Day-620 | Daily MCQs | UPSC Prelims | GEOGRAPHY

Answer: C
Explanation: Ocean currents are not influenced by the revolution of earth.
Ocean currents are influenced by two types of forces namely:
Primary forces:
● Heating by solar energy: Heating by solar energy causes the water to expand. That is why, near the equator the ocean water is about 8 cm higher in level than in the middle latitudes. This causes a very slight gradient and water tends to flow down the slope.
● Wind: Wind blowing on the surface of the ocean pushes the water to move. Friction between the wind and the water surface affects the movement of the water body in its course.
● Gravity: Gravity tends to pull the water down the pile and create gradient variation.
● Coriolis force: The Coriolis force intervenes and causes the water to move to the right in the northern hemisphere and to the left in the southern hemisphere.These large accumulations of water and the flow around them are called Gyres.These produce large circular currents in all the ocean basins.
Secondary forces:
● Differences in water density: It affects vertical mobility of ocean currents. Water with high salinity is denser than water with low salinity and in the same way cold water is denser than warm water. Denser water tends to sink, while relatively lighter water tends to rise.
● Temperature of water: Cold-water ocean currents occur when the cold water at the poles sinks and slowly moves towards the equator. Warm-water currents travel out from the equator along the surface, flowing towards the poles to replace the sinking cold water.

Answer: B
Explanation:
Demographic transition theory can be used to describe and predict the future population of any area. The theory tells us that the population of any region changes from high births and high deaths to low births and low deaths as society progresses from rural agrarian and illiterate to urban industrial and literate society. These changes occur in stages which are collectively known as the demographic cycle.
Statement 1 is correct:
● The first stage has high fertility and high mortality because people reproduce more to compensate for the deaths due to epidemics and variable food supply.
● Two hundred years ago all the countries of the world were in this stage.
● Fertility remains high in the beginning of the second stage but it declines with time. This is accompanied by a reduced mortality rate. Improvements in sanitation and health conditions lead to decline in mortality. Because of this gap the net addition to population is high.
● In the last stage, both fertility and mortality decline considerably. The population is either stable or grows slowly.
Statement 2 is correct and Statement 3 is incorrect:
● The population growth is slow and most of the people are engaged in agriculture where large families are an asset. Life expectancy is low, people are mostly illiterate and have low levels of technology.

Answer: B
Explanation: Oman and Iran are the countries that don’t have borders with the Red Sea.
Red Sea:
● The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia.
● Its connection to the ocean is in the south, through the Bab-el-Mandeb strait and the Gulf of Aden.
● To its north lie the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez (leading to the Suez Canal).
● It is underlain by the Red Sea Rift, which is part of the Great Rift Valley.
Countries having borders with the Red Sea:
● Egypt
● Saudi Arabia
● Sudan
● Eritrea
● Yemen
● Djibouti

Answer: C
Explanation: Statement-I is correct but Statement-II is incorrect
● As many rivers are east flowing and the coast is an emergent coast where delta forms easily, therefore, major estuaries in India occur on the west coast.
● As the west coast is a submergence coast due to faulting, the continental shelves along the west coast of India is wider that of the east coast.

Answer: B
Explanation: Option 1 and 2 are correct
Diastrophism is the process of deformation of the Earth’s crust which involves folding and faulting. Diastrophism can be considered part of geotectonics. The study of diastrophism encompasses the varying responses of the crust to tectonic stresses. These responses include linear or torsional horizontal movements (such as continental drift) and vertical subsidence and uplift of the lithosphere (strain) in response to natural stresses on Earth’s surface such as the weight of mountains, lakes, and glaciers.
● Orogeny, mountain-building event, generally one that occurs in geosynclinal areas.
● In contrast to Epeirogeny, an orogeny tends to occur during a relatively short time in linear belts and results in intensive deformation. Orogeny is usually accompanied by folding and faulting of strata, development of angular unconformities (interruptions in the normal deposition of sedimentary rock).
Sudden processes:
● An earthquake is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth’s lithosphere that creates seismic waves.
● The theory of plate tectonics states that the Earth’s solid outer crust, the lithosphere, is separated into plates that move over the asthenosphere, the molten upper portion of the mantle. Oceanic and continental plates come together, spread apart, and interact at boundaries all over the planet.
● Volcanism: Disruptions on the Earth’s surface are a common cause of many volcanic eruptions. These movements on the earth’s surface are caused by endogenous forces and come from the great depths of the Earth. These forces act very rapidly and can cause disastrous consequences under the Earth and on the surface within minutes.