Fluvio-glacial landforms





Fluvio-glacial Landforms

Characteristics and formation of landforms resulting from the melt-water in glacial environments.

Landforms:


•Meltwater channels
•Eskers
•Kames
•Outwash plains

What you need to know:


•Recognise features
•Explain how formed
•Interpret data associated with deposits forming features

Meltwater 

Plays an important role in glacial processes and the formation of glacial features (previous learning)…

•Meltwater helps to enlarge Nivation Hollows* that will eventually form corries.
•Meltwater lubricates the bottom of glaciers and promotes movement (Glacial Surges).
•Meltwater transports moraine beneath the ice helping to “arm” the glacier and promote erosion.
•Re-freezing meltwater attaches glacier base to rocks below allowing plucking to take place.
•Meltwater rivers form on glaciers and beneath them.

•Flowing meltwater erodes channels in front of and below glaciers.
*Nivation Hollows – Patches of snow considered to be the progenitor of corries.

Nivation is the localized form of erosion associated with isolated patches of snow that remain through the summer season. 
It involves three separate processes:

1. Frost shattering - as temperatures (especially at the margins of the snow patch fluctuate above and below zero degrees Celsius.


2. Meltwater erosion – water flowing below the snow patch may remove soil and rock fragments. Meltwater may be derived from the snow patch it-self.

3. Slumping – insulation of the surface below the snow patch, saturation from meltwater and the effect of gradient may lead to the downslope slump of material.







Meltwater Channels

  • Post glaciation, these are identifiable as steep-sided, dry channels carved into the landscape.

  • Distinct from the meltwater rivers discussed earlier, these are often the result of overspills from lakes built up by water trapped by and between glaciers and highland.

Example: Newtondale Overspill channel, N Yorkshire.

70 – 10,000 YBP, water was trapped between the North York Moors and the vast ice sheets to the north, east and west forming a series of lakes.

Newtondal channel resulted from the overspill from Lake Wheedale south into Lake Pickering.

When the ice retreated, the lakes emptied and the overspill channel was left as a distinctive gorge some 80 metres deep and about 5km in length. 

1. Study the image left and then print a copy of it.

 2. Shade the areas of ICE in pencil (light grey/graphite)

















View of Newtondale today












Kames and Eskers – Depositional features that form in contact with the ice of a glacier
Eskers.
Long ridges comprised of sand and gravel up to 30m high. Often dissected by post-glacial processes into discontinuous lines of hills. Their line tends to meander suggesting their fluvial origin.
Likely to have formed as glaciation ending… lots of meltwater and a lack of glacial movement would allow them to persist.


Kames.
Also comprised of sand and gravels. Relatively minor features.
Three types:
•Kame Terrace – formed from deposits marking an in-filled, marginal glacial lake
•Kame Delta – Formed from stream deposits as englacial or sub-glacial streams          flowed into a marginal lake. Distinguished by delta-like deposits.
•Crevasse Kame – Deposits in glacial crevasses are dropped on valley floors as ice melts as ice age ends. Form small hummocks, but lack the sediment organisation displayed in Kame deltas.



To distinguish… Eskers and Kames, lack the Till composition of surroundings (clay rich!). Their sands and gravels tend to cause different type of vegetation to flourish on them.



Outwash Plains

At the front of a glacier, extensive, gently sloping areas of sand and gravels are deposited by meltwater streams and rivers (Outwash Plains)

During glaciation, meltwater flow and deposition is often very seasonal (ie in summer only). At the end of glaciation though, huge quantities of sediments will be spread across the outwash plain by the vast torrents of water from melting of the glacier.

Due to sediment load and the seasonal flows, braided river systems develop across these plains.



Activities: 
A. Copy the illustration above to a G-Drive document (Share to edit) and then add the labels to identify the following...
  1. Outwash plain
  2. Braided channels
  3. End moraine
  4. Medial moraine
  5. Lateral moraine
B. Explain the difference between Eskers and Kames.

C. Answer the two following Examination Practice Questions (Copy and Print the images and answer on G-Drive document):



D. Visit the following website... read and, particularly, study the illustrations - HERE

Msytery Feature:
Look at the photo below... notice the ridges running across the slope... what are they?





Below are the same slopes from a distance... maybe this will help 




Need some more help? Click HERE
















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