Page 75 - Journeys Through Society-7

to heat and later solidify to form igneous rocks. All undergone weathering are carried away and
rocks crumble when exposed to pressure causing the deposited to form sedimentary rocks once again, and
debris to form sedimentary rocks. the cycle goes on.
Igneous rocks are again subjected to weathering and
erosion which breaks them down into fragments.
These fragments are carried away to other places and
deposited to form sedimentary rocks once again.
Heat and pressure also convert igneous rocks into
metamorphic rocks. When metamorphic rocks are
heated to extremely high temperatures, they melt to
form magma. When the magma is cooled and
solidified it forms igneous rocks which are then
subjected to weathering. The particles that have
Rock cycle

Revision Notes

• The Earth has a hard outer layer called the crust beneath which lies the mantle, and deep inside it
lies the core.
• Rocks are made up of minerals.
• There are three types of rocks—igneous rocks, sedimentary rocks and metamorphic rocks.
• Igneous rocks are hard, crystalline rocks that solidify out of molten magma.

• Sedimentary rocks are made up of fragments and sediments of other rock material that get cemented
together.

• Metamorphic rocks are those that have been subjected to intense heat and pressure for a long time
and undergo a complete change.
• The rock cycle describes how each type of rock is altered or destroyed when it is forced out of its
equilibrium conditions.

Evaluation Corner

Multiple Choice Questions

• Choose the correct option: OMR Sheet
1. This rock is formed by rock fragments.
Use only blue/black ball
a. Igneous b. Sedimentary pen to fill the circles. It
should be darkened
c. Metamorphic d. Mantle
completely and properly.
2. The internal heat of the Earth is circulated in this layer: Wrong methods
a. Crust b. Mantle
Correct method
c. Core d. None of these
3. This is an igneous rock:
a. Sandstone b. Granite 1. a b c d
c. Marble d. Limestone 2. a b c d

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