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
Opal (given name) in the 1950s. It was the 344th most common name for females in the United States in the 1990 census. Eighty girls born in the United States in 2010 were given the name and 92 girls born in 2011 were given the name. Opal (given name) Opal is a feminine given name derived from the name of the gemstone opal. The gemstone is the birthstone for October. Its name is derived from the Sanskrit उपल or "upala", which means ""jewel". It came into use along with other gemstone names during the late Victorian era. Opal was among the 100 most