Apo volcano is the highest mountain in the Philippines, and its name means "Master" or "Grandfather". Apo volcano is an a basaltic to basaltic-andesitic stratovolcano and part of the Central Mindanao Arc, but its volcanic history is poorly known. The densely forested volcano has a flat summit with 3 peaks, the highest of which in the SW is known as Davao volcano and has a 500 m wide crater with a small lake. The youngest crater is located on the northern peak. Several fumaroles and sulfur deposits occur on the volcano, most notably fumaroles along a fissure on the SE side down to 2400 m elevation. The Mt. Apo Geothermal Field is a 8.4 km2 geothermal exploration field near Mt Apo, which has been being exploited since October 1996.