Yellowstone Supervolcano Bigger Than Thought

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Yellowstone Supervolcano Bigger Than Thought

LiveScience.com Ouramazingplanet Staff,

livescience.com – Mon Apr 11, 4:50 pm ET

The gigantic underground plume of partly molten rock that feeds the Yellowstone

supervolcano might be bigger than previously thought, a new image suggests.

The study says nothing about the chances of a cataclysmic eruption at

Yellowstone, but it provides scientists with a valuable new perspective on the

vast and deep reservoir of fiery material that feeds such eruptions, the last of

which occurred more than 600,000 years ago.

Earlier measurements of the plume were produced by using seismic waves — the

waves generated by earthquakes — to create a picture of the underground region.

The new picture was produced by examining the Yellowstone plume's electrical

conductivity, which is generated by molten silicate rocks and hot briny water

that is naturally present and mixed in with partly molten rock.

" It's a totally new and different way of imaging and looking at the volcanic

roots of Yellowstone, " said study co-author B. , professor emeritus

and research professor of geophysics at the University of Utah, and a

coordinating scientist of the Yellowstone Volcano Observatory.

Ancient eruptions

Almost 17 million years ago, the deep plume of partly molten rock known as the

Yellowstone hot spot first breached the surface in an eruption near what is now

the Oregon-Idaho-Nevada border.

As North America drifted slowly southwest over the hot spot, there were more

than 140 gargantuan caldera eruptions — the largest kind of eruption on Earth —

along a northeast-trending path that is now Idaho's Snake River Plain.

The hot spot finally reached Yellowstone about 2 million years ago, yielding

three huge caldera eruptions about 2 million, 1.3 million and 642,000 years ago.

Two of the eruptions blanketed half of North America with volcanic ash,

producing 2,500 times and 1,000 times more ash than the 1980 eruption of Mount

St. Helens in Washington state. Smaller eruptions occurred at Yellowstone in

between the big blasts and as recently as 70,000 years ago.

Underground images

said the geoelectric and seismic images of the Yellowstone plume look

somewhat different because " we are imaging slightly different things. " Seismic

images highlight materials such as molten or partly molten rock that slow

seismic waves, while the geoelectric image is sensitive to briny fluids that

conduct electricity.

Seismic images of the plume made by in 2009 showed the plume of molten

rock dips downward from Yellowstone at a 60-degree angle and extends 150 miles

(240 kilometers) west-northwest to a point at least 410 miles (660 km) under the

Montana-Idaho border — as far as seismic imaging could " see. "

The new electrical conductivity images show the conductive part of the plume

dipping more gently, at an angle of perhaps 40 degrees to the west, and

extending perhaps 400 miles (640 km) from east to west. The geoelectric image

can " see " to a depth of only 200 miles (320 km).

The lesser tilt of the geoelectric plume image raises the possibility that the

seismically imaged plume, shaped somewhat like a tilted tornado, may be

enveloped by a broader, underground sheath of partly molten rock and liquids,

Zhdanov and say.

" It's a bigger size " in the geoelectric picture, said. " We can infer there

are more fluids " than shown by seismic images. Despite differences, he said,

" this body that conducts electricity is in about the same location with similar

geometry as the seismically imaged Yellowstone plume. "

The new study has been accepted for publication in Geophysical Research Letters,

a journal of the American Geophysical Union, which plans to publish it within

the next few weeks.

[Guest guest]

Interesting. That thing is a real monster. There are a few others around the world, maybe a dozen or so. One thing that had me interested is that the big quakes in New Zealand weren't that far from another major volcano like Yellowstone, one that is located at the northern tip of the north island. Funny side note: while I was researching that volcano, an ad came up about buying islands in New Zealand. Turns out that some of the islands are inside the caldera, which is mostly underwater and not visible to prospective buyers.

In a message dated 4/12/2011 12:21:33 A.M. Eastern Daylight Time, no_reply writes:

Yellowstone Supervolcano Bigger Than Thought

[Guest guest]

Kinda goes with those adds for land in Florida. Swampland of course.

Administrator

Interesting. That thing is a real monster. There are a few others around the

world, maybe a dozen or so. One thing that had me interested is that the big

quakes in New Zealand weren't that far from another major volcano like

Yellowstone, one that is located at the northern tip of the north island. Funny

side note: while I was researching that volcano, an ad came up about buying

islands in New Zealand. Turns out that some of the islands are inside the

caldera, which is mostly underwater and not visible to prospective buyers.