Crust (geology) crustal rocks formed before 2.5 billion years ago are located in cratons. Such old continental crust and the underlying mantle asthenosphere are less dense than elsewhere in Earth and so are not readily destroyed by subduction. Formation of new continental crust is linked to periods of intense orogeny; these periods coincide with the formation of the supercontinents such as Rodinia, Pangaea and Gondwana. The crust forms in part by aggregation of island arcs including granite and metamorphic fold belts, and it is preserved in part by depletion of the underlying mantle to form buoyant lithospheric mantle. A theoretical protoplanet named
Alan (given name) what is today Brittany, France. An early figure who bore the name was St Alan, a 5th-century bishop of Quimper. This saint became a cult figure in the Brittany during the Middle Ages. Another early bearer of the name was St Alan, a 6th-century Cornish saint, who has a church dedicated to his memory in Cornwall (for example see St Allen, a civil parish in Cornwall named after this saint). Today the use of the given name (and its variants) is due to its popularity among the Bretons who imported the name to England, to Cornwall, and later to Ireland.