Pyroclastic Flows

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.

Mount Shasta is located in the Cascade Range in northern California about 65 km (40 mi) south of the Oregon-California border. One of the largest and highest (14,162 ft) of the Cascade volcanoes, the compound stratovolcano is located near the southern end of the range that terminates near Lassen Peak.

Mount Shasta erupts episodically with ten or more eruptions occurring in short (500-2,000 year) time periods separated by long intervals (3,000-5,000 years) with few or no eruptions. Evidence suggests that magma most recently erupted at the surface about 3,200 years ago.

If pyroclastic flows occur in the future, they may affect low- and flat-lying areas almost anywhere within about 20 km (12.4 mi) of the source vent for the eruption.

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.

Shastina is a large subsidiary cone that rises to 3,758 m (12,330 ft) and lies on the flank of Mount Shasta, 3 km (1.8 mi) west of the volcano's summit.

Black Butte is a group of overlapping dacite domes about 13 km (8 mi) west of Mount Shasta.