A 20-pound sedimentary rock formed on a mountain cliff near the sea. The rock was made up of grains of sand, pebbles, and exoskeletons of tiny insects. It was held together by calcite. One day, the rock fell into the ocean and over time was buried deep inside Earth. Once inside, the rock was no longer sedimentary but instead turned into a metamorphic rock. After many years, it returned to Earth’s surface. Why did the rock not become an igneous rock?
