Rockall part of the deeply eroded Rockall Igneous Centre that was formed as part of the North Atlantic Igneous Province, approximately 55 million years ago, when the ancient continent of Laurasia was split apart by plate tectonics. Greenland and Europe separated and the northeast Atlantic Ocean was formed between them, eventually leaving Rockall as an isolated islet. The RV "Celtic Explorer" surveyed the Rockall Bank in 2003. The Irish Light Vessel "Granuaile" (the same name as the steamer on the RIA 1896 botany survey) was chartered by the Geological Survey of Ireland, on behalf of the Department of Communications, Marine and
Benue Trough under oxygen-deficient bottom conditions. In the Upper Cretaceous, the Benue Trough probably formed the main link between the Gulf of Guinea and the Tethys Ocean (predecessor of the Mediterranean Sea) via the Chad and Iullemmeden Basins. Towards the end of this period the basin rose above sea level, and extensive coal forming swamps developed, particularly in the Anambra Basin. The trough is estimated to contain 5,000 m of Cretaceous sediments and volcanic rocks. A common explanation of the trough's formation is that it is an aulacogen, an abandoned arm of a three-armed radial rift system. The other two arms continued