Yellowstone magma much bigger than thought

This graphic provided by University of Utah geophysicists shows the first large-scale picture of the electrical conductivity of the gigantic underground plume of hot and partly molten rock that feeds the Yellowstone supervolcano. 

The plume of molten rock feeding the supervolcano under the surface of Yellowstone National Park is much larger than previously thought, according to University of Utah geophysicists whose findings will be published in Geophysical Research Letters. 

AP Photo/University of Utah

The hot molten rock beneath Yellowstone National Park is 2 ½ times larger than previously estimated, meaning the park's supervolcano has the potential to erupt with a force about 2,000 times the size of Mount St. Helens, according to a new study.

By measuring seismic waves from earthquakes, scientists were able to map the magma chamber underneath the Yellowstone caldera as 55 miles (88.5 kilometers) long, lead author Jamie Farrell of the University of Utah said Monday.

The chamber is 18 miles (29 kilometers) wide and runs at depths from 3 to 9 miles (5 to 14 1/2 kilometers) below the earth, he added.

That means there is enough volcanic material below the surface to match the largest of the supervolcano's three eruptions over the last 2.1 million years, Farrell said.

The largest blast—the volcano's first—was 2,000 times the size of the 1980 eruption of Mount St. Helens in Washington state.

A similar one would spew large amounts of volcanic material in the atmosphere, where it would circle the earth, he said.

"It would be a global event," Farrell said. "There would be a lot of destruction and a lot of impacts around the globe."

The last Yellowstone eruption happened 640,000 years ago, according to the U.S. Geological Survey. For years, observers tracking earthquake swarms under Yellowstone have warned the caldera is overdue to erupt.

A large earthquake at Yellowstone is much more likely than a volcano eruption, Farrell said.

The 7.5-magnitude Hebgen Lake earthquake killed 28 people there in 1959.

Farrell presented his findings last week to the American Geophysical Union. He said he is submitting it to a scholarly journal for peer review and publication.

Brigham Young University geology professor Eric Christiansen said the study by Farrell and University of Utah Professor Bob Smith is very important to understanding the evolution of large volcanos such as Yellowstone's.

"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."

Feb 2013 video: Mount Etna erupts from 'new crater'

Europe's most famous active volcano has been erupting, sending plumes of ash into the air.

The activity at Mount Etna on the island of Sicily was reported to be taking place at a new crater at a height of 2,900m (9,500ft).

It is part of a series of eruptions, but the ash is not thought to have disrupted flights at the nearby Catania airport.

Kilauea: Tiny Gravity Changes Show Magma's Underground Movements

Kilauea's current eruption is still going strong after 29 years.

CREDIT: USGS/HVO.

The secret movements of magma deep inside a volcano can be detected by tracking the subtle changes in gravity they cause.

Surprising readings from a Hawaiian volcano have researchers hoping to better understand volcanic activity through gravity monitoring.

Continuous gravity measurements of active volcanoes are relatively rare, with most results coming from Mount Etna in Italy.

"One problem is the expense," researcher Michael Poland, a geophysicist at the U.S. Geological Survey's Hawaiian Volcano Observatory, explained.

"Gravity measurements have always been a really expensive endeavor. The big users are oil and mining companies."

Now scientists have monitored the gravity at Kīlauea, a popular tourist destination on Hawaii's Big Island, and discovered a regular cycle of fluctuations that suggest magma is churning a kilometer (0.6 miles) below the surface.

The way magma churns in underground chambers below volcanic vents is key to understanding how persistent volcanoes are, and whether or not they might catastrophically erupt in the future.

However, what goes on deep under the Earth's surface is difficult to monitor.

One way to peer underground is by looking at Earth's gravity, the researchers said. Anything that has mass has a gravity field that pulls objects toward it.

The strength of this field depends on the amount of mass. Since the Earth's mass is not spread out evenly, this means the strength of the planet's gravitational pull is stronger in some places and weaker in others.

As such, the flow of magma from one place to another can be detected from above.

Most active volcano

"Kīlauea is the world's most active volcano," Poland said. "It's erupted almost continuously since 1983. It's a natural 'lab volcano' ―a great place to try and study something like gravity measurements."

The researchers installed two continuous gravity meters at the summit of the volcano in 2010. One was about 1.2 miles (2 kilometers) northwest of the eruptive vent at the summit and recorded measurements every10 seconds, while the other was placed about 500 feet (150 meters) east and recorded data every second.

They detected gravity fluctuations that came in a cycle about 150 seconds long.

"There was no expectation for that kind of result," Poland reported. "That gravity oscillation came out of nowhere. It points to the idea that there's probably a lot of things going on in volcanoes, glaciers, wherever you look, but we haven't developed the tools to detect these sorts of things."