b. crystallization above ground and crystallization below ground
Explanation:
The magma undergoes transition when it moves from the mantle layer toward the lithosphere. The reason for this is that the pressure and temperature drastically change. With other words, the magma starts to cool off as it comes toward the surface of the Earth. As the magma cools off it starts to crystallize, resulting in the formation of igneous rocks. When the magma comes out on the surface, known as lava in those cases, it cools of very quickly because the temperature and pressure are much lower. Because the cooling off occurs very quickly, the magma crystallizes quickly, so the crystals are small, and it forms extrusive igneous rocks. When the magma cools off underground, but still relatively close to the surface, the temperature and pressure are slightly bigger than those on the surface. Because of this, the magma cools off slower, thus it crystallizes slower. This results in the formation of larger crystals, and intrusive igneous rocks.
