In the close up shot, they appear brittle. That's probably not the case though.
"A majority of Meadow Valley (which lies along U.S. Route 93 from the towns of Caliente to Panaca) was covered by a freshwater lake nearly 1 million years ago during the Pliocene Era. The richly colored canyons of Cathedral Gorge (called the Panaca Formation) are remnants of this ancient lakebed. Over centuries, the lake began to gradually drain. Erosion began working away at the exposed portions of sediment and gravel that once composed the lake bottom. Rainwater and melting snow carved rivulets in the soft siltstone and clay shale, splitting tiny cracks and fissures into larger and larger gullies and canyons."So it's siltstone (a new term to me) and clay shale. The surface of the stuff is a little powdery. It seems like it would crumble more than sandstone. Even though the shapes were cause by erosion, there are some areas that look like they were formed by sand dribbling.https://www.youtube.com/watch?v=mylmdIr1n6M
Sand dribbling must be like water torture for rocks. Thanks for the info.