As a glacier melts, all of the debris it collected has to end up somewhere, right? Well this formation is called a kame, it is a large concentration of heavier sands and gravel. Just picture in your mind raging streams full of sediments, still flowing under the cover of hollowed out ice. Every so often the flow will reach a point where the heavier sediments can no longer be carried along, and in this case the heavier sediments have fallen into a pot-hole. As in the case of Maple Ridge, this kame is surrounded by much softer sediments which were compressed when the level of the lake rose. Consequently it has taken on the look of a mound today because of its higher resistance to compaction.