![]() 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. 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. 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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