West Thumb Geyser Basin

West Thumb Geyser Basin is the largest geyser basin on Yellowstone Lake, a lakeshore field of hot springs, mud pots and dormant geysers. Its easy boardwalk loop covers 0.6 mile and takes about 30–60 minutes. The inner loop is a quarter mile and the outer loop is a half mile, so you can take a shorter look or linger over the whole basin. Come for the mix of thermal features and lake scenery; geysers erupt infrequently, so a major eruption is not something to plan around.

The basin shifts between deep blue pools, pastel mud pots and stark white sinter terraces. Heat-loving microbes add orange, pink and green along some channels and pool margins. Abyss Pool is about 53 feet deep; Black Pool reaches roughly 35 to 40 feet. From the boardwalk, look for how abruptly their clear surfaces give way to steep, dark sides.

Fishing Cone is a mineral cone at the shore that may be covered when the lake is high. Its best-known story says early visitors caught a trout from the cold lake and cooked it in a nearby hot spring. The tale may have grown from a tall story, but the practice is firmly in the past: fishing here is prohibited. Hydrothermal vents continue beneath the lake, and several sinter cones can rise above its surface.

West Thumb is a caldera nested within Yellowstone Caldera. Its collapsed basin later filled with water and became part of Yellowstone Lake. The name comes from the lake’s hand-like outline: this west-side bay is its thumb. Dissolving rhyolite and sinter helps form steep-sided pools, while minerals and heat-loving microbes leave bright bands around their edges.

In spring, bears may be near streams where cutthroat trout spawn, and elk cows with calves are often seen in May and June. Bald eagles and osprey fish over the bay; loons and ducks use the water. These are seasonal possibilities, not a promise of a sighting.

The loop starts and ends at the West Thumb parking area in southern Yellowstone. Stay on the boardwalks and keep children close: hydrothermal water can cause severe burns. The area has designated accessible parking, restrooms, picnic tables and a bookstore and information station in the historic ranger station; there is no food service at the basin, pets are not allowed on the trail, and park entrance fees may apply. For the classic view, frame a pool or pale mineral ground with Yellowstone Lake and the Absaroka Range beyond it; you do not need a separate hike to reach the boardwalk views.