What kind of rock is formed from the alteration of existing rocks through heat, pressure, or chemical activity?

Metamorphic rock is formed through the alteration of existing rocks when subjected to heat, pressure, or chemical activity. This process, known as metamorphism, alters the original rock's mineralogy and structure without the rock completely melting. As a result, it can transform sedimentary rocks, igneous rocks, or other metamorphic rocks into a new rock type with distinct physical and chemical properties.

For example, the metamorphosis of limestone under heat and pressure can create marble, while shale can transform into schist. The key factor that defines metamorphic rocks is their formation through deeply buried geological processes, as opposed to the processes that create sedimentary or igneous rocks. Sedimentary rocks form from the accumulation and compaction of sediments, whereas igneous rocks originate from the cooling and solidification of molten rock. Felsic rock refers specifically to a category of igneous rock that is rich in lighter-colored minerals, such as quartz and feldspar, and does not relate to the alteration of existing rocks as metamorphic rocks do.