Here is a quick sketch of a what the expedition could possibly see when arriving towards the plateau, barely visible through the heavy mist. This is very early idea, so it is still quit similar to what could be found in the real world with no real design innovations. The dinosaurs are included to stay true to the original text.
Here is the development. I started with a quick defining of the mountains, added some textures to created a the flora, added a white gradient on the top and then added quick drawings of pterodactyls.