Ice On The Land

Front 1

Ribbon Lake Formation

Back 1

A glacier moves over alternate bands of soft and hard bedrock. Sharp-edged boulders picked up by the glacier (moraine) erode the softer the softer rock more through abrasion, forming a hollow called a rock basin. This also leads to scratches on the valley floor called striations. On either sides of the rock basin, the more resistant rock is eroded less, leading to outcrops of harder rock known as rock bars- these act as dams which rainwater may accumulate in after an ice age. This fills up the basin forming a ribbon lake.

Front 2

Corrie Formation

Back 2

Corries form where neves accumulate in shallow hollows on high mountainsides. As the snow accumulates, the lower layers are compressed by the weight of the snow above- forms a small glacier as all of the air is squeezed out of the snow thus turning it to ice. Over time, the glacier gets bigger and moves down the slope. Some ice is trapped and follows a circular motion called a rotational slip, continuing to gouge out a deep bowl-shaped hollow. Freeze-thaw and plucking makes the back wall steeper, however there is a reduced rate of erosion at the front of the corrie due to thinner ice- leads to a raised lip. As the glacier retreats, moraine may be deposited here, so when the ice melts water may be trapped behind the lip forming a tarn.

Front 3

Truncated Spur Formation

Back 3

A river carves a V-shaped valley, however often meanders meaning that there will be outcrops of land known as interlocking spurs. During an ice age, snows fills the valley and is compacted to form a firn, which then turns to glacial ice. Gravity and the glaciers watery layer cause the glacier to move forwards. The bits of land that stick out are ground down through abrasion and plucking. The power of the ice chops of the ends of the spurs making them truncated.

Front 4

Glacial Trough Formation

Back 4

Glacial troughs are created when a glacier erodes a river valley, making the shape transform from a V to a U. As the glacier advances, it erodes the rock through abrasion and plucking, as leaving striations along the valley floor. This erosion makes the valley wider, steeper and deeper (altering the shape.) Glacial throughs usually have smaller valley hanging next to them- hanging valleys. These tributary valleys are left hanging high above because, during the ice age, their glaciers were smaller and of a much lesser mass. This means that these valleys weren't eroded as much due to their glaciers lesser strength. When the ice melts and water returns, these hanging valleys often end in waterfalls.

Front 5

Abrasion

Back 5

Occurs when bits of rock and stone become embedded in the base and sides of the glacier. These then rub against the bedrock (bottom of the glacier) and the rock faces (sides of the glacier) as the glacier advances. This causes the wearing away of the landscape as the glacier behaves like sandpaper. It leaves behind smooth, polished surfaces which may have scratches in them called striations.

Front 6

Plucking

Back 6

Occurs when rocks and stones become frozen to the base or sides of the glacier and are plucked from the ground or rock face of the glacier moves. It leaves behind a jagged landscape.

Front 7

Bulldozing

Back 7

When loose material is pushed in front of the glacier.

Front 8

Freeze-Thaw Weathering

Back 8

Water (from the glacier) gets into the cracks of rocks. It then freezes and expands, putting pressure on the rock, causing bits of rock to fall off.

Front 9

Drumlin Formation

Back 9

Form where the ice is pushing forwards across low land areas, but is overloaded with moraine and melting. A small obstacle, such as a rock outcrop, is enough to encourage deposition. Most deposition occurs around the upstream end of the obstacle, forming the drumlins blunt end. The rest of the boulder clay deposited is then moulded into shape around the obstacle by moving the ice to form a tapered end, down stream.