Upheaval Dome was a mystery for many years. The name comes from the original explanation: that the mysterious bowl-like structure surrounded by rings of disturbed and uptilted strata had once been a huge salt dome, which had collapsed. The National Park service still favors this explanation, but nearly all geologic texts favor a different interpretation.
Eugene Shoemaker was the person to come up with the real answer. He suspected that Upheaval was really the site of a huge, ancient meteor impact. Subsequent studies, by the Shoemakers and other geologists, increasingly support this explanation. For one thing, there's not much salt underneath the inside of the dome -- not enough to explain the salt-dome theory (though there is quite a bit of it in the local rocks, as we found when we hiked in). For another thing, minerals have been found inside shocked in ways consistent with other known meteor impacts, but with no other known event.
The impact explanation should come as no surprise to any lunar observer. One glance at Upheaval dome from the top and you'll immediately see familiar features, such as concentric rings, which look very much like their counterparts on the moon. Of course, the colors are very different -- the sheer, dark red walls of Wingate sandstone contrasting with the weird greens and greys of the sandy inner area, and with the chocolate-brown of the spires comprising the central ring.
The inside of Upheaval is a bit difficult to get to. On our first trip to Canyonlands, rain discouraged us from doing much hiking, but we vowed to come back and try again. The weather was hot for our second trip; we attempted to hike from the rim down into the crater, but we ran out of water and had to make our retreat. But it turns out that there's another way to get to the center: there's a dirt road (the "Horsethief Trail") which cuts off from the Island highway and then descends the Wingate walls via a series of narrow, torturous switchbacks, then follows the Green river for several miles (sometimes through deep sand) to Upheaval Bottom, from which one can take a trail about 4.5 miles in to the center of the crater. Just the thing for a couple of newlyweds with a 4Runner!
So we did it. The road was great fun, if a bit unnerving on the way down. The guidebooks said that a street car should have no trouble with the road, and that's true down from the highway down to the river, as long as you're not afraid of heights. Along the river to Upheaval Bottom, there are some sections of deep sand that I think most street cars would have trouble negotiating. Of course, one could leave the car and lengthen the hike; but we found it a fairly full day as it was, and didn't have time to do quite all the exploring in the crater's center as we might have liked. Still, we made it out with plenty of time to spare, and only a few minor blisters and other injuries. :-)
You may also be interested in Dave's photos and narrative.
Next: Bowtie Bend.
Next: Bowtie Bend.