Lassen Volcanic National Park is known primarily for its geothermal and volcanic sites. The park itself is home to all four types of volcanoes: cinder cones, lava domes, shield volcanoes, and composite volcanoes. From these active volcanic areas also emerge the geothermal areas.
The most popular and largest in the park is Bumpass Hell. This hydrothermal area contains Big Boiler, the largest fumurole in the park. A fumurole is a vent in which volcanic gasses escape from the ground into the atmosphere. The presence of fumuroles always indicates active volcanicism. Typically the emerging gasses are very hot. In the case of Big Boiler the gasses reach as high as 322 degrees, making it one of the hottest fumuroles in the world. On the farther end of the area, liquid pyrite (iron sulfide, or fool’s gold) can be seen on the surface of one of the boiling pools.
The peculiar name of this site comes from an early pioneer. Kendall Bumpass was walking through the hydrothermal area when suddenly the thin soil broke and he fell into a boiling pool, severely burning his leg. Thus the area was named Bumpass Hell. This is also a great example of what can happen if someone steps off of the boardwalks and designated trails.