Indonesia is tectonically highly unstable, making it the site of numerous volcanoes and frequent earthquakes. The archipelago lies on the Pacific Ring of Fire where the Indo-Australian Plate and the Pacific Plate are pushed under the Eurasian plate and where they melt at about 100 km (62 mi) below the earths’ surface. A string of volcanoes runs southeastward through Sumatra, Java, Bali, and Nusa Tenggara, and then fishhooks north and westward to the Banda Islands of Maluku and North Sulawesi. Of the 400 or so Indonesian volcanoes, around 130 are active. The photo shows a dormant but smoking volcano on the island of Sumatra.