English: Geysers are hot springs that episodically erupt columns of water. They occur in few places on Earth. The highest concentration of geysers anywhere is in Yellowstone’s Upper Geyser Basin (northwestern Wyoming, USA). Sponge Geyser is a cone-type geyser in the central Geyser Hill Group of Yellowstone's Upper Geyser Basin. Its raised geyserite cone is about 2.5 to 3 meters in diameter. The geyser sits atop a larger mound. Several relatively small geysers occur nearby, such as Plate Geyser, Slot Geyser, and Boardwalk Geyser. Sponge has "eruptions" about once a minute involving boiling, roiling, very low spouting, and overflow. Most runoff drains northward from the northern edge of the crater's pool, but some overflow heads east, south, and west. Eruptions vary from lazy to moderately energetic, but none involve the prominent spouting and splashing seen in "normal" geysers. Lowering of water levels occurs after eruptions. Post-eruption audible boiling indicates that water level decreases end up just a bit below the surface.