Continental crust is that portion of the Earth’s crust composed mainly of low-density siliceous (granitoid) rock. It occupies about one-third of the total crust and underlies most of dry land. Its thickness varies from ≤10 km in rifts to up to 80 km beneath mountain belts. Dominant constituents are granitic rocks and their metamorphic equivalents (gneiss) and metasedimentary or metavolcanic sequences. Continental crust forms above subduction zones and contains a large proportion of the Earth’s budget of incompatible trace elements and heat-producing elements. The presence of continental crust is a signature of plate tectonics that distinguishes Earth from other planets.
Because continental crust is made of lighter (granitoid) material than (basaltic) oceanic crust and its overall density is therefore less, the lithospheric segments that contain continental crust float higher on the asthenospherethan those without it. Liquid water on Earth thus usually only covers its...