Indonesia Natural Environment

The word “ Indonesia ” is quite an appropriate name for the country.   It is derived from “ Indus ” meaning India , and the Greek word “nesos” meaning island.   Indeed, Indonesia for many centuries was ruled by many Indianised kingdoms, and it has 17,508 islands, the largest archipelago in the world.

As the archipelago stretches thousands of km from east to west, Indonesia has three time zones.   The Western time zone, which is 7 hours ahead of GMT, includes Sumatra , Java, and eastern Kalimantan , and ends between Java and Bali .   The Central time zone is 8 hours ahead and includes western Kalimantan , Nusa Tenggara, and Sulawesi .   The Eastern time zone is 9 hours ahead and includes the Malukus and Irian Jaya. The boundary between the western and central time zones--established in 1988--is a line running north between Java and Bali through the center of Kalimantan .

The country has a total land area of 1,919,440 sq km, with Asia to its north and Australia to its southeast, straddling the equator.   The larger of its islands include Java, Sumatra , Sulawesi , Kalimantan , Papua.   The world-renowned resort island of Bali is relatively small.   Only about 6,000 of the islands are inhabited.   Jakarta, on Java, is the capital and the nation's largest city.  

As Indonesia is made up of many islands, it shares land borders with several countries on separate islands: Malaysia on the islands of Borneo and Sebatik, Papua New Guinea on the island of New Guinea, and East Timor on the island of Timor.   It is separated from Singapore and Malaysia by the narrow Strait of Singapore and the Strait of Malacca.   From Singapore, one can see the island of Batam and cross over to the island of Bintan in no more than 30 minutes.   Indonesia is also separated from the Philippines by a narrow strip of water.

Whereas many islands in Indonesia are densely populated, Kalimantan (occupying about two-thirds of Borneo) is covered mainly by mountains, rivers, caves and jungles.   It has an area of just below 550,000 sq km, and has a population of around 11 million.

Java is the world’s most populous island.   In order to have the country’s population more evenly distributed, the government has, in the past two decades, encouraged “trans-migration” to other islands.   This has met with some success.

Geologically, Indonesia sits on the south Asia section of the “Ring of Fire”, the seismically active zone around the edge of the Pacific Ocean dotted by volcanoes and frequented by earthquakes.   Just counting active volcanoes alone, Indonesia has at least 150 of them, with the island of Sumatra having 35 – all on the western edge facing the Indian Ocean.

The volcano on the island of Krakatoa in the strait between Java and Sumatra, which erupted in 1883, blew off the entire island and since 1927 has been growing again at the rate of about 5 meters a year by height.  

The most deadly volcano in recent times is Tambora on the island of Sumbawa east of Java erupted in 1815, killing at least 70,000 people.   The eruptions in 1883 and 1815 were so violent that world weather patterns were affected for many months after the eruptions.  

The largest volcanic eruption in world history occurred with the Toba volcano in Sumatra about 70,000 years ago, which blew the top off the volcano and created a giant 1,145 sq km lake crater lake.  

The most active, though less deadly, volcano is Mt Merapi near Yogyakarta in Central Java.   Another well known active volcano is Mt Bromo as it is a popular tourist attraction in eastern Java.

Apart from volcanoes, movement of the tectonic plates off the western coast of Sumatra caused the 2004 tsunami, which killed over 200,000 people in countries ringing the Indian Ocean.

Destructive as they are, the volcanoes in Indonesia have provided fertile soil to the country which has helped to support its population of about 238 million.
 
 
 

Hot is the word which fairly accurately describes the climate in Indonesia throughout the country and throughout the year.  As all the islands in the country lie near the equator, there are no seasonal variations in climate, with average temperature constantly being in the 25 to 33 °C range.   Mountains and land in higher elevations are cooler.   Kalimantan, with its tropical rainforests, generally has the same weather pattern as the rest of the country, but has some local variations because of vegetation and topography.

Dryer weather comes in the June to September period when the east monsoon arrives.  A lot more rain falls between December to March, brought by the west monsoon.   There are regional variations in the rainfall pattern, with lowlands receiving average rainfall of over 180 cm a year, and mountains and western Sumatra getting as much as 600 cm a year.

Relative humidity stays high throughout the year, being close to 100% at times.