Got a couple of hours at this and hopefully made some progress. The first job was to alter the main mesa to take away the impression that it shared an edge with the one behind. Thanks to Bill Cramer for spotting that. I did some work on the relative values and changed some of the shadow work. There are one or two things to sort before it's finished, the main one being to take down a little the bluff on the right of the picture. After that a handful of small details should complete it.
Grand Canyon - Oil on canvas board 20" x 16"