How thick is the earths crust?
The crust is only about 3-5 miles (8 kilometers) thick under the oceans(oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust). http://volcano.und.edu/…/Earths_layers4.
We present a new contour map of the thickness of the Earth’s crust. We use a 10 km contour interval plus the 45 km contour. This contour map was created directly from the 5 deg. by 5 deg. gridded crustal model CRUST 5.1 (Mooney et al., 1998) plus complimentary information. An initial contour map was created using the command “grdcontour” in GMT, and the resultant map was adjusted in Adobe Illustrator to honor individual point measurements and newly available information from Russia. The final contour map honors all available seismic refraction measurements for features with a dimension greater than 2 degrees. To a first approximation, the continents and their margins are outlined by the 30 km contour. That portion of the continental interior enclosed by the 40 km contour, and regions with crustal thickness of 45 to 50 km are found on all well surveyed continents (i.e., North and South America, Australia, and Eurasia). Continental crust with a thickness in excess of 50 km is exceedingly
