Official name: Republic of Indonesia
Area: 1,919,440 square kilometers (741,096 square miles)
Highest point on mainland: Puncak Jaya (5,030 meters/16,503 feet)
Lowest point on land: Sea level
Hemispheres: Northern, Southern, and Eastern
Time zones: Western, 7 P.M. = noon GMT; Central, 8 P.M. = noon GMT; Eastern, 9 P.M. = noon GMT
Longest distances: 5,271 kilometers (3,275 miles) from east to west; 2,210 kilometers (1,373 miles) from north to south
Land boundaries: 2,774 kilometers (1,719 miles) total boundary length; East Timor 172 kilometers (106 miles); Malaysia 1,782 kilometers (1,104 miles); Papua New Guinea 820 kilometers (508 miles)
Coastline: 54,716 kilometers (33,999 miles)
Territorial sea limits: 22 kilometers (12 nautical miles)
Indonesia is an archipelago in Southeast Asia, located between the Indian Ocean on the west and south and the Pacific Ocean on the east and north.
Indonesia shares parts of Borneo with Malaysia and Brunei and parts of the province of Papua (located on the island of New Guinea and formerly known as Irian Jaya) with Papua New Guinea. Indonesia disputes ownership of Sipadan and Ligitan Islands with Malaysia.
Indonesia has a tropical climate, with high humidity (an average of 82 percent) and high temperatures. There are two basic seasons: a rainy season from November to March; and a hot, drier season from April through October. Temperatures in Indonesia's capital, Jakarta, generally range from 23°C (73°F) to 33°C (91°F). Average yearly rainfall for Indonesia as a whole is approximately 200 centimeters (78 inches). In lowland areas, the average annual rainfall ranges from 180 to 320 centimeters (70 to 125 inches); while in the mountains it can reach as much as 610 centimeters (238 inches). The fearsome typhoons of the South China Sea spend themselves before reaching Indonesian waters, and the gales that blow from time to time through the Torres Strait, between Australia and New Guinea, seldom move farther than the extreme southeastern islands of the archipelago, so the seas of Indonesia are generally calm.
Indonesia consists of more than thirteen thousand islands scattered over a distance of about 5,149 kilometers (3,200 miles) above and below the equator between the Indian and Pacific Oceans, in the largest archipelago in the world. Five major islands make up 90 percent of Indonesia's land area. These are Sumatra, Java, Sulawesi, plus parts of Borneo and New Guinea. Indonesia also contains about thirty smaller island groups, the largest of which is Nusa Tenggara, which includes the islands of Lombok, Sumba, Sumbawa, Flores, and Timor. In 1999, East Timor gained its independence from Indonesia.
Along the length of Indonesia's island chain the landscape is highly varied, and volcanic mountains stand out in sharp relief on most of the larger islands.
Citizens of Indonesia often refer to their country as "Tanah Air Kitah," "Our Land and Water," which illustrates the importance of the seas surrounding the archipelago. Indonesia forms a natural barrier between the Indian Ocean to the south and west, the open Pacific Ocean to the northeast, and the South China Sea to the north. South of the island of Java is the lowest point in the Indian Ocean, the Java Trench, some 7,300 meters (24,000 feet) deep. Between Timor and Australia is the Timor Trough, which is approximately 3,000 meters (9,842 feet) deep. In the waters directly off the islands of Indonesia are at least 10 percent of the world's coral reefs. Fishing practices and land erosion increasingly endangers these important marine ecosystems.
There are a vast number of straits and passages found around the islands of Indonesia. The Karimata Strait connects the South China Sea to the Java Sea. The Strait of Malacca, running between Sumatra and mainland Malaysia and connecting the South China Sea to the Bay of Bengal, is one of the busiest waterways in the world. Most ships heading to the east coast of Asia from the west pass through this strait, as does most traffic from East Asia heading west. The Sunda Strait between Java and Sumatra is also heavily traveled. The Great Channel separates the northernmost tip of Sumatra from India's Nicobar Islands. Further east among the islands is the Makassar Strait between Borneo and Sulawesi. It connects the Sulawesi (Celebes) Sea in the north with the Java, Bali, and Flores Seas in the south.
The islands of Indonesia are part of the Malay Archipelago, which also includes the Philippines. The Indonesian part of the archipelago includes more than thirteen thousand islands, many of them only a few acres in size. Not all of these islands have been officially named, and only about one thousand are inhabited.
Most of the islands rise from the submerged Sunda shelf, considered a continuation of the Asian continent. The western and central islands are known as the Sunda Islands. Sumatra, Java, Borneo (the Indonesian part of which is called Kalimantan), and Sulawesi, along with the surrounding islands, are known as the Greater Sunda Islands. Borneo is the largest of these; at 751,929 square kilometers (290,320 square miles), it is the third-largest island on Earth. Smaller islands in this region include Bangka, Belitung, and the Mentawi Islands.
Further east are the Lesser Sunda Islands. They begin with Bali and extend to Timor. Lombok, Sumbawa, Flores, and Sumba are the other large islands in this chain, which is also known as Nusa Tenggara. Along with Savu and Roti Islands, they enclose the Savu Sea. Even further to the east are the Maluku Islands, formerly called the Moluccas. Most of the Maluku are found in groups of small and medium-sized islands, such as the Tanimbar Islands, Aru Islands, Kai Islands, and Sula Islands. Halmahera, Wetar, Buru, and Ceram are the largest individual islands.
New Guinea, the island of which Indo-nesia's Papua state is the western half, is the second-largest island in the world (884,824 square kilometers/341,631 square miles).
Indonesia has one of the world's longest coastlines. The southwestern islands are similar in that their shores tend to be steep, with few sandy beaches, while their northern and eastern coasts are mostly flat in terrain. Sulawesi is formed from four peninsulas, with the long, northernmost, Minahasa Peninsula curved around the Tomini Gulf, while the two southern arms enfold the Bone Gulf. Between the two is the Gulf of Todo. Kalimantan has a jagged coastline with numerous river deltas that empty into the South China Sea, Java Sea, Makassar Strait, and Celebes Sea. At the far side of the archipelago, the northwest region of Papua is known as the Bird's Head Peninsula.
More than five hundred lakes are scattered across Indonesia. By far the largest Indonesian lake is Lake Toba in northern Sumatra, covering more than 1,300 square kilometers (502 square miles) between towering cliffs that once were the rim of a volcanic crater. Toba is one of the deepest lakes in the world, plunging over 450 meters (1,476 feet). It is also one of the highest, at 900 meters (2,953 feet) above sea level. In addition to Toba, notable Sumatran lakes include Manindjau and Singkarak.
The central region of Sulawesi has a pair of deep lakes: Lake Towuti, which is 48 kilometers (30 miles) wide, and Lake Matana. Lake Poso is in north-central Sulawesi. In northern Sulawesi, lakes include Limboto and Tandano. Kalimantan's lakes include the three Mahakam lakes. The Mahakam River basin, an important bird habitat, contains ninety-six lakes altogether. The island of Flores is famous for a trio of lakes at the top of volcanic Mount Keli Mulu, each of which has water of a different color (green, maroon, and black) due to variation in mineral content.
Rivers are found in every part of the islands. Although most rivers are short, they are often important for irrigation. Major rivers can be found on Kalimantan, Java, Papua, and Sumatra. Indonesia's longest river, the Kapuas, which is 1,143 kilometers (710 miles) long, is in Kalimantan, flowing from the north-central mountains to the South China Sea. Other major rivers in Kalimantan are the Barito, Mahakham, and Rajang. Southern Kalimantan is crisscrossed with a network of hundreds of smaller rivers.
Sumatra's rivers include the Batanghari and Musi in the south, and the Indragiri and Kampar in the center of the island. Java's rivers are used for irrigation; they include the Solo, which is Java's longest at 560 kilometers (348 miles), Tarum, and Brantas. Many rivers wind through Papua, including the Mamberamo, which runs into the Pacific Ocean.
There are no deserts in Indonesia.
Many of the Lesser Sunda Islands, including Sumba, Lombok, Sumbawa, and Timor, have extensive grassland areas, as do parts of Sumatra, Kalimantan, Sulawesi, and Papua. Most of these grasslands are areas where forests have been cut or burned. Bamboo, both wild and cultivated, grows in many parts of Indonesia, although wild bamboo is also being cleared.
Indonesia has a variety of forest types: rainforests in Sumatra, Kalimantan, and Papua; monsoon forests in the Lesser Sunda Islands; coastal mangrove forests; and alpine forests in the mountains of Papua. Indonesia has been estimated to be the habitat of 12 percent of the world's mammal species and 16 percent of the bird species, as well as 11 percent of plant species.
Many hill areas on Bali and Java are covered with rice terraces, which help to prevent soil erosion. On Java, tea plantations occupy numerous hillsides as well. The area of volcanic foothills of the Bandung district is the best-known hill region of Java. The islands of Nusa Tenggara, including Lombok and Timor, have grass-covered hills. Much of Sulawesi is highland, including the region called Torojaland in the south of the island. Kalimantan's north-central region is distinguished by hilly terrain.
The mountains of Indonesia are chains that run underneath the sea and show their peaks and ridges above it in the form of islands. Sulawesi is extremely mountainous, with peaks rising in places to well over 2,438 meters (8,000 feet).
The Barisan Mountains of Sumatra follow the island's west coast. The highest peaks reach more than 3,600 meters (12,000 feet), with Kerintji (3,805 meters/12,483 feet) being the tallest. On Java, the mountains also lie close to the shoreline of the Indian Ocean. The highest peaks are in the Tengger Mountains in the east. Many of the islands of Nusa Tenggara and the Maluku (the islands between Sulawesi and New Guinea) are mountainous. On Bali, Lombok, and Ceram, there are peaks of over 3,048 meters (10,000 feet).
Papua in New Guinea has towering non-volcanic mountains, the highest in Indonesia. The Maoke Mountains extend almost the entire length of the province. Some peaks are covered with snow throughout the year, including Puncak Jaya, (5,030 meters/16,503 feet) the country's loftiest peak. Puncak Jaya is counted (for the continent of Australia/Oceania) as one of the "Seven Summits" sought by mountaineers who attempt to climb the highest peak on every continent.
The Muller Mountains of Borneo run mainly along Indonesia's northern border with Malaysia. Mount Raya (2,278 meters/7,474 feet) is the highest peak.
Lying along the borders of the Eurasian, Australian, and Philippine Tectonic Plates, Indonesia is the most highly volcanic region in the world. More than one hundred peaks either are active or were active until recently. The greatest population density is to be found in the regions where volcanoes have erupted. Thus Java, with the most volcanoes, is by far the most densely populated of the islands.
Rivers have carved dramatic canyons in some regions of Sumatra and Java. In Sumatra, notable canyons include Sianok Canyon, a 150-meter (492-feet)-deep limestone gorge that is 15 kilometers (9 miles) long; the Harau Valley nature reserve, which is 492 to 1,312 feet (150 to 400 meters) wide, with walls 80 to 300 meters (262 to 984 feet) deep; and the Anai Valley gorge. The Green Canyon, a nature reserve, is situated in western Java close to the coast. Many caves also can be found in Java on the Thousand Hills (Gunung Sewu) Plateau.
The island of Sumatra has significant plateau areas, including Tanah Karo with approximately 5,000 square kilometers (1,930 square miles) of fertile volcanic soil; the Agam Plateau; and the Maninjau Plateau, which rises 700 meters (2,296 feet) above Maninjau Lake. The landscape of Java is elevated in the Thou-sand Hills Plateau and the Dieng Plateau, an area famous for its mineral lakes and ancient Hindu temple ruins.
Due to the abundance of lakes, dams are common in Indonesia and provide power for many households. These dams create many artificial lakes, most notably along the Asahan River.
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