The cliffs at Cathedral Rocks are only 500 feet shorter than the 3,000 foot precipice of El Capitan on the north side of the valley. Both are composed of the relatively unjointed and therefore highly resistant El Capitan granite. The largest glaciers that moved through Yosemite Valley around one million years ago (the Sherwin stage) scoured out deep basins approaching 2,000 feet deep in the upper valley, but the ice river was constricted at the "gateway" between El Capitan and Cathedral Rocks, and the sediments below the valley floor there are only 300 feet thick.
The glaciers of the younger Tahoe and Tioga stages only reached the base of the two cliffs, and had nothing to do with the sculpting of the high cliffs. A series of terminal and recessional moraines are found on the valley floor beneath the steep walls of granite.Of course, it's hard to ignore El Capitan when you stand beneath it! Once again, a series of pictures provide a sense of scale of these immense cliffs. The picture above is a view of the entire cliff from near El Capitan Meadow. Zooming on the vertical cliffs near the summit, one can see a diagonal crack casting a shadow. Can you see a dot to the left of the crack?
*For the uninitiated, Carmen Sandiego was a popular computer franchise that involved the theft of unusual objects like the Eiffel Tower.