He looks longingly at the place he just used for his shadow tip direction finding technique . If he were backpacking this would be a good site, water close at hand, wood and rocks nearby. He knows, however, that capable backpackers, deprived of their equipment, have died because they selected the same sorts of camping sites they did when they had all of their equipment for protection. He begins to climb the side of the canyon. When he is higher than the canyon floor by the height of the highest tree in the canyon, he goes a little higher and starts to search for a spot to make his shelter.
Cold air goes down, warm air rises.
This basic information forms the basis of a number of survival oriented decisions. At night, cold air settles into a valley. In a canyon, it settles to the bottom and then moves down, following the drainage. The movement of air is called wind. If you were in the bottom of a canyon you would be in the coldest air as well as in a wind caused by the movement of that cold air.