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There are several ways that metamorphic rocks form at
or near plate boundaries. There is localized metamorphism called contact
metamorphism. Usually this occurs near molten magma or lava, under
high temperature and low pressure. Metamorphism affecting a large area
or regional metamorphism involves large increases of temperature
and pressure. Contact metamorphism is common at both convergent
and divergent plate boundaries, in areas where molten rock is
produced. Regional metamorphism largely occurs at convergent plate
boundaries.
Each of these types of metamorphism produces
typical metamorphic rocks, but they may occur in different sequences.
For example, both regional and contact metamorphism produce schists and
shales. However, gneiss would be common in regional metamorphism.
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