southeast flank during the late-19th and early-20th centuries. San Joaquin, also known as Pico Biao or Pico do Moka, is 2,009 m high, on the southeast of the island. The summit is cut by a small lake-filled caldera, and there is a crater lake on the NE flank. San Joaquin has been active during the last 2,000 years.

The southwestern side of Bioko is rainy for most of the year, with annual rainfall