Unit 4b Flashcards
(22 cards)
How long ago was the Devensian glaciation?
120,000 - 10,000 ybp
What was the are covered by Irish sea ice?
Upland areas in the UK, such as the Scottish highlands, Lak District and Snowdonia converged in the lowlands, creating this moving body of ice
During the Devensian period how much lower were the sea levels than present day?
100m lower, created a low lying valley where the Irish Sea is found today
In which direction did the glaciers that originated in northern Snowdonia travel in?
travelled northwards and westwards out of the mountains
When the Snowdonia glaciers made their way out towards what is now the Irish sea, what happened?
They deposited large amounts of glacial tills (also known as boulder clay) across the landscape
Which area did the Snowdonia glacier erode?
Isle of Anglesey
What is an example of an area where glacial lodgement till (boulder clay) found in the UK?
Aberogwen
What are the soil characteristics of Aberogwen?
deposited subglacially, its unsorted deposit with large rocks and small clay particles (rock flour) mixed together
The till in this location has been brought from two different directions
What are the two types of till, and where where they brought from in Aberogwen?
Irish Sea till - predominately red sandstone and limestone matrix
Welsh till from the Ogwen Valley and Idwal area, with dark grey matrix from slate and igneous rock
What proglacial landform are varves usually found in?
Pro glacial lakes
What is an esker and how is it formed?
an esker is a subglacial stream deposit, formed by a stream beneath the glacier
- channel is under hydrostatic pressure and is confined within a tunnel of ice
- deposits are left on the floor, due to seasonal fluctuations in temp
What is the example of an Esker in UK highlands?
The Pentir Esker
What is the morphology of the Pentir Esker?
eskers are in linear shape: long and thin and sinuous (they meander like streams because they were formed by subglacial streams)
What is the size and shape of the Pentir esker?
is around 400m in length and 5-10m height
What is the composition of the Pentir esker?
course sands, gravels and large pebbles
What is an example of a Kame in the U.K?
The Pentir Kame
How does a kame form? (brief explanation)
a kame is formed where moraines and other glacial deposits have been moved short distances by meltwater streams into a supraglacial lake, or if material has fallen into a crevasse
(less regular shape than drumlin and esker)
Where in the U.K where several Kettle holes formed?
around the area of Pentir and Caernarfon
What are the properties of a Kettle Hole near the Kame at Pentir?
its low hollow, around 75m in diameter, filled with hydrophytic (water loving) plants such as he yellow iris and willow tree
What is an example of a drumlin in the UK?
throughout the Conwy Valley drumlins were deposited under glacial ice flowing down from the mountains of North Wales
- up to 50m in height and 500m in length
- created when subglacial lodgement till was deposited into streamlined deposits
What is an example of a solifluction deposit in the UK?
Eglysbach
How does solifluction deposit occur?
(the material is all local in origin having moved down the hill when the top of the ground thawed in summer in periglacial environment.)
- top layer thawed, became saturated in water, could not move down through the permafrost
- saturated material mould slide slowly downhill
- as it slowly moved downhill the material would re-orientate itself in line with the flow direction
- material = angular and immature
