Depositional Features Flashcards
Esker
Meandering ridges of layered sand and gravel.They are made up of meltwater sands and gravel streams in or underneath a glacier. These are sorted by size with large stones at the base because larger stones are dropped first by flowing water. The stones also tend to be more rounded than glacial deposits, because of the action of flowing water rounding the edges by erosion. As the glacier melts, sub - glacial streams flow through tunnels and the load is deposited on the channel bed.
Drumlin
Elongated, oval shaped hills made up of unsorted glacial deposits, comprising till, boulder or clay. These are formed as the glacier becomes overloaded with sediment and deposits it, streamlining the sediment as it flows over it. The steep ‘stoss’ slope faces up-valley and the more gently-sloping ‘lee’ slope faces down-valley. These are found in groups or swarms, with the tapered end of each hill pointing in the direction of glacier flow – these swarms are sometimes likened to a ‘basket of eggs.’ These occur widely within the moulded and streamlined scenery of the central lowlands of Scotland. Although they come in a variety of shapes, the glacier side is always high and steep, while the lee side is smooth and tapers gently in the direction of ice movement.
Terminal Moraine
A ridge across the valley and made up of glacial deposits/till/boulder clay; which is unsorted. As the glacier moves downhill it acts like a bulldozer, pushing sediment in front of its snout as it goes. On reaching lower altitudes and when temperatures rise, the glacier melts, losing power and depositing the moraine. Glaciers carry moraine at the sides of the glacier, called lateral moraine, in the middle of the glacier called medial moraine, and at the base of the ice called ground moraine. This marks the furthest point that the glacier reaches (where it terminates). The longer the ice continues to melt at the same place, the higher the terminal moraine. Once the ice has retreated, the terminal (or end) moraine can often form a natural dam, creating a ribbon lake.
