What type of rock is created by the effects of heat and pressure on existing rock?

Metamorphic rock is formed through the alteration of existing rocks—either igneous, sedimentary, or other metamorphic rocks—due to significant heat and pressure over time. This process, known as metamorphism, can lead to changes in the mineral composition and texture of the rock, resulting in a completely new type of rock. For example, limestone can transform into marble, and shale can become schist under the right conditions of heat and pressure.

The other types of rocks listed do not result from this transformation process. Sedimentary rock forms from the accumulation and compaction of mineral and organic particles over time, usually in water. Granite, on the other hand, is an igneous rock that forms from the slow crystallization of molten rock beneath the Earth's surface. Lastly, igneous rock is created by the solidification of molten material called magma or lava. Each of these processes is distinct in the rock cycle, making the understanding of metamorphic rocks essential in geology.