The rock cycle
Chemistry · Key Stage 2 · The School
Three types, three stories
IGNEOUS rock forms when melted rock cools and turns solid. SEDIMENTARY rock forms when layers of sand, mud or shell get pressed together. METAMORPHIC rock forms when heat and pressure change a rock that already exists. Each type has its own story.
One type can become another
Rock does not stay the same type forever. Weathering breaks igneous rock into tiny grains. Those grains can be pressed into sedimentary rock. Heat and pressure can squeeze that rock into metamorphic rock. Enough heat can even melt it back into magma.
A loop with no end
Follow one grain of sand. It began as granite, high in a mountain. Rain and wind wore the granite down into grains. Rivers carried the grains to the sea, where they settled in layers. Pressure squeezed those layers into sandstone. That grain could still change again.
Why this matters
The rock cycle has no true start or end. It just keeps turning, very slowly, over millions of years. Rock under your feet today has likely been through this cycle before. Nothing is wasted. It is only ever changed. A grain of sand on a beach might once have been part of a mountain. One day it might be part of a brand new rock.