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Japan Composition, Topography, and Drainage
The mountainous islands of the Japanese Archipelago
form a
crescent off the eastern coast of Asia
(see
fig. 1). They
are
separated from the mainland by the Sea of Japan, which
historically
served as a protective barrier. Japan's insular nature,
together
with the compactness of its main territory and the
cultural
homogeneity of its people, enabled the nation to remain
free of
outside domination until its defeat in World War II
(see World War II and the Occupation, 1941-52
, ch. 1). The country
consists of
four principal islands: Hokkaido, Honshu, Shikoku, and
Kyushu; more
than 3,000 adjacent islands and islets, including Oshima
in the
Nampo chain; and more than 200 other smaller islands,
including
those of the Amami, Okinawa, and Sakishima chains of the
Ryukyu
Islands. The national territory also includes the small
Bonin
Islands (called Ogasawara by the Japanese), Iwo Jima, and
the
Volcano Islands (Kazan Retto), stretching some 1,100
kilometers
from the main islands. A territorial dispute with the
Soviet Union,
dating from the end of World War II, over the two
southernmost of
the Kuril Islands, Etorofu and Kunashiri, and the smaller
Shikotan
and Habomai Islands northeast of Hokkaido remained a
sensitive spot
in Japanese-Russian relations as the mid-1990s approached
(see
Relations with Russia
, ch. 7). Excluding disputed
territory, the
archipelago covers about 377,000 square kilometers. No
point in
Japan is more than 150 kilometers from the sea.
The four major islands are separated by narrow straits
and form
a natural entity. The Ryukyu Islands curve 970 kilometers
southward
from Kyushu.
The distance between Japan and the Korean Peninsula,
the
nearest point on the Asian continent, is about 200
kilometers at
the Korea Strait. Japan has always been linked with the
continent
through trade routes, stretching in the north toward
Siberia, in
the west through the Tsushima Islands to the Korean
Peninsula, and
in the south to the ports on the south China coast.
The Japanese islands are the summits of mountain ridges
uplifted near the outer edge of the continental shelf.
About 75
percent of Japan's area is mountainous, and scattered
plains and
intermontane basins (in which the population is
concentrated) cover
only about 25 percent. A long chain of mountains runs down
the
middle of the archipelago, dividing it into two halves,
the "face,"
fronting on the Pacific Ocean, and the "back," toward the
Sea of
Japan. On the Pacific side are steep mountains 1,500 to
3,000
meters high, with deep valleys and gorges. Central Japan
is marked
by the convergence of the three mountain chains--the Hida,
Kiso,
and Akaishi mountains--that form the Japanese Alps (Nihon
Arupusu),
several of whose peaks are higher than 3,000 meters. The
highest
point in the Japanese Alps is Kitadake at 3,192 meters.
The highest
point in the country is Mount Fuji (Fujisan, also called
Fujiyama
in the West but not in Japan), a volcano dormant since
1707 that
rises to 3,776 meters above sea level in Shizuoka
Prefecture. On
the Sea of Japan side are plateaus and low mountain
districts, with
altitudes of 500 to 1,500 meters.
None of the populated plains or mountain basins is
extensive in
area. The largest, the Kanto Plain, where Tokyo is
situated, covers
only 13,000 square kilometers. Other important plains are
the Nobi
Plain surrounding Nagoya, the Kinki Plain in the
Osaka-Kyoto area,
the Sendai Plain around the city of Sendai in northeastern
Honshu,
and the Ishikari Plain on Hokkaido. Many of these plains
are along
the coast, and their areas have been increased by
reclamation
throughout recorded history.
The small amount of habitable land prompted significant
human
modification of the terrain over many centuries. Land was
reclaimed
from the sea and from river deltas by building dikes and
drainage,
and rice paddies were built on terraces carved into
mountainsides.
The process continued in the modern period with extension
of
shorelines and building of artificial islands for
industrial and
port development, such as Port Island in Kobe and the new
Kansai
International Airport in Osaka Bay. Hills and even
mountains have
been razed to provide flat areas for housing.
Rivers are generally steep and swift, and few are
suitable for
navigation except in their lower reaches. Most rivers are
fewer
than 300 kilometers in length, but their rapid flow from
the
mountains provides a valuable, renewable resource:
hydroelectric
power generation. Japan's hydroelectric power potential
has been
exploited almost to capacity. Seasonal variations in flow
have led
to extensive development of flood control measures. Most
of the
rivers are very short. The longest, the Shinano, which
winds
through Nagano Prefecture to Niigata Prefecture and flows
into the
Sea of Japan, is only 367 kilometers long. The largest
freshwater
lake is Lake Biwa, northeast of Kyoto.
Extensive coastal shipping, especially around the
Inland Sea
(Seto Naikai), compensates for the lack of navigable
rivers. The
Pacific coastline south of Tokyo is characterized by long,
narrow,
gradually shallowing inlets produced by sedimentation,
which has
created many natural harbors. The Pacific coastline north
of Tokyo,
the coast of Hokkaido, and the Sea of Japan coast are
generally
unindented, with few natural harbors
(see
fig. 3).
Data as of January 1994
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