SHIKHAR MAINS 2022- DAY 33 Model Answer English

Q1. सुनामी की उत्पत्ति के कारणों की विवेचना कीजिए।

Discuss the reasons for the origin of Tsunami.

Approach: 

• Define Tsunami in introduction.
• Enlist the reasons for the origin of the Tsunami.

 Answer:

The word “tsunami” comprises the Japanese word “tsu” (meaning harbour) and “nami” (meaning wave). A tsunami is a series of enormous waves created by an underwater disturbance usually associated with earthquakes occurring below or near the ocean.

 Causes of tsunamis: 

• Earthquakes: It can be generated by movements along fault zones associated with plate boundaries. Most strong earthquakes occur in subduction zones where an oceanic plate slides under a continental plate or another younger ocean plate.
  For example, 
• The Great 1960 Chilean tsunami was generated by a magnitude 9.5 earthquake that had a rupture zone of over 1,000 km. 
• The Indian Ocean Tsunami of 2004 was caused by an undersea earthquake with a magnitude of 9.1 which struck off the coast of the Indonesian island of Sumatra.

·       Landslides: A landslide that occurs along the coast can force large amounts of water into the sea, disturbing the water and generate a tsunami. Underwater landslides can also result in tsunamis when the material loosened by the landslide moves violently, pushing the water in front of it.

For example:

• On July 10, 1958 Southeast Alaska - A magnitude 7.8 earthquake triggered a number of submarine landslides, rock falls, and ice falls that generated tsunamis.
• Volcanic Eruption: Although relatively infrequent, violent volcanic eruptions represent also impulsive disturbances, which can displace a great volume of water and generate extremely destructive tsunami waves in the immediate source area. 
• On January 15, 2022, a mostly submerged volcanic cauldron in the South Pacific named Hunga Tonga-Hunga Ha‘apai caused a tsunami in the Kingdom of Tonga.
• One of the largest and most destructive tsunamis ever recorded was generated on August 26, 1883 after the explosion and collapse of the volcano of Krakatoa (Krakatau), in Indonesia. This explosion generated waves that reached 135 feet, destroyed coastal towns and villages along the Sunda Strait in both the islands of Java and Sumatra, killing 36, 417 people.
• Extra-terrestrial Collision: Tsunamis caused by extra-terrestrial collision (i.e., asteroids, meteors) are an extremely rare occurrence. Although no meteor/asteroid induced tsunami has been recorded in recent history, scientists realize that if these celestial bodies strike the ocean, a large volume of water would undoubtedly be displaced to cause a tsunami. Scientists have calculated that if a moderately large asteroid, 5-6 km in diameter, strike the middle of the large ocean basin such as the Atlantic Ocean, it would produce a tsunami that would travel all the way to the Appalachian Mountains in the upper two-thirds of the United States.

India has developed the Indian National Centre for Ocean Information System (INCOIS), for early detection of Tsunami and preparedness of impacts of Tsunami.

Q2.  समुद्री धाराएँ क्या होती हैं? ये तटीय क्षेत्रों की जलवायु को कैसे प्रभावित करती हैं? व्याख्या कीजिए।

What are ocean currents? How do they affect the climate of coasts? Illustrate.

 Approach:

·        First of all, bring out factors which are responsible for the origin and modification of the ocean currents and elaborate them briefly.

·        Then, with examples, elaborate how ocean currents determine the climate of surrounding regions.

Answer:

OCEAN CURRENTS- Ocean currents are like river flow in oceans. They represent a regular volume of water in a definite path and direction.

The factors responsible for the origin and modifications of ocean currents can be enumerated as:

·        Origin – It is attributed to density differences in different layers of ocean waters. Heavier water sinks and causes the overlying surface water to move in its space. This gives rise to global oceanic circulation.

·        Other factors – Accumulation of water on east coasts leads to gravity induced movements down the slope.

·        Expansion due to heat – Even though water is considered practically incompressible, minor expansion due to excess solar heat in equatorial regions causes a slight gradient and water tends to flow down the slope.

·        Modification – Wind, Coast line and inundation, large river discharge, presence of partially enclosed seas.

·        Periodic reversals due to heating and accumulation can also cause modification such as in case of El Nino current caused by a stronger counter equatorial current.

·        Coriolis force - This force intervenes and causes the water to move to the right in Northern Hemisphere and to the left in the Southern Hemisphere. These produce large circular currents in all the Ocean basins. One such circular current is in the Sargasso Sea.

Ocean currents have direct and indirect effects on the climate of the regions. These can be enumerated as:

·        West coasts of the continents in Tropical and subtropical are bordered by cold currents. Their average temperatures are relatively low with narrow diurnal and annual ranges. There is fog, but generally areas are arid due to the desiccating effect leading to formation of deserts in the area. For example, Cold Peruvian current- Atacama Desert.

·        East coasts of the continents in the middle and higher latitudes are bordered by warm currents which cause a distinct marine climate. They are characterized by cool summer and relatively mild winters. E.g., China type of climate.

·        Warm currents flow parallel to east coasts of the continents in tropical and subtropical latitudes. This result in warm and rainy climates. E.g., Florida.

·        Foggy weather and drizzle in the mixing zones of warm and cold current.