British Isles British Isles The British Isles are an archipelago in the North Atlantic Ocean off the north-western coast of continental Europe that consists of the islands of Great Britain, Ireland, the Isle of Man and over six thousand smaller isles. They have a total area of about 315,159 km and a combined population of just under 70 million, and include two sovereign states, the Republic of Ireland (which covers roughly five-sixths of the island of Ireland) and the United Kingdom of Great Britain and Northern Ireland. The islands of Alderney, Jersey, Guernsey and Sark, and their neighbouring smaller islands, are sometimes
British Isles also taken to be part of the British Isles, even though, as islands off the coast of France, they do not form part of the archipelago. The oldest rocks in the group are in the north west of Scotland, Ireland and North Wales and are 2.7 billion years old. During the Silurian period the north-western regions collided with the south-east, which had been part of a separate continental landmass. The topography of the islands is modest in scale by global standards. Ben Nevis rises to an elevation of only , and Lough Neagh, which is notably larger than other lakes