Produces extensive sheets of volcanic tuffs, e.g. Yellowstone National Park. Formed when pyroclastic flow meets a river of snowbank, e.g. Nevado del Ruiz in Columbia. Produces massive destructive landslide. Volcanic gases . All phenomena associated with circulating groundwater that reaches buried cooling magma.
Water is heated and returns to surface as hot springs and geysers.
Geyser is a hot water fountain that spouts intermittently with great force.