G - Fluvioglacial landforms Flashcards
What is an outwash plain?
A layer of gravel, sand, clay that forms in front of of where the snout of the melting glacier used to be
What is the material of an outwash plain like?
Sorted with the coarsest material found closest to the snout (as this is the first material to be dropped as the water looses energy)
The next deposits is sands and clays which are further away from the snout
What are kettle holes and how are they formed?
Blocks of ice that have broken off from the front of the glacier can get surrounded and partly buried by the fluvioglacial deposits - when the blocks of ice melt, they leave holes in the outwash plain called kettle holes
What are the landforms associated with an outwash plain?
Braided streams, varves and kettle holes
What are braided streams? (inc. how they form)
They form as the channel becomes chocked with sediment caused by marked seasonal variations in discharge of the river - as one area is blocks the channel splits into many streams
What are varves?
Distinct layers of silt and sand that represent one years deposition in lakes close to the snout of a glacier
Explain the seasonal differences in varves?
The coarser lighter layer is representative of the deposition associated with the summer melt
→This is due to high rates of ablation which produce powerful meltwater streams that are able to transport relativity coarse debris into lakes
The darker silt is representative of material deposited in winter because
→There is less turbulent lake conditions (ice sometimes covers the lake) which enable fine suspended sediments to settle onto the floor
What are Eskers?
Long, sinuous ridges composed of sorted coarse sands and gravels that run in the same direction as the glacier
How are eskers formed?
They’re deposited by meltwater streams flowing in tunnel underneath the glacier - when the glacier retreats and the stream dries up, the load remains as an Esker
Whats an example of an esker? (+sizing)
In Wolverhampton - 50km wide, 20m high, 20km long
What are Kames?
Undulating (‘wavy form/outline’) mounds of sand and gravel found on the valley floor
How are Kames formed?
Meltwater streams on top of glaciers collect in depression and deposit layer of debris - when the ice melts the debris is dumped onto the valley floor
What is a kame terrance?
Piles of deposits left against the valley wall by meltwater streams that run between the glacier and the valley sides
How can you tell its a Kame terrance and not lateral moraine?
KTs are sorted into layers - meltwater streams deposit their heaviest load first - so kame terrances have gravel at the bottom and sand at the top
What are pro glacial lakes?
They can form infront of glaciers - as meltwater streams flow into a proglacial lake, they slow down and deposit their sediment on the ice - there deposits are known as deltas
→ When the ice melts, these deltas are dumped on the valley floor, forming delta kames
