Lithosphere - Glaciation Flashcards
Explain Abrasion
Abrasion is the sandpapering effect of rocks embedded in glacial ice being scraped along the valley bottom and sides. Abrasion makes a valley wider and flatter.
Explain Plucking
Plucking occurs when glacial ice freezes into cracks in a valley side and then rips out or ‘plucks’ pieces of the rock as the glacier moves. Plucking steepens, deepens and straightens a valley.
Explain Freeze-thaw weathering
Freeze-thaw weathering occurs in mountain areas when meltwater enters cracks in rocks and freezes and expands, shattering the rock. Over time the rocks split apart. Freeze-thaw weathering makes mountain sides and tops more jagged and creates loose rock which can add to the erosive power of glaciers if it moves down the mountainside and falls into/onto the glacial ice.
Explain the formation of a glacier.
Snow accumulates in a hollow, high up on a NORTH or NORTH EAST facing slope. The northerly direction means that the snow is in in the shade from the sun and is less likely to melt.
Over time the layers of snow become COMPRESSED and COMPACTED. The air is squeezed out and NEVE is formed.
Seasonal MELTING and FREEZING removes more air from the snow until ice is formed.
Explain how a glacier moves.
A glacier moves downhill under it’s own weight and the force of gravity.
Basal sliding causes the glacier to slide on top of melting ice.
Explain the formation of a U-shaped valley
A V-shaped river valley (with steep sides, a narrow bottom and interlocking spurs of harder rock) fills with glacial ice during the ice age.
Plucking (EXPLAIN WHAT THIS PROCESS IS) removes rock from the valley sides making them steeper and straighter.
Abrasion (EXPLAIN WHAT THIS PROCESS IS) erodes the valley bottom and sides making then flatter and wider.
Freeze-Thaw Weathering( EXPLAIN WHAT THIS PROCESS IS) erodes the mountain tops above the valley making them steep and jagged and the broken rock adds to the effect of abrasion.
When the ice melts the valley has been eroded into a U-Shape with straight, steep sides and wide flat valley bottom.
The interlocking spurs have been eroded into truncated spurs at the valley sides.
Tributary river valleys may be left as hanging valleys above the sides of the new U-shaped valley.
A small river called a misfit river may form in the valley base. It has not eroded the valley, hence its ‘misfit’ name.
A ribbon or finger loch (long and narrow) may fill the valley if it is dammed by a moraine or flooded by seawater due to post-glacial sea-level change.
Explain the formation of a Corrie.
A corrie is a steep sided, flat bottomed hollow found high on a north or north east facing mountainside.
EXPLAIN HOW SNOW TURNS TO ICE
EXPLAIN HOW A GLACIER MOVES
The back and sides of the hollow are steepened by PLUCKING (explain this process).
The base of the hollow is widened and flattened by ABRASION (explain this process).
The tops of the mountain is eroded and made steeper by FREEZE-THAW ACTION (explain this process).
When the ice melts the hollow is larger, has a steep backwall and a flat base.
A rock ‘LIP’ forms where the glacier has overdeepened the hollow and loses energy as it moves uphill out of the corrie.
As it loses energy the glacier DEPOSITS rock waste or moraine.
The lip may dam water that fills the hollow and this is known as a TARN or LOCHAN.
Explain the formation of a drumlin
A drumlin is a depositional feature glacial which may form when a glacier loses energy, The glacier deposits its load of rock waste known as moraine and then readvances over these deposits. Drumlins are made of unsorted rock waste or moraine.
There may be a rock ‘core’ of harder, more resistant rock beneath the drumlin which has caused the glacier to deposit moraine as it loses energy moving around and over this harder rock.
A drumlin is an oval shaped mound approx 400m long and 35m high. They are found in groups called ‘swarms’ and form a ‘basket of eggs’ scenery.
Drumlins have a Stoss end which has been blunted due to pushing by moving ice and a Lee slope which is the more gentle slope and becomes lower as you move away from the source of the ice. This means that the highest point will always be at the Stoss end of the drumlin, and the lowest point will be the end of the Lee slope. The lee slope points in the direction of ice movement.
Explain the formation of Terminal Moraine
A terminal moraine is made of unsorted rock waste and soil which has been eroded, transported and deposited by a glacier.
The terminal moraine is ‘bulldozed’ infront of the glacier snout. The terminal moraine marks the furthest point that the glacier reached in a valley and stretches right across the valley from side to side. Behind this there may be a series of END moraines which mark the points where the glacier stopped as it melted back up the valley.
After the ice age a new river system may form and will either break through the moraine to continue down the valley or may form a ribbon or finger loch which is dammed by the moraine.
Glaciated Landscape - Landuses
Name 4 landuses of an upland glaciated area
Forestry
Recreation and Leisure
Water storage/reservoirs
Hill sheep farming
Explain why the landscape is suitable for one landuse in upland glaciated area
You must link landscape features with the landuse you have chosen.
Weather, slope and thin soil may also be factors that you should include
