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 eruption began on May 30, 1914, with more than 150 explosions of various sizes
occurring during the year. By mid-May 1915, the eruption changed in character, and lava began to flow over the crater walls. On May 19, 1915, lava in a snowfield resulted in lahar that reached more than 18 miles down Lost Creek.
The eruption continued until about the middle of 1917, when all activity ceased.
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