Scientists mapped out a detailed image of the subterranean magma chamber of Mount Rainier for the first time. The volcano is the highest peak in the Cascade Mountains Range and sits approximately 50 miles southeast of Seattle, Washington.

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

The study showed that the magma chamber ventures out 6-10 miles to the northwest of the volcano, approximately 30-45 miles from the Seattle-Tacoma metropolitan area. The extensive reservoir is five miles underground, and “appears to be 5 to 10 miles thick, and 5 to 10 miles wide in east-west extent,” according to Wannamaker. “We can’t really describe the north-south extent because it’s a slice view.”

However, the study did not analyze the network of dikes and fissures that will ultimately expel the lava in the next eruption, nor did it reveal any information about the timing of the inevitable eruption. Rather, it shows the process of water and partially molten rock generating 50 miles underground in a subduction zone, as the Juan de Fuca plate slowly dives eastbound and down beneath the North American plate, and how those molten materials then travel to the magma chamber of Mount Rainier.

The study used both seismic imaging and magnetotelluric measurements, which make images by showing how electrical and magnetic fields in the ground vary due to differences in how much underground rock and fluids conduct or resist electricity.

Wannamaker said it is the most detailed cross-section view yet under a Cascades volcanic system using electrical and seismic imaging. Earlier seismic images indicated water and partly molten rock atop the diving slab. The new image shows melting “from the surface of the slab to the upper crust, where partly molten magma accumulates before erupting,” he added.