P1 - Glaciation Flashcards
Name 4 pro glacial landforms
- pro-glacial lakes
- kettleholes
- sandurs (outwash plains)
- Meltwater channels
Describe how a pro-glacial lake is formed
- Formed along the front of glaciers and ice sheets where melt water from the glacier becomes impounded with a deposition blocked by glacier ice and bounded by high grounds
Describe how kettles are formed
During ice retreat, blocks of dead ice become detached. Sediment builds up around the dead ice and when they eventually melt, a small hollow is formed in which water accumulates to form a lake
Describe how a sandur (outwash plain) is formed
What is it?
- a flat expanse of sediment deposited in form of a glacier
How does it form?
-as the melt water streams gradually lose energy due to entering lowland areas, they deposit their material. The largest material is deposited nearest the snout and the finest further a way.
Describe how a melt water channel is formed
Melt water on the surface of the glacier melts its way through the glacier to the base through a ‘moulin’. Once the melt water comes out from the base of the glacier it forms a channel in front of to the glacier
Name three fluvioglacial landforms
Esker, Kame, Kame terrace
Describe how an esker is formed
Subglacial streams carry large amounts of rock debris due to their hydrostatic pressure inside the tunnels. The stream often meanders beneath the glacier, when the glacier retreats, the debris load is deposited at a consistent rate and forms a ridge.
Describe what an esker is
A long, narrow, sinuous (widening and meandering) ridge of sand and gravel
Describe how a Kame is formed
A meltwater stream emerges into an outwash plain or peri glacial lake at the glacier snout, their velocity falls and energy is lost causing sediment to be deposited.
Describe what a Kame is
An undulating mound of sand and gravel deposited on the valley floor
Describe how a Kame terrace is formed
During the summer, the valley sides radiate heat. This melts the edge of glacier forming a meltwater stream. This deposits sediment. When the glacier retreats, the sediment will fall to the valley floor, forming a Kame terrace.
Describe what a Kame terrace is
A flat, linear deposit of sand and gravel along the valley sides
Name 3 peri glacial landforms
Pingo (open and closed), patterned ground, ice wedges
Describe how a closed system pingo is formed
The lake insulates the talik preventing it running to permafrost. Water begins to drain from the lake reducing the amount of talik. Pressure from the advancing permafrost allows land (talik) to settle above.
Hydrostatic pressure causes the water to turn to ice. Hydrostatic pressure also pushes the land above causing the land to be disformed.
What is talik
Unfrozen ground in a periglacial area that surrounds the permafrost
Describe how ice wedges are formed
A thin piece of ice (around 3-4 metres in length) causes a crack in the rock. In the winter, ice freezes and expands. When the temperature rises, the ice melts. More water fills the crack and permafrost freezes it. This process repeats itself until a polygon of ice goes deep into the ground.
Describe what an ice wedge is
It is a wedge of ice extending 3-4 metres underground, usually in a polygon shape
Describe how patterned ground is formed
Ice wedges form underneath granite. As the ice wedges continue to expand (by 10%) the land above buckles and creates a trough with small mounds. Ice wedges melt causing land to fall in its place. This leaves new mounds in between where the ice wedges used to be.
Describe how an open system pingo is formed
Groundwater moves through the ground and eventually finds a weakness in the permafrost. Hydraulic pressure causes the water to rise up through the cracks. As the water gets closer to the surface, the temperature decreases turning into ice. Hydrostatic and hydraulic pressure causes the ice to continue moving upwards. This creates an open system pingo
Name 5 macro erosion landforms
U-shaped valley, hanging valley, ribbon lake, pyramidal peak, corrie/cirque
Describe how a ribbon lake is formed
Meltwater at the glacier base plays a role, and where PMP is exceeded, the glacier can basically slide encouraging even more erosion.
Differential erosion= some parts of the valley floor are over dependant creating ribbon lakes.
Describe how a corrie is formed
Snow accumulates in a hollow. Snow compacts making a neve/firn and glacial ice. Ice becomes too big for the hollow and moves down the slope. It will move in a rotational slip. The hollow deepens through invasion, abrasion and plucking. Freeze thaw shatters rocks above the hollow and delivers shattered rock (scree) to the ice - abrasion. Pressure melting point is often surpassed allowing melting to exist which allows basal slippage. This creates a steep back wall and a hollow known as a corrie.
Describe how a pyramidal peak is formed
If three or more corries development on all sides of a mountain a pyramidal peak is formed. The feature has steep sides and several arêtes radiating from the central peak.
Name an example of a pyramidal peak
The Matterhorn, Alps