Scientists are tracking changes at the giant supervolcano that lies under Yellowstone National Park, but there’s no need to worry at the moment.
“The western part of the Yellowstone caldera is waning,” said Ninfa Bennington, a volcano geophysicist with the U.S. Geological Survey and the lead author on a paper in Wednesday’s edition of the journal Nature.
(The caldera is the enormous volcanic crater left from the last time Yellowstone experienced a giant eruption, 640,000 years ago. It covers an area about 30 by 45 miles.)
The findings mean that the future of volcanic activity at Yellowstone is in the northeastern part of the park, and there’s no chance it’s going to blow any time soon.
“This volcanic system is not capable of producing that sort of eruption,” said Bennington.
For now, Yellowstone’s mud pots will keep boiling, the hot springs will keep steaming, the geysers will keep spraying, the Earth will keep shaking and the fumaroles will keep venting. The massive underground pools of magma below the storied park are still red hot, ranging between 2,512 and 1,247 degrees, said Bennington.
Learning more about the magma under Yellowstone
Yellowstone is one of the planet’s largest volcanic systems, a place where a plume of the Earth’s molten core rises up through the solid rock of crust, heating and melting it to form reservoirs of magma between 2.5 and and 30 miles below the surface.
In the past this was often pictured as a single underground lake of lava beneath volcanos, but newer mapping and imaging techniques make it possible to see the complex systems of reservoirs the magma had gathered in.
An imaging technique that produces more precise maps of the large reservoirs of magma under the park shows large pods of deep magma leading up to more shallow ones closer to the surface in the northeast, which tie into the park’s famed hydrothermal systems.
To know how likely a volcano is to erupt, vulcanologists calculate something called a melt fraction. It’s the ratio of how much magma (which they call “melt”) to the total volume of crust.
“Think of the earth like a sponge,” said Bennington. But instead of water filling the holes and crevices, it’s molten rock. In a volcanically active area, there’s a greater proportion of magma to earth. The higher the proportion of magma, the more eruptible the area is.
Visitors are asked to stay on boardwalks to not only protect themselves, but fragile thermal features of Yellowstone National Park.
The mapping was done using magnetotellurics that measure the electrical conductivity of what lies below the Earth’s surface. Melted rock, magma, is extremely good at conducting electricity so it makes precise mapping of areas where magma is stored possible. The testing was conducted over several months by scientists from USGS, Oregon State University and the University of Wisconsin-Madison.
What they showed was that while there are multiple enormous reservoirs of magma under Yellowstone, they’re separated from one and other.
“It would be difficult to mobilize into a single eruption because they’re not connected,” said Bennington.
When will Yellowstone erupt again?
It’s still possible that the northeastern portion of the park could erupt in a massive explosive eruption similar to the ones that have occurred at Yellowstone in the past 2.1 million years. In those, volcanic ash reached from the Pacific ocean to Canada to Mexico.
They tend to reoccur about every 600,000 to 800,000 years, according to the U.S. Geological Survey.
The most recent one was 640,000 years ago. It’s known as a super eruption because it released an estimated 250 cubic miles of material – one thousand times larger than the Mount St. Helen’s eruption in Washington state in 1980.
For now, the spaces in the sponge aren’t full enough of magma to support an eruption. For that to happen, the system would need more magma to fill more spaces in the crust’s “sponge.” Once the system got to some critical fraction of those spaces being filled with magma, it could cause an eruption.
“But we’re not nearly there now,” Bennington said. “We’re talking geological time scale.”
That’s hundreds of thousands of years – and possibly much longer.
This article originally appeared on USA TODAY: Changes reported at Yellowstone’s volcano. Could it erupt?
