Photo: This is a caldera of a supervolcano that erupted in Long Valley, east of the Sierra Nevada mountain range in California, 760,000 years ago. Credit: NASA/JPL
Supervolcanoes are volcanoes that have had eruptions of magnitude 8 on the Volcano Explosivity Index, and spewed at least 240 cubic miles' worth of deposits of lava and other materials. There are about 20 known supervolcanoes around the world, including one inside Yellowstone National Park in Wyoming. Fortunately, they don't explode very often -- the most recent supervolcano eruption was in New Zealand, 26,500 years ago -- they have the potential to spew enough material into the atmosphere to devastate the entire planet.
RELATED: North Korea Lets in Outsiders to Study Huge Volcano
Now, scientists have discovered that supervolcanoes probably give only about a year's warning before they blow.
In a study published in the journal PLOS ONE, Guilherme Gualda, an associate professor of earth and environment sciences at Vanderbilt University, and University of Chicago senior scientist Stephen Sutton did a microscopic analysis of quartz crystals in pumice taken from the Bishop Tuff in eastern California, the site of the super-eruption that formed the Long Valley Caldera 760,000 years ago.
Gualda explained in a Vanderbilt press release that while the processes that prime the crust and ultimately lead to an eruption can take thousands of years, the final stage of the process is a relatively quick one in geologic time.
RELATED: Quakes Could Trigger Massive Supervolcano Eruptions
"The onset of the process of decompression, which releases the gas bubbles that power the eruption, starts less than a year before eruption." he said.
According to Gualda, the decompression period would likely be accompanied by the expansion of the magma body which should have detectable effects on the Earth's surface, and that those signs would intensify as the eruption neared.
More work needs to be done to identify what the signs given off by a supervolcano would be, Gualda said. With smaller volcanoes, scientists have discovered a number of signs, including an increase in seismic activity and movement of quakes closer to the surface, and ground deformation, according to Oregon State University's Volcano World website.