Underneath the continents, the Earth’s crust is the thickest. Under the oceans are the thinnest regions. Geographic location and whether the crust is continental or oceanic affect average thickness substantially.
The thickness of the continental crust, or the crust that underlies the continents, is typically between 30 and 45 kilometres. These thicknesses can be found on almost every continent and are determined by altitude above sea level and the presence of mountains. According to the United States Geological Survey, or USGS, fewer than 10% of the total area of the Earth’s crust is more than 50 kilometres thick, despite the fact that there are some rare regions that are thicker than 70 kilometres.
Oceanic crust is a term used to describe thicknesses less than 30 kilometres, which are normally found only under the ocean. Only about five kilometres thick, or a minuscule percentage of the thickness of the thickest portions of the continental crust, make up the thinnest areas of the crust. Since the thickness of the oceanic crust varies widely from coast to coast and everywhere in between, it is challenging to determine its thickness by focusing just on latitude or proximity to continents. The oceanic crust, for instance, is between 10 and 30 kilometres thick along the eastern coast of the United States, according to the USGS.