shows the physiography of India. The country is divided into five major physiographic divisions
The Himalayas The North Indian Plains The Peninsula Coastal Plains Island groups.
Himalayas: The Himalayas is one
of the young fold mountains in the world. The Himalayas extend from Pamir Knot in Tajikistan to the east. It is a major mountain system of the Asian continent. In India, it extends from Jammu and Kashmir to Arunachal Pradesh.
The Himalayas is not a single mountain range. There are many parallel ranges in the system. The southernmost is known as Siwaliks. It is also the youngest range. Next to Siwaliks are Lesser Himalayas, Greater Himalayas (Himadri) and Trans Himalayan ranges from south to north. These ranges are young to old respectively.
These mountain ranges are also divided into Western Himalayas (or Kashmir Himalayas), Central Himalayas (or Kumaun Himalayas) and Eastern Himalayas (or Assam Himalayas).
North Indian Plains: This division lies
between Himalaya Mountains in the north and the Peninsula in the south. Similarly, it extends from Rajasthan and Punjab in the west to Assam in the east. It is mostly a flat low lying area. The North Indian Plains are divided into two parts. The part lying to the east of the Aravalis is the basin of the river Ganga and is therefore known as the Ganga Plains. It slopes eastward.
Most of the West Bengal State of India.
and Bangladesh together constitute the delta of Ganga-Brahmaputra system. It is known as Sunderbans. It is considered to be the world's largest delta.
The western part of the North Indian Plains is occupied by desert. It is also known as Thar Desert or Marusthali. Most of Rajasthan is occupied by this desert. To the north of the desert lie the plains of Punjab. This region is spread to the west of Aravalis and Delhi ranges. These plains have formed as a result of the depositional work by river Sutluj and its tributaries. The slope of the plains is towards the west. Because the soil here is very fertile, agriculture is largely practised in this region.
The Peninsula: The area lying to the south of North Indian Plains and tapering towards the Indian Ocean is called Indian Peninsula. It consists of many plateaus and hill ranges. The Aravalis in the north are the oldest fold mountains here. It includes a series of plateaus bordering the Plains, Vindhyas and Satpuda ranges in the central part and the hilly regions of Western and Eastern Ghats.
On the basis of Fig 3.1, answer the following questions:
In which direction do the Aravalis lie ?
Aravali ranges act as a water divide between which rivers?
Name the hills located on the plateaus to the east of Aravalis.
Across which states has the Deccan Plateau spread?
Which hill ranges lie to the west of the Deccan Plateau?
➤ Enumerate the characteristics of the Western Ghats.
➤ Compare the Eastern and the Western Ghats.
➤ Why are the Western Ghats called a water divide?
The Coastal Plains: India is blessed with
a long coastline extending for approximately 7500 km. It lies to the western and eastern part of the Peninsula. Its western and eastern coastlines show remarkable dissimilarities.
The western coast borders the Arabian Sea. It is by and large a rocky coast. At places, spurs taking off from the Western Ghats have extended right up to the coast. Its width is also less. Rivers originating from Western Ghats are short and swift and hence they form estuaries and not deltas.
The eastern coast borders the Bay of Bengal. It has formed as a result of depositional work of rivers. Many east flowing rivers starting from the Western and Eastern Ghats meet this. coast. Because of the gentle slope of the land, rivers flow at lower velocities and deposit the sediments brought with them at the coast. As a result, deltas are found along this coast.
The Island group India has many small and large islands along the coast of the mainland. These are included in the coastal island group. Besides, India has two large group of islands, one each in the Arabian Sea and in Bay of Bengal. The islands in the Arabian Sea are known as Lakshadweep whereas the islands in the Bay of Bengal are called the Andaman and Nicobar Islands.
Most of the islands in Lakshadweep are. atoll islands. They are small in extent and not very high.
Islands in the Andaman group are mainly volcanic islands. They are large with hills in their interior parts of includes an island called Barren Island which has the only active volcano in India. There are atolls in the Nicobar group too.
Brazil:
Even a cursory look at the map will make you realize that a large part of Brazil is occupied by highlands, plateaus and small mountains. There are no very high and long extending mountains in the country. Except for the northern Amazon basin and in southwest along the upper parts of Paraguay basin, there are no wide plains in the country. Even the coastal plains are restricted in their expanse. The physiographic divisions of Brazil are as follows.
The Highlands
The Coastal region
The Great Escarpment
The Island groups
The Plains.
The Highlands The southern Brazil is occupied by an extensive plateau. It is differently described as Brazilian Highlands or Brazilian Shield or Brazilian Plateau. Brazilian and Guyana Highlands together form the core of South American continent.
The main part of the Guyana highlands is in Venezuela and extends upto French Guiana. In Brazil, it covers the states of Roraima, Para and Amapa in the north. The lower part of these highlands is found in Brazil. But the highest peak of Brazil, Pico de Neblina, is 3014 m high and lies on the border between Brazil and Venezuela.
The regions to the east and south of the Brazilian highlands have an altitude of more than 1000m. But in other parts, the altitude is between 500 to 1000m. The highlands gradually slope towards north and slopes are not very steep. The tributaries of Amazon flowing through this region make rapids and waterfalls. Towards the north the slopes are steep but not abrupt. A number of rivers take off from the terminal portion of the highlands and flow northwards to meet Atlantic Ocean Some major rivers like Uruguay, Paraguay and Parana originate from the southern slopes of the highlands and enter Argentina. Its slope towards the east is steep and it appears in the form of an escarpment.
The Great Escarpment Though it occupies a very small area, the nature of its slope and the effect it has on the climate makes it a separate physiographic region. The eastern side of the Highlands is demarcated because of the escarpment. In this region, the altitude of the escarpment is 790m. In some regions, the height decreases gradually. The escarpment is very steep particularly from Sao Paulo to Porto Alegre. The escarpment act as a barrier to the Southeast Trade winds giving rise to the rain--shadow area in the northeastern part of the highlands. The region to the north of this area is called 'Drought Quadrilateral".
The coasts Brazil has a coastline of about 7400 km. One may divide that into two parts namely northern and eastern coast. The northern coast extends from Amapa province in the north to Rio Grande do Norte in the east. This can be called as the North Atlantic coast. From there, the eastern coast extends towards the south.
The northern coast is characterized by mouths of many rivers including the Amazon. Therefore this region is a low-lying region. On this coast lie the Marajo island, Marajo and Sao Marcos Bays. Marajo is a large coastal island located between the mouths of River Amazon and River Tocantins,
The eastern coast receives large number of smaller rivers. The only major river which meets the Atlantic Ocean here is Sao Francisco. The Brazilian coast is characterized by a large number of beaches and sand dune complexes. The Brazilian coast is protected in some areas by coral reefs and atoll islands.
The Plains The plains in Brazil are confined to two areas namely the Amazon basin in the north and Paraguay-Parana source region in the southwest. Amazon plains lying between the two highlands form the largest plain land. of Brazil. Amazon plains lying in the northern parts of Brazil generally slope eastwards. The Amazon basin is quite wide in the west (about 1300 km) and it narrows eastward. Its width is minimum where the Guyana Highlands and Brazilian Highland come closer. (240 km.) As the river approaches the Atlantic Ocean, the width of the plains increases. These are mostly forested areas and largely inaccessible due to frequent flooding and dense undergrowth. Most of the Amazon plains are covered by tropical rainforests.
The other plains in Brazil are located to the southwestern part of the highlands. They form the source region of Paraguay and Parana rivers. The source region of Paraguay slopes towards the south while the source region of Parana slopes towards the southwest.
Pantanal is one of the largest wetlands in the world. It lies towards the southwest part of the highland areas. It is a region of swamps and marshes in northwestern Mato Grosso do Sul in Brazil and it extends into Argentina too.
Islands Besides the mainland, some islands are also included in Brazil. They can be classified into coastal islands and marine islands. Most of the coastal islands have formed due to deposition. Marine islands were a part of the mainland. They are more than 300 km away from the mainland in the Atlantic Ocean. These islands are mostly rocky and they are the top of the submerged mountains. The islands near the coast of the South Atlantic Ocean are coral islands and they are called atolls.
Maps showing major rivers of Brazil and India are shown in figure 3.3 and 3.4. Take two tracing papers and prepare drainage basin maps of Amazon and Ganga. Name the basins.
Write a comparative note on the basins of Ganga and Amazon river. You may consider following points for the comparison.
Size of catchment area (consider the map)
Their relative location within respective countries
Headwater regions of rivers.
Orientation of the rivers
Major tributaries and their orientation.
Drainage of Brazil: As far as the drainage
in Brazil is concerned, there are three major river Basins.
Amazon Basin
Paraguay-Parana system in the southwest
Sao Francisco in the eastern part of highland and other rivers at the coasts
Amazon basin: Amazon collects its headwaters
from the eastern slopes of Andes Mountains in Peru. Amazon River receives huge discharge. This is about 2 lakh m3/s. As a result, Amazon washes off the load supplied to it from the catchment. Consequently, sediments are not deposited even at the mouth. A dense network of distributaries, which is a characteristic feature of river mouth areas, is by and large absent in the mouth region of Amazon. Instead we find a series of islands developed along the mouth of Amazon beyond the coast line in to the Atlantic Ocean. It will be interesting to note that at the mouth the width of Amazon channel is 150 km. (Take into consideration a place which is 150kms away from your home. You will get an idea of the width). Most of the course of the Amazon river is suitable for navigation.
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