Category: Nature Geoscience

Largest volcano on Earth discovered lurking beneath Pacific Ocean and named after Texas A&M University

On By A.P.In Mauna Loa, Nature Geoscience, Olympus Mons, Pacific Ocean, Tamu Massif, University of Houston, Volcano, William SagerLeave a comment

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The world’s largest volcano lurks beneath the Pacific Ocean, researchers announced Thursday in the journal Nature Geoscience.

Called the Tamu Massif, the enormous mound dwarfs the previous record holder, Hawaii’s Mauna Loa, and is only 25 percent smaller than Olympus Mons on Mars, the biggest volcano in Earth’s solar system, said William Sager, lead study author and a geologist at the University of Houston.

“We think this is a class of volcano that hasn’t been recognized before,” Sager said. “The slopes are very shallow. If you were standing on this thing, you would have a difficult time telling which way was downhill.”

Tamu is 400 miles (650 kilometers) wide but only about 2.5 miles (4 km) tall. It erupted for a few million years during the early Cretaceous period, about 144 million years ago, and has been extinct since then, the researchers report.

Like other massive volcanoes, Tamu Massif seems to have a central cone that spewed lava down its broad, gentle slopes. The evidence comes from seismic surveys and lava samples painstakingly collected over several years of surveys by research ships. The seismic waves show lava flows dipping away from the summit of the volcano. There appears to be a series of calderas at the summit, similar in shape to the elongated and merged craters atop Mauna Loa, Sager said.

Until now, geologists thought Tamu Massif was simply part of an oceanic plateau called Shatsky Rise in the northwest Pacific Ocean. Oceanic plateaus are massive piles of lava whose origins are still a matter of active scientific debate. Some researchers think plumes of magma from deep in the mantle punch through the crust, flooding the surface with lava. Others suggest pre-existing weaknesses in the crust, such as tectonic-plate boundaries, provide passageways for magma from the mantle, the layer beneath the crust. Shatsky Rise formed atop a triple junction, where three plates pulled apart.

Tamu Massif’s new status as a single volcano could help constrain models of how oceanic plateaus form, Sager said. “For anyone who wants to explain oceanic plateaus, we have new constraints,” he told LiveScience. “They have to be able to explain this volcano forming in one spot and deliver this kind of magma supply in a short time.”

Geochemist David Peate of the University of Iowa, who was not involved in the study, said he looks forward to new models explaining the pulses of magma that built Shatsky Rise. Tamu Massif is the biggest and oldest volcano, and the cones grow smaller and younger to the northeast of Tamu. Sager and his colleagues suggest that pulses of magma created the volcanic trail.

“It seems that in many oceanic plateaus the melting is continuous, but here you have a big shield volcano,” Peate told LiveScience. “Understanding the source of the volume of that magma, the rate of production of the magma and the time interval between those pulses will help give better constraints to feed into those models,” he said.

Sager said other, bigger volcanoes could be awaiting discovery at other oceanic plateaus, such as Ontong Java Plateau, located north of the Solomon Islands in the southwest Pacific Ocean. “Structures that are under the ocean are really hard to study,” he said.

Oceanic plateaus are the biggest piles of lava on Earth. The outpourings have been linked to mass extinctions and climate change. The volume of Tamu Massif alone is about 600,000 cubic miles (2.5 million cubic km). The entire volcano is bigger than the British Isles or New Mexico.

Despite Tamu’s huge size, the ship surveys showed little evidence the volcano’s top ever poked above the sea. The world’s biggest volcano has been hidden because it sits on thin oceanic crust (or lithosphere), which can’t support its weight. Its top is about 6,500 feet (1,980 meters) below the ocean surface today.

“In the case of Shatsky Rise, it formed on virtually zero thickness lithosphere, so it’s in isostatic balance,” Sager said. “It’s basically floating all the time, so the bulk of Tamu Massif is down in the mantle. The Hawaiian volcanoes erupted onto thick lithosphere, so it’s like they have a raft to hold on to. They get up on top and push it down. And with Olympus Mons, it’s like it formed on a two-by-four.”

Sager and his colleagues have studied Shatsky Rise for decades, seeking to solve the puzzle of oceanic plateaus. About 20 years ago, they named Tamu Massif after Texas A&M University, Sager’s former employer, he said.

http://www.nbcnews.com/science/its-largest-volcano-earth-it-lurks-beneath-pacific-ocean-8C11085698

Thriving bacteria discovered at the deepest point in the ocean

On By A.P.In Aarhus University, Bacteria, Bacteria, Challenger Deep, Denmark, extreme environment, Hans Røy, James Cameron, Mariana Trench, Nature, Nature Geoscience, Odense, Pacific Ocean, Ronnie Glud, Science, University of Southern DenmarkLeave a comment

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Hollywood director James Cameron found little evidence of life when he descended nearly 11,000 metres to the deepest point in the world’s oceans last year. If only he had taken a microscope and looked just a few centimetres deeper.

Ronnie Glud at the University of Southern Denmark in Odense, and his colleagues, have discovered unusually high levels of microbial activity in the sediments at the site of Cameron’s dive – Challenger Deep at the bottom of the western Pacific’s Mariana Trench.

Glud’s team dispatched autonomous sensors and sample collectors into the trench to measure microbial activity in the top 20 centimetres of sediment on the sea bed. The pressure there is almost 1100 times greater than at the surface. Finding food, however, is an even greater challenge than surviving high pressures for anything calling the trench home.

Any nourishment must come in the form of detritus falling from the surface ocean, most of which is consumed by other organisms on the way down. Only 1 per cent of the organic matter generated at the surface reaches the sea floor’s abyssal plains, 3000 to 6000 metres below sea level. So what are the chances of organic matter making it even deeper, into the trenches that form when one tectonic plate ploughs beneath another?

Surprisingly, the odds seem high. Glud’s team compared sediment samples taken from Challenger Deep and a reference site on the nearby abyssal plain. The bacteria at Challenger Deep were around 10 times as abundant as those on the abyssal plain, with every cubic centimetre of sediment containing 10 million microbes. The deep microbes were also twice as active as their shallower kin.

These figures make sense, says Glud, because ocean trenches are particularly good at capturing sediment. They are broad as well as deep, with a steep slope down to the deepest point, so any sediment falling on their flanks quickly cascades down to the bottom in muddy avalanches. Although the sediment may contain no more than 1 per cent organic matter, so much of it ends up at Challenger Deep that the level of microbial activity shoots up.

“There is much more than meets the eye at the bottom of the sea,” says Hans Røy, at Aarhus University in Denmark. Last year, he studied seafloor sediments below the north Pacific gyre – an area that, unlike Challenger Deep, is almost devoid of nutrients. Remarkably, though, even here Røy found living microbes.

“With the exception of temperatures much above boiling, bacteria seem to cope with everything this planet can throw at them,” he says.

Journal reference: Nature Geoscience, DOI: 10.1038/ngeo1773

http://www.newscientist.com/article/dn23277-deepest-point-in-the-ocean-is-teeming-with-life.html?cmpid=RSS|NSNS|2012-GLOBAL|online-news

Water in faults vaporizes during an earthquake, depositing gold

On By A.P.In Alpine Fault, Australia, Australian National University, Canberra, Dion Weatherley, Earthquake, flash vaporization, gold, Imperial College London, Jamie Wilkinson, Nature Geoscience, New Zealand, OurAmazingPlanet, quartz, Queensland, Richard Henley, Science, United Kingdom, University of QueenslandLeave a comment

gold-ed
The tyrannosaur of the minerals, this gold nugget in quartz weighs more than 70 ounces (2 kilograms).

Earthquakes have the Midas touch, a new study claims.

Water in faults vaporizes during an earthquake, depositing gold, according to a model published in the March 17 issue of the journal Nature Geoscience. The model provides a quantitative mechanism for the link between gold and quartz seen in many of the world’s gold deposits, said Dion Weatherley, a geophysicist at the University of Queensland in Australia and lead author of the study.

When an earthquake strikes, it moves along a rupture in the ground — a fracture called a fault. Big faults can have many small fractures along their length, connected by jogs that appear as rectangular voids. Water often lubricates faults, filling in fractures and jogs.

About 6 miles (10 kilometers) below the surface, under incredible temperatures and pressures, the water carries high concentrations of carbon dioxide, silica and economically attractive elements like gold.

During an earthquake, the fault jog suddenly opens wider. It’s like pulling the lid off a pressure cooker: The water inside the void instantly vaporizes, flashing to steam and forcing silica, which forms the mineral quartz, and gold out of the fluids and onto nearby surfaces, suggest Weatherley and co-author Richard Henley, of the Australian National University in Canberra.

While scientists have long suspected that sudden pressure drops could account for the link between giant gold deposits and ancient faults, the study takes this idea to the extreme, said Jamie Wilkinson, a geochemist at Imperial College London in the United Kingdom, who was not involved in the study.

“To me, it seems pretty plausible. It’s something that people would probably want to model either experimentally or numerically in a bit more detail to see if it would actually work,” Wilkinson told OurAmazingPlanet.

Previously, scientists suspected fluids would effervesce, bubbling like an opened soda bottle, during earthquakes or other pressure changes. This would line underground pockets with gold. Others suggested minerals would simply accumulate slowly over time.

Weatherley said the amount of gold left behind after an earthquake is tiny, because underground fluids carry at most only one part per million of the precious element. But an earthquake zone like New Zealand’s Alpine Fault, one of the world’s fastest, could build a mineable deposit in 100,000 years, he said.

Surprisingly, the quartz doesn’t even have time to crystallize, the study indicates. Instead, the mineral comes out of the fluid in the form of nanoparticles, perhaps even making a gel-like substance on the fracture walls. The quartz nanoparticles then crystallize over time.

Even earthquakes smaller than magnitude 4.0, which may rattle nerves but rarely cause damage, can trigger flash vaporization, the study finds.

“Given that small-magnitude earthquakes are exceptionally frequent in fault systems, this process may be the primary driver for the formation of economic gold deposits,” Weatherley told OurAmazingPlanet.

Quartz-linked gold has sourced some famous deposits, such as the placer gold that sparked the 19th-century California and Klondike gold rushes. Both deposits had eroded from quartz veins upstream. Placer gold consists of particles, flakes and nuggets mixed in with sand and gravel in stream and river beds. Prospectors traced the gravels back to their sources, where hard-rock mining continues today.

But earthquakes aren’t the only cataclysmic source of gold. Volcanoes and their underground plumbing are just as prolific, if not more so, at producing the precious metal. While Weatherley and Henley suggest that a similar process could take place under volcanoes, Wilkinson, who studies volcano-linked gold, said that’s not the case.

“Beneath volcanoes, most of the gold is not precipitated in faults that are active during earthquakes,” Wilkinson said. “It’s a very different mechanism.”

Understanding how gold forms helps companies prospect for new mines. “This new knowledge on gold-deposit formation mechanisms may assist future gold exploration efforts,” Weatherley said.

In their quest for gold, humans have pulled more than 188,000 tons (171,000 metric tons) of the metal from the ground, exhausting easily accessed sources, according to the World Gold Council, an industry group.

http://www.livescience.com/27953-earthquakes-make-gold.html

Ancient Lost Continent Discovered in Indian Ocean

On By A.P.In Bjørn Jamtveit, Conall Mac Niocaill, France, Geology, Jérôme Dyment, lost continent, Madagascar, Mauritia, Mauritius, microcontinent, Nature, Nature Geoscience, Norway, Oslo, Paris Institute of Earth Physics, RHUM-RUM, Rodinia, Science, United Kingdom, University of Oslo, University of Oxford, zirconLeave a comment

new-micro-continent-found-near-mauritius_64654_600x450

Evidence of a drowned “microcontinent” has been found in sand grains from the beaches of a small Indian Ocean island, scientists say.

A well-known tourist destination, Mauritius (map) is located about 1,200 miles (2,000 kilometers) off the coast of Africa, east of Madagascar. Scientists think the tiny island formed some nine million years ago from cooling lava spewed by undersea volcanoes.

But recently, researchers have found sand grains on Mauritius that contain fragments of the mineral zircon that are far older than the island, between 660 million and about 2 billion years old.

In a new study, detailed in the current issue of the journal Nature Geoscience, scientists concluded that the older minerals once belonged to a now vanished landmass, tiny bits of which were dragged up to the surface during the formation of Mauritius.

“When lavas moved through continental material on the way towards the surface, they picked up a few rocks containing zircon,” study co-author Bjørn Jamtveit, a geologist at the University of Oslo in Norway, explained in an email.

Most of these rocks probably disintegrated and melted due to the high temperatures of the lavas, but some grains of zircons survived and were frozen into the lavas [during the eruption] and rolled down to form rocks on the Mauritian surface.”

Jamtveit and his colleagues estimate that the lost microcontinent, which they have dubbed Mauritia, was about a quarter of the size of Madagascar.

Furthermore, based on a recalculation of how the ancient continents drifted apart, the scientists concluded that Mauritia was once a tiny part of a much larger “supercontinent” that included India and Madagascar, called Rodinia.

The three landmasses “were tucked together in one big continent prior to the formation of the Indian Ocean,” Jamtveit said.

But like a prehistoric Atlantis, Mauritia was eventually drowned beneath the waves when India broke apart from Madagascar about 85 million years ago.

Scientists have long suspected that volcanic islands might contain evidence of lost continents, and Jamtveit and his team decided to test this hypothesis during a layover in Mauritius as part of a longer research trip in 1999.
The stop in tropical Mauritius “was a very tempting thing to do for a Norwegian in the cold month of January,” Jamtveit said.

Mauritius was a good test site because it was a relatively young island and, being formed from ocean lava, would not naturally contain zircon, a tough mineral that doesn’t weather easily.

If zircon older than nine million years was found on Mauritius, it would be good evidence of the presence of buried continental material, Jamtveit explained.

At first, the scientists crushed rocks from Mauritius to extract the zircon crystals, but this proved difficult because the crushing equipment contained zircon from other sites, raising the issue of contamination.

“That was a show stopper for a while,” Jamtveit said.

A few years later, however, some members of the team returned to Mauritius and this time brought back sand from two different beaches for sampling.

The scientists extracted 20 zircon samples and successfully dated 8 of them by calculating the rate that the elements uranium and thorium inside of the samples slowly break down into lead.

“They all provided much older ages than the age of the Mauritius lavas,” Jamtveit said. “In fact they gave ages consistent with the ages of known continental rocks in Madagascar, Seychelles, and India.”

Jérôme Dyment, a geologist at the Paris Institute of Earth Physics in France, said he’s unconvinced by the work because it’s possible that the ancient zircons found their way to the island by other means, for example as part of ship ballast or modern construction material.

“Extraordinary claims require extraordinary evidence, which are not given by the authors so far,” said Dyment, who did not participate in the research.

“Finding zircons in sand is one thing, finding them within a rock is another one … Finding the enclave of deep rocks that, according to the author’s inference, bring them to the surface during an eruption would be much more convincing evidence.”

Dyment added that if Mauritia was real, evidence for its existence should be found as part of a joint French and German experiment that installed deep-sea seismometers to investigate Earth’s mantle around Réunion Island, which is situated about 120 miles (200 kilometers) from Mauritius.

“If a microcontinent lies under Réunion, it should be depicted by this experiment,” said Dyment, who is part of the project, dubbed RHUM-RUM.

But Conall Mac Niocaill, a geologist at the University of Oxford in the U.K. who was also not involved in the study, said “the lines of evidence are, individually, only suggestive, but collectively they add up to a compelling story.”
The zircons “produce a range of ages, but all yield ages older than 660 million years, and one is almost 2 billion years old,” he added.

“There is no obvious source for them in Mauritius, and they are unlikely to have been blown in by the wind, or carried in by human activity, so the obvious conclusion is that the young volcanic lava sampled some older material on their way through the crust.”

Based on the new findings, Mac Niocaill and others think other vanished microcontinents could be lurking beneath the Indian Ocean.

In fact, analyses of Earth’s gravitational field have revealed other areas in the world’s oceans where the rock appears to be thicker than normal and could be a sign of continental crusts.

“We know more about the topography of Mars than we do about the [topography] of the world’s ocean floor, so there may well be other dismembered continents out there waiting to be discovered.”

http://news.nationalgeographic.com/news/2013/02/130225-microcontinent-earth-mauritius-geology-science/

Evidence of water on the moon discovered in samples obtained from original Apollo missions

On By A.P.In Anne Peslier, Apollo 11, Apollo missions, Department of Earth and Environmental Sciences, Genesis Rock, Hejiu Hui, LCROSS, Lunar Crater Observation and Sensing satellite, lunar formation theory, lunar highlands, Moon, NASA, Nature Geoscience, Space and Time, The Moon, University of Michigan, water, Youxue ZhangLeave a comment

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Called the “Genesis Rock,” this lunar sample of unbrecciated anorthosite collected during the Apollo 15 mission was thought to be a piece of the moon’s primordial crust. In a paper published online Feb. 17 in Nature Geoscience, a University of Michigan researcher and his colleagues report that traces of water were found in the rock. (Credit: Photo courtesy of NASA/Johnson Space Center)

Traces of water have been detected within the crystalline structure of mineral samples from the lunar highland upper crust obtained during the Apollo missions, according to a University of Michigan researcher and his colleagues.

The lunar highlands are thought to represent the original crust, crystallized from a magma ocean on a mostly molten early moon. The new findings indicate that the early moon was wet and that water there was not substantially lost during the moon’s formation.

The results seem to contradict the predominant lunar formation theory — that the moon was formed from debris generated during a giant impact between Earth and another planetary body, approximately the size of Mars, according to U-M’s Youxue Zhang and his colleagues.

“Because these are some of the oldest rocks from the moon, the water is inferred to have been in the moon when it formed,” Zhang said. “That is somewhat difficult to explain with the current popular moon-formation model, in which the moon formed by collecting the hot ejecta as the result of a super-giant impact of a martian-size body with the proto-Earth.

“Under that model, the hot ejecta should have been degassed almost completely, eliminating all water.”

A paper titled “Water in lunar anorthosites and evidence for a wet early moon” was published online Feb. 17 in the journal Nature Geoscience. The first author is Hejiu Hui, postdoctoral research associate of civil and environmental engineering and earth sciences at the University of Notre Dame. Hui received a doctorate at U-M under Zhang, a professor in the Department of Earth and Environmental Sciences and one of three co-authors of the Nature Geoscience paper.

Over the last five years, spacecraft observations and new lab measurements of Apollo lunar samples have overturned the long-held belief that the moon is bone-dry.

In 2008, laboratory measurement of Apollo lunar samples by ion microprobe detected indigenous hydrogen, inferred to be the water-related chemical species hydroxyl, in lunar volcanic glasses. In 2009, NASA’s Lunar Crater Observation and Sensing satellite, known as LCROSS, slammed into a permanently shadowed lunar crater and ejected a plume of material that was surprisingly rich in water ice.

Hydroxyls have also been detected in other volcanic rocks and in the lunar regolith, the layer of fine powder and rock fragments that coats the lunar surface. Hydroxyls, which consist of one atom of hydrogen and one of oxygen, were also detected in the lunar anorthosite study reported in Nature Geoscience.

In the latest work, Fourier-transform infrared spectroscopy was used to analyze the water content in grains of plagioclase feldspar from lunar anorthosites, highland rocks composed of more than 90 percent plagioclase. The bright-colored highlands rocks are thought to have formed early in the moon’s history when plagioclase crystallized from a magma ocean and floated to the surface.

The infrared spectroscopy work, which was conducted at Zhang’s U-M lab and co-author Anne Peslier’s lab, detected about 6 parts per million of water in the lunar anorthosites.

“The surprise discovery of this work is that in lunar rocks, even in nominally water-free minerals such as plagioclase feldspar, the water content can be detected,” said Zhang, the James R. O’Neil Collegiate Professor of Geological Sciences.

“It’s not ‘liquid’ water that was measured during these studies but hydroxyl groups distributed within the mineral grain,” said Notre Dame’s Hui. “We are able to detect those hydroxyl groups in the crystalline structure of the Apollo samples.”

The hydroxyl groups the team detected are evidence that the lunar interior contained significant water during the moon’s early molten state, before the crust solidified, and may have played a key role in the development of lunar basalts.

“The presence of water,” said Hui, “could imply a more prolonged solidification of the lunar magma ocean than the once-popular anhydrous moon scenario suggests.”

The researchers analyzed grains from ferroan anorthosites 15415 and 60015, as well as troctolite 76535. Ferroan anorthosite 15415 is one the best known rocks of the Apollo collection and is popularly called the Genesis Rock because the astronauts thought they had a piece of the moon’s primordial crust. It was collected on the rim of Apur Crater during the Apollo 15 mission.

Rock 60015 is highly shocked ferroan anorthosite collected near the lunar module during the Apollo 16 mission. Troctolite 76535 is a coarse-grained plutonic rock collected during the Apollo 17 mission.

Co-author Peslier is at Jacobs Technology and NASA’s Johnson Space Center. The fourth author of the Nature Geoscience paper, Clive Neal, is a professor of civil and environmental engineering and earth sciences at the University of Notre Dame. The work was supported by NASA.

http://www.sciencedaily.com/releases/2013/02/130218132355.htm

West Antarctica Ice Sheet is Warming Up

On By A.P.In Antarctica, Byrd Station, Climate Change, Gloabl Warming, Nature Geoscience, Ray Gaudette, WAIS, West Antarctica Ice SheetLeave a comment

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One of the big environmental stories of 2012 was the record melting of sea ice in the Arctic, which reached its smallest extent this summer since satellite data began being kept in the late 1970s. But it’s not the Arctic alone that’s reacting to manmade climate change by transforming into a large puddle. On the other end of the Earth, the continent of Antarctica contains enough ice to swamp just about every coastal city on the planet were it all to melt. The Arctic is transforming before our eyes, but it’s changes in Antarctica that could make Waterworld into a documentary.

That day is still in the distant future—in fact, sea ice in Antarctica has actually increased in recent years, as more powerful northward winds refreeze ice on the continent. But as a new study published in Nature Geoscience shows, temperatures are on the increase in the massive West Antarctica Ice Sheet (WAIS)—and so is melting.

Using data from Byrd Station, a scientific outpost in West Antarctica, researchers from Ohio State University and other institutions have report that average annual temperatures in the region have risen by 2.4 C (4.3 F) since 1958. That’s nearly twice as much warming as had been previously estimated, and the data shows for the first time an increase in warming trends during the summer. The timing of the temperature increase is particularly alarming because while temperatures in Antarctica remain well below freezing for nearly the entire year, the Antarctic summer is when any melting is likely to occur—just as it does in the Arctic.

As lead author David Bromwich put it in a statement:

Our record suggests that continued summer warming in West Antarctica could upset the surface mass balance of the ice sheet, so that the region could make an even bigger contribution to sea level rise than it already does.

Even without generating significant mass loss directly, surface melting on the WAIS could contribute to sea level indirectly, by weakening the West Antarctic ice shelves that restrain the region’s natural ice flow into the ocean.

Today melting from the WAIS adds only a few millimeters to the ongoing global sea level rise. But there is potential for much, much more—if all the ice in the 10 million sq. mile WAIS were to melt, it would be enough to add 3.05 m (10 ft.) to sea levels. To put that in perspective, all the warming the world has experienced since the Industrial Revolution has cause sea levels to rise by a few inches. That’s scary, world-changing stuff.

Antarctica: It’s Getting Hot at the Bottom of the Planet

Thanks to Ray Gaudette for bringing this to the attention of the It’s Interesting community.