Physiography and Drainage Class 10 Geography Notes Maharashtra State Board
Geographical Explanation of India:
The figure 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
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 are 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 the Lesser Himalayas, Greater Himalayas (Himadri) and Trans Himalayan ranges from south to north. These ranges are from 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 the Himalayan 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-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 the 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 the Aravalis and Delhi ranges. These plains have formed as a result of the depositional work by river Sutlej and its tributaries. The slope of the plains is towards the west. Because the soil here is very fertile, agriculture is largely practiced in this region.
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, Vindnyas and Satpuda ranges in the central part and the hilly regions of Western and Eastern Ghats.
The Coastal Plains:
India is blessed with a long coastline extending for approximately 7500 km. It lies in the western and eastern parts 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 the 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 the depositional work of rivers. Many east-flowing rivers using 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 groups of islands, one each in the Arabian Sea and the 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 including an island called Barren Island which has the only active volcano in India. There are atolls in the Nicobar group too.
Geographical Explanation of 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 the southwest along the upper parts of the 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 Great Escarpment
- The Coastal region
- The Plains
- The Island Groups
The southern Brazil is occupied by an extensive plateau. It is differently described as Brazilian Highlands Brazilian Shield or Brazilian Plateau. Brazilian and Guyana Highlands together form the core of the South American continent. The main part of the Guyana highlands is in Venezuela and it 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 the north and slopes are not very steep. The tributaries of the Amazon flowing through this region make rapids and waterfalls. Towards the north, the slopes are steep but not abrupt. Several rivers take off from the terminal portion of the highlands and flow northwards to meet the 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 acts 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 the ‘Drought Quadrilateral’.
Brazil has a coastline of about 7400 km. One may divide that into two parts namely the northern and eastern coast. The northern coast extends from Amapa province in the north to Rio de Grande de Norte in the east. This can be called the North Atlantic coast. From there, the eastern coast extends towards the south. The northern coast is characterized by the 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 a 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 dune complexes. The Brazilian coast is protected in some areas by coral reefs and atoll islands.
The plains in Brazil are confined to two areas namely the Amazon basin in the north and the 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 minimal where the Guiana Highlands and Brazilian Highlands 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 in 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.
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.
Praia do Cassino or Casino Beach is the southernmost beach on the Brazilian coast on the South Atlantic Ocean. It is considered to be the longest sandy beach in the world. It is a continuous beach extending for more than 200 km.
Some more information:
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 the highland and other rivers at the coasts
Amazon collects its headwaters from the eastern slopes of the Andes Mountains in Peru.. Amazon River receives a 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 the Amazon. Instead, we find a series of islands developed along the mouth of the Amazon beyond the coast line into the Atlantic Ocean. It will be interesting to note that at the mouth the width of the 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.
These two rivers are located in the southwestern part of Brazil. Both rivers form the catchment of River Plata in Argentina. These two rivers and river Uruguay in the extreme south of the highlands collect their headwaters from the southern portion of the highlands.
It is the third most important river in Brazil. The entire basin of this river is within Brazil. It occupies the eastern portion of the highlands. The river flows towards the north for a distance of about 1000 km over the plateau and then takes a sharp eastward turn to enter the coastal strip along the Atlantic Ocean. The river is navigable for a distance of about 250 km in its downstream reaches.
Brazil has several short coastal rivers. The coastal area being densely populated these rivers attain significance. River Paraniba and River Itapecuru flowing northwards meet the North Atlantic Ocean. The rivers that enter the South Atlantic Ocean collect their headwaters along the escarpment. River Puraguaco enters the Atlantic Ocean near Salvador town.
Drainage of India:
Rivers in India are largely classified according to their source region into Himalayan and Peninsular rivers.
Most of the major rivers in the Himalayas originate from various glaciers. In summers when glaciers melt, the discharge of water increases in summer. They flood during monsoons too. They are perennial rivers. The drainage covers two major river systems as Sindhu River system and the Ganga River system. Sindhu and its tributaries (Jhelum, Chenab, Ravi, and Satluj) drain the Western Himalayas i.e. they flow through the state of Jammu and Kashmir. They flow almost parallel to each other. A major tributary of river Sindhu, the Satluj, originates near Man Sarovar and flows westwards. Punjab Plains have formed from the depositional work of this river and its tributaries. Sindhu flows through Pakistan and then meets the Arabian Sea.
The river Ganga originates from the Gangotri glacier and crosses the Himalayas to become an east-flowing river. Many tributaries of the Ganga also flow similarly. Yamuna, originating at Yamunotri, is a major tributary of Ganga. Another major tributary of the Ganga flows through the northern part of the Greater Himalayas and crosses the Himalayas to enter India. When it flows through the Himalayas it is called Tsang Po. When it crosses the Himalayas, it is called Dihang and its eastward flow thereafter is called Brahmaputra. From time to time, Ganga meets its tributaries, hence its discharge increases. Ganga receives Brahmaputra as its tributary in its lower reaches in Bangladesh. The huge volume of water and huge deposition have led to the formation of a large delta. Besides these Himalayan rivers, the Ganga receives several tributaries from the Peninsula like Chambal, Ken, Betawa, Shon, Damodar, etc.
The Peninsular river systems can further be divided into east-flowing (meeting the Bay of Bengal) and west-flowing (meeting the Arabian Sea). The Western Ghats form a major water divide in the Peninsula. The peninsular rivers, being rain-fed rivers, seldom face the problem of floods. They are seasonal. The west-flowing rivers occupying the area between the Western Ghats and the Arabian Coastline are short in length but swift. This condition of short and swift river system exists in the states of Kerala, Karnataka, Maharashtra, and Southern Gujarat.
The coastal rivers in Kerala have long-extending backwaters near their mouths. These water bodies are locally known as ‘Kayals’. Further northwards one comes across the river system flowing into the Gulf of Khambhat. These river systems are Tapi, Narmada, Mahi, and Sabarmati. Tapi and Narmada flow slowly through rift valleys. Mahi River flows from North East to South West direction whereas River Sabarmati collecting its headwaters from the southern slopes of the Aravali ranges flows in a somewhat North-South direction. Another noteworthy river forming the catchment of the Arabian Sea is the River Luni. It originates along the western slopes of the Aravali range flows in a somewhat northwest-to-southeast direction and flows into the Gulf of Kutchch.
Rivers Meeting the Bay of Bengal:
Most of the area of the Peninsula is drained by the rivers flowing towards the Bay of Bengal. The important river systems of this group are Mahanadi, Godavari, Krishna, and Kaveri. Mahanadi basin occupies the northeastern part of the Peninsula. Godavadri, Krishna, and Kaveri originate in the eastern slopes of the Western Ghats. River Godavari is the second largest river system in India in terms of the catchment area. To the south of Godavari is located the basin of River Krishna. Its major tributaries are Bhima and Tungbhadra. River Kaveri Basin flows through the states of Karnataka and Tamil Nadu. It is one of the major rivers of the Peninsula. It is a river that has been harnessed for irrigation for a long time. The Chola king constructed a dam on the river Kaveri in the 2nd century A.D. near Tiruchirapalli and started irrigation in this deltaic region. Till today, the dam and its canals are operational.
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