Debris Avalanche

Future eruptions like those of the last 10,000 years will probably produce deposits of ash, lava flows, domes, and pyroclastic flows, and could endanger infrastructure that lie within several tens of kilometers of the volcano.

The deposits of an exceptionally large debris avalanche extend from the base of Mount Shasta volcano northward across the floor of Shasta Valley in northern California.

The next eruption at Mount Shasta would likely involve weeks to months of precursory earthquakes and ground deformation followed by a series of steam explosions blasting a deep crater at the summit of the volcano.

Hundreds of small hills, called hummocks, extend from the base of Mount Shasta at least 45 km (27 mi) NNW across the floor of Shasta Valley. The hummocky landslide deposit was emplaced between 380,000 and 300,000 years ago during a massive debris avalanche that is not believed to be associated with volcanic activity.