section_path: Geography/Geology
section_name: Geology
paragraph_text: Geology
  
  Indonesia's geology is shaped by its position on the Pacific Ring of Fire, where the Indo-Australian and Pacific plates subduct beneath the Eurasian plate, where they melt at about 100 kilometres (62 miles) deep. This tectonic activity makes the region highly unstable with volcanoes and earthquakes. A chain of volcanoes stretches from Sumatra through Java, Bali and the Lesser Sunda Islands, and the Banda Islands of Maluku to northeastern Sulawesi. Of the 400 volcanoes, around 130 are active. While volcanic ash has made agriculture unpredictable in some areas, it has also created fertile soils that have historically sustained the high population densities of Java and Bali. Between 1972 and 1991, Java experienced a total of 29 volcanic eruptions.
  
  The archipelago has witnessed several powerful volcanic eruptions with global repercussions. A massive supervolcano erupted with a maximum volcanic explosivity index (VEI) of 8 at present-day Lake Toba around 74,000 BCE, causing a global volcanic winter, cooling the climate, and possibly influencing human evolution. The eruption of Mount Tambora in 1815, the most recently confirmed VEI-7 eruption, made much of the Northern Hemisphere without summer in 1816. The eruption of Mount Krakatoa in 1883, a VEI-6 eruption, produced the loudest sound in recorded history, with additional effects around the world years after the event. Recent catastrophic disasters due to seismic activity include the 2004 Indian Ocean earthquake and the 2018 Sulawesi earthquake.