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Glacial Landforms, Kames - Coggle Diagram
Glacial Landforms
Deposition
Moraines
Terminal- A ridgeline of unsorted till formed mark the position of maximum
advance of the ice so the glacier cannot go any further. Where the snout is with debris running across the valley.
Lateral- A ridgeline of unsorted till. Material that accumulates on the top of the glacier has been weathered from the exposed valley sides. As the glacier melts or retreats this material sinks through the ice to the ground and is deposited
Recessional- Glacier stands still and the material melts out of the glacier. Form during a temporary still-stand in retreat so not a terminal moraine as the glacier can still advance.
Kames- Mounds of sediment are deposited along the front of a slowly melting or stationary glacier/ice sheet. Rocks and sediments fall into crevasses into the glacier, the glacier moves and is deposited in the bed. This is sorted till as there is meltwater involved on top of the glacier. Gets sorted into layers due to the runoff
Kame Terrace- A deposited mound of sediment at the side of the valley. Pressure between the valley sides and glacier forms an ice-marginal channel river at the sides of a glacier. As water carrying sediment travels into the valley, it collects here. The Ice marginal channel is not flowing so it deposits the material When the glacier retreats leave sediment at the valley sides. Ice can also retreat and drop all the sediment. This is sorted as it has been formed by a river.
Esker- A long sinous ridgeline of till which contains stratified layers of sediment. This is due to a river flowing on the Supraglacial, englacial and subglacial layers of the glacier which as the glaciers snout retrats due to the increase in thermal energy it will deposit the sorted sediment in a linear mound parallel to the path of the original glacier
Varves- Found in the deposits of glacial lakes. Each varve consists of two distinct layers of sediment, a lower layer of light coloured sandy material and an upper layer of darker silt. Most melting of the glacier occurs in spring and early summer, so at these times the meltwater streams flow fastest and carry their greatest loads. Fine material is held in suspension in the lake whilst heavier material is deposited. As autumn and winter approach, the capacity and competence of the meltwater streams is reduced because there is less melting and less meltwater.
Proglacial lakes - A lake at the snout of the glacier and as it melts and retreats it is trapped by a terminal moraine forming a lake. Moraine cannot be breached or the water will escape but if there is a solid moraine an ice damned lake is formed.
Kettle lakes - Formed by blocks of ice that are separated from the main glacier by either the glacial ice retreating or by blocks calving off the glacier snout and falling forwards. The ice then gets surrounded and possibly buried by subsequent meltwater deposits and outwash. Eventually, when the temperature increases and the ice block melts it leaves a large depression in the ground that the ice occupied.
Sandhurs- Formed in front of a glacier and where material is deposited over a wide area, carried out from the glacier by meltwater. The finest sediments are carried further away from the glacier. Coarser materials are deposited nearer to the snout of the glacier as the meltwater drops these first as its energy declines
Erosion
Corries- Armchair shaped hollows found on mountainsides. Have an over deepened basin and often have a lip at the front. They are formed initially by nivation where repeated freeze-thaw occurs causing the fracturing of the rocks. As ice accumulates in the hollow it begins to rotate due to the overlying pressure, and abrasion and plucking deepen the hollow further allowing it to develop a steep back wall.
Aretes - Aretes are a narrow ridge of rock which separates two valleys. It is typically formed when two glaciers erode parallel U-shaped valleys. Arêtes can also form when two glacial cirques erode headwards towards one another
Pyramidal Peaks An angular, sharply pointed mountain peak which results from the cirque erosion due to multiple glaciers diverging from a central point.
U-Shaped Valley- The interlocking spurs in the narrow V-shaped river valley are cut-off by the ice, creating truncated spurs. After glaciation, a misfit stream/river can sometimes occupy the floor of the U-shaped valley.
Roche Moutonnees- A roche moutonnees is where advancing ice passes over a rock and there is pressure melting on the up valley side which is smoothed and polished via abrasion often causing striations. On the down valley the pressure is reduced refreezing the meltwater causing for plucking to occur
Striations- When a glacier moves across the underlying rock, the process of abrasion wears it away. Larger rock fragments leave deep scratch marks behind them. These scratch marks are straight parallel lines that reveal the direction of ice movement.
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