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 1982 and the UK declared that no ship would be allowed within a radius of the rock. However, in 1997, the UK ratified the United Nations Convention on the Law of the Sea (UNCLOS), limiting territorial sea claims to a 12-nautical-mile, or 14 mile (22 km), radius, and therefore allowing free passage in waters beyond this. In 1988, the United Kingdom and Ireland signed an EEZ boundary agreement for which "the location of Rockall was irrelevant to the determination of the boundary". In 1997, the UK ratified UNCLOS, which states that "Rocks which cannot sustain human habitation or economic life