Lassen Volcanic National Park is in California. It is in the northeastern part of the state. Lassen Peak is the southernmost active volcano in the Cascade Mountain Range. The last eruption at Lassen Peak was in 1915. Lassen Peak is the largest volcano out of a group of thirty volcanoes in the park. The volcanoes in this group do not erupt regularly.
Scientists love to study the volcanoes here. The mountains are peaceful and quiet. But you can also find fumaroles. A fumarole is a vent in the side of a volcano that lets gasses escape. They can be small or large cracks. You can also find boiling mud pots. A mud pot is a small hole filled with boiling acidic water and mud. These give evidence that there is a lot of heat under the ground.