Friday, August 28, 2015

[Geology2] Catastrophic Volcanoes Blamed for Earth's Biggest Extinction



Catastrophic Volcanoes Blamed for Earth's Biggest Extinction

by Charles Q. Choi, Live Science Contributor   |   August 28, 2015
A view from the Siberian Traps
The view from atop a sill of the Siberian Traps, the largest series of volcanic eruptions in geologic history, looking out at mountains composed of similar lavas and sills.
Credit: Seth Burgess

Geologists hauling hundreds of pounds of 250-million-year-old rocks from Siberia, through Russian and American customs, say luck was on their side. Not only did they successfully transport the huge haul, but they also may have confirmed the cause of Earth's worst mass extinction.

The culprit? Catastrophic volcanic eruptions that spewed enough lava to cover Australia led to the die-off at the end of the Permian era, the researchers found. That die-off occurred about 250 million years ago and was the greatest mass extinction in Earth's history; 90 percent of marine species and 75 percent of land dwellers were wiped off the face of the planet over the course of about 60,000 years.

Ancient volcanic rocks now provide the best evidence yet that catastrophic volcanic activity triggered the extinction, researchers say.

"The main question we and many other research teams are trying to answer is, 'What causes mass extinction?'" said study lead author Seth Burgess, a geochronologist at the U.S. Geological Survey in Menlo Park, California. "These events shape the evolutionary trajectory of life on our planet, and are thus some of the most important events to occur in the 600 million years that complex life has inhabited Earth." [Wipe Out! History's 7 Most Mysterious Extinctions]

Scientists knew that a key factor behind this disaster may have been one of the biggest continental volcanic eruptions on record. It occurred in what is now Siberia, currently called the Siberian Traps, and spewed out as much as 2.7 million square miles (7 million square kilometers) of lava. This magmatism, or movement of magma, may have injected massive amounts of global warming gases into the atmosphere, wreaking havoc on the environment. These eruptions also led to acid rain that may at times have made the ground as acidic as lemon juice.

However, until now, scientists could not pinpoint when exactly the mass extinction and eruptions happened in relation to each other. To settle whether the mass extinction followed the eruptions, researchers investigated crystals within ancient volcanic rocks from 21 sites in Siberia.

"Getting to arctic Siberia isn't easy, and getting many hundreds of kilos of rock back through Russian and American customs is no picnic, either," Burgess told Live Science. "I consider getting all the samples back that we did a mixture of luck and preparedness."

The scientists found that the eruptions started about 300,000 years before the mass extinction, continued during the die-off and lasted for at least 500,000 years after species stopped dying off. Most of the lava, about two-thirds of the total, spewed out before and during the mass extinction.

"We are now able to resolve the relative timing of magmatism and mass extinction, and can finally say with confidence that magmatism precedes mass extinction, and by how much," Burgess said.

Key to these findings is nearly a decade's worth of advances in the dating of the age of ancient rocks by measuring their levels of uranium and lead, which enabled more accurate results, Burgess said. Also, more-sensitive electronics, cleaner labs and other factors led to more-precise results, helping to pinpoint the age of rocks. In addition, since all the dating took place in the same lab using identical procedures and analytical equipment, the researchers could eliminate up to 2.5 million years' worth of uncertainty in the results.

One important question remains, Burgess said: Why did the mass extinction occur over tens of thousands of years even though the eruptions stretched over hundreds of thousands of years? That could be due to at least a couple of reasons, he said. Perhaps a specific cluster of eruptions was key to the mass extinction, or the die-off only happened after a critical amount of lava was spewed, he said.

Burgess and his colleague Samuel Bowring, a professor of geology at the Massachusetts Institute of Technology, detailed their findings online today (Aug. 28) in the journal Science Advances.

http://www.livescience.com/52017-catastrophic-volcanoes-caused-biggest-extinction.html?cmpid=NL_LS_weekly_2015-08-28
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[Geology2] Lava flows from Hawaii's Kilauea Volcano



Lava flows from Hawaii's Kilauea Volcano

A fast-moving river of molten lava from erupting volcano Kilauea creeps over Hawaii's Big Island.

A thick stream of lava has erupted from a volcano on Hawaii's Big Island and had crept into the surrounding forest, the US. Geological Survey said, but it did not pose a threat to surrounding communities.

The lava flowed on Thursday (local time) from the east side of the Kilauea Volcano, one of the most active volcanoes in the world, and was still spreading, the US Geological Survey said.

A witness said lava had moved about 0.8 km in less than 24 hours, and was now headed toward the subdivision of Eden Roc, on the eastern side of the island, and home to about 450 people.

Lava from the volcano oozes around a fence at the Pahoa transfer station last November.
REUTERS

Lava from the volcano oozes around a fence at the Pahoa transfer station last November.

But scientists said the flow, one of several breakouts from the Eastern Rift Zone, was not expected to threaten populated areas. "None of the lava flows currently pose a threat to communities but are being monitored closely," the US Geological Survey said.

A magnitude 3.8 earthquake also occurred early on Thursday beneath the volcano's south flank, but "seismicity within the volcano remains at a low level," the federal agency said.

http://www.stuff.co.nz/world/americas/71562326/lava-flows-from-hawaiis-kilauea-volcano

​See the video at the above link or see a variety of them here:

​https://www.youtube.com/results?search_query=lava+flows+from+hawaii%27s+kilauea+volcano&lclk=today&filters=today

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[Geology2] Ash and smoke at Cotopaxi



28 August: The Cotopaxi volcano, one of the world's highest active volcanoes, spews ash and smoke as seen from Quito, Ecuador. Ecuadorian authorities are monitoring activity at Cotopaxi volcano, which prompted Ecuador's President Rafael Correa to declare a state of emergency and authorities to maintain a yellow alert for eruptions as bursts of ash keep spewing from the snow-encircled crater of the volcano and falling in gusts on residential communities. Reuters/Gary Granja

28 August: The Cotopaxi volcano, one of the world's highest active volcanoes, spews ash and smoke as seen from Quito, Ecuador. Ecuadorian authorities are monitoring activity at Cotopaxi volcano, which prompted Ecuador's President Rafael Correa to declare a state of emergency and authorities to maintain a yellow alert for eruptions as bursts of ash keep spewing from the snow-encircled crater of the volcano and falling in gusts on residential communities. Reuters/Gary Granja

http://www.firstpost.com/world/picofthelot-ash-and-smoke-at-cotopaxi-2406866.html
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[Geology2] What would a tsunami in the Mediterranean look like?



What would a tsunami in the Mediterranean look like?

Date:
August 27, 2015
Source:
European Geosciences Union (EGU)
Summary:
Researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal areas in southern Italy and Greece.

A team of European researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal areas in southern Italy and Greece. The study is published today (27 August) in Ocean Science, an open access journal of the European Geosciences Union (EGU).

Though not as frequent as in the Pacific and Indian oceans, tsunamis also occur in the Mediterranean, mainly due to earthquakes generated when the African plate slides underneath the Eurasian plate. About 10% of all tsunamis worldwide happen in the Mediterranean, with on average, one large tsunami happening in the region once a century. The risk to coastal areas is high because of the high population density in the area -- some 130 million people live along the sea's coastline. Moreover, tsunami waves in the Mediterranean need to travel only a very short distance before hitting the coast, reaching it with little advance warning. The new study shows the extent of flooding in selected areas along the coasts of southern Italy and Greece, if hit by large tsunamis in the region, and could help local authorities identify vulnerable areas.

"The main gap in relevant knowledge in tsunami modelling is what happens when tsunami waves approach the nearshore and run inland," says Achilleas Samaras, the lead author of the study and a researcher at the University of Bologna in Italy. The nearshore is the zone where waves transform -- becoming steeper and changing their propagation direction -- as they propagate over shallow water close to the shore. "We wanted to find out how coastal areas would be affected by tsunamis in a region that is not only the most active in the Mediterranean in terms of seismicity and tectonic movements, but has also experienced numerous tsunami events in the past."

The team developed a computer model to represent how tsunamis in the Mediterranean could form, propagate and hit the coast, using information about the seafloor depth, shoreline and topography. "We simulate tsunami generation by introducing earthquake-generated displacements at either the sea bed or the surface," explains Samaras. "The model then simulates how these disturbances -- the tsunami waves -- propagate and are transformed as they reach the nearshore and inundate coastal areas."

As detailed in the Ocean Science study, the team applied their model to tsunamis generated by earthquakes of approximately M7.0 magnitude off the coasts of eastern Sicily and southern Crete. Results show that, in both cases, the tsunamis would inundate the low-lying coastal areas up to approximately 5 metres above sea level. The effects would be more severe for Crete where some 3.5 square kilometres of land would be under water.

"Due to the complexity of the studied phenomena, one should not arbitrarily extend the validity of the presented results by assuming that a tsunami with a magnitude at generation five times larger, for example, would result in an inundation area five times larger," cautions Samaras. "It is reasonable, however, to consider such results as indicative of how different areas in each region would be affected by larger events."

"Although the simulated earthquake-induced tsunamis are not small, there has been a recorded history of significantly larger events, in terms of earthquake magnitude and mainshock areas, taking place in the region," says Samaras. For example, a clustering of earthquakes, the largest with magnitude between 8.0 and 8.5, hit off the coast of Crete in 365 AD. The resulting tsunami destroyed ancient cities in Greece, Italy and Egypt, killing some 5000 people in Alexandria alone. More recently, an earthquake of magnitude of about 7.0 hit the Messina region in Italy in 1908, causing a tsunami that killed thousands, with observed waves locally exceeding 10 metres in height.

The team sees the results as a starting point for a more detailed assessment of coastal flooding risk and mitigation along the coasts of the Eastern Mediterranean. "Our simulations could be used to help public authorities and policy makers create a comprehensive database of tsunami scenarios in the Mediterranean, identify vulnerable coastal regions for each scenario, and properly plan their defence."

Animation: http://www.egu.eu/medialibrary/image/1504/sicily-tsunami-animation/

Animation: http://www.egu.eu/medialibrary/image/1501/crete-tsunami-animation/

Story Source:

The above post is reprinted from materials provided by European Geosciences Union (EGU). Note: Materials may be edited for content and length.

Journal Reference:

  1. A. G. Samaras, Th. V. Karambas, R. Archetti. Simulation of tsunami generation, propagation and coastal inundation in the Eastern Mediterranean. Ocean Science, 2015; 11 (4): 643 DOI: 10.5194/os-11-643-2015

European Geosciences Union (EGU). "What would a tsunami in the Mediterranean look like?." ScienceDaily. ScienceDaily, 27 August 2015. <www.sciencedaily.com/releases/2015/08/150827083528.htm>.

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Thursday, August 27, 2015

[Geology2] Unforgettable Images Capture Volcano Rumbling to Life





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[Geology2] Could radon and one of its radioactive isotopes reliably predict an earthquake?



Could radon and one of its radioactive isotopes reliably predict an earthquake?

Aug 26, 2015

A combined analysis of the concentrations of radon and one of its radioactive isotopes called "thoron" may potentially allow for the prediction of impending earthquakes, without interference from other environmental processes, according to new work done by researchers from Korea. The team monitored the concentrations of both isotopes for about a year and observed unusually large peaks in the thoron concentration only in February 2011, preceding the Tohoku earthquake in Japan, while large radon peaks were observed in both February and the summer. Based on their analyses, the researchers suggest that the anomalous peaks observed in that month were precursory signals related to that earthquake that followed the following month.

Earthquake prediction remains the holy grail of geophysics, and an oft-proposed but highly contested method for quake forecasting revolves around the detection of abnormal quantities of certain gaseous tracers in soil and groundwater. These are believed to be released through pre-seismic stress and the micro-fracturing of rock in the period immediately before an earthquake.

Cloudy with a chance of tremors?

While a number of such precursors have been proposed – including radon, chloride and sulphate – their application to earthquake forecasting has not been realized. The problem here lies in how abnormal concentrations of these tracers can also occur through other environmental processes. For example, signals from radon (222Rn) – an easy-to-detect radioactive gas whose short half-life of 3.82 days makes it highly sensitive to short-term fluctuations – can be disrupted by meteorological phenomena and tidal forces. Radon has no stable isotopes, but has a host of radioactive isotopes including a very short-lived isotope called thoron (220Rn, half-life = 55.6 s).

In a new study, Guebuem Kim and Yong Hwa Oh of Seoul National University propose that an underground, dual-tracer analysis – using both radon and thoron – might be able to overcome these limitations. With its half-life of only 56 seconds, measured thoron activity in the stagnant air of a cave should typically be very low if the recording detector is placed sufficiently far (0.2 m) from the cave floor. "Thoron – through diffusive flows – decays away before it reaches the detector," explains Kim. "Thus, at an optimum position, only advective flows of thoron – earthquake precursors – reach the detector."

To test this concept, the researchers took hourly measurements of the radon and thoron concentration in the Seongryu Cave, in eastern Korea's Seonyu Mountain, over a period of 13 months. The cave – which formed around 250 million years ago – is around 330 m long and varies from 1 to 13 metres in height. Recordings were taken in a part of the cave that is isolated from the air flow from the outside, preventing any thoron anomalies that may arise from a wind-induced surface flow along the cave floor.

Unexpected peaks

An unusually large peak in thoron concentration – above those caused by seasonal variations or daily temperature fluctuations, and unexplainable by a precipitation event – was recorded in the February of 2011, preceding the magnitude 9.0 Tohoku earthquake in Japan, 1200 km away, a month later. In contrast, radon peaks were observed not only during February but also in the preceding summer period, when atmospheric stratification is believed to better trap radon within the cave system. While the thoron measurements alone are capable of recording earthquake signals, Kim says, the anomalous peaks detected were clearer when plotted in tandem with radon activity.

The single station used in the study would not be able to localise or assess the magnitude of an impending earthquake, but the team suggest this may be done using a large network of such detectors. Though the researchers undertook their measurements in a natural limestone cave system, the principle could also be applied to man-made caverns, the researchers report, with the method not being dependant on a particular lithology of rock.

Heiko Woith, a hydrogeologist at the Helmholtz-Zentrum Potsdam in Germany who was not involved in the Korean team's work, is sceptical about the new method. "The length of the time series is too short to judge the reliability of a precursor," he says, cautioning that a non-tectonic origin for the thoron anomaly still cannot be ruled out. "Certainly, the radon–thoron approach is interesting to follow in future studies, but it is premature and misleading to call it a new 'reliable earthquake precursor' at this stage," he concludes.

With this initial study complete, the researchers are now looking to further explore the potential of their radon–thoron technique by setting up a remote monitoring system within an artificial cave, powered by a solar panel on the surface. Ultimately, Kim suggests, these system might be deployed on a larger scale.

The research is described in Scientific Reports.

About the author

Ian Randall is a science writer based in New Zealand


http://physicsworld.com/cws/article/news/2015/aug/26/could-radon-and-one-of-its-radioactive-isotopes-reliably-predict-an-earthquake

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[Geology2] Mechanism behind 'strange' earthquakes discovered



Mechanism behind 'strange' earthquakes discovered

Currents of semi-liquid rock key to seismicity away from tectonic plate boundaries

Date:
August 26, 2015
Source:
University of Southern California
Summary:
Scientists have discovered the mechanism that generates earthquakes that occur away from tectonic plate boundaries.
St. Louis skyline in State of Missouri. Seismicity on the North American plate occurs as far afield as southern Missouri, where earthquakes between 1811 and 1812 estimated at around magnitude 7 caused the Mississippi River to flow backward for hours.
Credit: © digidreamgrafix / Fotolia

It's not a huge mystery why Los Angeles experiences earthquakes. The city sits near a boundary between two tectonic plates -- they shift, we shake. But what about places that aren't along tectonic plate boundaries?

For example, seismicity on the North American plate occurs as far afield as southern Missouri, where earthquakes between 1811 and 1812 estimated at around magnitude 7 caused the Mississippi River to flow backward for hours.

Until now, the cause of that seismicity has remained unclear.

While earthquakes along tectonic plate boundaries are caused by motion between the plates, earthquakes away from fault lines are primarily driven by motion beneath the plates, according to a new study published by USC scientist Thorsten Becker in Nature on Aug. 27.

Just beneath the Earth's crust is a layer of hot, semi-liquid rock that is continually flowing -- heating up and rising, then cooling and sinking. That convective process, interacting with the ever-changing motion of the plates at the surface, is driving intraplate seismicity and determining in large part where those earthquakes occur. To a lesser extent, the structure of the crust above also influences the location, according to their models.

"This will not be the last word on the origin of strange earthquakes. However, our work shows how imaging advances in seismology can be combined with mantle flow modeling to probe the links between seismicity and mantle convection," said Becker, lead author of the study and professor of Earth sciences at the USC Dornsife College of Letters, Arts and Sciences.

Becker and his team used an updated mantle flow model to study the motion beneath the mountain belt that cuts north to south through the interior of the Western United States.

The area is seismically active -- the reason Yellowstone has geysers is that it sits atop a volcanic hotspot. Previously, scientists had suggested that the varying density of the plates was the main cause. (Imagine a mountain's own weight causing it to want to flow apart and thin out.)

Instead, the team found that the small-scale convective currents beneath the plate correlated with seismic events above in a predictable way. They also tried using the varying plate density or "gravitational potential energy variations" to predict seismic events and found a much poorer correlation.

"This study shows a direct link between deep convection and shallow earthquakes that we didn't anticipate, and it charts a course for improved seismic hazard mapping in plate interiors," said Tony Lowry, co-author of the paper and associate professor of geophysics and geodynamics at Utah State University.

Story Source:

The above post is reprinted from materials provided by University of Southern California. The original item was written by Robert Perkins. Note: Materials may be edited for content and length.

Journal Reference:

  1. Thorsten W. Becker, Anthony R. Lowry, Claudio Faccenna, Brandon Schmandt, Adrian Borsa, Chunquan Yu. Western US intermountain seismicity caused by changes in upper mantle flow. Nature, 2015; 524 (7566): 458 DOI: 10.1038/nature14867

University of Southern California. "Mechanism behind 'strange' earthquakes discovered: Currents of semi-liquid rock key to seismicity away from tectonic plate boundaries." ScienceDaily. ScienceDaily, 26 August 2015. <www.sciencedaily.com/releases/2015/08/150826135726.htm>.

NOTE: If anyone has this paper, could you share? Thanks... Lin

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