Scientists found silica-rich magma can sit in the Earth's upper crust for thousands of years without causing an eruption.
The modeling research suggests areas that have seen major eruptions, even if they were thousands of years prior, could have magma waiting patiently beneath the surface, a University of Washington press release reported.
A volcano in Yellowstone National Park erupted 600,000 years ago, and there could be a large pool of magma still "festering beneath it." The area still may not be at risk of a major eruption in the foreseeable future.
"You might expect to see a stewing magma chamber for a long period of time and it doesn't necessarily mean an eruption is imminent," Sarah Gelman, a UW doctoral student in Earth and space sciences, said.
Past research models have suggested magma must be "injected into the Earth's crust at a high rate" in order to create the pressure needed to spawn an eruption.
The research team incorporated "changes in the crystallization behavior of silica-rich magma in the upper crust" into their study to come up with the new findings.
The scientists found magma could creep in slowly and remain molten for long periods of time, contrary to previous beliefs.
Volcanos usually contain two types of lava: Plutonic magma (which solidifies and never erupts), and volcanic (which is molten and associated with eruptions).
Researchers believe plutonic magma remains in the volcano after an eruption and turns to granite.
Gelman and her team think the Earth's crust could "consist of a core of partially molten material feeding volcanoes surrounded by more crystalline regions that ultimately turn into plutonic rock."
As magma moves up the volcano's chamber it crystallizes. As the magma moves higher the crystals drop out, leaving the plutonic rock with higher silica levels. Researchers can use the silica content to measure how the magma has behaved in the Earth's upper crust.
"These time scales are in the hundreds of thousands, even up to a million, years and these chambers can sit there for that long," Gelman said.
The study implies the existence of volcanic "arcs" where one tectonic plate is moving below another. Scientists have the ability to detect the presence of magma beneath theses arcs, but cannot tell how long it has been there.
"If you see melt in an area, it's important to know how long that melt has been around to determine whether there is eruptive potential or not," Gelman said. "If you image it today, does that mean it could not have been there 300,000 years ago? Previous models have said it couldn't have been. Our model says it could. That doesn't mean it was there, but it could have been there."
Scientists predict there is about a one-in-10,000 chance of the Yellowstone volcano erupting at any time, the Huffington Post reported.