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
Rogue wave existence has also since been confirmed by video and photographs, and satellite imagery and radar of the ocean surface, by stereo wave imaging systems, by pressure transducers on the sea-floor and notably by oceanographic research vessel. In February 2000, a British oceanographic research vessel, the RRS "Discovery", sailing in the Rockall Trough west of Scotland encountered the largest waves ever recorded by scientific instruments in the open ocean, with a SWH of and individual waves up to . "In 2004 scientists using three weeks of radar images from European Space Agency satellites found ten rogue waves, each or higher." A