A researcher at the University of Utah and colleagues elsewhere have developed a detailed map of a massive reservoir of molten magma beneath Mount Rainier in Washington, and they predicted the volcano will erupt again someday.

In conjunction with a study published in the journal Nature this week, the researchers measured how fast the Earth conducts electricity and seismic waves, and created a road map of the corridor that partly molten rock takes to proceed upward to where it is trapped for eruption. According to the researchers, the findings will help experts better understand the processes inside the volcano and predict any future eruption.

“This is the most direct image yet capturing the melting process that feeds magma into a crustal reservoir that eventually is tapped for eruptions,” Phil Wannamaker, a geophysicist at the University of Utah, said in a statement. “But it does not provide any information on the timing of future eruptions from Mount Rainier or other Cascade Range volcanoes.”

Wannamaker and Rob L. Evans, a geophysicist at the Woods Hole Oceanographic Institution, conceived the study. First author R. Shane McGary -- then at Woods Hole and now at the College of New Jersey -- did the data analysis. Their co-authors were Jimmy Elsenbeck of Woods Hole and Stéphane Rondenay of the University of Bergen.

Mount Rainier last erupted in the 19th century. It is the tallest volcano and the fifth-highest peak in the contiguous U.S., Reuters reported. It noted the volcano is about 14,410 feet tall and located about 58 miles southeast of Seattle.

According to the researchers, the newly developed map shows that the top of the magma reservoir is 5 miles underground and “appears to be 5 to 10 miles thick, and 5 to 10 miles wide in east-west extent.”

Wannamaker said, “We can’t really describe the north-south extent because it’s a slice view.” He added that the reservoir could be roughly 30 percent molten.

The U.S. Geological Survey also has described Mount Rainier as “an active volcano that will erupt again.” Sitting atop volcanic flows as much as 36 million years old, Rainier has erupted explosively dozens of times during the past 11,000 years, spewing ash and pumice.