Question

How would you differentiate between intrusive and extrusive rocks?

Answer 1

The key difference between intrusive and extrusive rocks is that the intrusive rocks are formed from magma whereas the extrusive rocks are formed from lava. Before discussing further differences between both rocks, let us see what is a rock and what are intrusive rocks and extrusive rocks. Most of the earth’s surface is covered with rocks of various types. These rocks are formed because of the action of high pressure, high temperatures, and water. Rocks containing different mineral compounds are classified into three major types namely igneous rocks, sedimentary rocks, and metamorphic rocks. This classification also takes into account the manner in which rocks have been formed. Rocks that bear very high pressure and heat within the earth’s crust melt down to form lava. When this liquid lava gets cooled, it solidifies and gets converted into igneous rocks. Intrusive and extrusive are two types of these igneous rocks. It is the difference between intrusive and extrusive rocks that creates confusion in the minds of students. Hope it helps you

Answer 2

Answer:

Extrusive or volcanic rocks:

These rocks are formed when magma breaks through the crust and reaches the surface of the earth (where it is called lava). It cools rapidly and solidifies to form rocks. The common rocks formed in this manner are basalt and obsidian.

Instrusive or plutonic rocks:

These rocks are formed when magma fails to break through the crust and cools slowly under the crust  forming rocks. Because of slow cooling it solidifies into rocks with large grains of crystals. The common eg of rocks formed in this manner are granite and dolerite.

I Hope this will help uh ! :)