You are standing on a rocky ledge known as a “bathtub ring.” In geologic terms, it’s called a lava subsidence terrace. When the lava lake grew higher than the vent, fountains stopped erupting. Molten lava drained back into the vent, dragging pieces of the lake’s crust with it. Lava often poured back into the vent four times faster than it was erupted, generating a noisy whirlpool of red-hot, liquid lava and black slabs of solid rock.

Lush forests survived above the lake’s high lava mark. As the lake partially drained, its surface dropped nearly 50 feet, leaving behind a crusty lava “bathtub ring” to indicate its highest level.