Quaternary deposits and features Flashcards
(30 cards)
Where do most corries form? Why?
NE face of mountains
North face because it is colder, so there is more snow and less melting. The South face gets the most sun (it rises in East and sets in West so the whole face gets it too) so snow cannot be supported, there will be less of it and there will be more melting.
East side because the prevailing wind is from the South West, so the wind will blow the snow away from the West side of the mountain.
What are the characteristics of an unconsolidated deposit?
Sediments that are not stuck together
Also known as drift
What are the characteristics of a glacial deposit?
- angular
- poorly sorted
- structureless (no stratification)
- no alignment
What are the characteristics of a fluvioglacial deposit?
- sub rounded
- stratified
- right angles to the direction of flow
- more sorted
- imbrication
- indicates a paleocurrent
What are the characteristics of a periglacial deposit?
- dominated by freeze-thaw
- permafrost
What are the characteristics of an interglacial deposit?
- plants (peat)
- beach
In what order are the deposits from the ablation of a glacier arranged?
Till
Outwash
Head
Peat
What are the glacial depositional landforms?
DRUMLINS
MORAINES:
- lateral
- medial
- end
- terminal
What is the
a) shape
b) orientation
c) texture
d) location
of a lateral moraine?
a) long and thin
b) parallel to the glacier
c) poorly sorted
d) side
What is the
a) shape
b) orientation
c) texture
d) location
of a medial moraine?
a) long and thin
b) parallel to the glacier
c) poorly sorted, angular, no orientation, no stratification
d) middle
What is the
a) shape
b) orientation
c) texture
d) location
of end moraines?
a) long and thin
b) perpendicular to the glacier
c) poorly sorted, angular, no orientation, no stratification
d) end middle
What is the
a) shape
b) orientation
c) texture
d) location
of a drumlin?
a) egg shaped with a tapering end/tail
b) parallel to the glacier
c) angular, alignment, no stratification
d) middle
What is the difference between end moraine and terminal moraine?
End moraines are the series of moraines deposited as the glacier retreats and advances, whereas the terminal moraine is the last one
What are lacustrine deposits?
sedimentary deposits formed in lakes (glacial lakes)
How do lacustrine deposits form?
- glacial lakes are a temp. feature of the natural landscape, forming at the end of a glacial when ice sheets melt away then remain during the following climatic episode
- in time, they may become infilled with sediment from inflowing streams and rivers, and organic material (e.g. plants) grow along their margin
- deposits are often thinly flat-laminated, each lamination varying in grain size relating to the strength of water currents entering the lake
- strong currents = coarser sediment, weaker currents = finer sediment`
What are varves?
- glacial lake deposits
- thin layers of clay and silt of contrasting colour and texture which represent the deposit of a single year (summer and winter) in a lake
- the layers can be measured to determine the chronology of glacial sediments
SUMMER = meltwater, higher energy flowing into the lake
WINTER = glaciation. no meltwater. The clay in suspension settles out
What are fluvioglacial deposits?
Give the fluvioglacial deposits
Deposits relating to meltwater produced by a glacier
- eskers
- kames
- outwash plains
Where can meltwater from a glacier (then used in fluvioglacial deposits) come form?
- ablation (summer)
- subglacial pressure melting
- precipitation
- retreating glacier/deglaciation
How does an esker form?
What do they show?
- meltwater that flows at the base of an ice sheet carves itself a winding channel or ice cave in which to flow
- during summer lots of material is carried which is deposited as the flow slows
- sands and gravels are deposited on the floor of the cave so that after the ice has gone a ridge of sand and gravel winding over the outwash plain remains
They can show the general trend of meltwater and ice movement by their orientation
- you can also see stratification in them because they are built up seasonally
What are the other names for outwash plains?
What are outwash plains?
Sandur/proglacial plains
- area in front of the glacier made up of a mixture of sediments that have been washed out of the glacier
What are the types of deposits?
Glacial
Fluvioglacial
Lacustrine
What is a periglacial landscpe?
a very cold but not glaciated area around the edges of a glacial landscape characterised by intense cycles of freezing and thawing
What are the features of a periglacial landscape?
Permafrost
Ice wedge
Ice wedge cast
Solifluction
Head
What is permafrost?
- permanently frozen ground
- in the summer the temperatures may increase enough to allow melting of the top portion of the soil to take place
- the soil below remains permanently frozen - this frozen portion is the permafrost layer; it is impermeable
- the top layer of the soil, when it thaws in summer, becomes saturated and mobile - the active layer
