 Starting 10 million years ago , vertical movement along the Sierra fault started to uplift the Sierra Nevada . Subsequent tilting of the Sierra block and the resulting accelerated uplift of the Sierra Nevada increased the gradient of western @-@ flowing streams . The streams consequently ran faster and thus cut their valleys more quickly . Additional uplift occurred when major faults developed to the east , especially the creation of Owens Valley from Basin and Range @-@ associated extensional forces . Uplift of the Sierra accelerated again about two million years ago during the Pleistocene . 
