Bumpass Hell via Cold Boiling Lake

Bumpass Hell via Cold Boiling Lake is a 5.2-mile out-and-back from Kings Creek Picnic Area to the east edge of Bumpass Hell Basin. Allow about three hours. The first 0.8 mile to Cold Boiling Lake is fairly level; the last 1.9 miles climb 750 feet along a narrow, steep hillside. Most of the work comes after the lake. The distance ends at the basin’s eastern edge; walking farther around its boardwalk adds to the outing. If that’s more than you want, Cold Boiling Lake makes a worthwhile 1.6-mile round-trip turn-around.

About a quarter-mile before the lake, a junction branches toward Twin Meadows. Keep on the Cold Boiling Lake route. At the lake, the small amount of bubbling can be easy to miss: look along the shore, and at the smaller neighboring pond where bubbles may show more clearly. It is a brief stop before the sustained climb, not a hot pool like the features ahead.

From Cold Boiling Lake, the trail turns toward the basin and climbs steadily for 1.9 miles. The route stays on a narrow hillside tread; it does not cross the basin floor. As the slope opens, you get a broad look into the pale hydrothermal ground and blue-gray pools below. The path reaches the basin’s eastern edge. The 5.2-mile figure doesn’t include any added walking on the basin boardwalk, which gives the close-up look at the vents and pools.

Cold Boiling Lake is a waning hydrothermal area, but small gas bubbles still rise near parts of its shore. Across the park, rain and snowmelt travel underground and are heated by hot or molten rock beneath Lassen Peak. Rising hot water makes the boiling pools and mud pots; superheated steam escaping through cracks forms fumaroles. Bumpass Hell packs those features together, so stay on the marked trail and boardwalk. The crust can hide acidic, boiling water or mud, and leaving the path can cause severe burns.