Huge Magma Chamber Discovered Beneath Mount St. Helens

http://www.weather.com/science/environment/news/huge-magma-chamber-discovered-under-mount-st-helens

Scientists have discovered a huge magma chamber buried deep beneath Mount St. Helens, which may provide new insight into how the deadly volcano erupts and when it may do so again.

The giant pool of molten rock lies between seven to 25 miles below the surface and is connected to a slightly smaller known chamber that lies directly beneath the mountain, Science magazine reports.

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Researchers think that the large magma chamber pumps molten rock into the smaller one directly below Mount St. Helens, which builds pressure before eruptions.   (Craig Mitchelldyer/Getty Images)

Back in 1980, in the months before Mount St. Helens erupted, a series of small earthquakes was detected along a peculiar, seemingly unexplainable path, Science reports. Researchers now think those tremors may have marked the pumping of magma from the lower to the upper chamber, which soon pressurized to the point of eruption.

“We can only now understand that those earthquakes are connecting those magma reservoirs,” Eric Kiser, a seismologist at Rice University, told the UK Daily Mail. “They could be an indication that you have migration of fluid between the two bodies.”

(WATCH: Huge Magma Chamber Discovered Below Yellowstone)

In other words, they could be an early warning system. Small quakes along the same line may mean that Mount St. Helen’s dual-chamber magma system is building itself up for another blowout.

Better understanding of the seismic activity around the volcano is just a small part of huge amounts of new information gathered by researchers on the Imaging Magma Under St. Helens project.

iMUSH began in 2014, when researchers stuck 2500 seismometers in the ground on trails and logging roads around the volcano. They then detonated 23 explosive shots, each with the force of a small earthquake, sending waves of energy into the crust. Seismometers picked up reflections, enabling researchers to map the heretofore unknown magma chamber.

(MORE: 12 Volcanoes that Could Erupt at Any Time)

“Mount St. Helens and other volcanoes in the Cascade Range threaten urban centers from Vancouver to Portland,” Alan Levander, a Rice professor of Earth science and lead scientist for the experiment, said in a press release last year. “We’d like to better understand their inner workings in order to better predict when they may erupt and how severe those eruptions are likely to be.”

Mount St. Helens' last major eruption occured May 18, 1980, when a 5.1 magnitude earthquake caused the volcano's bulge and summit to slide away in a huge landslide, which depressurized the volcano's magma system and triggered powerful explosions. Rocks, ash, volcanic gas, and steam were blasted outward at at least 300 miles per hour.

The blast cloud traveled as far as 17 miles northward from the volcano. The lateral blast produced a column of ash and gas (eruption column) that rose more than 15 miles into the atmosphere in only 15 minutes. Over the course of the day, prevailing winds blew 520 million tons of ash eastward across the United States and caused complete darkness in Spokane, Washington, 250 miles from the volcano.