* Crust: This is the outermost layer, and it's incredibly thin compared to the other layers. It's made up of solid rock and ranges in thickness from about 3-5 miles (5-8 kilometers) under the oceans (oceanic crust) to about 25 miles (40 kilometers) under the continents (continental crust).

* Upper Mantle: This is the outermost part of the mantle, and it's also relatively thin compared to the lower mantle. It extends from the base of the crust down to a depth of about 410 miles (660 kilometers).

While the upper mantle is significantly thicker than the crust, it's still considered thin compared to the lower mantle.