Near Little Hot Springs Valley is Bumpass Hell, which is a hydrothermally altered geothermal area that spans 16 acres (65,000 m²) and has hot springs, fumaroles, and mud pots. Never part of Mount Tehema's main vent, Bumpass Hell is the result of fissures that tap the volcanic heat (which is thought to be a cooling mass of andesite, perhaps three miles (5 km) below the surface).

It is named after Kendall Vanhook Bumpass, a cowboy who worked in the Lassen area in the 1860s. One day Bumpass stumbled upon the area and his leg was badly scalded when it broke though a thin crust above a mud pot. He told his friends and townspeople about it, describing it as "hell." A newspaper editor was interested in the story and convinced Bumpass to take him to this place. Unfortunately, Bumpass' leg broke through the crust again - this time it had to be amputated.

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