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Posts tagged ‘Nature Geoscience’

Extreme Global Warming Seen Further Away than Previously Thought.


Extreme global warming is less likely in coming decades after a slowdown in the pace of temperature rises so far this century, an international team of scientists said on Sunday.

Warming is still on track, however, to breach a goal set by governments around the world of limiting the increase in temperatures to below 2 degrees Celsius (3.6 Fahrenheit) above pre-industrial times, unless tough action is taken to limit rising greenhouse gas emissions.

“The most extreme rates of warming simulated by the current generation of climate models over 50- to 100-year timescales are looking less likely,” the University of Oxford wrote about the findings in the journal Nature Geoscience.

The rate of global warming has slowed after strong rises in the 1980s and 1990s, even though all the 10 warmest years since reliable records began in the 1850s have been since 1998.

The slowdown has been a puzzle because emissions of heat-trapping greenhouse gases have continued to rise, led by strong industrial growth in China.

Examining recent temperatures, the experts said that a doubling of carbon dioxide concentrations in the atmosphere above pre-industrial times – possible by mid-century on current trends – would push up temperatures by between 0.9 and 2.0 degrees Celsius (1.6 and 3.6F).

That is below estimates made by the U.N. panel of climate scientists in 2007, of a rise of between 1 and 3 degrees Celsius (1.8-5.4F) as the immediate response to a doubling of carbon concentrations, known as the transient climate response.

OCEANS

The U.N. panel also estimated that a doubling of carbon dioxide, after accounting for melting of ice and absorption by the oceans that it would cause over hundreds of years, would eventually lead to a temperature rise of between 2 and 4.5 C (3.6-8.1F).

Findings in the new study, by experts in Britain, the United States, Canada, Australia, France, Germany, Switzerland and Norway, broadly matched that range for the long-term response.

But for government policy makers “the transient response over the next 50-100 years is what matters,” lead author Alexander Otto of Oxford University said in a statement.

The oceans appear to be taking up more heat in recent years, masking a build-up of carbon dioxide in the atmosphere that passed 400 parts per million this month for the first time in human history, up 40 percent from pre-industrial levels.

Professor Reto Knutti of ETH Zurich, one of the authors, said that the lower numbers for coming decades were welcome.

But “we are still looking at warming well over the two degree goal that countries have agreed upon if current emission trends continue,” he said.

Temperatures have already risen by about 0.8 Celsius (1.4F) since the Industrial Revolution and two degrees C is widely viewed as a threshold to dangerous changes such as more floods, heatwaves and rising sea levels.

“The oceans are sequestering heat more rapidly than expected over the last decade,” said Professor Steven Sherwood of the University of New South Wales in Australia, who was not involved in the study.

“By assuming that this behaviour will continue, (the scientists) calculate that the climate will warm about 20 percent more slowly than previously expected, although over the long term it may be just as bad, since eventually the ocean will stop taking up heat.”

He said findings “need to be taken with a large grain of salt” because of uncertainties about the oceans.

© 2013 Thomson/Reuters. All rights reserved.
Source: NEWSmax.com

Striking gold: Earthquakes deposit precious metal.


Solid gold can be deposited in Earth’s crust “almost instantaneously” during earthquakes, said a study published in the journal Nature Geoscience on Sunday.

The gold is formed when a tremor splits open a fluid-filled cavity in the Earth’s crust, causing a sudden drop in pressure, according to a team of Australian researchers.

This, in turn, causes the fluid to expand rapidly and evaporate, and any gold particles that had been dissolved in it to “precipitate almost immediately”, said a Nature press release.

“Repeated earthquakes could therefore lead to the build up of economic-grade gold deposits.”

The researchers said much of the world’s known gold was derived from quarts veins that were formed during geological periods of mountain building as long as three billion years ago.

The veins formed during earthquakes, but the magnitude of pressure fluctuations or how they drove gold mineralisation were not known.

For this study, researchers used a numerical model to simulate the drop in pressure experienced in a fluid-filled fault cavity during an earthquake.

In so doing, they answered a long-standing question about the world’s gold resources — how the metal becomes so concentrated from a highly dissolved state to a solid, mineable one.

The study said single tremors would not generate economically viable gold deposits, which were built up one thin coating at a time.

To form a 100 tonne gold vein deposit would take less than 100,000 years, the team wrote.

Source: YAHOO NEWS.

AFPBy AFP | AFP

Ancient ‘Micro-Continent’ Found Under Indian Ocean.


 

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The remains of a micro-continent scientist call Mauritia might be preserved under huge amounts of ancient lava beneath the Indian Ocean, a new analysis of island sands in the area suggests.

These findings hint that such micro-continents may have occurred more frequently than previously thought, the scientists who conducted the study, detailed online Feb. 24 in the journal Nature Geoscience, say.

Researchers analyzed sands from the isle of Mauritius in the western Indian Ocean. Mauritius is part of a volcanic chain that, strangely, exists far from the edges of its tectonic plate. In contrast, most volcanoes are found at the borders of the tectonic plates that make up the surface of the Earth.

Investigators suggest that volcanic chains in the middle of tectonic plates, such as the Hawaiian Islands, are caused by giant pillars of hot molten rock known as mantle plumes. Theserise up from near the Earth’s core, penetrating overlying material like a blowtorch. [What Is Earth Made Of?]

Mantle plumes can apparently trigger continental breakups, softening the tectonic plates from below until they fragment — this is how the lost continent of Eastern Gondwana ended about 170 million years ago, prior research suggests. A plume currently sits near Mauritius and other islands, and the researchers wanted to see if they could find ancient fragments of continents from just such a breakup there.

Digging in the sand

The beach sands of Mauritius are the eroded remnants of volcanic rocks created by eruptions 9 million years ago. Collecting them”was actually quite pleasant,” said researcher Ebbe Hartz, a geologistat the University of Oslo in Norway. He described walking out from a tropical beach, “maybe with a Coke and an icebox, and you dig down underwater into sand dunes at low tide.”

Within these sands, investigators discovered about 20 ancient zircon grains (a type of mineral) between 660 million and 1,970 million years old. To learn more about the source of this ancient zircon, the scientists investigated satellite maps of Earth’s gravity field. The strength of the field depends on Earth’s mass, and since the planet’s mass is not spread evenly, its gravity field is stronger in some places on the planet’s surface and weaker in others.

[Slideshow: Ancient pyramids found in Sudan]

The researchers discovered Mauritius is part of a contiguous block of abnormally thick crust that extends in an arc northward to the Seychelles islands. The finding suggests Mauritius and the adjacent region overlie an ancient micro-continent they call Mauritia. The ancient zircons they unearthed are shards of lost Mauritia.

The researchers meticulously sought to rule out any chance these ancient grains were contaminants from elsewhere.

“Zircons are heavy minerals, and the uranium and lead elements used to date the ages of these zircons are extraordinarily heavy, so these grains do not easily fly around — they did not blow into Mauritius from a sandstorm in Africa,” Hartz told OurAmazingPlanet.

“We also chose a beach where there was no construction whatsoever — that these grains did not come from cement somewhere else,” Hartz added. “We were also careful that all the equipment we used to collect the minerals was new, that this was the first time it was used, that there was no previous rock sticking to it from elsewhere.”

Peeling continent pieces

After analyzing marine fracture zones and ocean magnetic anomalies, the investigators suggest Mauritia separated from Madagascar, fragmented and dispersed as the Indian Ocean basin grew between 61 million and 83.5 million years ago. Since then, volcanic activity has buried Mauritia under lava, and may have done the same to other continental fragments.

“There are all these little slivers of continent that may peel off continents when the hotspot of a mantle plume passes under them,” Hartz said. “Why that happens is still mind-boggling. Why, after something gets ripped apart, would it rip apart again?”

Finding past evidence of lost continents normally involves tediously crushing and sorting volcanic rocks, Hartz explained. The researchers essentially let nature do the work of pulverization for them by looking at sand.

“We suggest lots of scientists try this technique on their favorite volcanoes,” Hartz said.

Source: YAHOO NEWS.

By Charles Q. Choi, OurAmazingPlanet Contributor | LiveScience.com

Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter@OAPlanet. We’re also on Facebook & Google+.

Copyright 2013 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Water on Mars May Not Mean Life, but May Mean Trouble.


It has been an axiom that where there is water, particularly on Mars, there may well be life. Microbial life has been found to have survived in even the most extreme environments, according to JPL, as long as water is present.

Thus the hope persists that if scientists can find liquid water on Mars, life might be present. However a couple of stories suggests that not only that may not be the case, but if, say, the Curiosity rover were to find water on Mars, it could be more trouble than not.

Why water may mean life on other worlds

NASA’s Jet Propulsion Laboratory explains that since the 1980s, scientists have noted that life can exist in some of the most extreme environments on Earth, in areas of extreme heat, extreme cold, or extreme pressure that are inhospitable to humans or complex animals. From this insight, it has been extrapolated that extraterrestrial life might exist in tiny niches, say in sub surface bodies of water. Thus the search for life on Mars has actually been the search for water, which may have mixed with minerals crucial for the formation of life billions of years ago.

Water may not mean life on Mars

A new theory, reported in the Los Angeles Times, suggests that water may not mean life on Mars after all. According to a new paper published in the journal Nature Geoscience, clay deposits on Mars, which have been cited as evidence that Mars at one time had liquid surface water, may have been formed by volcanic magma that was rich in water. Such magma would have been too hot for any kind of life, even microbial, to have survived. This goes against the two prevailing theories that the clays were formed by relatively cool water, either on the surface or underground, warmed by Mars’s internal heat. On the other hand, all three theories may hold true, depending on what part of Mars one is looking at.

Water on Mars may mean trouble for explorers

On the other hand, also according to the Los Angeles Times, if Mars Curiosity discovers liquid water, it may be obliged to steer clear of it. That is because of the suspicion that the rover’s drill bits have been contaminated with Earth bacterial. If Earth bacteria were to be transferred to Martian bodies of water and were to take hold, whatever ecosystem Mars might have would be contaminated. The problem, at least from the point of view of astrobiologists, becomes particularly acute when one considers human explorers or settlers on Mars. An argument between those who want to explore and settle Mars and those who want to maintain the planet as pristine, even on the microbial level, may be a feature of politics later this century.

 Source: YAHOO NEWS.

By  | Yahoo! Contributor Network

Mark R. Whittington is the author of Children of Apollo and The Last Moonwalker. He has written on space subjects for a variety of periodicals, including The Houston Chronicle, The Washington Post, USA Today, the L.A. Times, and The Weekly Standard.

Magma Pooling Beneath Infamous Greek Volcano.


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Molten rock is pooling beneath Greece’s Santorini volcano, the site of one of the largest eruptions in the past 10,000 years. That eruption, which took place about 3,600 years ago, wiped out the Minoan civilization of the Greek islands and may have spawned the legend of the lost city of Atlantis.

In the past 1.5 years, the magma chamber beneath the volcanic island has ballooned by as much as 350 million cubic feet (20 million cubic meters), or up to 15 times the size of London’s Olympic Stadium. This giant mass of magma has caused the island to rise by as much as 5.5 inches (14 centimeters), according to a new study published yesterday (Sept. 9) in the journal Nature Geoscience.

This research follows reports earlier in the year of renewed earthquake activity beneath the volcanoafter it had been silent for the past 25 years. The reports have spurred concerns the volcano could erupt in the near future, but when that might happen is still unclear, researchers said in a statement.

“Before this work, we didn’t really know how the volcano behaved during the periods of time between eruptions,” David Pyle, an Oxford University researcher and study co-author, told OurAmazingPlanet. “Now, it looks as though the magma chambers beneath volcanoes like Santorini grow in spurts.”

When the volcano erupted in approximately 1620 B.C., it created tsunamis 40 feet (12 meters) tallthat destroyed much of the civilization flourishing in and around the Aegean Sea. Much of the previous island of Santorini was destroyed or submerged.From the air, the resulting caldera, or volcanic crater, appears as a small cluster within the bigger collection of Greek islands in the Aegean Sea.

Earlier this year, global positioning system (GPS) sensors placed on the caldera detected renewed movement, measuring a series of small earthquakes. Seismic activity can trigger eruptions and are often a clue that a volcano may be preparing an outburst in the near future. But the connection is far from well-understood; and in the past few months, seismic activity has dropped off once again, according to the statement.

If the volcano did erupt, it wouldn’t be likely to create nearly as much havoc is it did in the time of the Minoans, since it is much smaller today than it was in the past. But it’s still important to keep an eye on the volcano, the researchers warn.  [History’s 10 Biggest Eruptions]

“Although Santorini is well known for its large explosive eruptions, these probably only happen every 20,000 years or so,” Pyle said.

There has been much speculation as to whether the Santorini eruption inspired the legend of Atlantis, which Plato said drowned in the ocean. Although someexperts think the legend of Atlantis was just invented, others say the explosion might have given rise to the tale of a lost empire by helping to wipe out the real-life Minoan civilization that once thrived in the Mediterranean.

Source: YAHOO NEWS.

By Douglas Main, OurAmazingPlanet Staff Writer | LiveScience.com

Reach Douglas Main at dmain@techmedianetwork.com. Follow him on Twitter @Douglas_Main. Follow OurAmazingPlanet on Twitter @OAPlanet. We’re also on Facebook and Google+.

Copyright 2012 OurAmazingPlanet, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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