Mount Sinabung, January 2014 Eruption, Karo Regency, North Sumatra, Indonesia

Geology
Most of Indonesian volcanism stems from the Sunda Arc, created by the subduction of the Indo-Australian Plate under the Eurasian Plate. This arc is bounded on the north-northwest by the Andaman Islands, a chain of basaltic volcanoes, and on the East by the Banda Arc, also created by subduction.
Sinabung is an andesitic-dacitic stratovolcano with a total of four volcanic craters, only one being active.