Question

What are rocks? Name the types of rocks. Explain each one of them.

Answer 1

Instructions:

• Define/Explain rocks in a sentence. (1 Mark)
• Name the types of rocks(1 Mark)
• Explain all the three. (1 X 3 Marks)

Solution:

• Any natural mass of the mineral matter that make up the Earth's crust is called a Rock.
• The three types of rocks are Igneous Rock, Sedimentary Rock, Metamorphic Rock. The characteristics of the rocks are as follows :

1. Igneous Rock : The middle layer of Earth called Mantle is very hot and contains molten mixture of minerals called Magma. When this Magma finds a way through the mantle and comes to the crust, it cools down and solidifies. The solidified magma is called Igneous Rock. E.g. Granite, Basalt, etc
2. Sedimentary Rock : When agents like River, Glacier and wind carry bits of soils and rocks, these bits are often deposited in layers. Over millions of years, these deposits may harden and form sedimentary rock. e.g. Sandstone, Chalk, Coal, etc
3. Metamorphic Rocks : Metamorphosis means change of form. When Igneous or Sedimentary rocks are subjected to extreme heat and pressure, it completely changes its form and character. E.g. Granite changes into Gneiss, Basalt changes into Schist, Limestone changes to Marble, Sandstone into Quartzite.