Most common rock type at the surface of the continental crust

Approximately 75% of Earth’s continental crust has sedimentary rocks at its surface. Usually a thin veneer over igneous and metamorphic rocks, these sedimentary rocks, including sandstone, mudstone, chalk and breccias, formed as small particles became buried over geological time and subjected to great pressures. Erosional and tectonic forces can cause them to be exposed to the surface again.

Despite their abundance at the surface, sedimentary rocks only make up around 8% of the mass of Earth’s crust.