Lassen Peak

On May 22, 1915, an explosive eruption at Lassen Peak, the southernmost active volcano in the Cascade Range, devastated nearby areas and rained volcanic ash as far away as 200 miles to the east. This explosion was the most powerful in a 1914-17 series of eruptions that were the last to occur in the Cascades before the 1980 eruption of Mt. St. Helens. Lassen Peak is the largest of a group of more than 30 volcanic domes erupted over the past 300,000 years in Lassen Volcanic National Park. Lassen Peak, also known as Mount Lassen, is the southernmost active volcano in the Cascade Range. It is part of the Cascade Volcanic Arc which is an arc that stretches from southwestern British Columbia to northern California. Located in the Shasta Cascade region of Northern California, Lassen rises 2,000 ft above the surrounding terrain and has a volume of 0.5 cu mi, making it one of the largest lava domes on Earth. It was created on the destroyed northeastern flank of now gone Mount Tehama, a stratovolcano that was at least 1,000 ft higher than Lassen Peak. On May 22, 1915, a powerful explosive eruption at Lassen Peak devastated nearby areas, and spread volcanic ash as far as 200 mi to the east. This explosion was the most powerful in a series of eruptions from 1914 through 1917. Lassen Peak and Mount St. Helens are the only two volcanoes in the contiguous United States to erupt during the 20th century. Lassen Volcanic National Park was created in Shasta County, Calif., to preserve the devastated areas as they were, for future observation and study, and to preserve the nearby volcanic features. Unlike most lava domes, Lassen Peak is topped by craters. A set of these craters exists around the summit of Lassen Peak, although two of them have been covered up by solidified lava and sulfur deposits. Lassen Peak is the largest of a group of more than 30 volcanoes that have erupted over the past 300,000 years in the Lassen Peak volcanic area.