The crust of the Earth is thickest beneath the continents. The thinnest areas are beneath the oceans. Average thickness varies greatly depending on geography and whether the crust is continental or oceanic.
The continental crust, or the crust that lies beneath the continents, usually ranges from around 30 to 45 kilometers thick. These thicknesses are found on most continents and are dependent on height above sea level and mountainous regions. Although there are rare areas that exceed 70 kilometers thick, according to the United States Geological Survey, or USGS, less than 10 percent of the total area of the Earth's crust exceeds 50 kilometers thick.
Thicknesses below 30 kilometers are typically only found under the ocean and are called oceanic crust. The thinnest sections of the crust are only approximately five kilometers thick, which is a small fraction of the thickness of the thickest parts of the continental crust. The thickness of oceanic crust is difficult to estimate by looking only at proximity to continents or latitude, since the crust varies greatly from coast to coast and everywhere in between. For example, along the eastern coast of the United states, the oceanic crust ranges from 10 to 30 kilometers thick, according to the USGS.