Question

How are extrusive and intrusive igneous rocks formed class 7?

Answer 1

Extrusive igneous rocks are formed at the crust ' s surface as a result of the partial melting of rocks with in the mantel and crust.

And Intrusive Igneous rocks are formed by the cooling of molten magma on the earth ' s surface.

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.

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Explanation: