer, continuous sediment sequences, which can only be obtained by drilling. An Arctic drilling expedition (which is still a major scientific and technical challenge for the marine geosciences) is now planned for 2018 in our study area on the Lomonosov Ridge, and it will be carried out as part of the international drilling programme IODP (International Ocean Discovery Program). The preliminary investigations carried out by our Polarstern expedition have played a significant role in selecting the precise drilling locations,” Ruediger Stein, who will be one of the expedition leaders of the IODP campaign in 2018, explains.

Reference:
Ruediger Stein, Kirsten Fahl, Michael Schreck, Gregor Knorr, Frank Niessen, Matthias Forwick, Catalina Gebhardt, Laura Jensen, Michael Kaminski, Achim Kopf, Jens Matthiessen, Wilfried Jokat, Gerrit Lohmann. Evidence for ice-free summers in the late Miocene central Arctic Ocean. Nature Communications, 2016; 7: 11148 DOI: 10.1038/ncomms11148

Note: The above post is reprinted from materials provided by Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research.

Supernovae showered Earth with radioactive debris

Supernovae showered Earth-GeologyPage
Artist’s impression of supernova. Credit: Greg Stewart, SLAC National Accelerator Lab

An international team of scientists has found evidence of a series of massive supernova explosions near our solar system, which showered Earth with radioactive debris.

The scientists found radioactive iron-60 in sediment and crust samples taken from the Pacific, Atlantic and Indian Oceans.

The iron-60 was concentrated in a period between 3.2 and 1.7 million years ago, which is relatively recent in astronomical terms, said research leader Dr Anton Wallner from The Australian National University (ANU).

“We were very surprised that there was debris clearly spread across 1.5 million years,” said Dr Wallner, a nuclear physicist in the ANU Research School of Physics and Engineering. “It suggests there were a series of supernovae, one after another.

“It’s an interesting coincidence that they correspond with when the Earth cooled and moved from the Pliocene into the Pleistocene period.”

The team from Australia, the University of Vienna in Austria, Hebrew University in Israel, Shimizu Corporation and University of Tokyo, Nihon University and University of Tsukuba in Japan, Senckenberg Collections of Natural History Dresden and Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany, also found evidence of iron-60 from an older supernova around eight million years ago, coinciding with global faunal changes in the late Miocene.

Some theories suggest cosmic rays from the supernovae could have increased cloud cover.

A supernova is a massive explosion of a star as it runs out of fuel and collapses.

The scientists believe the supernovae in this case were less than 300 light years away, close enough to be visible during the day and comparable to the brightness of the Moon.

Although Earth would have been exposed to an increased cosmic ray bombardment, the radiation would have been too weak to cause direct biological damage or trigger mass extinctions.

The supernova explosions create many heavy elements and radioactive isotopes which are strewn into the cosmic neighbourhood.

One of these isotopes is iron-60 which decays with a half-life of 2.6 million years, unlike its stable cousin iron-56. Any iron-60 dating from Earth’s formation more than four billion years ago has long since disappeared.

The iron-60 atoms reached Earth in minuscule quantities and so the team needed extremely sensitive techniques to identify the interstellar iron atoms.

“Iron-60 from space is a million-billion times less abundant than the iron that exists naturally on Earth,” said Dr Wallner.

Dr Wallner was intrigued by first hints of iron-60 in samples from the Pacific Ocean floor, found a decade ago by a group at TU Munich.

He assembled an international team to search for interstellar dust from 120 ocean-floor samples spanning the past 11 million years.

The first step was to extract all the iron from the ocean cores. This time-consuming task was performed by two groups, at HZDR and the University of Tokyo.

The team then separated the tiny traces of interstellar iron-60 from the other terrestrial isotopes using the Heavy-Ion Accelerator at ANU and found it occurred all over the globe.

The age of the cores was determined from the decay of other radioactive isotopes, beryllium-10 and aluminium-26, using accelerator mass spectrometry (AMS) facilities at DREsden AMS (DREAMS) of HZDR, Micro Analysis Laboratory (MALT) at the University of Tokyo and the Vienna Environmental Research Accelerator (VERA) at the University of Vienna.

The dating showed the fallout had only occurred in two time periods, 3.2 to 1.7 million years ago and eight million years ago. Current results from TU Munich are in line with these findings.

A possible source of the supernovae is an aging star cluster, which has since moved away from Earth, independent work led by TU Berlin has proposed in a parallel publication. The cluster has no large stars left, suggesting they have already exploded as supernovae, throwing out waves of debris.

Reference:
A. Wallner, J. Feige, N. Kinoshita, M. Paul, L. K. Fifield, R. Golser, M. Honda, U. Linnemann, H. Matsuzaki, S. Merchel, G. Rugel, S. G. Tims, P. Steier, T. Yamagata, S. R. Winkler. Recent near-Earth supernovae probed by global deposition of interstellar radioactive 60Fe. Nature, 2016; 532 (7597): 69 DOI: 10.1038/nature17196

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

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