Answer the following questions.
Q.1 What is the river system?
Answer:
A river system consists of a catchment area, watershed, divider, tributaries, and distributaries.
Catchment area:
The catchment area of a river refers to all the area of land over which rain falls and is caught to serve a watershed.
Watershed:
A watershed is an area of land drained by the main river and its tributaries. The boundary of a watershed is marked by a ridge of higher land which is called a divider.
Divider:
A divider separates one watershed from the neighbouring watershed.
Tributaries:
A river or stream flowing into a larger river is called a tributary of the larger river.
Distributaries:
As a river passes through a delta, it splits into channels called distributaries. Distributaries are common in river deltas.
Q 2. How are depositional plains formed?
Answer:
Depositional plains are formed by depositing sediments on lowlands brought by rivers, glaciers, and the winds. For example, The Indo-Gangetic plains.
Q 3. Differentiate between erosional and Coastal plains.
Answer:
i) Erosional plains:
When a mountain plateau area is reduced to a low-lying plain by weathering and erosion over a long period, an erosional plain is formed, called a peneplain. The plains of Northern Europe and Northern Canada are erosional plains.
ii) Coastal Plains:
These planes were formed when a part of the sea floor bordering a continent was uplifted. They occurred in Scotland and along the sea coast of the USA. In Pakistan, coastal plains are located along Sindh and Makran coasts.
Q 4. Differentiate between plains and Mountains.
Answer:
i) Mountains:
A mountain is the natural elevation of the earth's surface that rises at least 1000 metres above sea level and at least 50% of its surface. Consists of steep slopes.
i) Plains:
A plain is a flat or gently rolling land surface. Rivers, glaciers, and winds are major agents that develop the following types of plains through erosional and depositional processes. These are River plains, overwash/ Till plains, Loess plains, Coastal plains, and Structural plains.
Q 5. Compare Hot and Cold Deserts.
Answer:
i. Hot Deserts:
Hot deserts are located in subtropical areas. These include The Sahara Desert in North Africa. Great Australian Desert in Australia. In summers average temperature range is, from 26.7 °C to 32.2 °C, and in winter average temperature is 15.5 °C
ii. Cold deserts:
The Tundra is a treeless plain desert Located in the Northern lands of the earth. It is a cold desert and a desolate land covered with lakes, ponds, and marshes. Permafrost is an important feature of this climate. It occupies the Northern fringe of Asia, Europe, the North American Islands, and the coastland of Greenland.
Source: Class 7 Geography Book (National Book Foundation, Pakistan)
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