Cratons are the ancient, stable cores that hold our continents together for billions of years.

Nature · Published 3 October 2026 Swipe more like this →

In short: Deep beneath the surface of our continents lie cratons, massive, stable slabs of rock that have survived eons of tectonic chaos. These ancient foundations possess deep, cold roots extending hundreds of kilometers into the mantle, acting as the enduring anchors for the Earth's shifting surface plates.

Cratons represent the oldest continental crust on Earth, primarily formed during the Archean eon between 4 and 2.5 billion years ago. Defined by their remarkable long-term stability, these coherent domains have resisted internal deformation throughout geological history. They consist of two distinct components: the crystalline basement, which is sometimes exposed at the surface as a shield, and the platform, a layer of younger, weakly deformed sedimentary rock covering the basement.

The secret to a craton's longevity lies in its unique lithospheric roots. While typical oceanic or non-cratonic continental lithosphere is about 100 kilometers thick, cratonic roots can extend up to 400 kilometers into the mantle. These roots are composed of peridotite, a mantle material depleted of heavier elements like calcium and iron, and enriched in lightweight magnesium. This chemical composition gives the roots a low density and high viscosity, preventing them from sinking into the hotter, denser mantle below.

Scientists are still debating exactly how these roots formed. Thomas H. Jordan's influential 1978 model suggests that high temperatures in the early Earth allowed for massive partial melting of the upper mantle, leaving behind a buoyant, solid residue. Other theories propose that repeated continental collisions 'kneaded' the crust, or that rising plumes and subducting oceanic slabs helped underplate the continents. A more recent, 2015 hypothesis even suggests that massive asteroid impacts on the early Earth created lava ponds that cooled to form these deep, stable foundations.

Regardless of their precise origin, cratons remain distinct from the more geologically active regions of the planet. Their presence is confirmed by mantle tomography and the study of xenoliths—rock fragments brought to the surface by kimberlite pipes. These samples reveal an unusually dry, strong composition that has allowed cratons to persist while other parts of the Earth's crust have been recycled through constant tectonic movement.

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