The National Park Service is reporting a very large rockfall at Ahwiyah Point near Half Dome on Saturday morning has knocked down trees and forced the closure of the Mirror Lake Loop trail.
NPS: The rock fall originated near the summit of Ahwiyah Point and fell roughly 1800 feet to the floor of Tenaya Canyon, striking ledges along the way. Debris extended well out into Tenaya Canyon, knocking down hundreds of trees and burying the southern portion of the Mirror Lake loop trail.
Reminiscent of the 1996 Happy Isles rock fall, there appears to have been a small airblast associated with impact on the valley floor. Fortunately, due to the event occurring in the early morning, there were no injuries.
The impact generated ground shaking that was recorded by numerous seismometers across California, registering as the equivalent of a local magnitude 2.5 earthquake.
The volume of the Ahwiyah Point rock fall is still being determined, but it was clearly one of the largest rock falls in the past decade; for perspective this rock fall was many times the size of the recent October 2008 rock falls behind Curry Village. Numerous smaller rock falls have occurred from Ahwiyah Point since the initial failure, and the southern portion of the Mirror Lake loop trail remains closed until further notice.