CHEMISTRY [2 Mark Question Answer]

The sediments or particles settle at the bottom of lakes, seas, oceans and rivers layer by layer and over a period of time, under pressure, transform into sedimentary rock. Hence, the layers of sediments are formed during the formation of these rocks, and these rocks contain layers.

Pumice is a porous rock which is formed when lava cools quickly above the ground. It has many tiny pores which are formed by gases trapped inside them at the time of formation. These rocks are so light that many pumice rocks actually float on water.

Igneous rocks are rocks formed by the cooling, solidification and crystallization of the magma and lava of volcanic eruptions. Since, they are the first rocks to be formed, they are also called as primary rocks. They are generally hard, have no layers, do not contain fossils and are crystalline and non- porous.
Examples : Granite, pumice, tuff, basalt.