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California's Lassen Peak violently erupted, the only volcanic eruption in the contiguous U.S. in the 20th century until Mount St. Helens erupted in 1980.
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Lassen Peak
Active volcano in California, United States
Lassen Peak, commonly referred to as Mount Lassen, is a 10,457-foot (3,187 m) lava dome volcano in Lassen Volcanic National Park in Northern California. Located in the Shasta Cascade region above the northern Sacramento Valley, it is the southernmost active volcano in the…Source: Wikipedia (CC BY-SA)
Volcanic eruption
Volcanic event
A volcanic eruption occurs when material is expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may…Source: Wikipedia (CC BY-SA)
Contiguous United States
48 states of the US apart from Alaska and Hawaii
The contiguous United States, also known as the U.S. mainland, officially referred to as the conterminous United States, consists of the 48 adjoining U.S. states and the District of Columbia of the United States in central North America. The term excludes the only two…Source: Wikipedia (CC BY-SA)
Mount St. Helens
Volcano in Washington, U.S.
Mount St. Helens is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States. It lies 52 miles (83 km) northeast of Portland, Oregon, and 98 miles (158 km) south of Seattle. Mount St. Helens takes its English name from…Source: Wikipedia (CC BY-SA)