A moraine is a ridge of till or unsorted glacial deposits left after a glacier receeds. We know that glaciers came down the canyons from the high Sierra Nevada because of these deposits. They are obvious when they are out in an open area, but a bit more difficult to identify in a canyon where rivers have eroded away much of the evidence. in this case it appears that a glacier came down Silver Creek Canyon and possibly the East Fork Carson as well. Where the confluence is of both the streams and the glaciers, this is where the moraine forms. One good piece of evidence for moraines is the varied type and sizes of rocks in the deposit.
Pretty easy access to this cache: At Centerville Flat Campground turn south onto Wolf Creek Rd., cross the creek and climb up to the top of the crest where there are a couple of campsites. From there it should be an easy find.