28 November 2023

Q1. Conditions favourable for Delta Formation are:

1. No strong current running at right angle to the river mouth.
2. Absence of Continental shelf.
3. Presence of large lake in the way of the river.
4. The coast should be sheltered preferably without tides.

How many of the above statements is/are correct?

(a) Only one

(b) Only two

(c) Only three

(d) All four

Solution: b)

• Statements 1 and 4 are correct.
• Conditions favourable for the formation of deltas:
• Lateral erosion and vertical erosion in the upper course of the river to provide extensive sediments to be eventually deposited as deltas.
• The coast should be sheltered and preferably without tides.
• The sea should be shallow near the delta region or else the load will disappear in the deep water.
• There should not be the presence of large lakes in the river course to filter off the sediments.
• The currents should be weak and no strong current should run at right angles to the river mouth as it can wash the sediment away.

Q2. With reference to Aurora or Northern lights, consider the following statements:

1. Auroras are the glowing lights at high latitude.
2. Auroras can be normally observed in stratosphere.
3. Change in the atmospheric temperature cause Auroras.

How many of the above statement is/are correct?

(a) Only one

(b) Only two

(c) All three

(d) None

• Solution: a)
• Only statement 1 is correct.
• An aurora, sometimes referred to as polar lights, northern lights (aurora borealis) or southern lights (aurora australis), is a natural light display in the Earth’s sky, predominantly seen in the high latitude regions (around the Arctic and Antarctic).
• Auroras are produced when the magnetosphere is sufficiently disturbed by the solar wind. It usually occurs in upper atmosphere (thermosphere/exosphere) due to Earth’s magnetic field.

Q3. Consider the following statements:

1. Earth’s crust is the thinnest of all the major layers of earth.
2. The crust is thicker on the continent than on the ocean floor.
3. The oceanic crust mainly consists of manganese and iron.

How many of the above statement is/are correct?

(a) Only one

(b) Only two

(c) All three

(d) None

Solution: b)

• Statement 3 is incorrect.
• The uppermost layer over the earth’s surface is called the crust. It is the thinnest of all the layers. It is about 35 km. on the continental masses and only 5 km on the ocean floors.
• The main mineral constituents of the continental mass are silica and alumina. It is thus called sial (si-silica and al-alumina). The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (si-silica and ma-magnesium).

Q4. Hot Spots within the earth help produce Geothermal Energy. What are these ‘Hot Spots’?

1. a) Areas of intense magnetic activity within the upper mantle.
2. b) Areas of intense pressure inside the mantle.
3. c) Regions of high volcanism on earth’s surface.
4. d) Region in crust where hot molten rocks are trapped.

Solution: d)

• Due to geological changes, molten rocks formed in the deeper hot regions of earth’s crust are pushed upward and trapped in certain regions called ‘hot spots’.
• When underground water comes in contact with the hot spot, steam is generated. Sometimes hot water from that region finds outlets at the surface. Such outlets are known as hot springs.

Q5. Consider the following statements:

1. Almost all the world deserts are confined within the 30 to 45 degrees parallels of latitude north and south of the equator.
2. Deserts lie in the trade wind belt on the western parts of the continents where Trade winds are off-shore.

Which of the above statements is/are incorrect?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Solution: a)

• The pattern that can be identified in the location of the world’s deserts is that almost all the deserts are confined within 15 to 30 degrees parallels of latitude north and south of the equator.
• They lie in the trade wind belt on the western parts of the continents where Trade winds are off-shore. They are bathed by cold currents which produced a ‘desiccating effect’ so that moisture is not easily condensed into precipitation.
• Dryness or aridity is the key note. Such deserts are tropical hot deserts or ‘Trade wind deserts’. They include the Great Sahara Desert; Arabian, Iranian and Thar Deserts; Kalahari, Namib, and Atacama Deserts; the Great Australian Deserts and the deserts of the south-west U.S.A, and northern Mexico.
• In the continental interiors of the mid-latitudes, the deserts such as the Gobi and Turkestan are characterised by extremes of temperatures.