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
Rockall often given as 8 July 1810, when a Royal Navy officer named Basil Hall led a small landing party from the frigate to the summit. However, research by James Fisher of the landing (see below), in the log of the Endymion and elsewhere, indicates that the actual date for this first landing was on Sunday 8 September 1811. The landing party left the "Endymion" for the rock by boat. Whilst there, the "Endymion", which was taking depth measurements around Rockall, lost visual contact with the rock as a haze descended. The ship drifted away, leaving the landing party stranded. The