Which type of metamorphism involves large-area pressure and temperature increases, producing foliation?

Which type of metamorphism involves large-area pressure and temperature increases, producing foliation?

• A. Regional metamorphism
• B. Contact metamorphism
• C. Shock metamorphism
• D. Burial metamorphism

Answer: (A)

Foliation arises when rock minerals with flat or elongated shapes realign under directed pressure as heat also increases. This combination—a broad, long-lasting compression over a large area with rising temperature—causes minerals like mica to parallel each other and form layered or banded textures. That widespread high-temperature, high-pressure setting is characteristic of regional metamorphism, which develops over large regions, typically at convergent plate boundaries during mountain-building. The result is foliated rocks such as slate, phyllite, schist, and gneiss. In contrast, contact metamorphism is driven mainly by heat from nearby magma with relatively little differential stress, so rocks tend to be nonfoliated. Burial metamorphism involves deeper burial with increased pressure and temperature but generally lacks the strong directed stress that yields foliation. Shock metamorphism from meteorite impacts produces high pressures and distinctive mineral phases rather than broad foliation.

Foliation arises when rock minerals with flat or elongated shapes realign under directed pressure as heat also increases. This combination—a broad, long-lasting compression over a large area with rising temperature—causes minerals like mica to parallel each other and form layered or banded textures. That widespread high-temperature, high-pressure setting is characteristic of regional metamorphism, which develops over large regions, typically at convergent plate boundaries during mountain-building. The result is foliated rocks such as slate, phyllite, schist, and gneiss.

In contrast, contact metamorphism is driven mainly by heat from nearby magma with relatively little differential stress, so rocks tend to be nonfoliated. Burial metamorphism involves deeper burial with increased pressure and temperature but generally lacks the strong directed stress that yields foliation. Shock metamorphism from meteorite impacts produces high pressures and distinctive mineral phases rather than broad foliation.