The 13 mile thick area covering the face of the Earth where living things can exist is called the biosphere.

It's important to note that the biosphere isn't a perfectly defined layer with hard boundaries. It extends from the deepest ocean trenches to the highest mountain peaks, and includes everything in between.

Here's a breakdown:

* Depth: The deepest parts of the ocean where life has been found are about 7 miles down.

* Height: The highest elevation at which life exists is about 5.5 miles up (on Mount Everest, for example).

So, while 13 miles represents a general range, the biosphere is more accurately described as a complex, dynamic zone that varies in thickness depending on location and environmental factors.