What conditions cause sedimentary or igneous rock to change into metamorphic rock?

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During metamorphic processes, increased pressure and temperature can affect the of minerals in rock. rocks subjected to very high pressure are typically than others because mineral grains are squeezed together, and the atoms are more closely packed. during metamorphic processes, water facilitates the transfer of ions between and within minerals, which can the rate at which metamorphic reactions take place. the growth of new minerals within a rock during metamorphism has been estimated to be about per million years. metamorphism is commonly associated with convergent plate boundaries, where two plates move toward each other. during contact metamorphism, a large intrusion will contain thermal energy and will cool much more slowly than a small one. metamorphosed sandstone is known as the metamorphic rock made from metamorphosed shale, was once used to make blackboards for classrooms

Which type of seismic waves are confined at the surface