craton

A craton is the stable interior portion of a continental lithosphere, comprising crust and a thick, buoyant lithospheric mantle root. It has remained geologically stable for long periods, often billions of years, and is insulated from the tectonic collisions that deform younger orogenic belts at plate boundaries.

Cratons consist of two main zones: the shield, which is exposed ancient crystalline basement, and the platform, where that basement is overlain by relatively undeformed sedimentary cover. The crust is typically old, dating from the Archean to early Proterozoic, and the lithospheric root is thick, contributing to low heat flow and high seismic velocities.

Stability results from the thick, buoyant lithosphere and cooling of the mantle, which suppresses subduction and major deformation. Cratons preserve ancient geological records, including zircon cores and mineral assemblages, and can be reactivated during later orogenic events, though generally retain their core structure.

Formation and evolution occur mainly in the Archean and Proterozoic, through crustal growth, accretion, collision, and magmatic addition. Once formed, cratons are long‑lived and can acquire complex histories with episodic reactivation, but they remain relatively intact compared with mobile belts at plate boundaries.

Examples include the Canadian Shield, the Baltic Shield, the East European Craton, the West African Craton, the Kaapvaal and Pilbara cratons, and the Yilgarn and Superior cratons. These regions host some of the oldest rocks on Earth and are key to understanding continental growth and tectonic evolution.