Yosemite Half Home Climbing Routes | Half Dome is a dome-shaped valley floor round . From Washburn Point , Half Dome looks like a thin stone ridge . On March 28, 2009 , here there was a huge rock slide with an area of 1,500,000 cubic feet ( 42,000 m3 ) occurs from Ahwiyah Point . The collapse damaged a large area under the dome . As a result of the avalanche was knocked down hundreds of trees and a portion of the mirror Lake trail buried .