Our Changing Earth | Geography VII | Class 7th | Questions and Answers

 

JANDKNCERT | Social Science | Our Environment

Our Changing Earth | Geography VII | Class 7th | Questions and Answers

 

Chapter 3: Our Changing Earth

1. Answer the following questions

Question (i): Why do the plates move?
Answer: The plates move because of the movement of molten magma inside the Earth. This movement generates convection currents that cause the plates to shift.

Question (ii): What are exogenic and endogenic forces?
Answer:
(i) Exogenic forces are external forces that act on the Earth's surface, like wind, water, and ice.
(ii) Endogenic forces are internal forces that originate from within the Earth, like earthquakes and volcanoes.

Question (iii): What is erosion?
Answer: Erosion is the wearing away of the Earth's surface by agents like water, wind, and ice.

Question (iv): How are flood plains formed?
Answer: Flood plains are formed when rivers overflow their banks during floods and deposit layers of fine soil and sediments on their banks.

Question (v): What are sand dunes?
Answer: Sand dunes are small hills of sand formed in deserts when wind deposits sand in one place.

Question (vi): How are ox-bow lakes formed?
Answer: Ox-bow lakes are formed when a river meanders and the curve becomes so sharp that it cuts off from the main flow of the river, creating a crescent-shaped lake.

2. Tick the correct answer

Question (i): Which is not an erosional feature of sea waves?
Answer: (c) Beaches

Question (ii): The depositional feature of a glacier is
Answer: (a) Moraine

Question (iii): Which is caused by the sudden movements of the Earth?
Answer: (a) Earthquake

Question (iv): Mushroom rocks are found in
Answer: (b) Deserts

Question (v): Ox-bow lakes are found in
Answer: (c) River valleys

3. Match the following

Question	Answer
(i) Glacier	(c) Rivers of ice
(ii) Meanders	(d) Loop-like bends of a river
(iii) Beach	(e) Sea waves deposit sediments
(iv) Sand dunes	(a) Formed by wind deposition
(v) Waterfall	(b) Sudden fall of river water

4. Give reasons

Question (i): Some rocks have a shape of a mushroom.
Answer: In deserts, winds blow sand against the rocks. The sand erodes the lower part more than the upper part, creating a mushroom shape.

Question (ii): Flood plains are very fertile.
Answer: Flood plains are very fertile because the river deposits rich alluvial soil during floods, which is ideal for farming.

Question (iii): Sea caves are turned into stacks.
Answer: Sea waves erode the rocks to form sea caves. Over time, the roof of the cave collapses due to continuous erosion, leaving behind a pillar-like structure called a stack.

Question (iv): Buildings collapse due to earthquakes.
Answer: Buildings collapse during earthquakes because of the intense ground shaking caused by sudden movements of the Earth’s crust, especially if the structures are not earthquake-resistant.