(9/27 and 9/28) Geology notes.
In and west of Zion, we saw part of the same cross-section of rock layers we saw at Capitol Reef, with the early Mesozoic Moenkopi formation at the bottom and the mid-Mesozoic Navajo sandstone near the top. The difference is that, at Capitol Reef, the relatively thin Navajo layer was the frosting on the cake. In Zion, the canyon walls rise very high above the valley floor and they are mostly Navajo sandstone--huge monoliths of it.
As we proceeded upriver in the canyon, we rose above the softer underlying layers so that at the end only the Navajo was left. No longer being undercut by erosion of softer sediments, the Navajo was now cut only by the Virgin River itself, and the canyon walls came very close together in a section called the Narrows. The only way to continue upriver would have been to wade in the river itself. We did not, but many others (mostly young people) did.
On 9/28, we decided we were ready to get away from the crowds for a while, so drove to a dry wash and a reservoir west of the park to look for birds. We saw only a few birds, but did recognize some of the same rock layers we had seen at Capitol Reef, and did enjoy having some of the desert to ourselves for a while.
