Pacaya Volcano, Guatemala

Abstract

Pacaya (14°23′N, 90°36′W) is a 2,552 m high volcanic complex, consisting of an older stratovolcano with domes, flows, tephra, and a younger basaltic stratovolcano. Most of the complex has been formed in the last 23,000 years. Little is known about its early historic eruptions; however, since 1565, Pacaya has erupted at least 23 times; the strongest eruption was recorded in 1775.

Pacaya complex creates a part of a chain of volcanoes stretching along the Pacific coast of Guatemala. Tectonically, the whole chain was formed by the subduction of the Cocos Plate underneath the Caribbean Plate. The mountain itself is located at the southern edge of a sizable caldera formed in the Pleistocene age. The caldera has been the source of at least nine large explosions over the last 300,000 years, during which some 70 km³ of magma erupted. Since the last caldera-forming eruption, several smaller vents within and around the caldera displayed eruptive activities. About 1,100 years ago, the volcano's edifice collapsed, which initiated a huge landslide, whose deposits were transferred about 25 km off the volcano down to the Pacific coastal plain. The landslide left a large crater, within which the present active cone has grown. The presence of a magma chamber in the shallow depth beneath Pacaya indicates that the older distortion of the cone, leading to the structural instability, remains and represents a certain hazard to the surrounding area.