SAND DUNE, people. Sloping. Uneven.
Here's a shot from DC where the guys are standing on solid ground.
You will note that Trip is closer to the camera and it is a slightly top down shot. That is a textbook method of giving items/characters to the back greater perceived height. If it was someone else in the scene with Trip the camera angle would have been low to make Trip look taller. They do this throughout the series.