Big Cone is a geyser in Yellowstone National Park’s West Thumb Geyser Basin, distinguished by its position in Yellowstone Lake just off the shore. Formed as a sinter cone about 7 metres wide, it rises from the lake near land and has a vent about 80 centimetres across. Mineral deposits built the cone, while its location gives it an unusual connection to changing lake levels, sometimes leaving it completely submerged when the water is high. Big Cone also erupts only rarely, and then only to about 1 foot or less, making it a modest but distinctive thermal feature in the West Thumb area.