1. Melting: This is the process where existing rocks (igneous, sedimentary, or metamorphic) are heated to a high enough temperature that they melt into magma or lava. This can occur due to various factors, such as:
* Plate Tectonics: Subduction zones where one tectonic plate slides beneath another generate heat, melting the rock.
* Volcanism: Hot spots in the Earth's mantle create magma that rises to the surface.
* Intrusions: Magma can intrude into existing rock, heating and melting it.
2. Crystallization: This is the process where the molten magma or lava cools and solidifies. As the magma or lava cools, the minerals within it start to crystallize and form a solid rock. The rate of cooling affects the size and arrangement of the crystals, which in turn determines the texture of the igneous rock.
Therefore, melting and crystallization are the two essential processes in the rock cycle for forming igneous rocks.
