What is a key outcome of metamorphism regarding crystal size?

What is a key outcome of metamorphism regarding crystal size?

• A. Growth of new or larger crystals
• B. Melting to magma
• C. Erosion of minerals
• D. Formation of glass

Answer: (A)

When rocks are subjected to higher temperatures and pressures while staying solid, minerals can recrystallize and rearrange their internal structures. This solid-state diffusion allows crystals to grow larger or for new crystals to form that are stable under the new conditions. As a result, metamorphic rocks often develop coarser textures with bigger crystals, and grains may align into bands as pressure reorients mineral grains. Melting to magma isn’t typical in metamorphism because the process occurs without melting (though very high temperatures can cause partial melting in some rocks, which is more specific to migmatites). Erosion is a surface process that wears rocks down, not something metamorphism does in the deeper crust. Glass forms from rapid cooling of melted rock, not from the solid-state recrystallization that characterizes metamorphism.

When rocks are subjected to higher temperatures and pressures while staying solid, minerals can recrystallize and rearrange their internal structures. This solid-state diffusion allows crystals to grow larger or for new crystals to form that are stable under the new conditions. As a result, metamorphic rocks often develop coarser textures with bigger crystals, and grains may align into bands as pressure reorients mineral grains.

Melting to magma isn’t typical in metamorphism because the process occurs without melting (though very high temperatures can cause partial melting in some rocks, which is more specific to migmatites). Erosion is a surface process that wears rocks down, not something metamorphism does in the deeper crust. Glass forms from rapid cooling of melted rock, not from the solid-state recrystallization that characterizes metamorphism.