Wonderful job so far! I really like the perspective, and your colour palette is absolutely gorgeous. That mountain range in particular looks amazing. I wish I could paint like that. *is jealous*

Something does seem a bit...not quite right with the canyon. To me, it looks kind of like a thin lip (like with a bowl) sticking up above the ground behind it, instead of a 90-degree angle where the top of the canyon wall should meet the ground. I think that might be because there's too much white/light colours along the edge of it? Maybe you could try using darker colours all along the edge, and gradually blend them back into the lighter colour of the terrain behind? I hope that makes sense... Heh.

Also, the left and right sides of the foreground look very close to the edge of the canyon. I think it might look better if we could see that deep drop (like how you've shown it right in the front) on both sides. Just a suggestion!