A submarine eruption from Anak Krakatau on 13 June 1930, produces both a vertical eruption plume and a base surge extending radially from the vent along the surface of the sea. Submarine eruptions were first observed in December 1927, forming several ephemeral islands. By 12 August 1930 Anak Krakatau had become a permanent island.
A column of ash and steam rises above a new submarine vent off the western coast of Fayal Island in early October 1957. Horizontally traveling base surges form a ring at the base of the eruption column. Explosive eruptions began on September 27 and formed a small island that eventually was joined to the main island, partially burying the Capelinhos lighthouse, which is visible on the center shoreline (bottom). Lava effusion was continuous for the last five months of the 13-month eruption.
