Accidental Discovery of a Large Magma Reservoir Beneath This Volcano-Free Region

In Alaska, a region devoid of any volcanoes might be concealing a surprising geological phenomenon beneath its surface. Researchers have recently shed light on the potential existence of a magma reserve about 7 miles (11 kilometers) below the ground, a discovery that challenges previous knowledge about the area known as the "Denali volcanic gap."


Denali, the highest peak in North America, formerly known as Mount McKinley, is situated about 62 miles (100 kilometers) above one of the most active fault zones in the United States. Surrounded by volcanoes to the east and west, this area had until now shown no classic signs of volcanic activity, such as molten rocks or hot springs on its surface. This observation had earned this region its nickname of the "Denali volcanic gap."


The revelation of this magma reserve comes from the work of a team studying the local seismic activity. This discovery, published in December 2023 in the Journal of Geophysical Research: Solid Earth, occurred after the installation of hundreds of seismometers following a magnitude 7.1 earthquake in Anchorage in November 2018. The instruments, deployed near the Denali Fault, captured ground movements caused by local and distant earthquakes, thus offering a new perspective on the Earth's crust and upper mantle in the Alaska subduction zone area.

During the data analysis, researchers identified a "seismic velocity anomaly," meaning a slowdown in seismic waves, a likely indicator of the presence of a slowly moving magma reservoir. This area is situated beneath two unusual volcanic deposits, Buzzard Creek Maars and Jumbo Dome, and above the point where the subducting plate plunges into the mantle.

Although the amount of magma and the size of the volcanoes in this region are considerably smaller than those observed in active volcanic arcs, this discovery raises new questions about the composition and geological activity of the area. To get a clearer picture of this anomaly, and potentially confirm the presence of magma, it will be necessary to install seismic monitoring instruments directly above this area, a significant challenge given the difficult terrain of Alaska's interior.