Once upon a time, some 300 million years ago, southeastern Utah was covered by a sea. When the sea retreated 250 million years ago, it left behind thick salt beds. The wind picked up sand grains and carried them to the region, depositing them on top of the salt. By 200 million years ago, the area looked like the Sahara. Then the sand dunes hardened into rock. The weight of the rock liquified the underlying salt beds, which started moving along the ground (not unlike the way glaciers move) and the movement cracked the rock above. Water seeped into and further scored the fractured rock. The effect of water and ice freezing and thawing year after year widened the cracks, increasing the porosity and permeability of the sandstone, which permitted the entry of yet more water and, eventually, created the buttes, spikes, hoodoos, arches and other fantastical formations we see today. It also exposed some of the sand beds, sinuous fissures in the enormous landscape.
As the minerals in the Entrada (red) and Navajo (buff) sandstone met the atmosphere and oxidized, the iron turned red, the manganese turned black, and the clay minerals turned purple and green. The glorious results are on vivid display in Canyonlands and Arches National Parks. Visiting them is like visiting the moon and Mars, too. The grandeur and depth are hard to capture photographically, but I did what I could. (See below.)
You get a strong sense of the vastness of geologic time when you consider that water was and is the main sculpting agent in all this (as it is everywhere on earth), even though this region gets only 10 inches of rain annually. As the professor in our geology course reiterated, we don't have to worry about time in geology - we have all the time in the world.
After spending most of our day in Arches and Canyonlands, we decide to drive the La Sal Mountain Loop Road at sunset. This turns out to be a 50-mile paved loop that climbs up to 8,000 feet or so (with minimal terrifying switchbacks) from the Mars-like red sandstone of Moab up to verdant plains and tree-covered mountain peaks, then back down into the red and buff backside of Arches NP along the Colorado River. It's a drive of surpassing beauty, the calm green of the forested mountain slopes and the cascading water (murky with eroded red rock though it is) providing a restful optical counterpoint to the stark magnificence of the sandstone spectacle.
Utah is a state of extraordinary beauty. It looks, depending on where you are, like the Alps, the Sahara, the plains, the moon, another planet altogether. Although we fell in love with Montana, we recognize that Utah is the money state for scenic travel: five eye-popping National Parks, countless dense forests, craggy escarpments, lush high-altitude plains for grazing cattle, and damn good French fries just about everywhere you go.