It's a very typical mesa such as are all over the west. The rocky core is exposed by weathering, you can see where boulders have cracked off and fallen down the slopes. Eventually it will all be a pile of rocks. I used to hunt for arrowheads on the slopes when in high school in Denver. Can't remember if we climbed to the top--the indented area right of center looks promising, more broken rocks. Eventually the town of Castle Rock tried to discourage that sort of thing because of trash, graffiti, and fires. Before then I lived in New Mexico near a bigger mesa which was basically lava rock, but the erosion evolution was the same.