Our Changing Earth

Glossary

1. Weathering: Disintegration or decomposition of rocks over the surface of the earth.

2. Denudation: The process of weathering and erosion is called denudation.

3. Erosion: Removal of uppermost layer of earth’s surface by the action of water and wind.

4. Delta: Deposition of sediments or alluvium on the mouth of a river.5. Sand dunes: A sand dune is basically a mound, or hill or a ridge of

sand with a crest or a definite summit.6. Stack: Due to erosion by the sea waves the natural bridge falls down

into the sea and the remaining arch keeps standing like a pillar which is known as stack.

7. Gorge: It is a narrow and steep sided valley made by down cutting action of the river.

8. Crevasses: The series of cracks developed on the glacier due to the splitting up of ice because of the unequal movement.

9. Degradation: The wearing and tearing of rocks.

10 Aggradation: The process which is related to filling up of the rock particles by various agents into the depressions or on the surface of the earth.

Answer the following questions:

1. Differentiate between Exogenetic and Endogenetic forces with suitable examples.

Ans Endogenetic forces are related to the contraction, expansion, upliftment, subsidence etc. These forces contribute to the formation of landforms. The force that shakes the earth rapidly are sudden endogenetic forces. Eg. Earthquake and volcano etc.

Exogenetic forces take place on the outermost layer of the earth’s crust. These forces take place on the outer shell of the earth which is either formed or deformed by various forces like solar radiation, temperature and pressure conditions. Eg. Gradation ( Degradation-weathering and erosion) Aggradation

2. List the factors that influence the rate of weathering and erosion?

Ans The factors which influence the rate of weathering and erosion are : temperature and rainfall, vegetation cover, change in land use, type of soil and shape/slope of the land, energy of a stream.

3. Define the terms Weathering and Erosion?

Ans The process by which rocks exposed on the surface gets broken up into smaller particles is called weathering.

Erosion is the removal of fragment of rocks by the action of running water, blowing wind and ice.

4. What causes an earthquake? How is it measured?

Ans The earthquake refers to the passage of vibratory waves on the earth’s surface brought about by natural forces. An earthquake is the result of a sudden release of energy in the earth’s crust that creates seismic waves. The study of earthquake waves is called seismology, and the person studying the earthquake is called as seismologist.

The exact point within the earth from where an earthquake starts is called as ‘Foci’ and the point on the surface of the earth above the focus is called ‘Epicenter’ The instrument that records the earthquake waves is called seismometer. The Richter scale is used to measure the intensity of the earthquake waves.

5. How are flood plains formed?

Ans The flood plains are formed by the deposition of fine soil particles and other materials called sediments along rivers banks.

6. Explain the formation of sand dunes.

Ans Sand dunes are formed when there is an obstacle on the way of the wind, obstacle can be anything- a plant, bush, a boulder or a dead remain of an animal.

7. Different features are formed by the sea waves. Explain.

Ans Sea waves hit the shores with a gale force, break the rocks and take away the loose and unconsolidated particles. The features formed are: Sea Cliffs, Sea Caves, Stack, Blow hole.

8. What are Ox bow lakes?

Ans Due to continuous erosion and deposition along the sides of the meanders, the ends of meanders loop come closer and closer. In due course of time the meander loop cuts off from the river and form a cut off lake which is called Ox Bow lake.

9. Draw a labelled diagram of a Volcano

10. Find out about any a dormant volcano which has erupted in the recent years. Paste pictures in your notebook.