Gliders in the Grand Canyon

Marty Shapiro writes:

There is a real nice picture of Marble Canyon taken about 3 months ago
at http://airnav.com/airport/L41 It clearly shows the airport at the top
of the canyon, not in the canyon. Of course, MXmoron is too lazy to try
and look anything up. If he had, he would have also noticed that the
pictures of Cliff Dweller's Lodge and Grand Canyon Bar Ten also show them
at the top of the canyon, not in the canyon.

I looked it all up. On a topographic map it is clear that these are all in
the canyon. And if you look closely you'll see that the canyon is about 2000
feet deep where these airports sit.