This is an image of Lassen Peak, in California, USA.
Click on image for full size
Image from: U.S. Geological Survey
Lassen Peak is an example of what is called a "volcanic dome".
The most recent eruptive activity occurred at Lassen Peak in 1914-1917. The eruption began on May 30, 1914, with a small vent
near the summit of the peak. More than 150 explosions of various sizes
occurred during the following year. By mid-May 1915, the
eruption changed in character, and lava began to flow over the east
crater walls. Lava on the upper east side of Lassen Peak on May 19 resulted in an avalanche of hot rock onto a snowfield. A lahar was generated that reached more than 18 miles down Lost Creek.
Intermittent eruptions of variable intensity continued until about the middle of 1917.
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