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India
Indo-Gangetic Plain
In social and economic terms, the Indo-Gangetic Plain is the most
important region of India. The plain is a great alluvial crescent
stretching from the Indus River system in Pakistan to the Punjab
Plain (in both Pakistan and India) and the Haryana Plain to the
delta of the Ganga (or Ganges) in Bangladesh (where it is called
the Padma). Topographically the plain is homogeneous, with only
floodplain bluffs and other related features of river erosion and
changes in river channels forming important natural features.
Two narrow terrain belts, collectively known as the Terai, constitute
the northern boundary of the Indo-Gangetic Plain. Where the foothills
of the Himalayas encounter the plain, small hills known locally
as ghar (meaning house in Hindi) have been formed by coarse
sands and pebbles deposited by mountain streams. Groundwater from
these areas flows on the surface where the plains begin and converts
large areas along the rivers into swamps. The southern boundary
of the plain begins along the edge of the Great Indian Desert in
the state of Rajasthan and continues east along the base of the
hills of the Central Highlands to the Bay of Bengal . The hills,
varying in elevation from 300 to 1,200 meters, lie on a general
east-west axis. The Central Highlands are divided into northern
and southern parts. The northern part is centered on the Aravalli
Range of eastern Rajasthan. In the northern part of the state of
Madhya Pradesh, the Malwa Plateau comprises the southern part of
the Central Highlands and merges with the Vindhya Range to the south.
The main rivers that flow through the southern part of the plain--the
Narmada, the Tapti, and the Mahanadi--delineate North India from
South India (see Rivers, this ch.).
Some geographers subdivide the Indo-Gangetic Plain into three parts:
the Indus Valley (mostly in Pakistan), the Punjab (divided between
India and Pakistan) and Haryana plains, and the middle and lower
Ganga. These regional distinctions are based primarily on the availability
of water. By another definition, the Indo-Gangetic Plain is divided
into two drainage basins by the Delhi Ridge; the western part consists
of the Punjab Plain and the Haryana Plain, and the eastern part
consists of the Ganga-Brahmaputra drainage systems. This divide
is only 300 meters above sea level, contributing to the perception
that the Indo-Gangetic Plain appears to be continuous between the
two drainage basins. The Punjab Plain is centered in the land between
five rivers: the Jhelum, the Chenab, the Ravi, the Beas, and the
Sutlej. (The name Punjab comes from the Sanskrit pancha
ab , meaning five waters or rivers.)
Both the Punjab and Haryana plains are irrigated with water from
the Ravi, Beas, and Sutlej rivers. The irrigation projects emanating
from these rivers have led to a decrease in the flow of water reaching
the lower drainage areas in the state of Punjab in India and the
Indus Valley in Pakistan. The benefits that increased irrigation
has brought to farmers in the state of Haryana are controversial
in light of the effects that irrigation has had on agricultural
life in the Punjab areas of both India and Pakistan.
The middle Ganga extends from the Yamuna River in the west to the
state of West Bengal in the east. The lower Ganga and the Assam
Valley are more lush and verdant than the middle Ganga. The lower
Ganga is centered in West Bengal from which it flows into Bangladesh
and, after joining the Jamuna (as the lower reaches of the Brahmaputra
are known in Bangladesh), forms the delta of the Ganga. The Brahmaputra
(meaning son of Brahma) rises in Tibet (China's Xizang Autonomous
Region) as the Yarlung Zangbo River, flows through Arunachal Pradesh
and Assam, and then crosses into Bangladesh. Average annual rainfall
increases moving west to east from approximately 600 millimeters
in the Punjab Plain to 1,500 millimeters around the lower Ganga
and Brahmaputra.
The Himalayas
The Himalayas, the highest mountain range in the world, extend
along the northern frontiers of Pakistan, India, Nepal, Bhutan,
and Burma. They were formed geologically as a result of the collision
of the Indian subcontinent with Asia. This process of plate tectonics
is ongoing, and the gradual northward drift of the Indian subcontinent
still causes earthquakes (see Earthquakes, this ch.). Lesser ranges
jut southward from the main body of the Himalayas at both the eastern
and western ends. The Himalayan system, about 2,400 kilometers in
length and varying in width from 240 to 330 kilometers, is made
up of three parallel ranges--the Greater Himalayas, the Lesser Himalayas,
and the Outer Himalayas--sometimes collectively called the Great
Himalayan Range. The Greater Himalayas, or northern range, average
approximately 6,000 meters in height and contain the three highest
mountains on earth: Mount Everest (8,796 meters) on the China-Nepal
border; K2 (8,611 meters, also known as Mount Godwin-Austen, and
in China as Qogir Feng) in an area claimed by India, Pakistan, and
China; and Kanchenjunga (8,598 meters) on the India-Nepal border.
Many major mountains are located entirely within India, such as
Nanda Devi (7,817 meters) in the state of Uttar Pradesh. The snow
line averages 4,500 to 6,000 meters on the southern side of the
Greater Himalayas and 5,500 to 6,000 on the northern side. Because
of climatic conditions, the snow line in the eastern Himalayas averages
4,300 meters, while in the western Himalayas it averages 5,800 meters.
The Lesser Himalayas, located in northwestern India in the states
of Himachal Pradesh and Uttar Pradesh, in north-central India in
the state of Sikkim, and in northeastern India in the state of Arunachal
Pradesh, range from 1,500 to 5,000 meters in height. Located in
the Lesser Himalayas are the hill stations of Shimla (Simla) and
Darjiling (Darjeeling). During the colonial period, these and other
hill stations were used by the British as summer retreats to escape
the intense heat of the plains. It is in this transitional vegetation
zone that the contrasts between the bare southern slopes and the
forested northern slopes become most noticeable.
The Outer or Southern Himalayas, averaging 900 to 1,200 meters
in elevation, lie between the Lesser Himalayas and the Indo-Gangetic
Plain. In Himachal Pradesh and Uttar Pradesh, this southernmost
range is often referred to as the Siwalik Hills. It is possible
to identify a fourth, and northernmost range, known as the Trans-Himalaya.
This range is located entirely on the Qinghai-Xizang Plateau, north
of the great west-to-east trending valley of the Yarlung Zangbo
River. Although the Trans-Himalaya Range is divided from the Great
Himalayan Range for most of its length, it merges with the Great
Himalayan Range in the western section--the Karakoram Range--where
India, Pakistan, and China meet.
The southern slopes of each of the Himalayan ranges are too steep
to accumulate snow or support much tree life; the northern slopes
generally are forested below the snow line. Between the ranges are
extensive high plateaus, deep gorges, and fertile valleys, such
as the vales of Kashmir and Kulu. The Himalayas serve a very important
purpose. They provide a physical screen within which the monsoon
system operates and are the source of the great river systems that
water the alluvial plains below (see Climate, this ch.). As a result
of erosion, the rivers coming from the mountains carry vast quantities
of silt that enrich the plains.
The area of northeastern India adjacent to Burma and Bangladesh
consists of numerous hill tracts, averaging between 1,000 and 2,000
meters in elevation, that are not associated with the eastern part
of the Himalayas in Arunachal Pradesh. The Naga Hills, rising to
heights of more than 3,000 meters, form the watershed between India
and Burma. The Mizo Hills are the southern part of the northeastern
ranges in India. The Garo, Khasi, and Jaintia hills are centered
in the state of Meghalaya and, isolated from the northeastern ranges,
divide the Assam Valley from Bangladesh to the south and west.
Data as of September 1995
India
The Peninsula
The Peninsula proper is an old, geologically stable region with
an average elevation between 300 and 1,800 meters. The Vindhya Range
constitutes the main dividing line between the geological regions
of the Indo-Gangetic Plain and the Peninsula. This range lies north
of the Narmada River, and when viewed from there, it is possible
to discern the prominent escarpments that rise between 800 and 1,400
meters. The Vindhya Range defines the north-central and northwestern
boundary of the Peninsula, and the Chota Nagpur Plateau of southern
Bihar forms the northeastern boundary. The uplifting of the plateau
of the central Peninsula and its eastward tilt formed the Western
Ghats, a line of hills running from the Tapti River south to the
tip of the Peninsula. The Eastern Ghats mark the eastern end of
the plateau; they begin in the hills of the Mahanadi River basin
and converge with the Western Ghats at the Peninsula's southern
tip.
The interior of the Peninsula, south of the Narmada River, often
termed the Deccan Plateau or simply the Deccan (from the Sanskrit
daksina , meaning south), is a series of plateaus topped
by rolling hills and intersected by many rivers. The plateau averages
roughly 300 to 750 meters in elevation. Its major rivers--the Godavari,
the Krishna, and the Kaveri--rise in the Western Ghats and flow
eastward into the Bay of Bengal.
The coastal plain borders the plateau. On the northwestern side,
it is characterized by tidal marshes, drowned valleys, and estuaries;
and in the south by lagoons, marshes, and beach ridges. Coastal
plains on the eastern side are wider than those in the west; they
are focused on large river deltas that serve as the centers of human
settlement.
Offshore Islands
India's offshore islands, constituting roughly one-quarter of 1
percent of the nation's territory, lie in two groups located off
the east and west coasts. The northernmost point of the union territory
of the Andaman and Nicobar Islands lies 1,100 kilometers southeast
of Calcutta. Situated in the Bay of Bengal in a chain stretching
some 800 kilometers, the Andaman Islands comprise 204 islands and
islets, and their topography is characterized by hills and narrow
valleys. Although their location is tropical, the climate of the
islands is tempered by sea breezes; rainfall is irregular. The Nicobar
Islands, which are south of the Andaman Islands, comprise nineteen
islands, some with flat, coral-covered surfaces and others with
hills. The islands have a nearly equatorial climate, heavy rainfall,
and high temperatures. The union territory of Lakshadweep (the name
means 100,000 islands) in the Arabian Sea, comprises--from north
to south--the Amindivi, Laccadive, Cannanore, and Minicoy islands.
The islands, only ten of which are inhabited, are spread throughout
an area of approximately 77,000 square kilometers. The islands are
low-lying coral-based formations capable of limited cultivation.
Data as of September 1995
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