What type of rock is formed by heat and pressure or chemical action?

What type of rock is formed by heat and pressure or chemical action?

• A. Igneous
• B. Metamorphic
• C. Sedimentary
• D. Extrusive

Answer: (B)

Rocks can be transformed by heat, pressure, or chemically active fluids, which creates metamorphic rocks. When rock is buried deeper in the crust or squeezed during mountain building, the minerals inside rearrange and recrystallize without melting, forming new textures and mineral compositions. This can create layered, foliated rocks like slate, phyllite, schist, and gneiss, where minerals align or become coarser due to pressure and heat. The chemical action of fluids can also drive reactions that change minerals, producing metamorphic rocks such as marble from limestone or quartzite from sandstone. In contrast, igneous rocks come from molten rock that cools and solidifies, and sedimentary rocks form from particles that are deposited, compacted, and cemented. Extrusive refers to rapid cooling of lava at the surface, which is a type of igneous process, not metamorphism.

Rocks can be transformed by heat, pressure, or chemically active fluids, which creates metamorphic rocks. When rock is buried deeper in the crust or squeezed during mountain building, the minerals inside rearrange and recrystallize without melting, forming new textures and mineral compositions. This can create layered, foliated rocks like slate, phyllite, schist, and gneiss, where minerals align or become coarser due to pressure and heat. The chemical action of fluids can also drive reactions that change minerals, producing metamorphic rocks such as marble from limestone or quartzite from sandstone. In contrast, igneous rocks come from molten rock that cools and solidifies, and sedimentary rocks form from particles that are deposited, compacted, and cemented. Extrusive refers to rapid cooling of lava at the surface, which is a type of igneous process, not metamorphism.