Lassen Volcanic National Park guide · 1 min read
Bumpass Hell: Lassen's Largest Hydrothermal Basin
Bumpass Hell is the park's biggest hydrothermal area, a 16-acre basin where hot water and steam rise through the ground.
Snowmelt and rainfall on the high ground sink far underground, where rock beneath Lassen Peak that is either hot or molten warms the water. Steam, heated well past boiling, pushes up through cracks in the earth and escapes at the surface as fumaroles, which are vents that let out steam and volcanic gas. All of this is linked to the volcanic activity that still shapes the park.
The Bumpass Hell Trail covers 3 miles round trip and starts at a parking area beside the park highway, about 7 miles from the Southwest Entrance. Difficulty falls between easy and moderate, and most visits take one to three hours. Along the way you get views of Lake Helen, the valley below and the peaks nearby, since the path follows a slope. The first mile is mostly flat. Once you reach the one-mile mark, the basin first comes into sight below you, and a steep but short descent takes you down into it.
On the basin floor, a short boardwalk loop carries you past the features, with up-close looks at fumaroles and mud pots. The basin also has boiling pools, which form when rising hot water boils. Stay on the boardwalk, because the crust over these features can be thin. Visitors who have stepped off trail in the park's hydrothermal areas have broken through it or suffered serious burns.
Bumpass Hell is the most popular hike in the park, so arrive early, since parking tends to fill. The trail usually opens in mid-July, and snow covers it for much of the rest of the year, which makes it mainly a summer and early fall hike.
