Inside Our Earth — Social Studies STD 7 — Question

Extrusive rock: When molten lava comes on the earth’s surface, it rapidly cools down and becomes solid. Rocks formed in such a way on the crust are called extrusive igneous rocks. They have a very fine grained structure.
Intrusive rocks: Sometimes the molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous.