Igneous Rocks

Question 1

What are Igneous Rocks?

Answer 1

Igneous rocks are rocks that form from the cooling/solidification of lava or magma. (When lava’s deep under the earth, it’s magma. When it’s erupted onto the surface it’s lava.)

Question 2

What are Intrusive Igneous Rocks?

Answer 2

Intrusive Igneous Rocks are formed from magma, which cools slowly. It has larger crystals, which formed larger because they cooled slower.

Question 3

What are Extrusive Igneous Rocks?

Answer 3

Extrusive Igneous Rocks are made by lava that has cooled quickly. The crystals are much smaller - equal to or less than 1mm in diameter. Often there are no crystals at all. It also may be vesicular (containing air bubbles.)

Question 4

What is the effect on cooling rate on crystal size?

Answer 4

The faster the lava/magma cools, the smaller the crystal size will be.
The slower the lava/magma cools, the bigger the crystal size will be.