I recently moved from New York to Los Angeles. I drove the entire way. It took me three days and three thousand cups of coffee. Anyway most of the trip is a complete boring blur of corn, desert and gospel on every single radio station. What stood out the most, which I would never have guessed, was Utah. I never have seen a more beautiful landscape. The colors and shapes seem unreal. I never knew the land that Wiley Coyote lived in was real. Or was it? Was if just a caffeine hallucination? If not then how was this landscape made?
I won’t embarass myself by trying to put anything about geological history into my own words, but here’s an article on the formation of Zion National Park. If you’re super-duper interested the Ken Burns National Parks special had segments on Utah parks as well. (And ye of little faith: do you really think they’d put something in a Wile E. Coyote cartoon that wasn’t true?)
The (so-called) short answer is that the Colorado Plateau, which is the whole area of high country around the four corners area, has for some reason been very stable and responded to tectonic stresses as a single unit. Part of the story is that because of this the rocks on the plateau didn’t get deformed and broken up (much) during the various events that formed the Rockies and so there are really thick sections of rock that accumulated (there was a shallow inland sea during the various mountain building events) and remained cohesive and roughly horizontal.
Later on (and into the present), the whole southwest underwent uplift and extension. In inland California and Nevada this has been accommodated by the land breaking apart and forming the “basin and range”, which consists of a series of wide valleys separated by high mountain ranges. In the Colorado Plateau, though, everything stayed together and so the whole region has been uplifting as a single unit (and the extension is accommodated by the opening of the Rio Grande Rift in central New Mexico).
Streams erode down to their “baseline” elevation, which is the elevation of the still body of water they flow into. Since the land on the Colorado Plateau has risen to fairly high elevation and there aren’t the convenient basins for lakes to form in like there are in Nevada, in most places the nearest still body of water (historically, not counting reservoirs) is the ocean. Because of the huge difference in land elevation and baseline elevation, the streams have enormous erosive potential (even though many of the “streams” in the area don’t flow most of the time, they have very powerful flash flood events).
So you have streams with high erosive power cutting through thick fairly resilient cliff-forming rocks, with the result of deep canyons and high mesas (which are remnants from when the rest of the landscape has been eroded away). There’s certainly other things going on on the local scale, in terms of small scale folding, salt domes, more resistant rock units, etc, but that’s sort of the big picture.
The colors are the result of iron-rich minerals that are oxidizing. I’m not really sure why exactly those rocks are so iron-rich though, but a lot of rocks from that general time period are. Maybe someone else can give a better answer for that.
It’s too bad you didn’t stop to explore some of the amazing National Parks in southern Utah, especially Bryce and Arches . . . but you may have driven the section of Route 12 connecting Capitol Reef and Bryce.
There’s a saying that pretty well summarizes the force of erosion:
“Every drop of water and every grain of sand seeks the ocean.”