Geography of Indonesia
Indonesia is an archipelagic country extending about from east to west and from north to south. According to a geospatial survey conducted between 2007 and 2010 by National Coordinating Agency for Survey and Mapping (Bakosurtanal), Indonesia has 13,466 islands. While earlier survey conducted in 2002 by National Institute of Aeronautics and Space (LAPAN) stated Indonesia has 18,307 islands. According to the CIA World Factbook, there are 17,508 islands. The discrepancy between the surveys is likely caused by the earlier different survey method including tidal islands, sandy cays and rocky reefs that surface during low tide and submerge during high tide. There are 8,844 named islands according to estimates made by the government of Indonesia, with 922 of those are permanently inhabited. It comprises five main islands: Sumatra, Java, Borneo (known as "Kalimantan" in Indonesia), Sulawesi, and New Guinea; two major island groups (Nusa Tenggara and the Maluku Islands) and sixty smaller island groups. Four of the islands are shared with other countries: Borneo is shared with Malaysia and Brunei; Sebatik, located off the northeastern coast of Kalimantan, shared with Malaysia; Timor is shared with East Timor; and the newly divided provinces of Papua and West Papua share the island of New Guinea with Papua New Guinea.
Geography of Indonesia
Most of the larger islands are mountainous, with peaks ranging between meters above sea level in Sumatra, Java, Bali, Lombok, Sulawesi, and Seram. The country's tallest mountains are located in the Jayawijaya Mountains and the Sudirman Range in Papua. The highest peak, Puncak Jaya (, is located in the Sudirman Mountains. A string of volcanoes stretches from Sumatra to Nusa Tenggara, and then loops around through to the Banda Islands of Maluku to northeastern Sulawesi. Of the 400 volcanoes, approximately 150 are active. Two of the most violent volcanic eruptions in modern times occurred in Indonesia; in 1815 Mount Tambora in Sumbawa erupted killing 92,000 and in 1883, Krakatau, erupted killing 36,000. While volcanic ashes resulted from eruption has positive effects for the fertility of the surrounding soils, it also makes agricultural conditions unpredictable in some areas.Indonesia has relatively high tectonic and volcanic activities. It lies on the convergence between the Eurasian, Indo-Australian, Pacific, and Philippine Sea Plate. The Sunda megathrust is a 5,500 km long fault located off southern coasts of Sumatra, Java and Lesser Sunda Islands, where the Pacific Plate is thrusting northeastward towards the subducting Sunda Plate. Tectonic movement in this fault is responsible for the creation of the Sunda Trench, and mountain ranges across Sumatra, Java, and the Lesser Sunda Islands. Many great earthquakes occurred in the vicinity of the fault, such as the 2004 Indian Ocean earthquake. Mount Merapi, located in the Java portion of the megathrust, is the most active volcano in Indonesia and is designated as one of world's Decade Volcanoes due to the hazard it poses to the surrounding populated areas.