Cratons to Continents

Variations within individual cratons, as well as across different cratons, are readily apparent at the Earth’s surface, providing indirect insight into the processes governing the formation and evolution of the under- lying regions. However, our views at depth are more limited. As such, there is a risk of interpreting the cratonic lithosphere as a monolith. Recent modeling and advances in seismological imaging have enhanced our perspective of vertical variations within the cratonic lithosphere, which has helped build a general conceptual model. While lateral variations also are increasingly identified, their significance still presents unanswered questions. In this review, we summarize the current state of knowledge of cratonic lithospheric structure and demonstrate the importance of lateral heterogeneity in craton evolution and stability.

Although a significant volume of crust was extracted from the mantle early in Earth’s history, the contribution of felsic rocks to the sedimentary record was minimal until ~3.0 Ga. On a hotter Earth, this conundrum dissipates if we consider that the felsic crust was buried under thick basaltic covers, continents were flooded by a near-global ocean, and the crust was too weak to sustain high mountains, making it largely unavailable to erosion. Gravitational forces destabilized basaltic covers within these weak, flat, and flooded continents, driving intra-crustal tectonics and forcing episodic subduction at the edges of continents. Through secular cooling, this dual-mode geodynamics progressively transitioned to plate tectonics.

Studies of Archean cratons, and the rocks and minerals they contain, help us understand the processes that occurred on the early Earth, our place in the Solar System, and how the planet we live on today came to be. The articles in this issue examine different aspects of early Earth evolution from multiple perspectives relying on both theory and observation. We hope they will encourage you to investigate further this most fascinating time in Earth history. Here we introduce the basic characteristics of cratons, the challenges of inferring Earth evolution from the sparse Archean rock record, the concept of cratonic clans, the development of supercratons, and, by the end of the Archean, continents, supercontinents, and plate tectonics.