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Geology and geography
Island like a drunken spider

The peninsulas of Sulawesi are compared in the introduction with leaves of an orchid in the wind. With it's loose attachments the island can also be seen as a brunken spider. It's probably the worlds most strangely shaped island, which consists of a group of long stretched islands which have collided by movements in the earth, of which the results can still be seen. Flora and fauna are strongly influences by the nearby Philippines, the Lesser Sunda Islands (Nusa Tenggara) and Maluku, but not obviously by the neighboring Borneo. Still the natural history of Sulawesi isn't completely Asian; eucalyptus trees and animals which have originated from Australia.
The total land mass, including the concluding islands is 227,000, a little less than the United Kingdom. The distance from the most northern island Miangas, slightly less than 90 kilometers south of the Philippine island of Mindanao, to the most southern island of Satengar, is the same as that from Amsterdam to Moscow, 2000 kilometers.

A roaring start

About 250 milion years ago the earth was made up from two big continents, Laurasia (the current North-America, Europe and a big part of Asia) and Gondwana (the current South-America, Afria, India, Australia, Antarctica and the remaining part of Asia). Until ten years ago it was accepted that the geological history of Indonesia and the surrounding areas, Malacca, Sumatra, Jawa, Borneo and West-Sulawesi were a part of Lauriasia and were separated from East-Sulawesi, Timor, Seram and other islands that were part of the more southern Gondwana a short time (geologically seen) ago.
This image was changed due to recent geological survey. Proven is that Southern-Tibet, Birma, Thailand, Malakka and Sumatra were in fact a part of Gondwana and that they got de-attached from the Australian - New-Guinee part of the continent. It is assumed that West-Sulawesi, together with Sumatra, Borneo and other islands de-attached from Gondwana about 180 milion years ago. About 90 milion years ago East-Sulawesi separated itself together with New-Guinee, Maluku and Australia from Antarctica and hurried towards the north with a speed of about 10 centimeters a year.
About 15 milion years ago the current East-Sulawesi de-attached from New-Guinee and collided with another islans. It touched the current West-Sulawesi like an arrow and caused the southwestern peninsula to rotate anti-clockwise since then. The Gulf of Bone was formed between South- and Southeast-Sulawesi and the northern peninsula turned around 90 degrees clockwise.
People said, that West-Sulawesi collided with East-Borneo about 3 milion years ago, which caused the Selat Makassar to be closed, this is not proven however. Evidence for this theory is missing, but submarine contours from East-Borneo exactly match those of West-Sulawesi. Thick layers of sediment in Selat Makassar tell that this straigt has been open for at least 25 milion years.
The sealevel has fluctuated dramatically in the last 10 milion years, under the influence of ice ages. During periods with a low sealevel islands surfaced, mainly in the south. At times that the sealevel was 100 meters lower than it is now, there should have been an almost uninterrupted land mass between Southeast Borneo and Southwest-Sulawesi. Then seas were high, Sulawesi should have been several islands which were cut off by straits near Gorontalo and Danau Tempe. The last climax of the sealevel took place about 4000 years ago, when sealevels were four to six meters higher than nowadays. Inhabitants of Sulawesi tell storied about a time that travellers didn't have to go around the southern tip of the island, but they could cut through from the Gulf of Bone to Selat Makassar through the silty Danau Tempe. Active faultlines stretch from Gorontalo, from Palu to the south to Koro, through Danau Matana and near Lawuk. The main island still undergoes a process of fragmentation; it could form a group of islands in the far future, separated from eachother by small straits, like currently on the Philippines.

Coasts and reefs

With it's long and thin peninsula's, Sulawesi has a lot of coastal areas in comparison to it's land mass, in fact it has most coasts than any other Indonesian island. Not a single point on the main island is further away than 90 kilometers from the sea and most points only 50 kilometers. Above all, the provinces conclude over 110 islands with a surface larger than 1,5
Along most coasts you can find coral reefs. The most easy to reach (and the most damaged because of that) are the 16.000 reefs in the Sangkarang- or Spermonde archipelago. The reefs around Bunaken and the neighboring islands north of Manado are also reasonably good accessible. The coral reefs of the Togian Islands and the Tomini Bay are less well-known. These are unique in Indonesia because all important reef environments can be found here. Sulawesi also has a number of remote and almost untouched reefs and clifs, for example the end of the Tukang Besi Islands in Southeastern Sulawesi.
Sulawesi is mainly mountainous. The biggest part of the island is higher than 500 meters above sealevel, and one fifth is higher than 1000 meters. The highest peaks can be found in Central-Sulawesi and in the northern part of South-Sulawesi; the highest point of the island is Rantemario, north of Enrekang, on 3450 meters. This mountain can be climbed from the southern side. The ascend to the peak is intense and cold, and probably takes several days.
In South-Sulawesi are several dead vulcanoes. The rubble of these has contributed to the fertility of the surrounding plains, just like on Jawa. The most important is Lompobatang ('swollen belly'), southeast of Makassar.
The vulcanoes of North Sulawesi are all but dead. In 1983, a powerfull eruption exhausted a flume 15 kilometers into the atmosphere, some of it came down 900 kilometers away in Southeast Kalimantan. The explosion exterminated the small Pulau Unauna in Teluk Tomini. Luckily all islanders were evacuated. In 1991, Gunung Lokon erupted. A Swiss doctor which wanted to see the crater from a close location, died.
Sulawesi has 11 active vulcanoes (Jawa has 17 and Sumatra has 10) and many fumaroles (exhausts through which hot gasses escape) and boilers. Most of them are in Minahasa in North-Sulawesi. In the last decated Sopotan Aeseput, Lokon Empung and Api Sia (on the island Siau between the mainland and Pulai Sangihe) the most tough vulcanoes. Another vulcano on the Sangihe Talaud-archipelago, the Awu, erupted in 1966, and killed over 7300 people.
These vulcanoes are active because the seabed north of Tolitoli and east of the Minahasa and Sangihe Islands moves towards the northern arm of Sulawesi. Instead of piling up in a mountain, the seabed is forced under the exsisting island. The enourmous power and friction which is caused by this causes earthquakes and a heat which is so intense that the rock melts. Normally the molten rock cools down deeper in the earth, but sometimes it's forced up by a weak spot in the earths crust, to the vulcano on top of it erupts.
Parts of Sulawesi (in the south and southeast) have the biggest concentration of low pH rock in the workd. Because of the high level of magnesium and heavy metals the soil is very infertile. The spread of ultralow pH material is marked by the border of cultivated and uncultivated grounds (with exception of a very ambitious resettlement programs or cultivation projects, in which they tried to cultivate the soil, which no farmer wanted to try before).


Sulawesi is blessed with numerous mineral deposits. Parts of the north are going trough a 'gold rush' now, in which private people and small companies on one side are trying to extract metals with traditional methods. On the other hand the joint-ventures of Indonesian and foreign companies have extensive surveys and have ultramodern mining. Besides this, oilfields have been found, but they aren't commercially exploited on a large scale yet. A deposit has been found south of the eastern arm of Sulawesi, near Luwuk. Near Danau Tempe is liquid natural gas. The island Buton under Southeast-Sulawesi contains the biggest reserves of natural asphalt in Asia.
The biggest mine of the country, near Saroako at the coast of Danau Matana, exploits a big amount of nickle of low quality. The Canadian company Inco started here in 1968 with putting down a big production machine. The ore in the ultra low pH rock formations have changed the life of many farmers in the village completely. The once impenetrable jungle, the source of their existance, has been flattened.

Lakes and rivers

Sulawesi has 13 lakes (danau) which are larger than 5, among them Towuti and Poso, the second and third biggest lakes in Indonesia. During the wet season Danau Tempe equalises the surface of Danau Poso: surrounded by lowlands it can swell to three times it's normal size, from 10,000 hectares to 35,000 hectares. Some lakes, like the Tondano- and Moat lake in North-Sulawesi, are located in the craters of old vulcanoes, while others were formed by landslides. Several waters, like Danau Matana, are very deep. The deepest point lays over 450 meters below the surface and 160 meters under sealevel.
The form of Sulawesi makes the development of big rivers (sungai), like those which can be found on Sumatra or Kalimantan, impossible. The longest river on Sulawesi, Sungai Lariang, which mouths south of Palu in Selat Makassar, is hardly 200 kilometers long.


From September the cooler northwestern winds over the South China Sea, take in moisture. They arrive over the Sulawesi Sea somewhere in November in North-Sulawesi. Similar winds reach the western coast of South-Sulawesi around the end of November and come from the Jawa Sea. The westerncoast of Central-Sulawesi, protected from these winds because Borneo is so close, is relatively more dry.
Around April the changing humid winds blow from the southeast towards East-Sulawesi. Between this month and June there are percipation peaks along the southeastern coast and a little later in the northeast. Southeastern winds from the then dry and winterly, large area of Australia become more strong and more dry and influence the southern tips of Sulawesi. On the Southwestern peninsula, Jeneponto has a long dry season between April and November, while Manado on the northern peninsula has a short dry season from August to October.
The western coast of Sulawesi normally has most percipation in December, while the eastern coast has the most wet period around May. In between are areas with two dry seasons. Valleys which run north-south are almost year-round protected from the rain. Because the central part of Sulawesi is kind of protected, the Palu Valley is one of the most dry areas of Indonesia, with an annual percipation of less than 600 mm. Here, and on the dry tip of the southwestern peninsula, the wealthy cactus is evidence of the consistence of the climate.

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