Trident is a complex of three stratovolcanoes, the highest of which is tall, standing up to above their base. Trident has been intermittently active in historical times, primarily between 1953 and 1974. During that time about 0.7 cubic kilometers of material was erupted to form a new peak called Southwest Trident from the former site of a large fumarolic pit. Mount Martin is high, standing on a high ridge near Mount Mageik, partly overlapping the much older Alagogshak volcano. The summit has a diameter crater, containing fumaroles and sometimes a crater lake. A large lava flow extends from the mountain to fill the upper part of Angle Creek's valley with about five cubic kilometers of material. There have been no significant eruptions from Martin, but the summit emits steam and the volcano is the site of earthquake swarms. Mageik stands on the same sedimentary rocks as Martin. The composite structure has four vents, the highest at and three subsidiary vent cones. A small crater hold a lake and fumaroles on the highest cone's flank. Apart from steaming there has been no recent activity, but there was a large debris avalanche in 1912, probably associated with the eruption of Katmai, amounting to between 0.05 and 0.10 cubic kilometer in volume. Fourpeaked Mountain is a stratovolcano with a probable vent at the summit. Much of the mountain is covered by Fourpeaked Glacier. Fourpeaked produced phreatic eruptions in September 2006.