The thinnest crust of the Earth is found under the oceans, specifically in mid-ocean ridges.

Here's why:

* Oceanic crust is thinner and denser than continental crust.

* Mid-ocean ridges are areas where new oceanic crust is created through volcanic activity. This newly formed crust is relatively thin.

The thickness of oceanic crust at mid-ocean ridges can be as little as 3 kilometers (2 miles), compared to continental crust which can be up to 70 kilometers (43 miles) thick.