Consider the following statements with reference to salt weathering : 1. Salts in rocks expand due to thermal action, hydration and crystallization. 2. Salts like calcium, sodium, magnesium and barium have a tendency to expand. 3. Salt weathering is a typical example of chemical weathering. Which of the statements given above is/are correct?
- A.1 only
- B.1 and 2 only
- C.2 and 3 only
- D.1, 2 and 3
Correct answer
Explanation
The correct answer is B, 1 and 2 only. Salt weathering breaks rock by the physical pressure of growing salts, so it is a form of physical (mechanical) weathering, not chemical weathering.
Salts carried into the pores and cracks of rocks expand when they are heated, when they take up water (hydration) and when they crystallise as the water evaporates. Salts of calcium, sodium, magnesium, potassium and barium are known for this tendency to expand. The repeated pressure loosens grains and flakes off the rock surface. The process is strongest in hot deserts and along coasts, where evaporation is high and salt is plentiful, and it produces honeycomb-like hollows on rock faces.
A is wrong: it leaves out statement 2, which is correct.
C is wrong: it includes statement 3; the rock is broken by pressure, with no change in its chemical make-up, so salt weathering is physical.
D is wrong: all three cannot be correct because statement 3 is false.
Exam tip: Physical weathering: unloading, temperature change, frost wedging, salt weathering. Chemical weathering: solution, carbonation, hydration of minerals, oxidation.
Practice Questions
View allD performs her train journey by the shortest route from Bengaluru to New Delhi. Which one of the following rivers will she not cross while performing the journey?
- A.Narmada
- B.Yamuna
- C.Godavari
- D.Krishna
Show answer
The shortest rail route from Bengaluru reaches Delhi from the south through Agra and Mathura, which lie on the western side of the Yamuna, so the train never has to cross that river.
Read the full explanation →In India, the period of steady population growth refers to the decade(s) of:
- A.1981-2011
- B.1951-1981
- C.1921-1951
- D.1911-1921
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In the standard division of India's population history, the three decades from 1921 to 1951 are called the period of steady population growth.
Read the full explanation →Consider the following statements with reference to earthquakes:
1. Collapse earthquakes are most common.
2. Tsunamis are waves generated by the tremors and not an earthquake in itself.
3. High magnitude earthquakes i.e. 8+ are quite rare whereas 'tiny' types occur almost every minute.
Which of the statements given above are correct?
- A.1 and 2 only
- B.1 and 3 only
- C.2 and 3 only
- D.1, 2 and 3
Show answer
Statement 1 is false because tectonic earthquakes, not collapse earthquakes, are the most common type. Earthquakes are grouped by cause: tectonic (sliding of rocks along a fault), volcanic, collapse (the roofs of underground mines or caverns falling in), explosion (from nuclear or chemical blasts) and reservoir-induced.
Read the full explanation →With reference to earthquakes, which of the following statements are correct?
1. Earthquakes largely occur along the converging plate boundaries.
2. Point of origin of earthquake in lithosphere is known as focus/hypocentre.
3. Intensity of earthquake decreases with distance from the epicentre.
4. Epicentre of earthquake always remains over continents only.
Select the correct answer using the code given below.
- A.1 and 2 only
- B.1, 2 and 3
- C.2 and 3 only
- D.1 and 4
Show answer
The first three statements are true, while statement 4 is false because many earthquakes have their epicentre under the sea.
Read the full explanation →National Disaster Management Authority is headed by
- A.the Prime Minister.
- B.the Home Minister.
- C.the President.
- D.the Health Minister.
Show answer
Under the Disaster Management Act, 2005, the Prime Minister is the ex officio chairperson of the National Disaster Management Authority (NDMA).
Read the full explanation →