Which one of the following is not an agent of metamorphism?
- A.Heat
- B.Compression
- C.Decomposition
- D.Solution
Correct answer
Explanation
The correct answer is C, Decomposition. Decomposition breaks rocks down at the surface and is a process of weathering, whereas metamorphism changes rocks deep inside the crust through heat, pressure and chemically active solutions. Metamorphism means a change of form. When existing igneous or sedimentary rocks are subjected to high temperature, great pressure or hot mineral-rich fluids, their minerals recrystallise without melting, and new rocks form. Limestone becomes marble, sandstone becomes quartzite, shale becomes slate, and granite becomes gneiss. Decomposition, by contrast, is chemical weathering, in which minerals react with water and air and the rock crumbles. Option A is wrong because heat, for example from a nearby magma body, is the main agent of thermal or contact metamorphism. Option B is wrong because compression, or pressure from overlying rocks and earth movements, drives dynamic and regional metamorphism. Option D is wrong because solutions, the hot fluids that move through rocks, cause chemical change and are an agent of metamorphism. Exam tip: agents of metamorphism = heat, pressure, solutions; decomposition = weathering.
Practice Questions
View allD had recently visited Khardung La, Nubra Valley and several Buddhist monasteries. Which one of the following States / UT had she visited ?
- A.Himachal Pradesh
- B.Uttarakhand
- C.Sikkim
- D.Ladakh
Show answer
Khardung La, the Nubra Valley and monasteries such as Hemis, Thiksey and Diskit all lie in Ladakh, which became a separate Union Territory in 2019.
Read the full explanation →Consider the following statements about clouds : 1. Two major forms of clouds are stratiform and cumuliform. 2. According to the altitude, clouds are classified as high clouds, middle clouds and low clouds. 3. Stratus, nimbostratus and stratocumulus are types of high clouds. 4. Clouds having nimbo attached to their name produce precipitation. Which of the statements given above are correct ?
- A.1 and 2 only
- B.1, 2 and 4
- C.2 and 4 only
- D.1, 3 and 4
Show answer
Only statement 3 is wrong, because stratus, nimbostratus and stratocumulus are low clouds, not high clouds. Statement 1 is correct: clouds take two basic forms, layered stratiform sheets formed by gentle lifting of air and heaped cumuliform clouds formed by rising convection currents.
Read the full explanation →Which one of the following pairs of City and Lake is not correctly matched ?
- A.Buffalo : Erie
- B.Detroit : Superior
- C.Milwaukee : Michigan
- D.Toronto : Ontario
Show answer
Detroit stands on the Detroit River, which links Lake St. Clair to Lake Erie, and is far from Lake Superior.
Read the full explanation →Which of the following statements is/are correct with respect to Time Zone in India ? 1. There is one standard time for the whole country. 2. Andaman and Nicobar Islands and Lakshadweep Islands have different Time Zones. 3. Indian Standard Time (IST) is five and half hours behind GMT. Select the correct answer using the code given below:
- A.1 only
- B.2 only
- C.1 and 2 only
- D.1 and 3 only
Show answer
India follows a single standard time, Indian Standard Time, for the whole country, and it is ahead of GMT, not behind it.
Read the full explanation →Which one of the following is not a resultant of the El Nino effect ?
- A.Distortion of equatorial atmospheric circulation
- B.Flow of the South-East Trade Winds towards the Indian Ocean
- C.Irregularities in the evaporation of sea water
- D.Reduction in the amount of planktons which reduces the number of fish in the sea
Show answer
During El Nino the trade winds of the Pacific weaken or even reverse, so a steady flow of these winds is not one of its results.
Read the full explanation →