Chapter 2: Inside Our Earth
Interior of Earth
Rocks and Minerals
Ignious Rocks and their types
Sedimentary Rocks
Metamorphic Rocks
Rock Cycles
Use of rocks
Questions and Answers
Test Yourself
- Three Layers of the Earth
- Crust
- Mantle
- Core
A mass of mineral matter that makes up the crust of the earth is called rock.
Or
Aggregates of minerals are termed as rocks.
- Igneous Rocks
- Sedimentary Rocks
- Metamorphic Rocks.
Due to extreme heat in the interior of the earth, rocks are found in the form of molten material called magma.
When magma comes out on the surface of the earth, it cools down and turns into solid rocks. Such rocks are termed as extrusive rocks.
Examples:
★ Basalt.
★ Deccan Trap is built of basalt.
When the molten magma cools down within the interior of the earth, it becomes solid to form intrusive rocks.
Examples:
★ Granite.
★ Gabro.
Igneous rocks change into sedimentary rocks, igneous and sedimentary rocks under heat and pressure change into metamorphic rocks, metamorphic rocks into igneous rocks or sedimentary rocks due to melting or wearing down. This process is called the rock cycle.
- Hard rocks are used in making buildings and barrages.
- Houses and buildings are built of rocks (stones, slates, granite, marble).
- Stones are used in numerous games:
- Seven stones (phitthoo).
- Hopscotch (stapu, kit).
- Five stones (gitti).
- Rocks (stones and slates) are used in building bridges, embankments.
When under heat and pressure igneous rocks and sedimentary rocks change their form and more precious rocks are formed to be known as metamorphic rocks.
Examples:
★ Granite into granite gneiss.
★ Coal into slate.
★ Slate into schist.
★ Limestone into marble.