Question

give reason that why extrusive igneous rocks have generally small crystals

Answer 1

Lava, at the surface, is exposed to air and water which causes the moltenrock to cool rapidly. Solidifying rocksat the surface cool too quickly for largecrystals to form. ... Extrusive rocks have crystals that are too small to see without magnification. A common example of an extrusive igneous rockis basalt.

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 ! :)

Explanation: