The Tengger Caldera is all
that remains of an ancient, gigantic volcanic eruption. The resulting
crater is 16 km across and on the floor of the crater are several,
newer cones. The only one of these cones which is currently active
is Bromo which constantly belches out steam and gas. It's prone
to the occasional explosive event and in 2004, two tourists were
killed and five injured when the mountain erupted.