Geography of Indonesia


is an archipelagic country located in Southeast Asia, lying between the Indian Ocean and the Pacific Ocean. It is located in a strategic location astride or along major sea lanes connecting East Asia, South Asia and Oceania. Indonesia is the largest archipelago in the world. Indonesia's various regional cultures have been shaped—although not specifically determined—by centuries of complex interactions with its physical environment.

Overview

Indonesia is an archipelagic country extending about from east to west and from north to south. It is considered to be the largest archipelagic country in the world. According to a geospatial survey conducted between 2007 and 2010 by National Coordinating Agency for Survey and Mapping, Indonesia has 17,500 islands. While earlier survey conducted in 2002 by National Institute of Aeronautics and Space 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 being permanent. It comprises five main islands: Sumatra, Java, Borneo, Sulawesi, and New Guinea; two major island groups 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 New Guinea is shared with Papua New Guinea.
Indonesia has total land area of, including of inland seas. This makes it the largest island country in the world. The additional surrounding sea areas bring Indonesia's generally recognised territory to about 5 million km2. The government claims an exclusive economic zone of. This brings the total area to about 7.9 million km2.
During the Pleistocene, the Greater Sunda Islands were connected to the Asian mainland while New Guinea was connected to Australia. Karimata Strait, Java Sea and Arafura Sea were formed as the sea level rose at the end of the Pleistocene.

Geology

The main islands of Sumatra, Java, Madura, and Kalimantan lie on the Sunda plate and geographers have conventionally grouped them,, as the Greater Sunda Islands. At Indonesia's eastern extremity is western New Guinea, which lies on the Australian plate. Sea depths in the Sunda and Sahul shelves average or less. Between these two shelves lie Sulawesi, Nusa Tenggara, and the Maluku Islands, which form a second island group with deep, surrounding seas down to in depth. The term "Outer Islands" is used inconsistently by various writers but it is usually taken to mean those islands other than Java and Madura.
Sulawesi is an island lies on three separate plates, the Banda Sea plate, Molucca Sea plate, and Sunda plate. Seismic and volcanic activities are high on its northeastern part, evidenced by the formation of volcanoes in North Sulawesi and island arcs such as the Sangihe and Talaud Islands, southwest of the Philippine Trench.
Nusa Tenggara or Lesser Sunda Islands consists of two strings of islands stretching eastward from Bali toward southern Maluku. The inner arc of Nusa Tenggara is a continuation of the Alpide belt chain of mountains and volcanoes extending from Sumatra through Java, Bali, and Flores, and trailing off in the volcanic Banda Islands, which along with the Kai Islands and the Tanimbar Islands and other small islands in the Banda Sea are typical examples of the Wallacea mixture of Asian and Australasian plant and animal life. The outer arc of Nusa Tenggara is a geological extension of the chain of islands west of Sumatra that includes Nias, Mentawai, and Enggano. This chain resurfaces in Nusa Tenggara in the ruggedly mountainous islands of Sumba and Timor.
File:Erupsi Gunung Sinabung 9 Juni 2019 oleh Muh Ma'rufin Sudibyo.jpg|thumb|upright|2019 eruption of Sinabung in North Sumatra. Sinabung is one of the most active volcanoes in Indonesia.
The Maluku Islands are geologically among the most complex of the Indonesian islands, consisted of four different tectonic plates. They are located in the northeast sector of the archipelago, bounded by the Philippine Sea to the north, Papua to the east, and Nusa Tenggara to the southwest. The largest of these islands include Halmahera, Seram and Buru, all of which rise steeply out of very deep seas and have unique Wallacea vegetation. This abrupt relief pattern from sea to high mountains means that there are very few level coastal plains. To the south lies the Banda Sea. The convergence between the Banda Sea plate and Australian plate created a chain of volcanic islands called the Banda Arc. The sea also contains the Weber Deep, one of the deepest point in Indonesia.
Geomorphologists believe that the island of New Guinea is part of the Australian continent, both lies on Sahul Shelf and once joined via a land bridge during the Last glacial period. The tectonic movement of the Australian plate created towering, snowcapped mountain peaks lining the island's central east–west spine and hot, humid alluvial plains along the coasts. The New Guinea Highlands range some east to west along the island, forming a mountainous spine between the northern and southern portion of the island. Due to its tectonic movement, New Guinea experienced many earthquakes and tsunamis, especially in its northern and western part.

Tectonism and volcanism

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.
Image:Map indonesia volcanoes.gif|thumb|446x446px|A map of Indonesia's volcanoes.
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 Indo-Australian 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. The 2004 Indian Ocean earthquake and tsunami devastated the Indonesian provinces of Aceh and North Sumatra, resulting in approximately 225,000 deaths and leaving over 425,000 people homeless. The disaster caused significant damage to infrastructure, homes, and local industries. The Indonesian government, in partnership with international organizations like the IMF, World Bank, and ADB, coordinated relief and reconstruction efforts. Preliminary assessments estimated the reconstruction cost at $4-5 billion over five years. During a donor meeting in January 2005, nearly $4 billion in aid was pledged for reconstruction, with a focus on transparency and efficient fund management. Despite the severe local impact, the overall effect on Indonesia’s national GDP was limited, as the Aceh region contributed only about 2% of national output. The Paris Club also offered a temporary debt moratorium, which helped fund rebuilding without diverting domestic financial resources.
The northern part of Sulawesi and Maluku Islands lie on the convergence of Sunda Plate and Molucca Sea plate, making it an active tectonic region with volcanic chains such as the Sangihe and Talaud Islands. Northern Maluku and western New Guinea is located on the convergence of Bird's Head, Philippine Sea and Caroline plate. It is also a seismically active region, with the 7.6 Mw 2009 Papua earthquakes being the most recent great earthquake to date in the region.

Ecology

Borneo is the third largest island in the world and the native vegetation was mostly Borneo lowland rain forests although much of this has been cleared with wildlife retreating to the Borneo montane rain forests inland. The islands of North Maluku are the original Spice Islands, a distinct rainforest ecoregion. A number of islands off the coast of New Guinea have their own distinctive biogeographic features, including the limestone islands of Biak, in the entrance to the large Cenderawasih Bay at the northwest end of the island.
A recent global remote sensing analysis suggested that there were 14,416 km2 of tidal flats in Indonesia, ranking it 1st in the world in terms of how much tidal flat occurs there. Another global analysis also estimated that Indonesia experienced the greatest total tidal wetland change between 1999 and 2019 with a net loss of.

Time zones

Indonesia is divided into three time zones: