Geography [2 Mark Question Answer]

Destructive effects are the collapse of structures, submergence of coastal parts e.g. Dwarka submergence, these change the course of rivers, danger to human life, and motivation of tsunami waves causing drastic calamities.

Earthquakes cause energy release to put the earth in good shape; several landforms are uplifted to build large plains e.g. Sagami Bay uplifted 200 m, Landslides cause the formation of lakes in the Himalayan region.

Ritcher scale is used to measure the intensity of earthquake through a scale, which is motivated by a needle attached to this instrument The zigzag wavelength of the earthquake comes on the screen and calculated from 1 to 9 scale measured in centimeters.

Construction of large scale dams, the thrust of rivers along fault lines, dumping of chemical wastes also cause earthquakes due to imbalance in the isostatic balance of the earth’s landforms, e.g. Koyna dam caused an earthquake in Maharashtra.

Earthquakes cause rise and fall of landmasses, create fault scarps, offset streams, and other land features and cause landslides. Earthquakes waves also destroy houses and man-made structures, buckle and twist the railway lines electric and telegraph lines, etc.

Major earthquakes of India from 1991 to 1997

1. Latur -1991
2. Uttarkashi – 1993

The earthquakes are distributed along with two major belts namely circum Pacific earthquake belt (Ring of fire) and the Mid-World, Mountain Earthquake belt along the great fold mountain zone.

There is a close relationship between an earthquake and a volcano. Earthquakes and volcanoes occur in small belts, i.e. Mid world belt and Circum Pacific belt. Their distribution shows a similar pattern. Volcanic eruption leads to earthquakes. Volcanic eruptions are the local cause of earthquakes.

Ritcher scale and Mercalli scale are used to measure the intensity of earthquakes. Ritcher scale measures through a graphical scale in a zigzag graph from 1 to 9 and the Mercalli scale observes it from 1 to 12 points scale.

Tsunami is a very destructive sea wave rising high up to several metres and jump furiously along with the coastal areas like the hood of a snake. The name ‘tsunami’ is from the Japanese words: ‘Tsu’ and ‘nami’ meaning ‘harbour’ and ‘wave’ respectively. So tsunamis are harbour waves.