<Li> Continental: 30 km (20 mi) to 50 km (30 mi) thick and mostly composed of less dense, more felsic rocks, such as granite . </Li> <P> Because both continental and oceanic crust are less dense than the mantle below, both types of crust "float" on the mantle . This is isostasy, and it's also one of the reasons continental crust is higher than oceanic: continental is less dense and so "floats" higher . As a result, water pools in above the oceanic crust, forming the oceans . </P> <P> The temperature of the crust increases with depth, reaching values typically in the range from about 200 ° C (392 ° F) to 400 ° C (752 ° F) at the boundary with the underlying mantle . The temperature increases by as much as 30 ° C (54 ° F) for every kilometer locally in the upper part of the crust, but the geothermal gradient is smaller in deeper crust . </P> <P> The continental crust has an average composition similar to that of andesite . The most abundant minerals in Earth's continental crust are feldspars, which make up about 41% of the crust by weight, followed by quartz at 12%, and pyroxenes at 11% . Continental crust is enriched in incompatible elements compared to the basaltic ocean crust and much enriched compared to the underlying mantle . Although the continental crust comprises only about 0.6 weight percent of the silicate on Earth, it contains 20% to 70% of the incompatible elements . </P>

What is the temperature of earth's crust
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