Which statement correctly describes metamorphic rocks?

Which statement correctly describes metamorphic rocks?

• A. They are formed from existing rocks by heat and pressure
• B. They are formed from cooling lava
• C. They are formed from cemented shells
• D. They are formed by weathering and erosion

Answer: (A)

Metamorphic rocks form when existing rocks are changed by heat and pressure deep in the Earth's crust. This process doesn’t melt the rock; instead minerals recrystallize and become aligned, which often creates a layered or banded texture called foliation. The result is a new rock with different mineral textures and sometimes hardness. For example, shale can become slate, limestone can become marble, and granite can become gneiss. These changes happen under intense conditions during plate tectonics or deep burial. Rocks that form from cooling lava are igneous, not metamorphic. Rocks formed from cemented shells are sedimentary, created from layers of sediment pressed and glued together. Weathering and erosion break down rocks to form sediments, which then lithify into sedimentary rocks.

Metamorphic rocks form when existing rocks are changed by heat and pressure deep in the Earth's crust. This process doesn’t melt the rock; instead minerals recrystallize and become aligned, which often creates a layered or banded texture called foliation. The result is a new rock with different mineral textures and sometimes hardness. For example, shale can become slate, limestone can become marble, and granite can become gneiss. These changes happen under intense conditions during plate tectonics or deep burial.

Rocks that form from cooling lava are igneous, not metamorphic. Rocks formed from cemented shells are sedimentary, created from layers of sediment pressed and glued together. Weathering and erosion break down rocks to form sediments, which then lithify into sedimentary rocks.