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
Norma (given name) "Norseman". The name has fluctuated in popularity over the past 100 years. It is still a very common name in the United States, but the name was most often given to babies in the 1930s, and is now seldom given. [[Category:Feminine given names]] Norma (given name) Norma is a female name. A single instance of the name "Norma" is recorded 1203, where it perhaps derives from the Latin word "norma", meaning "precept". The name's general usage seems to be subsequent to the 1831 debut of Vincenzo Bellini's opera "Norma" whose librettist Felice Romani borrowed the name (and the plot) from