What is the rock cycle?

• A. A single process that forms rocks from molten material.
• B. A series of processes that only occur on the surface.
• C. Rocks are permanently fixed and never change.
• D. A series of processes on the surface and inside Earth that slowly changes rocks from one kind to another.

Answer: (D)

The rock cycle is about rocks continually changing from one type to another through processes that happen both on the surface and inside Earth. Weathering and erosion break rocks into sediments, which can become sedimentary rocks when they’re compacted and cemented. Deep underground, heat and pressure can transform rocks into metamorphic rocks, and melting can turn rocks into magma that later cools to form igneous rocks. Over long timescales, these steps link together so a rock can become another kind and the cycle continues. The other options don’t fit because rocks aren’t formed only from molten material in a single step, processes don’t occur only on the surface, and rocks are not permanently fixed but constantly changing through these interactions.