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Continental crust has a much more variable composition than oceanic crust. Continental crust can be generalized as “granitic” in composition, and is enriched in K₂O, Na₂O, and SiO₂ relative to average crust. Although igneous and metamorphic rocks of granitic composition are fairly common in the upper portion of continental crust, lower portions contain more rocks of intermediate dioritic and even basic gabbroic composition. Granites and related rocks tend to be light colored, lower density felsic rocks rich in quartz and potassium and sodium feldspars. Continental crust is generally much thicker than oceanic crust; depth to the Moho averages 30–40 km. Under areas of very high elevation, such as the Himalayas, its thickness approaches 85 km. The greater thickness and lower density of continental crust make it more buoyant than oceanic crust. As a result, the top of continental crust is generally located at higher elevations and the surfaces of continents with normal crustal thicknesses are above sea level. The distribution of Earth's land and sea is largely dictated by the distribution of continental and oceanic crust. Only the thinnest portions of continental crust, most frequently along thinned continental margins and in rifts, have surfaces below sea level.

Whereas modern oceans, with the exception of a small area in the Mediterranean Sea, are underlain by oceanic crust younger than 190 Ma, the oldest well‐documented continental crust includes 4.03 Ga rocks from the Northwest Territories of Canada (Stern and Bleeker 1998). Approximately 4 Ga rocks also occur in Greenland and Australia. Greenstone belts (Chapter 18) may date back as far as 4.28 Ga (O'Neill et al. 2008) which suggests that continental crust began forming within 300 million years of Earth's birth. Individual detrital zircon grains, derived from the erosion of older continental crust, occur in metamorphosed sedimentary rocks in Australia. These zircons have been dated at 4.4 Ga (Wilde et al. 2001) an age recently confirmed by Valley et al. (2014). These data suggest that continental crust may have existed no more than 150 Ma after Earth formed. The great age of some continental crust results from its relative buoyancy. In contrast to ocean crust, continental crust is largely preserved as its density is generally too low for it to be subducted on as large a scale. Table 1.1 summarizes the major differences between oceanic and continental crust.