Class 9 Rocks and the Rock Cycle Mock Test (ICSE)

Topics in Rocks and the Rock Cycle

• Igneous rocks
• Sedimentary rocks
• Metamorphic rocks
• Rock cycle

Rocks and the Rock Cycle practice questions with answers

1. Q1Multiple choice·1 mark
   Which of the following metamorphic rocks is formed from the metamorphism of limestone?

   1. (a)Marble
   2. (b)Gneiss
   3. (c)Quartzite
   4. (d)Slate
   Show answer and step marks

   1. Correct option: (a) Marble, which is formed when limestone undergoes thermal metamorphism.+1

   Answer: (a)
2. Q2Multiple choice·1 mark
   In the rock cycle, igneous rocks are primarily formed by the:

   1. (a)alteration of pre-existing rocks under intense heat and pressure
   2. (b)evaporation of mineral-rich water in arid basins
   3. (c)cooling and solidification of molten magma or lava
   4. (d)deposition and cementation of loose sediments in water bodies
   Show answer and step marks

   1. Correct option: (c) cooling and solidification of magma or lava.+1

   Answer: (c)
3. Q3Multiple choice·1 mark
   Which of the following is an example of an intrusive igneous rock?

   1. (a)Obsidian
   2. (b)Basalt
   3. (c)Granite
   4. (d)Pumice
   Show answer and step marks

   1. Correct option: (c) Granite, which cools slowly beneath the Earth's surface forming intrusive igneous rocks.+1

   Answer: (c)
4. Q4Multiple choice·1 mark
   Which of the following sedimentary rocks is formed from the remains of plants and animals?

   1. (a)Coal
   2. (b)Rock salt
   3. (c)Sandstone
   4. (d)Conglomerate
   Show answer and step marks

   1. Correct option: (a) Coal, which is an organically formed sedimentary rock derived from accumulated plant remains.+1

   Answer: (a)
5. Q5Long answer·4 marks
   Answer the following questions with reference to igneous rocks: (a) State two main characteristics of igneous rocks. [2] (b) Differentiate between acidic and basic igneous rocks on the basis of their silica content and provide one example for each. [2]
   Show answer and step marks

   1. (a) First characteristic, any one of: crystalline in structure; do not contain fossils; generally hard and impervious; called primary rocks as they form first, from cooled magma or lava.+1
   2. (a) Second characteristic, a different one from the same list.+1
   3. (b) Acidic igneous rocks have a high silica content (over $65\%$) and are light-coloured.+0.5
   4. (b) Basic igneous rocks have a low silica content (below $55\%$), are dark-coloured and rich in iron and magnesium.+0.5
   5. (b) Example of an acidic igneous rock: granite.+0.5
   6. (b) Example of a basic igneous rock: basalt (or gabbro).+0.5

   Answer: (a) Any two of: crystalline, contain no fossils, hard and impervious, primary rocks. (b) Acidic igneous rocks have over $65\%$ silica and are light-coloured, e.g. granite; basic igneous rocks have below $55\%$ silica and are dark and rich in iron and magnesium, e.g. basalt.
6. Q6Long answer·4 marks
   (a) Define metamorphism and state the two primary agents responsible for the formation of metamorphic rocks. [2] (b) Differentiate between thermal metamorphism and dynamic metamorphism on the basis of the primary agent involved. [2]
   Show answer and step marks

   1. (a) Metamorphism is the change in the form, structure or composition of pre-existing (igneous or sedimentary) rocks without melting.+1
   2. (a) First agent: heat.+0.5
   3. (a) Second agent: pressure.+0.5
   4. (b) Thermal metamorphism is caused mainly by great heat, from magma coming into contact with the surrounding rocks.+1
   5. (b) Dynamic metamorphism is caused mainly by great pressure, from earth movements (tectonic forces).+1

   Answer: (a) Metamorphism is the change in form or composition of pre-existing rocks; its agents are heat and pressure. (b) Thermal metamorphism is caused mainly by heat from magma; dynamic metamorphism mainly by pressure from earth movements.

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