A lateral eruption, also called a flank eruption or lateral blast if explosive, is a volcanic eruption that takes place on the flanks of a volcano instead of at the summit. Lateral eruptions are typical at rift zones where a volcano is breaking apart. Since it is easier for molten rock to flow laterally out the sides of weak flanks, the flank gives way before magma is pushed up through a conduit that feeds magma to the summit. These features are commonly found at shield volcanoes and produce basaltic lava flows and cinder cones.
Lateral blasts are understood to be created by immediate decompression of a magma chamber lying not far below the flanks of a volcano, similar to what occurred during the 1980 eruption of Mount St. Helens in the U.S. state of Washington, or along the base or flanks of a lava dome similar to what happened during the 1902 eruption of Mount Pelée on the northern tip of the French overseas department of Martinique in the Lesser Antilles island arc of the Caribbean.