Geography [4 Mark Question Answer]

Some Earthquakes which caused serious damage to property and life are :

1. Lisbon Earthquake of 1755
2. South Carolina Earthquake of August 1886
3. The Japan Earthquake of Oct. 28, 1891
4. Kanga (Himachal Pradesh) Earthquake of April 1905
5. Tokyo (Japan) Sep. 1923
6. Quetta 1935
7. Bihar 1934
8. California Earthquake of April 1966
9. Turkey Sep. 1975
10. Iran 1968
11. Peru 1970
12. Tangshan (China) Earthquake of July 1976
13. Broach Earthquake of 1970 affected part of Gujrat.
14. Earthquake of 1988, had its epicentre near Darbhanga and affected parts of North Bihar, Nepal, and Bangladesh.
15. The Bhuj earthquake of 2001 devastated many cities of Gujarat.

Earthquakes bring about changes on the surface of the earth which are very harmful to man.
Destructive Effects :

1. Many towns are destroyed and there is considerable loss of life and property.
2. They cause floods by the uplifting of land in the’ course of the river.
3. Some places are submerged under the sea.
4. Big cracks and fissures are formed on the surface of the river and they interrupt communications.
5. Some times rivers disappear or change their courses or get flooded. Railway lines are twisted.
6. They cause great tidal waves, which may bring havoc to the coastal areas.

Constructive Effects :

1. Precious metals and minerals come up to the surface for the use of man.
2. New lands for habitation above the surface of the sea are formed.
3. Some times new springs and waterfalls are formed which help in irrigation.
4. Violent earthquakes have led to the formation of hills and mountains.
5. Bays and gulfs are formed along the coastal land to provide new ports and harbours.

No-till now it is not possible to predict an earthquake. Earthquake prediction in the past was left to astrologers and mystics. Today it is a respectable scientific pursuit. The Russians were the first to discover P and S seismic waves in the 1960s on the basis of which predictions were made. These waves still are the only means available to seismologists to predict earthquakes.
The theory of Plate Tectonics offers another means of prediction on scientific lines. Japanese use the methods of measuring changes in sea level and variations in Earth’s magnetic field to predict earthquakes. However, no method is still foolproof as has been proved by recent earthquakes in Japan, India, and the USA.

Constructive effects :

1. Earthquakes help the earth release its stored up energy. The majority of the earthquake occur around. The plate margins. This energy release helps to keep the earth in good shape.
2. On account of both vertical and lateral displacement of the earth’s crust, earth-quakes may raise or lower parts of the earth especially near the seashore. Sagami Bay of Japan was uplifted 200 m in 1923.
3. Landslides triggered by earthquakes cause the formation of lakes as has happened at many places in the Himalayan region.

Destructive effects :

1. Human beings have settlements in active earthquake zones. Most often the houses and other structures collapse causing great loss of property.
2. The forces of uplift and subsidence also cause submergence of coastal parts. For example Dwarka in Gujarat which now lies submerged under the sea.
3. Earthquakes have changed the course of rivers in the past. They have thus rendered many areas unsuitable for irrigation and agriculture. They cause danger to human life.