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 Natural Resources, to conduct a seismic survey of the Rockall Bank and the Hatton Bank in July 2004, as part of the Irish National Seabed Survey. The island's only permanent macro-organism inhabitants are common periwinkles and other marine molluscs. Small numbers of seabirds, mainly fulmars, northern gannets, black-legged kittiwakes, and common guillemots, use the rock for resting in summer, and gannets and guillemots occasionally breed successfully if the summer is calm with no storm waves washing over the rock. In total there have been just over twenty species of seabird and six other animal species observed (including the aforementioned molluscs)