1. When
from volcanic activity cools down, it forms
rocks.
2. The grain or
in igneous rocks depends on the rate of
.
(a) If the magma cools
on the surface, the grain size is small forming rocks like
.
(b) If the cooling is
deep in the earth, the grain or
size is large forming rocks like
.
3. In volcanic eruptions the magma can flow out as
, or be blasted out as
.
4. Igneous rocks like pumice are not very
(light) because they contain trapped
of gas.
5a. Eventually all rocks of whatever type, get
and
back into magma.
5b. This happens
in the earth's crust.
5c. In the
the same material might come back out as magma and be changed into another rock form. This goes on all the time and is called the
.