Mount Tambora (or Tomboro) is an active stratovolcano, also known as a composite volcano, on Sumbawa islan, Indonesia. Sumbawa is flanked both to the north and south by oceanic crust, and Tambora was formed by the active subduction zones beneath it. This raised Mount Tambora as high as 4,300 m (14,000 ft), making it one of the tallest peaks in the Indonesian archipelago, and drained off a large magma chamber inside the mountain. It took centuries to refill the magma chamber, its volcanic activity reaching its peak in April 1815.