What is metamorphism in geology?

Metamorphism in geology refers to the transformation of existing rocks into new types of rock through the application of heat, pressure, and chemically active fluids. This process alters the mineral composition and structure of the rock without the rock melting, which distinguishes it from melting processes that lead to igneous rock formation.

During metamorphism, the conditions of heat and pressure can cause minerals within the rock to recrystallize, align, or even form new minerals that are more stable under the prevailing conditions. This leads to the formation of metamorphic rocks, such as schist, gneiss, and slate, which exhibit distinctive textures and mineralogy compared to their parent rocks.

The other options do not accurately describe metamorphism. The first option discusses sediment accumulation, which pertains to sedimentary processes rather than the transformation of existing rocks. The third option mentions erosion, which involves the wearing away of rock material from its original location, leading to landscape change but not metamorphism. The fourth option discusses dating methods, which relate to determining the age of rocks rather than processes that change their structure.