You are at the boundary between the unglaciated Beringian landscape and land that was covered either by a massive ice sheet, originating to the east, or small alpine glaciers that formed in the high valleys.
Several times over the last 2.5 million years glaciers have expanded and joined to form thick ice sheets over North America. Yukon was at the margin of these massive glaciations and all of them have left their mark here. Recent work on the Reid glaciations indicates that some areas of Yukon were glaciated 55,000 years ago while the Reid glaciations in the Mayo region occurred between 80,000 and 300,000 years ago.
Silver Trail Moraines
The high ridge of sand and gravel crossing the Silver Trail before you is a terminal moraine that marks the edge of the McConnell glaciation. The outermost edge of the pre-Reid glaciation limit lies about 70 km west of Stewart Crossing. Just north of Halfway Lakes, the Silver Trail is built on a lateral moraine that marks the south-eastern edge of the McConnell valley glacier that occupied the Haldane Creek valley.
The community near Keno Hill is positioned at the limit of the extensive Cordilleran ice sheet that glaciated this region. Alpine glaciers developed during the last ice age in the Gustavus Range east of Keno Hill and in places converged with the Cordilleran ice sheet. All that remains from these alpine glaciers are U-shaped valleys and thick gravel deposits.