Unraveling Alaska’s Volcanic Enigma: Probing the Depths of Inland Anomalies

Scientists Uncover Mystery Magma Reservoir in Volcano-Free Region of Alaska

In a serendipitous discovery while monitoring seismic activity around Denali, scientists have stumbled upon an anomaly suggesting the presence of magma. This revelation may mark the accidental revelation of magma lurking beneath a region in Alaska devoid of active volcanoes.

Despite its location just 60 miles (100 kilometers) above one of the most active fault zones in the U.S., Denali (formerly known as Mount McKinley) has long puzzled geologists with its lack of volcanic activity. Positioned amidst volcanoes to its east and west, the absence of molten rock or hot springs at the surface has earned the area the moniker of the “Denali volcanic gap.”

However, recent research published in December 2023 in the Journal of Geophysical Research: Solid Earth has unveiled evidence of a magma reservoir approximately 7 miles (11 km) beneath the surface. Carl Tape, a professor of geophysics at the University of Alaska Fairbanks and lead author of the study, expressed surprise at the findings, noting the typical association of surface volcanism with regions situated above downgoing subducting plates.

The study team embarked on data collection expeditions to the Denali volcanic gap region following a magnitude 7.1 earthquake in Anchorage in November 2018. Deploying numerous seismometers along the highway near the Denali fault and directly above it, they recorded local and distant earthquakes to document crustal and uppermost mantle variations within the Alaska subduction zone.

“Remarkably, the Earth exhibits continual ambient ground motion,” Tape explained, attributing this phenomenon to interactions between ocean waves and the seafloor, which can be harnessed to image subsurface Earth properties. Amidst data analysis, researchers identified a seismic-velocity anomaly—a region where seismic waves decelerated as they traversed the ground—likely indicating the presence of a slow-moving, molten magma reservoir, as detailed in the study.

This unexpected discovery sheds new light on the geological dynamics of the region and underscores the ongoing mysteries surrounding magma behavior in tectonically complex areas like Alaska.