Here's why:
* Crust: The crust is the outermost layer of the Earth, and it's incredibly thin compared to the other layers. It ranges in thickness from about 3-5 miles (5-8 km) under the oceans (oceanic crust) to about 25 miles (40 km) under the continents (continental crust).
* Atmosphere: The atmosphere extends upwards for hundreds of miles, but it's primarily concentrated in the lower layers. The troposphere, where most weather occurs, extends up to about 7 miles (11 km).
While the atmosphere is much thinner than the Earth's radius, it's still considerably thicker than the Earth's crust. However, when comparing relative thicknesses, the crust is the closest match.
