Calabozos Caldera (Chile)
Hidden in the Andes, this remote supervolcano has produced at least three major eruptions over its history. The most recent blast 300,000 years ago ejected 130 cubic miles of material. Snow covers much of the caldera most of the year. Hot springs attract occasional visitors to its isolated location. Geologists must trek through difficult terrain to study this overlooked giant. Recent satellite data shows subtle signs of activity.