SHIKHAR Mains 2023, Day 33 Model Answer English

Updated : 20th Jul 2023

Q1: चक्रवात से आप क्या समझते हैं ? उष्ण कटिबंधीय चक्रवात की सामान्य विशेषताओं की चर्चा कीजिए, और इसके उत्पत्ति के लिए अनुकूल दशाओं को भी समझाइये|

What do you understand by cyclone? Discuss the general characteristics of a tropical cyclone, and explain the favorable conditions for its origin.

Approach-

Begin the answer by explaining the meaning of cyclone in role.
Then list the general characteristics of a tropical cyclone.
Again conclude the answer by mentioning the necessary conditions for the development of a tropical cyclone.

Answer -

Cyclone, any large system of winds that circulates about a centre of low atmospheric pressure in a counterclockwise direction north of the Equator and in a clockwise direction to the south. Cyclones are divided into two parts according to their latitudinal location, namely tropical cyclone and temperate cyclone.

Tropical cyclone and its characteristics-

Tropical cyclones form in the tropics. Tropical cyclonic conditions are the result of low air pressure, in which the wind speed should be minimum 33 kmph. An increase in its intensity leads to the formation of a depression vortex, which causes cyclone.
With the increase in the intensity of cyclone, the pressure gradient force will increase, due to which the speed of wind will increase, at the same time the amount of rainfall will increase, and the degree of destruction will increase.
As the intensity of the cyclone increases, the area of the cyclone will get smaller, that is, the radius becomes smaller.
Winds coming from all directions are diverted by the Coriolis force to their right, due to which the wind inside the cyclone moves in anti-clockwise direction in northern hemisphere.
Before the cyclone, the weather remains calm, but during the cyclone (front wall) first there is a decrease in pressure, and temperature, after the cyclone, the temperature and pressure will increase.
Tropical cyclones produce clouds and cause heavy rainfall. Rainfall is followed by the calm conditions of the eye of the cyclone.
Calm conditions of the eye is followed by the back wall of the cyclone which has the same weather as the front wall but with less intensity.

Conditions favorable for the origin of cyclone -

Large sea surface with temperature higher than 27° C;
Presence of the Coriolis force;
Small variations in the vertical wind speed;
A pre-existing weaklow-pressure area or low-level-cyclonic circulation;
Upper divergence above the sea level system.

Cyclones are regional forms/consequences of atmospheric circulation that directly or indirectly affect human activities by causing seasonal changes/changes, amount of rainfall, distribution of rainfall.

Q2:भूकम्प के उत्पत्ति के कारकों को बताइए | साथ ही भूकम्प के वैश्विक वितरण को प्लेट विवर्तनिकी सिद्धांत के आधार पर स्पष्ट कीजिये |

Explain the factors of origin of earthquake. Also, give an account of the global distribution of earthquakes based on plate tectonics theory.

Approach-

Give general introduction with definition of earthquakes.
Write factors of origin of earthquake.
Finally, conclude the answer by stating the global distribution of earthquakes with the help of map.

Answer -

An earthquake is a vibration or oscillation in the crust, which occurs when there is a momentary disturbance in the elasticity of the rocks above or below the surface or in the equilibrium of gravity.

Factors of origin of earthquake -

Volcanic Action - During volcanism, magma, explosive gases and water vapor try to violently rise upwards and produce explosions with a strong impact on the crater, which causes vibrations in the rocks. Many times the magma tries to come out but due to the obstruction of hard rocks, it cannot come out and creates vibrations in the rocks above. In this way, earthquakes occur in volcanic areas, even without a volcanic eruption.

Folds and Fractures - These are related to the compression and stress arising in the rocks, which result in the origin of earthquakes. Due to stress, faults are formed in the rocks and vibrations are generated due to the movement of rocks along the fault bed.

Plate Tectonics - Most of the earthquakes and volcanoes of the world occur on different lithospheric plate edges. Earthquakes occur on the three sides of the plate, respectively, divergent, convergent and transform. Most volcanoes and earthquakes are active in a circular region around the Pacific Ocean, which is called a ring of fire.

Water load and elastic recirculation etc. can also be caused by the origin of earthquake.

Global distribution of earthquakes -

Peri-Pacific Belt - This region includes the coastline of North America, the coast of South America and East Asia. These regions are located on the eastern and western sides of the Pacific Ocean, respectively, and account for about 65 percent of the world's earthquakes.

Mid-continental belt - This belt is also called Mediterranean belt. tectonic earthquakes often occur in this region. This seismic belt includes the Alpine Mountains of Europe and its other parts, the seismic regions of the Mediterranean Sea, North Africa, East Africa and the Himalayas.

Mid-Atlantic Ridge Belt - It includes the Mid-Atlantic Ridge and several islands located nearby.

Other areas - A belt extends south in the eastern part of Africa through the Nile. It includes the seismic zone of the fault valley of East Africa. Some earthquakes also occur in the Red Sea, the Dead Sea and the Indian Ocean.