Jet Contrail in Background!
Approx half way through the movie.
Can't give exact due to viewing this on Comettv with commercials.
In 1955 this would be a rarity.
Even Ike's Air Force One was a propeller plane at the time.
There were jets around back then. Not commercial jets, but plenty of military jets. I bet this was filmed near base or testing grounds.
I saw it too as a character walked down into the crater. Seeing them in Westerns filmed same area was real gaffe that showed up on TV shows from the 50's a lot.