In the rock cycle, what is the process that transforms sedimentary rocks into metamorphic rocks?

The transformation of sedimentary rocks into metamorphic rocks occurs through the application of heat and pressure. This process, known as metamorphism, alters the mineralogy, texture, and sometimes the chemical composition of the original sedimentary rock. When sedimentary rocks are subjected to intense heat, typically from nearby magma or tectonic activity, and high pressure, often from the weight of overlying rocks or tectonic forces, the minerals within the sedimentary rock can recrystallize. This leads to the formation of new minerals and a denser, more durable rock structure that characterizes metamorphic rocks.

In contrast, melting refers to the process where rocks turn into magma, which is not relevant for the transformation of sedimentary to metamorphic rocks. Weathering involves the breakdown of rocks at the surface due to environmental factors, which is the initial step in the rock cycle but does not contribute to the transformation of one rock type into another in the manner stipulated by the question. Cooling refers to the process by which molten rock (magma or lava) solidifies into igneous rock, which again does not involve the metamorphic transformation of sedimentary rocks. Therefore, heat and pressure are the critical factors in converting sedimentary rocks into metamorphic rocks during the rock