Explain metamorphism and the difference between foliated and nonfoliated metamorphic rocks.

Explain metamorphism and the difference between foliated and nonfoliated metamorphic rocks.

• A. Metamorphism alters rocks via heat and pressure or chemically active fluids; foliated rocks show layered mineral alignment; nonfoliated rocks do not.
• B. Metamorphism is the cooling of molten rock to form igneous rocks.
• C. Metamorphism refers to weathering of rocks.
• D. Metamorphism is the deposition of sediments.

Answer: (A)

Metamorphism is the solid-state alteration of preexisting rocks as they are subjected to higher temperature and pressure, and sometimes to chemically active fluids, which drive recrystallization and the growth of new minerals without melting the rock. When pressure is directed, minerals realign themselves into flat or elongated grains that form a layered or banded texture called foliation; this is common in rocks like slate, phyllite, schist, and gneiss, where platy minerals such as micas align perpendicular to the direction of greatest stress. In contrast, when metamorphism happens mainly due to heat with little directional stress or with fluids that promote growth in all directions, the minerals recrystallize or interlock without any preferred orientation, producing nonfoliated rocks such as marble from limestone and quartzite from sandstone. These textures reflect how stress and fluids influence mineral alignment and growth during metamorphism, helping to distinguish foliated from nonfoliated rocks.

Metamorphism is the solid-state alteration of preexisting rocks as they are subjected to higher temperature and pressure, and sometimes to chemically active fluids, which drive recrystallization and the growth of new minerals without melting the rock. When pressure is directed, minerals realign themselves into flat or elongated grains that form a layered or banded texture called foliation; this is common in rocks like slate, phyllite, schist, and gneiss, where platy minerals such as micas align perpendicular to the direction of greatest stress. In contrast, when metamorphism happens mainly due to heat with little directional stress or with fluids that promote growth in all directions, the minerals recrystallize or interlock without any preferred orientation, producing nonfoliated rocks such as marble from limestone and quartzite from sandstone. These textures reflect how stress and fluids influence mineral alignment and growth during metamorphism, helping to distinguish foliated from nonfoliated rocks.