Answer:
Cools
Size
Step-by-step explanation:
The rate at which magma cools determines the size of the crystals in the new rock.
When magma cools rapidly, nucleation centers are much and they do not aggregate to form larger crystals. This will give a rock that is finely grained.
When magma cools slowly, the nucleation centers grows and much time is afforded for big crystals to form within the mass.
- Most intrusive igneous rocks usually have big crystals because the crystals have enough time to aggregate around nucleation centers.
- Extrusive igneous rocks cools rapidly and their crystals are very fine grained due to the condition prevalent on the surface.