Question

Explain about the rocks based on the formation.

Answer 1

Based on formation, rocks are classified as:

1. Igneous
2. Sedimentary
3. Metamorphic

a. Igneous:

1. When the lava on the surface cools down and solidified igneous rocks are formed.
2. Granite and basalt are examples of such rocks.
3. Igneous rocks are also called Primary or mother rocks because all other rocks are directly or indirectly formed from them.
4. These rocks are used in construction work and laying roads.

b. Sedimentary Rocks:

1. Rivers, glaciers, and winds cany lists of rock and soil and deposit them in layers.
2. After a few million years, these deposits harden into compact rocks.
3. They are called sedimentary rocks.
4. The bodies of plants and animals that fall on the deposits get embedded in the layers and form Fossils.
5. Sandstone, limestone, chalk, gypsum, coal are examples.
6. These rocks are useful in the manufacturing of wallboard, cement, plaster of Paris, construction and purification of iron in blast furnaces, etc.

c. Metamorphic Rocks:

1. When igneous or sedimentary rocks are subjected to extreme heat and pressure, they ‘ undergo a complete change in their form and character.
2. In course of time, granite may get transformed to gneiss, basalt to schist, limestone to marble, and sandstone to quartzite.
3. These rocks are used in Jewelry making, sculpture, and construction.