Geologic Trip, Mono Lakes Area
This large perched boulder near the June Lake Fire Station is a glacial erratic that was left here when the Reversed Creek glacier melted. The boulder sits on a small roche moutonnée that is being broken apart by jointing. The basin for June Lake was carved out by the Reversed Creek glacier. When the glacier melted, the debris that was being carried by the glacier was deposited as moraines and till in and along the glacial valley. This till covers much of the area on the east side of Reversed Peak between June Lake and Grant Lake and as far east as Highway 395.
Reversed Creek is unique. It is the only creek along the entire eastern Sierra that flows west toward the mountain front rather than away from the mountains. The reversed drainage was formed when the Reversed Creek glacier encountered hard rock in the valley floor after it left the base of the Sierra escarpment. The glacier rode up and over these hard rocks as it continued northeast toward Mono Lake. The direction of movement of a glacier depends on the slope of ice surface, not on the slope of the valley floor. As a glacier flows down a canyon, the bottom of the glacier can scoop out low spots and benches. Thus, the ice at the bottom of the glacier can travel upslope for some distance.