Under the Greenland ice sheet

Here are two classic images from a recent video of the landscape around the edge of the Greenland Ice Sheet near Thule, on the west coast.  They are superb illustrations of the amount of debris transported on the bed of the ice sheet.  In the top photo, the scale is difficult to estimate, but I reckon the basal dirty (ie debris-rich) layer is about 50m thick, packed with entrained boulders and till. 

In the bottom photo the very dirty basal layer is thinner, but above it there is a great thickness of layered ice with till concentrated on the contacts between layers.  This may be because we are looking at ablation surfaces with debris concentrations -- or that the layers are accretion ice layers originating on the glacier bed during the process of basal melting, thawing and sliding.