“Whitney says that the bottom has fallen out of the rocks here (which I most devoutly disbelieve)” (Letter from John Muir to Jeanne Carr, April 5, 1870 )

Early geologists believed that the Yosemite Valley was created by a series of earthquakes that sank the valley floor. Muir examined the land and concluded that glaciers had been the main agent for the valley’s creation – a theory that went against the likes of state geologist Josiah Whitney.