Benue Trough the Central African Shear Zone and for the volcanic island of St. Helena in the Atlantic ocean. Three periods of magmatic activity (volcanic action) have been identified, 147–106 Ma, 97–81 Ma and 68–49 Ma. The first is prominent in the north of the trough, and contemporary with magmatism in Brazil, probably occurring during a period of crustal extension before the Atlantic started to open. The second is found only in the south of the trough, and may belong to a period when the extension of the Atlantic had slowed down, ending with a period of compression. The third and last
Salton Trough Salton Trough The Salton Trough is an active tectonic pull-apart basin. It lies within the Imperial, Riverside, and San Diego counties of southeastern California. 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 Salton Sink is the topographic low area within the Salton Trough. 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