The islands have a varied geology and history and several have both ecclesiastical connections and were involved in military occupations throughout the centuries of recorded history. Various lighthouses and other aids to navigation have been erected on the islands and skerries, one dating to the 17th century, but only one of the islands is still permanently inhabited. The area has a diversity of bird and sea life and the scientific name for the northern gannet is derived from this bird's connection with the Bass Rock.