The Salton Sink is the topographic low area within the Salton Trough, an active tectonic pull-apart basin. The Salton Trough is a result of crustal stretching and sinking by the combined actions of the San Andreas Fault and the East Pacific Rise. The Brawley seismic zone forms the southeast end of the basin and connects the San Andreas Fault system with the Imperial Fault Zone to the south. The Salton Buttes are rhyolite lava domes within the basin which were active 10,300 (± 1000) years BP.