The Gran Desierto is located adjacent to a rapidly subsiding tectonic basin, the Salton Trough, which is a northern extension of the Gulf of California, itself an embayment created by rifting initiated during the Pliocene along the East Pacific Rise and the San Andreas fault system. Regional subsidence has propagated to the northwest as rifting and strike-slip faulting continues into the present day. The central portion of the nearby Salton Trough is more than below sea level; it is protected from marine embayment only by the natural dike of the Colorado River Delta.