* Heat and Pressure: Rocks deep within the Earth's crust and mantle are subjected to immense heat and pressure. This can come from:
* Magma: Molten rock rising from the Earth's interior.
* Friction: Plates grinding against each other in tectonic activity.
* Radioactive Decay: Heat generated from the decay of radioactive elements in the Earth's core.
* Transformation: This intense heat and pressure cause the existing rocks to melt, transforming them into magma. This magma is a hot, fluid mixture of minerals and gases.
* Cooling and Solidification: As the magma cools and solidifies, it crystallizes into igneous rocks. This can happen:
* Intrusively: Magma cools slowly underground, forming large crystals, resulting in intrusive igneous rocks like granite.
* Extrusive: Magma erupts onto the Earth's surface as lava, cools quickly, and forms smaller crystals, resulting in extrusive igneous rocks like basalt.
In essence, melting is a crucial step in the rock cycle, providing the source material for igneous rocks and setting the stage for further transformations within the cycle.
