From: Andy Soos, ENN
Published September 10, 2010 04:20 PM

Yellowstone Magna

Yellowstone Park is a somewhat dormant super volcano site full of fuming vents and hot geysers. A plume of molten rock rising from deep beneath Yellowstone National Park is probably what is fueling the region's volcanic activity, as well as tectonic plate oddities across the Pacific Northwest, new research suggests.

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Yellowstone, like Hawaii, is believed to lie on top of an area called a hotspot where light, hot, molten mantle rock rises towards the surface. While the Yellowstone hotspot is now under the Yellowstone Plateau, it previously helped create the eastern Snake River Plain (to the west of Yellowstone) through a series of huge volcanic eruptions. Although the hotspot's apparent motion is to the east-northeast, the North American Plate is really moving west-southwest over the stationary hotspot deep underneath.

Building on a growing body of evidence, Mathias Obrebski of the University of California, Berkeley, and his colleagues created the most convincing picture to date of a Yellowstone mantle plume — one that extends from about 621 miles below the surface of the Earth.

Debates have long been waged over whether erupting and shaking in the area over the last few millions of years — and a track marked out by a chain of volcanic calderas along the Yellowstone Snake River Plain in Idaho — could be the work of a column of hot rock rising up from deep within the Earth's mantle. The mantle is the layer of hot, viscous rock beneath the planet's crust.

Obrebski's team used data from a new, dense deployment of seismometers, called the Earthscope USArray, to get a high-resolution image of the elusive mantle, along with information on the unusual structure of the subducting Juan de Fuca slab to its west. The Juan de Fuca plate is a small tectonic plate jammed in between the much larger Pacific and North American plates.

The plume is thought to be more or less stationary, with the North American plate — and the Juan de Fuca subducting beneath it — slowly sliding southwesterly over the plume. So what is now Oregon probably sat where Yellowstone is today about 17 million years ago, baking and breaking over a hot plume of rock.

The findings were detailed in the July 22 edition of the journal Geophysical Research Letters.

The source of the Yellowstone hotspot is controversial. Some geoscientists hypothesize that the Yellowstone hotspot is the effect of an interaction between local conditions in the lithosphere and upper mantle convection. Others prefer a deep mantle origin (or mantle plume).

Part of the controversy is due to the relatively sudden appearance of the hotspot in the geologic record. Additionally, the Columbia Basalt flows appeared at the same approximate time, causing speculation about their origin.

For further information: http://www.livescience.com/environment/plume-fueling-yellowstone-volcanic-activity-100908.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+livescience%2Fenvironment+%28LiveScience.com+Environment%29&utm_content=Google+Reader

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