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Today in History: Lassen Peak erupts in rare 20th-century event

5/22/2025

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Summary

Story summary

On May 22, 1915, Lassen Peak in California erupted violently, marking the only volcanic eruption in the contiguous United States during the 20th century until Mount St. Helens erupted in 1980. This event highlighted the active geological processes within the Cascade Volcanic Arc and significantly impacted the surrounding environment.

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Story summary

On May 22, 1915, Lassen Peak in California erupted violently, marking the only volcanic eruption in the contiguous United States during the 20th century until Mount St. Helens erupted in 1980. This event highlighted the active geological processes within the Cascade Volcanic Arc and significantly impacted the surrounding environment.