Which of the following statements with reference to Glacial trough is/are correct ? 1. Alpine glaciers strip valleys of their soil, regolith and sediment to form glacial troughs. 2. When the sea level is below the floor of a glacial trough, the seawater enters as the ice front recedes, creating a fiord. Select the answer using the code given below :
- A.1 only
- B.2 only
- C.Both 1 and 2
- D.Neither 1 nor 2
Correct answer
Explanation
The correct answer is A, 1 only. Valley glaciers scour away soil, regolith and loose sediment and deepen their valleys into U-shaped glacial troughs, but a fiord forms only when the trough floor lies below sea level, not above it.
A river valley is V-shaped. When an alpine glacier moves down it, the ice plucks and grinds the rock, removes the loose cover and widens and deepens the floor, leaving a trough with steep walls and a flat bottom. Side valleys are left hanging above it. Along coasts such as Norway, Chile, Alaska and New Zealand, glaciers cut troughs well below present sea level. When the ice melts back, the sea floods the trough and creates a long, narrow and deep inlet called a fiord (fjord).
B is wrong because statement 2 reverses the condition: the sea can enter only if the trough floor is below sea level, that is, if sea level is above the floor. C is wrong because statement 2 is incorrect. D is wrong because statement 1 is correct.
Exam tip: river valley = V-shaped; glacial trough = U-shaped; drowned glacial trough = fiord.
Practice Questions
View allWhich one of the following is NOT a current of Pacific Ocean ?
- A.Oyashio current
- B.Alaska current
- C.Agulhas current
- D.California current
Show answer
The Agulhas current flows in the Indian Ocean, down the south-east coast of Africa, so it is not a Pacific current.
Read the full explanation →In a group discussion on shape and size of the Earth, three students stated the following points : 1. Student 1 : The shape of the Earth is basically an oblate spheroid. 2. Student 2 : The polar diameter of the Earth is more than the equatorial diameter. 3. Student 3 : Bulge along the equatorial region is due to revolution of the Earth. Who among the above students is/are correct?
- A.Student 1 only
- B.Student 1 and Student 2 only
- C.Student 2 and Student 3 only
- D.Student 1, Student 2 and Student 3
Show answer
The Earth is an oblate spheroid, slightly flattened at the poles and bulging at the equator, but the bulge comes from its rotation, and its polar diameter is the shorter one.
Read the full explanation →Identify the sea-port in India on the basis of the given characteristics : 1. It is more than a century old port on the west coast of India. 2. It is a natural harbour protected by a breakwater and also by a mole. 3. A deep draft channel of about 14 metres depth permits large vessels to enter the harbour. Select the correct sea-port from the options given below :
- A.Mormugao Port
- B.Deendayal Port
- C.Cochin Port
- D.Jawaharlal Nehru Port
Show answer
Mormugao in Goa, a natural harbour at the mouth of the Zuari estuary, was opened in the late nineteenth century and is sheltered by a breakwater-cum-mole, which fits every clue.
Read the full explanation →Which one of the following receives an average annual rainfall of below 50 cm in India, indicating highest inadequacy?
- A.Madhya Pradesh
- B.Haryana
- C.Ladakh
- D.Jharkhand
Show answer
Ladakh lies in the rain shadow of the Great Himalaya, so the monsoon winds hardly reach it and it is a cold desert with well under 50 cm of rain a year.
Read the full explanation →Which one of the following is an example of Salt-Crystal growth ?
- A.Chemical weathering
- B.Physical weathering
- C.Biological weathering
- D.Bio-chemical weathering
Show answer
When salt crystals grow inside the pores and cracks of a rock, they push the grains apart and break the rock mechanically, without changing its minerals.
Read the full explanation →