 half dome is a granite dome in yosemite national park, located in northeastern mariposa county, california, at the eastern end of yosemite valley â possibly yosemite's most familiar rock formation. the granite crest rises more than  above the valley floor. ==geology== thumb|250px|left|half dome from washburn point, showing its profile the impression from the valley floor that this is a round dome which has lost its northwest half is an illusion. from washburn point, half dome which can be seen as a thin ridge of rock oriented northeast-southwest, with its southeast side almost as steep as its northwest side except for the very top. although the trend of this ridge, as well as that of tenaya canyon, is probably controlled by master joints, 80 percent of the northwest "half" of the original dome may well still be there. on march 28, 2009, a large rock slide of  occurred from ahwiyah point. the slide happened at 5:26 a.m and damaged a large area under the dome. no one was injured but hundreds of trees were knocked down and a portion of the mirror lake trail was buried. the slide registered on seismographs as an earthquake reaching 2.5 on the richter scale. ==in culture== left|100px half dome was originally called "tis-sa-ack," meaning cleft rock in the language of the local native americans. tis-sa-ack is also the name of the fourth route on the formation, ascended by royal robbins and don peterson over eight days in october 1969. 
Granite_domes Mountains_of_Mariposa_County,_California Mountains_of_Yosemite_National_Park Visitor_attractions_in_Mariposa_County,_California