San Joaquin, also known as Pico Biao or Pico do Moka, is a 2009-m-high basaltic shield volcano on the SE side of Bioko (Fernando Poo) Island. A small lake-filled caldera cuts the summit of the forested shield volcano, and a crater lake lies on the NE flank of the volcano. San Joaquin was classified as having been active during the last 2000 years (International Association of Volcanology and Chemistry of the Earth's Interior, 1973), although little is known about its geologic history.