Which one among the following statements regarding igneous rock is correct ?
- A.When magma cools deep in the Earth's interior, it results in the formation of fine-grained igneous rocks.
- B.Basalt is a type of intrusive igneous rock.
- C.Most of the minerals of igneous rocks are silicates.
- D.Extrusive igneous rocks often undergo lithification.
Correct answer
Explanation
The correct answer is C, Most of the minerals of igneous rocks are silicates. Magma is mostly molten silicate, so the minerals that crystallise from it, such as feldspar, quartz, mica, pyroxene and olivine, are silicates.
Igneous rocks form when magma or lava cools and hardens, and they are called primary rocks because the others are made from them. The rate of cooling decides the grain size. Magma that cools slowly deep inside the crust forms intrusive (plutonic) rocks with large crystals, such as granite. Lava that cools quickly at the surface forms extrusive (volcanic) rocks with fine grains, such as basalt, which makes up the Deccan Traps.
A is wrong because slow, deep cooling produces coarse-grained, not fine-grained, rocks. B is wrong because basalt is an extrusive rock that forms from lava at the surface. D is wrong because lithification, the compaction and cementing of sediments, is how sedimentary rocks form.
Exam tip: Slow cooling deep = coarse grains (granite, intrusive); fast cooling at surface = fine grains (basalt, extrusive).
Practice Questions
View allWhich of the following pairs of Himalayan Glaciers and their location is/are correctly matched?
1. Siachen - Nubra Valley Region
2. Chungphar - Kumaon-Garhwal Region
3. Zemu - Central Nepal Region
4. Gasherbrum - Pir Panjal Range
Select the answer using the code given below :
- A.1 only
- B.1 and 2
- C.2 and 3
- D.3 and 4
Show answer
Only the Siachen pair is correct. The Siachen Glacier, about 76 km long, lies in the eastern Karakoram, and its meltwater gives rise to the Nubra river, which joins the Shyok; the Nubra Valley of Ladakh lies below its snout, so the glacier belongs to the Nubra Valley region.
Read the full explanation →Indore city in Madhya Pradesh is situated in which one of the following regions ?
- A.Bundelkhand
- B.Mahakoshal
- C.Malwa Plateau
- D.Nimar Region
Show answer
Indore stands on the Malwa Plateau in western Madhya Pradesh. Malwa is a volcanic upland of basalt rock, part of the Deccan Traps, lying north of the Vindhya Range; its black soil supports soybean, wheat and cotton, and the region also takes in Ujjain, Dewas, Ratlam and Mandsaur.
Read the full explanation →With regard to water transportation in India, which of the following statements are correct?
1. Headquarters of Central Inland Water Transport Corporation is located at Delhi.
2. Headquarters of Inland Waterways Authority of India is located at Noida.
3. National Inland Navigation Institute is located at Kolkata.
4. First National Inland Waterway was between Haldia and Allahabad.
Select the correct answer using the code given below.
- A.1 and 2 only
- B.2 and 3
- C.2 and 4 only
- D.1, 2 and 4
Show answer
Statements 2 and 4 are correct, while statements 1 and 3 name the wrong city. The Inland Waterways Authority of India (IWAI), set up in 1986, has its headquarters at Noida in Uttar Pradesh and develops and regulates the national waterways.
Read the full explanation →Which one of the following statements with regard to the Indian Railways is not correct?
- A.The Indian rail networks have been developed throughout the Konkan coast.
- B.There is very low density of railway lines in the Himalayan region.
- C.The north Indian plain has a dense network of railway.
- D.At present, India has the largest railway network in the world.
Show answer
India does not have the largest railway network in the world; the United States has the longest, followed by China and Russia, with India in fourth place.
Read the full explanation →Statement I : The interior part of Maharashtra does not receive adequate rain in the summer season.
Statement II : The interior part of Maharashtra lies in the rain shadow of the Western Ghats.
- A.Both the statements are individually true and Statement II is the correct explanation of Statement I
- B.Both the statements are individually true but Statement II is not the correct explanation of Statement I
- C.Statement I is true but Statement II is false
- D.Statement I is false but Statement II is true
Show answer
Both statements are true, and the rain shadow of the Western Ghats is exactly why interior Maharashtra gets little rain.
Read the full explanation →