Geodynamics of continental rift initiation and evolution

A rift is a nascent plate boundary where continental lithosphere is extended and possibly broken. In the geologic past, rifting played a major role in shaping the surface of our planet, while at present, continental rifts are of societal relevance by hosting key georesources such as geothermal energy and ore deposits. This Review discusses fundamental rift processes, geodynamic forces and their tectonic interactions over geological time scales, and identifies the mechanisms that lead to the large variety of rifts on Earth. Linking forces and processes is particularly relevant for rifts, as progressive thinning of the lithosphere prevents a steady-state configuration and prompts continuous changes in their force balance. Rifting initiates through multi-scale exploitation of inherited weaknesses, which generates dynamic spatiotemporal competition, cessation or localisation of rift structures. Successful continent-scale rifts feature an abrupt and roughly ten-fold increase of divergence velocity once the lithosphere is sufficiently weakened. We infer that mantle plumes exert major control on breakup, through dynamic topography and by generating melts that can weaken the lithosphere by an order of magnitude. Outstanding future challenges include unravelling where magmatism is a cause or a consequence of rifting, isolating the tipping points that separate successful from failed rifting, and deciphering the interaction of rift tectonics with fluid flow during georesource formation and volatile release.