Cerro Galan Caldera Located in a remote part of the Catamarca
province of northwestern Argentina, Cerro Galan is the best
exposed large caldera in the world. Investigations have been
carried out by Francis & Baker (1978), Francis et al. (1978,
1983,1989), and Sparks et al. (1985). Cerro Galan caldera is the
most recent component of a large silicic system which developed
along two prominent north-south faults about 20 km apart. Like
most large silicic systems, it has had a long and complex
history. Volcanism in the area began about 15 Ma ago with the
eruption of several andesite and dacite composite volcanoes.
Subsequently, activity has been dominantly explosive and at
least 9 major ignimbrite eruptions occurred between 7 and 4 Ma
ago. About 2.2 Ma ago eruption of more than 1000 km3 of crystal-
rich, homogeneous, dacitic magma formed the present 35 x 20 km
caldera and the resulting Cerro Galan ignimbrite which extends
for up to 100 km radially from the caldera rim. Caldera
formation was followed by resurgence o