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
The Trough Long Knob (1,725 feet) flanks the Trough. Sawmill Ridge ends at the mouth of the Trough at the point where Sawmill Run descends the ridge and joins the river. The communities of Sector and Glebe are located here to the west and east, respectively. The concrete piers of the old bridge that once carried Fleming-Sector Road (County Route 8/3) connecting these two communities are still visible here as well. A typical Trough canoe run ends at the Harmison's Public Access Site below the old bridge and behind The Trough General Store. The Trough is a popular canoeing/kayaking venue, although not