Socompa

Straddling the Chile-Argentina border, Volcán Socompa is a massive dacitic stratovolcano that lies immediately north of the only railway line between the two countries. It is the youngest and southernmost of a NE-SW-trending chain of volcanoes including Pular and Pajonales. In contrast to the latter two volcanoes, no glacial moraines have been observed on the relatively uneroded Socompa. Collapse of the NW portion of the volcano about 7200 years ago produced a 600 km2 debris-avalanche deposit that extends about 40 km from the summit and is one of the world's largest and best exposed. Undated post-collapse eruptions constructed dacitic lava domes that have filled much of the head of the collapse scarp. No historical eruptions are known.