Environment Practice #1 (desert cliff)

I can draw humans alright but I've never been good at drawing backgrounds, I've always had a hard time drawing things like sky, land, trees, grass, rivers etc. So I was considering getting out of my comfort zone for a change and try out some scenery type doodles. Here's the result of the first disaster.

Done on one layer, no refs, no textures.

Time taken: 40 minutes (Shouldn't have taken more than 20, I've no idea how it took so long).
Software: Photoshop CS5.
Pentablet: Wacom Bamboo Small.