June Lake's looped valley, often described as a horseshoe-shaped canyon, was formed by glacial action. The Rush Creek glacier split in two when it encountered the resistant rock of what is now known as Reversed Peak. The main glacier flowed toward the north creating the Rush Creek Canyon. Another glacial branch turned south and east, but its flow was impeded and eventually stopped as the granitic bedrock on this southern branch created an uphill path toward the volcanic area of the Mono Craters. When the glacier receded it left behind terminal moraine material in the area now known as Oh! Ridge.
Ian
That slope looks steep!