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) century, where it was about even with "Simon", and more numerous than "Henry". Early occurrences of the name in British records include: "Alanus" in 1066 (in the "Domesday Book"); and "Alain" in 1183. The name became popular in Scotland in part through the Stewarts. This family descends from Alan fitz Flaad, an Anglo-Breton knight, who possessed lands in what is modern day Shropshire, England. Alan (given name) Alan is a masculine given name in the English language. There are numerous differing etymologies attributed to the name. The name was first introduced into England by Bretons who took part in the