Rocks which are modified by the force of heat and pressure are called what?

Rocks that are modified by the forces of heat and pressure are classified as metamorphic rocks. This transformation occurs through a process called metamorphism, which involves changes in mineral composition and texture without the rock becoming molten. During metamorphism, existing rocks (which can be igneous, sedimentary, or even other metamorphic rocks) are subjected to high temperatures and pressures, causing physical and chemical changes.

Metamorphic rocks can exhibit unique characteristics, such as foliation (layering) or the presence of new minerals that were not there in the original rock. Common examples of metamorphic rocks include schist, gneiss, and marble, which originates from limestone under heat and pressure.

Understanding the metamorphic process is crucial in geology, as it provides insights into the conditions of the Earth's interior and the tectonic processes that shape our planet. The other types of rocks mentioned, such as igneous and sedimentary, are formed through different processes involving cooling from magma or the accumulation of sediments, respectively, which do not involve the heat and pressure factors that define metamorphic rocks.