USGS and UNAVCO seismic and geodetic networks provide real-time volcano monitoring data. Earthquake activity has been low for the last few decades and ground deformation is negligible. The record of eruptions over the last 10,000 years suggests that, on average, at least one eruption occurs every 800 to 600 years at Mt Shasta. In the last 1,000 years, more than 70 mudflows have inundated stream channels.

Non-volcanic shedding of young volcanic rock and ash from Mount Shasta’s steep slopes occurs during heavy rainfall or glacial floods. Hot springs and volcanic gases seep from the summit indicating a relatively young and still-hot system. The youngest dated eruption occurred about 3,200 years ago, producing block and ash flows on the volcano's north flank. In the last few millennia, smaller eruptions have broken out at the volcano’s summit and from vents on its upper east flank. Eruptions at about 11,000 years ago built Black Butte and Shastina on the western flanks of Mount Shasta. Activity over the last 300,000 years includes long intervals of quiet interrupted by shorter spans of frequent eruptions. It is the most voluminous of all the Cascade Range volcanoes, and the towns of Weed, Mt Shasta City, and McCloud lie in the shadow of its 4,317 m (14,163 ft) high snow- and ice-clad edifice. The collapse spawned one of the largest landslides known on Earth, covering more than 440 km 2 (170 mi 2) of Shasta Valley to the northeast. Shasta is a majestic, steep-sided stratovolcano located about 97 km (60 mi) north of Redding along the I-5 corridor in Northern California. Mount Shasta began forming on the remnants of an older, similar volcano that collapsed 300,000 to 500,000 years ago.

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