The debris insulated the surface, so for the first couple years after the landslide the debris got taller as the ice melted away around it. Over the years the center of the landslide sinks and the whole area spreads out as the density of the rock is about three times that of the glacier ice. You can see this in the crevasse pattern, whith crevasses near the toe pinching out and crevasses along the sides cutting across the landslide.