Terrain shapes and bedrock
COUNTRYAAH, Indonesia's many islands lie in arcuate rows along the
continental shelves, often with deep-sea tombs on the convex
side. In Indonesia, the Eurasian plate, the Pacific plate
and the Indian-Australian plate meet. Along the boundaries
between these large plates and a number of smaller ones
between them, different types of movements occur, such as
collisions, fracturing and rotation. Indonesia, together
with the surrounding mainland, forms a moving and fragmented
land area. Deep-sea tombs and volcanoes form when one plate
dives below another. Thus, Borneo, Sumatra and Java as well
as Bali and the other Small Sunda Islands form part of the
Eurasian plate. This is bounded by the Java tomb in the
south, where the Indian-Australian plate dives. The Sulawesi
and the Moluccas with their associated tombs are an
extension of the Philippines and the Japanese islands.
Low alluvial plains spread along the coasts. At Borneo,
their average height falls below 200 m above sea level.
Sumatra, 1,700 km long, has two mountain ranges between
the two coastal plains, of which the western is volcanically
Java is 1,050 km long and has several longitudinal zones,
including a northern one with some 35 active volcanoes, of
which 17 have recently erupted. The many small islands have
similar structure and terrain.
Irian Jaya is penetrated by a wide and high mountain
range, whose highest peak reaches 5,030 m above sea level.
It has a core of gneisses and granites, most overlain by
young sediments, and belongs to the alpine mountain range.
Indonesia's location on both sides of the equator
provides a humid tropical climate. The temperature is high
and even all year round and varies more with the altitude
than with the latitude. The annual average temperature is
23-31 ～ C, but varies widely in the mountain areas. Only in
Irian Jaya is the height sufficient for snow to fall.
The rainfall in Indonesia follows the monsoon and varies
greatly. Most rain falls in December - March, while June -
October is dry season in the area from central Java and
east. The annual rainfall in most of Indonesia is
2,000-3,000 mm or more. The western monsoon from Southeast
Asia provides high rainfall in southern Sumatra, Java and
the Small Sunda Islands, while the eastern monsoon in June -
August introduces dry air from Australia. As it passes the
equator it becomes southwest monsoon and provides additional
Botanically, the area - along with tropical South America
- is the richest in the world, with perhaps 45,000 species
of vascular plants. It is dominated by tropical rainforests,
including species in the families palms (including sago
palm), mulberry plants (including figus), dipterocarpus
plants, cherimoyas plants and clusia plants. The rainforests
are rich in epiphytes, not least orchids (more than 2,000
species in New Guinea). Despite extensive forests, there are
still large areas of native forest, mainly on Sumatra,
Borneo and western New Guinea. The densely populated Java is
dominated by rice crops and has only fragments of natural
vegetation. In drier areas, there are sparse, deciduous
monsoon forests, which have often been transformed into
savannah or grassland dominated by, among other things. the
genus Imperata and Andropogon. At sea bays
and estuaries, mangrove vegetation occurs, often along with
the low-stemmed nipa palm.
Of the approximately 2,200 families in the area, 25% are
white, 25% Asian, 40% more or less endemic, 5% Australian,
and a few (mainly on mountain peaks) of Holarctic origin.
Australian elements include the genus iron trees and
eucalyptus. The world's southernmost pine species,
Piʹnus merkuʹsii, grows on Sumatra.
Since colonial times, Leiden in the Netherlands has been
the center of exploration of Indonesia's flora; where
coordinated the Flora Malesiana project (started in
the 1940s). One of the world's largest botanical gardens is
found in Bogor near Jakarta.
Wildlife is very rich and includes more than 500 species
of mammals (of which almost 200 are endemic), about 1,500
species of birds, about 1,000 species of amphibians, about
7,000 species of fish and probably well over 100,000 species
of insects. The richness of the species is because
rainforest biome dominates, because isolated islands provide
a prerequisite for species formation and because Indonesia
lies within two different animal geographic regions with
different fauna: the oriental region west of
Sulawesi and the Australian region (compare animal
geography). Within the former region there are a number of
large placental mammals, such as Indian elephant, orangutan
(Borneo and Sumatra), nose monkey (Borneo), macaques, leaf
monkeys, gibbones, tiger (Sumatra) and other cats, Malay
bear, deer, scabies, java horn, Sumatran rhino (Sumatra and
Borneo) and a variety of Asian bird groups; in the other
region there are marsupials, paradise birds, deciduous birds
Many islands have endemic species, on Sulawesi almost all
mammals, including anoa and dwarf genoa (two related species
of ox animals) and two species of ghost animals, on Borneo
79 species of mammals, on Bawean Kuhl's deer (Ceʹrvus
kuʹhli); silver-colored gibbon (Hyloʹbates moʹloch),
on Komodo and Rinca the giant Komodo Waran and on New
Guinea, among others. long- billed marsupial pigs (Zagloʹssus
bruiʹjni) and a wide variety of bird species.
There are three species of crocodiles in Indonesia: delta
crocodile (formerly widespread throughout the area, now
rare), New Guinea crocodile (Crocodyʹlus
noʹvaeguineʹae; endemic in New Guinea) and false gavial
(on Borneo and Sumatra). Among the insects are the large
colorful bird butterflies, up to more than 30 cm long
wandering sticks, wandering leaves and very large cicadas.
See also Borneo and New Guinea.
In 2010, Indonesia had 50 national parks (including three
marinas). Of these, six were World Heritage sites. About 15%
of Indonesia's land area has some form of nature protection.