see: http://sanfrancisco.cbslocal.com/2015/07/07/colossal-rock-fall-changes-face-of-yosemites-half-dome/
FRESNO, Calif. (CBS/AP) — Officials at Yosemite National Park say a massive sheet of rock has fallen from the vertical face of Half Dome on the most popular route used by climbers.
Park geologist and climber Greg Stock said Tuesday that officials are now determining how the new route changes the climb.
Nobody was injured or witnessed the fall believed to have happened one night last week.
Stock says the relatively thin sheet of rock that peeled off measured roughly 100 by 200 feet.