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Indonesia Geographic Regions
Unavailable
Figure 5. Topography and Drainage
Indonesia is a huge archipelagic country extending
5,120
kilometers from east to west and 1,760 kilometers from
north to
south. It encompasses 13,667 islands (some sources say as
many as
18,000), only 6,000 of which are inhabited. There are five
main
islands (Sumatra, Java, Kalimantan, Sulawesi, and Irian
Jaya), two
major archipelagos (Nusa Tenggara and the Maluku Islands),
and
sixty smaller archipelagos. Two of the islands are shared
with
other nations; Kalimantan (known in the colonial period as
Borneo,
the world's third largest island) is shared with Malaysia
and
Brunei, and Irian Jaya shares the island of New Guinea
with Papua
New Guinea. Indonesia's total land area is 1,919,317
square
kilometers. Included in Indonesia's total territory is
another
93,000 square kilometers of inlands seas (straits, bays,
and other
bodies of water). The additional surrounding sea areas
bring
Indonesia's generally recognized territory (land and sea)
to about
5 million square kilometers. The government, however, also
claims
an exclusive economic zone, which brings the total to
about 7.9
million square kilometers
(see National Territory: Rights and Responsibilities
, this ch.).
Geographers have conventionally grouped Sumatra, Java
(and
Madura), Kalimantan (formerly Borneo), and Sulawesi
(formerly
Celebes) in the Greater Sunda Islands. These islands,
except for
Sulawesi, lie on the Sunda Shelf--an extension of the
Malay
Peninsula and the Southeast Asian mainland
(see
fig. 5,
Topography
and Drainage). Far to the east is Irian Jaya (formerly
Irian Barat
or West New Guinea), which takes up the western half of
the world's
second largest island--New Guinea--on the Sahul Shelf. Sea
depths
in the Sunda and Sahul shelves average 200 meters or less.
Between
these two shelves lie Sulawesi, Nusa Tenggara (also known
as the
Lesser Sunda Islands), and the Maluku Islands (or the
Moluccas),
which form a second island group where the surrounding
seas in some
places reach 4,500 meters in depth. The term
Outer Islands (see Glossary)
is used inconsistently by various writers but it
is
usually taken to mean those islands other than Java and
Madura.
Tectonically, this region--especially Java--is highly
unstable,
and although the volcanic ash has resulted in fertile
soils, it
makes agricultural conditions unpredictable in some areas.
The
country has numerous mountains and some 400 volcanoes, of
which
approximately 100 are active. Between 1972 and 1991 alone,
twentynine volcanic eruptions were recorded, mostly on Java. The
most
violent volcanic eruptions in modern times occurred in
Indonesia.
In 1815 a volcano at Gunung Tambora on the north coast of
Sumbawa,
Nusa Tenggara Barat Province, claimed 92,000 lives and
created "the
year without a summer" in various parts of the world. In
1883
Krakatau in the Sunda Strait, between Java and Sumatra,
erupted and
some 36,000 West Javans died from the resulting tidal
wave. The
sound of the explosion was reported as far away as Turkey
and
Japan. For almost a century following that eruption,
Krakatau was
quiet, until the late 1970s, when it erupted twice.
Mountains ranging between 3,000 and 3,800 meters above
sea
level can be found on the islands of Sumatra, Java, Bali,
Lombok,
Sulawesi, and Seram. The country's tallest mountains,
which reach
between 4,700 and 5,000 meters, are located in the
Jayawijaya
Mountains and the Sudirman Mountains in Irian Jaya. The
highest
peak, Puncak Jaya, which reaches 5,039 meters, is located
in the
Sudirman Mountains.
Nusa Tenggara consists of two strings of islands
stretching
eastward from Bali toward Irian Jaya. The inner arc of
Nusa
Tenggara is a continuation of the chain of mountains and
volcanoes
extending from Sumatra through Java, Bali, and Flores, and
trailing
off in the Banda Islands. 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.
The Maluku Islands (or Moluccas) are geologically among
the
most complex of the Indonesian islands. They are located
in the
northeast sector of the archipelago, bounded by the
Philippines to
the north, Irian Jaya to the east, and Nusa Tenggara to
the south.
The largest of these islands include Halmahera, Seram, and
Buru,
all of which rise steeply out of very deep seas. This
abrupt relief
pattern from sea to high mountains means that there are
very few
level coastal plains.
Geographers believe that the island of New Guinea, of
which
Irian Jaya is a part, may once have been part of the
Australian
continent. The breakup and tectonic action created both
towering,
snowcapped mountain peaks lining its central east-west
spine and
hot, humid alluvial plains along the coast of New Guinea.
Irian
Jaya's mountains range some 650 kilometers east to west,
dividing
the province between north and south.
Data as of November 1992
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