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article imageYellowstone's magma lake much larger than previously thought

By Karen Graham     Dec 17, 2013 in Science
The heart of Yellowstone National Park is its caldera, a vast basin left behind after the last of three volcanic eruptions spanning a period of 2.1 million years. But what has scientists so concerned is what lies beneath the park's natural wonders.
In what has been described as "astounding," a new study on the size of the magma chamber beneath Yellowstone National Park was presented at the fall meeting of the American Geophysical Union (AGU), in San Francisco, Calif.
Using measurements from seismic waves from earthquakes, scientists were able to map the magma lake underneath Yellowstone's caldera as being 55 miles long, and 18 miles wide. The magma lake runs from 6 to 9 miles underneath the caldera.
Yellowstone s NW caldera rim at the Madison  Junction in the park. The rim is 500 m. tall  and was f...
Yellowstone's NW caldera rim at the Madison Junction in the park. The rim is 500 m. tall, and was formed when this area collapsed during the eruption that took place 640,000 years ago.
Robert Smith
This revelation puts the size of the magma chamber at 2 1/2 times larger than previously thought. This also means the volcano has the potential of erupting with a force 2,000 times greater than the 1980 eruption of Mt. St. Helen's in Washington state, according to the new study.
The team of scientists included Professor Robert Smith and lead author, Dr Jamie Farrell, from the University of Utah. Farrell said there is enough material below the surface to match the largest of the three eruptions that occurred over the last 2.1 million years.
In explaining how the mapping of the magma lake was done, Farrell said that by measuring the rate of movement of seismic waves as they traveled through the ground, it was found the waves traveled slower through hot and partially molten material. They were able to get more accurate measurements this way.
Another study was presented at the AGU fall meeting that looked at earlier, more ancient eruptions along the same continental plate that Yellowstone's volcano sits on. Dr Marc Reichow, from the University of Leicester, said “We looked at a time window of between 12.5 to 8 million years ago. We wanted to know how to identify these eruptions and find out how frequently they happened.”
Reichow's research showed while there were fewer volcanic eruptions during this time period, they were much larger, and more violent. This information is important to understanding how we think Yellowstone's volcano might behave. Scientists can't guess or forecast with any certainty when an eruption will occur, mainly because there is actually little data to go on.
With only three eruptions in the past 2.1 million years, Dr. Smith says basing any estimates of something possibly happening every 700,000 years is risky, not unlike taking a chance on the stock market. What is more telling is earthquakes, and their intensity. This is something that can be measured with a degree of accuracy, and studied.
The 1959 earthquake that hit Yellowstone Nat l. Park registered 7.4 on the Richter scale and killed ...
The 1959 earthquake that hit Yellowstone Nat'l. Park registered 7.4 on the Richter scale and killed 28 people. From the photo, the extent of the damage was quite evident.
National Park Service, Yellowstone Nat'l. Park
Farrell says, "We do believe there will be another eruption, we just don't know when. There are enough instruments monitoring the seismic activity of Yellowstone that scientists would likely know well ahead of time if there were unusual activity happening and magma was moving to the surface."
Geology professor Eric Christiansen of Brigham Young University, says the information presented by Dr. Smith and Dr. Farrell will go far in helping us to understand the workings of these large volcanoes. "It helps us understand the active system," Christiansen said. "It's not at the point where we need to worry about an imminent eruption, but every piece of information we have will prepare us for that eventuality."
More about Yellowstone, magma, New study, supervolcano, Larger
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