Sunday, April 20, 2014
Vernal Fall in Yosemite and a Sense of Scale (or, How to Feel Very Small)
We have a bunch of people apparently enjoying themselves on a flat slab of rock next to a fair sized river. But why the fence? Why aren't they letting people cool their feet in the river on this reasonably warm day?
594 feet (181 meters).
To the left of Nevada Falls is Liberty Cap, a glacially smoothed granitic dome. To the left of Liberty, the dark rounded form of Half Dome is seen from an unfamiliar angle. From this angle it is clear that if anything, it should be called Three-Quarters Dome, or even Four-Fifths Dome.
Half Dome was never covered by glacial ice, and was formed instead by exfoliation, the tendency of rocky monoliths to break off slabs of rock as the pressure is released as the rock is exposed at the surface. The slabs mostly remove corners and edges, giving the rock a rounded profile. The steep face of Half Dome was a prominent joint, a vertical crack that also forms from pressure release. The "missing" half was undercut by the glacier below in Tenaya Canyon and quarried away down the valley.
Feeling small yet?