Active Andean volcanism: its geologic and tectonic setting

The Andean volcanic arc includes over 200 potentially active Quaternary volcanoes, and at least 12 giant caldera/ignimbrite systems, occurring in four separate segments referred to as the Northern, Central, Southern and Austral Volcanic Zones. Volcanism results from subduction of the Nazca and Antarctic oceanic plates below South America. Active volcanoes occur where the angle of subduction is relatively steep (25°), and active arc segments are separated by regions below which subduction angle decreases and becomes relatively flat (<10°) at depths 100 km. Segments of low angle subduction formed beginning in the Miocene in association with subduction of buoyant oceanic plateaus and ridges, and current…