Friday, January 27, 2012

Recent (geologically) Death Valley Eruption

Here's an interesting article from National Geographic regarding the estimated age of a large crater in Death Valley.


Death Valley's Big Bang: Volcano "Potentially Active"

Ubehebe Crater's last eruption much more recent than thought.

Ubehebe Crater in Death Valley.
Dusk light reveals rock layers in Death Valley National Park's Ubebe Crater.
Photograph by Pete Ryan, National Geographic
Richard A. Lovett
for National Geographic News
Published January 25, 2012
A volcano in Death Valley National Park might be more dangerous than previously thought, a new study says.
A mile and a half wide (2.4 kilometers) and 600 feet (180 meters) deep,California's Ubehebe Crater came explosively into being long ago when rising magma hit water. (Video: Volcanoes 101.)
The bomblike steam eruption produced a mushroom cloud that, as it collapsed, sent rocky debris flowing out sideways at 200 miles an hour (320 kilometers an hour) to a distance of a few kilometers, according to a geologic analysis of rock deposits at the site, study co-author Brent Geohring said.
The question is, when?
Scientists had assumed the explosion occurred comfortably in the past, most likely several thousand years ago, when the Death Valley area was wetter.
The explosive mixing of magma and water, they thought, could be explained by the presence of lakes that have long since disappeared.
The new study, though, suggests the massive blast occurred more recently, when Death Valley was very much as it is today—which could mean that conditions are still ripe for an eruption.
"Very Young" Volcano
In 2008 Goehring, then with Columbia University's Lamont-Doherty Earth Observatory, and study co-author Peri Sasnett, then a Columbia undergrad, visited Death Valley on a geology field trip.
The two got to wondering exactly how old Ubehebe (YOU-bee-hee-bee) Crater really is. "It looks very young," Goehring said.
With permission from the Park Service, they collected samples from the crater for lab analysis. The specimens in question, he added, aren't lava, but are instead rocks from surface layers that were blown out of the crater by the explosion.
The samples, they discovered, contain rare isotopes created when rocks are bombarded by cosmic rays. Because this radiation doesn't penetrate deeply into the Earth, the isotopes can reveal how long a rock has been on the surface.
"We weren't dating the formation of the rock itself," Goehring emphasized—but rather the date when the rock had been thrust from the depths.
"We were literally atom counting," he said. "These [isotopes] are only produced at 10 to 15 atoms per year in a gram of rock. So they're at very, very low concentrations."
The Awkward Years
The study backed up the scientists' hunch that Ubehebe Crater was a relative newborn.
Rather than being several thousand years old, it and nearby smaller craters appear to have been the result of a series of explosions, the largest and most recent of which was 800 years ago.
The dating method "is very cool," said Kelly Russell, a volcanologist from the University of British Columbia in Vancouver, Canada, who was not part of the study team.
"To be able to date young volcanic events that precisely is something we're always seeking to do," Russell said. "That's the awkward period—these prehistoric events that are very young."
Conditions Right for Eruption?
According to the new data, the eruption was recent enough to suggest that the area might become volcanically active again.
"A volcano that young has to be considered potentially active," Russell said. And if there's still water around, he added, there is the potential for another explosion.
Goehring believes that it's quite likely that enough water still exists. The 800-year-old explosion, he said, came at a time when Death Valley was even drier than today, he noted.
If fact, he said, "there's actually water underneath the crater today. There are springs nearby."
Nor does it take a gargantuan of water to create a giant eruption. "You need about a hundred Olympic-size swimming pools to generate enough steam to [produce] Ubehebe Crater," Goehring said.
Beyond that volume, in fact, the water could actually damp down a potential explosion. "You get the highest degree of explosivity with sort of a sweet spot, mixing water to magma," Russell said.
As for the other main ingredient—magma—there's no telling when some could begin rising toward the surface, and the groundwater.
Luckily, though, the popular tourist attraction probably won't explode without warning.
"You would expect to see some hydrothermal activity and seismic activity, much like you do at Mount St. Helens," Goehring said. (See pictures of the Mount St. Helens volcano before and after its 1980 blast.)
National Park Service education specialist Stephanie Kyriazis agrees. "Right now, we're not planning to issue an orange alert or anything like that," Kyriazis said in a statement.
If the Ubehebe volcano were to explode, however, the eruption would be spectacular—and hot—if the ancient mushroom cloud is any indication.
The rock "probably would have been a few hundred degrees C," study co-author Goehring said. "It wouldn't have been molten, but it would have been quite hot.
"It would be fun to see," he added, "But I wouldn't want to be nearby."
The Death Valley volcano study was published January 18 in the journalGeophysical Research Letters.
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Thursday, January 19, 2012

That's A Lot of Money!

As of today, NOAA counted 14 extreme weather events in the United States during 2011 that resulted in at least $1 billion in economic losses.

Click the link to see NOAA's article and video about the blizzards, tornadoes, floods, and tropical storms, that caused such economic hardship for so many Americans.

NOAA Weather Extremes 2011
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Sunday, January 15, 2012

US Volcano Monitoring

Here's an excellent article on the history of volcano monitoring in the US.  A timely article, indeed, given our current classroom discussions on plate tectonics and volcanoes.

Here's the link: USGS 100th Anniversary of Volcano Monitoring

The USGS has some excellent links attached so that you can further explore their website.

Check out this other excellent volcano site too: Volcano World Home
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Thursday, January 12, 2012

Nuclear Tour?

Check out this interesting article about a vacation where you can go for a tour of a decommisionsed nuclear reactor.  Actually, the reactor never came online.

Read on to find out more...Nat. Geographic - Nuclear Tour
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Wednesday, January 4, 2012

Continental Drift

An appropriately timed article appeared in ScienceDaily.com today on the 100th anniversary of Continental Drift.  Alfred Wegener first made his idea public in 1912.  He published a book on the subject in 1915.

Given our recent coverage of Wegener and his landmark hypothesis, the article is very interesting.


Flipped from Head to Toe: 100 Years of Continental Drift Theory

ScienceDaily (Jan. 4, 2012) — Exactly 100 years ago, on 6 January 1912, Alfred Wegener presented his theory of continental drift to the public for the first time. At a meeting of the Geological Association in Frankfurt's Senckenberg Museum, he revealed his thoughts on the supercontinent Pangaea, which broke apart and whose individual parts now drift across Earth as today's continents. In 1915, he published his book "The Origin of Continents and Oceans." Its third edition in 1922 was translated into the languages ​​of the world and today is considered the foundation stone of plate tectonics.
Wegener's genius idea did not only find friends, because it had the main disadvantage that it lacked the engine to break apart the supercontinent and move huge continental masses over Earth's surface. Indeed, only by the seismology of the 1950s and through scientific drilling in the oceans in the 1960s, the foundation for plate tectonics was laid -- at the same time, however, Wegener's groundbreaking theory was turned upside down.
Seismological insights
Earthquakes are not only terrible natural disasters, they also offer a view inside Earth. It was the geophysicists Wadati and Benioff, who in 1954 independently discovered the systematic arrangement of earthquakes in the places which we now know as plate boundaries. "More than 90% of the global seismic energy is released at the plate boundaries," says Professor Michael Weber, head seismologist at the German Research Centre for Geosciences GFZ. "We use these earthquakes for tomographic screening of the Earth." With modern methods of scientific seismology it is even possible to reconstruct how quickly the continents moved. The speed record is held by India, which started to make its way from East Gondwana ​​to Eurasia about 140 million years ago -- at a speed of 20 centimeters per year.
Drilling into the ocean floor
The real breakthrough, however, came only when those findings were combined with the research results from the great ocean drilling programs of the sixties. Previously, using magnetic measurements of the ocean floor and topography of the seabed the mid-ocean ridges had been discovered, as well as a magnetic polarization of the rocks in parallel strips either side of mid-ocean ridges. Now, the obtained cores showed: No piece of the drilled ocean floor was older than 200 million years, and therefore decidedly younger than Wegener had assumed. Continental rocks, in contrast, can achieve an age of more than four billion years. Secondly, it could be shown that the ocean floor is very young in the immediate vicinity of the mid-ocean ridges. With increasing distance from these undersea mountains, the rocks exhibit an increase in age. Thirdly, the ocean floors below the top layer of sediment are entirely of magmatic origin. "These results could in fact only allow one interpretation. From the interior of the Earth, hot, liquid rock rises to these ridges and pushes the ocean floor off to the side", explains Dr. Ulrich Harms, who at the GFZ directs the "Centre for Scientific Drilling." "Not the continents drift, but entire tectonic plates, which consist of continents , ocean floors, and parts of the upper mantle."
Ascending rocks and the engine of plate tectonics
All these findings in the second half of the sixties put Wegener's ingenious discoveries into a correct context, and also flipped his theory from the head to its feet: not only were his assumptions as to the age of oceans and continents completely reversed, the idea that the continents plow the ocean turns around so that continents and oceans move together as a common upper part of the lithospheric plates. The continents float on top as the lightest rocks, so to speak.
These tectonic plates move, collide, grind past each other or drift apart. All these processes are associated with earthquakes, which can thus be explained as part of the overall process. But what forces the heavy rock inside Earth to rise? The enormous heat inside Earth's core and mantle comes in one part from the formation of Earth, in another from the radioactive decay of elements in the mantle. The heated rock rises and induces the movement expressed on the surface as a displacement of the plates.
The quiet revolution in the theory of tectonics
The classical concept of tectonics as a quasi mechanical process of the movement and collision of rigid plates is now itself in disarray. "Recent findings show plate tectonics as a self-regulating system of interactions, in which all the subsystems of the planet earth are involved", explains Professor Onno Oncken. The Director of the Department "Geodynamics" at GFZ notes: "It is not a mechanical system, but rather complex feedback processes." The climate as example: high-altitude mountains have a decisive influence on the climate, of course. But that the climate in turn controls the tectonics, is a new discovery: the Andes, for example, are caused by the collision of the Nazca plate with South America. The humid climate of the South Andes leads to the erosion of material that ends up as sediment in the Pacific. The Nazca plate approaching from the west deposits this rock on the South American crust. The arid climate of the Northern and Central Andes, however, gives rise to no sediment, therefore the Nazca plate rasps off the continental crust here. The thus created great increase in friction in turn transmits a force that causes the Andean plateau to gain height and width. This in turn enhances the rain shadow on the west side of the Andes and additionally reduces erosion.
The classical notion of folded mountains as a result of a collision also had to be revised: "The Andes, for example, in their present form, exist for about 45 million years, the subduction of the Nazca plate beneath South America has been going on since the Paleozoic, so hundreds of millions of years longer," says Onno Oncken. Similarly, the interplay between the hot, rising rock masses and Earth's crust is much more complex than originally thought. When a hot rock bubble rises, the poorly heat-conductive lithosphere acts as a boundary layer to the surface like a blanket, which in turn increases the temperature further below. This heat buildup can eventually soften whole continents like a welding torch until they dissolve, as it happened around 140 to 130 million years ago, when Gondwana fell apart first in the East, then in the West.
At that time Africa also separated from South America, but it was exactly the contours of these two continents that sparked Wegener's idea. Professor Oncken: "Wegener's approach was the starting point, the plate tectonics of the previous century was the revolution in geoscientific perception. Today we see an equally thorough, quiet revolution in the theory of plate tectonics, because we understand our planet increasingly as a complete system."
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Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences (2012, January 4). Flipped from head to toe: 100 years of continental drift theory. ScienceDaily. Retrieved January 4, 2012, from http://www.sciencedaily.com­/releases/2012/01/120104133151.htm
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