Transcript Features of Glacial Deposition

Features of Glacial
Deposition
Firstly, what do glaciers have to
deposit?
As a glacier moves it tears off huge amounts of rocks and other
material from the valley surfaces. This material becomes
embedded within the glacier and is sorted into different layers
depending on the size of the material.
The material carried by the glacier is called moraine.
There are 4 different types of moraine;
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Lateral Moraine
Medial Moraine
Ground Moraine
Englacial Moraine
Lateral Moraine:
This is the material carried at the top of a glacier or ice sheet at its sides.
The material may have been derived from plucking of the valley sides or
from freeze thaw action on the valley sides.
When the ice melts, lateral moraine forms a ridge along the valley.
Medial Moraine
This is material transported on top of the ice sheet in the middle.
It is formed when 2 glaciers have joined together and their lateral moraine
merged.
If a glacier has many large tributaries joining it, many lines of medial
moraine form.
Ground Moraine
This is material carried along the base of the ice
The material has been plucked from underlying rock.
Most of the material is then abraded to become tiny particles called rock dust
When the glacier begins to melt it deposits the moraine.
Englacial Moraine
This is material carried inside the moving glacier
The material may be derived from surface moraine which has fallen into
or been washed into crevasses
diagram of glacier
Features of Glacial Deposition
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Teriminal Moraines
Recessional Moraines
Boulder Clay Plain
Drumlins
Erratics
Moraine-Dammed Lakes
Kettle Holes
Terminal Moraines:
• These are formed where ice melts and deposits all the moraine it was
transporting at the front of the glacier (snout).
• The ice sheet/glacier is still moving so material is constantly being
added to the terminal moraine
• The longer the ice continues to melt at the same place, the higher the
terminal moraine
• Its material will include lateral, medial and englacial moraines, ground
moraine and any loose rocks and soil bulldozed in front of it
• Therefore, terminal moraines are completely unsorted
• They may extend for many kilometers
• They mark the furthest point reached by the ice sheet or glacier
Terminal Moraine
Drumlins:
These are hummocky deposits of boulder clay
They are 100 – 800m long and 25 – 100m high and oval shaped
The side of the drumlin facing upvalley is steeper than the
downvalley side.
Hummocks may build up because ice pauses in its retreat or
because there is a slightly larger amount of moraine at that point
The hummocks then become streamlined by the moving glacier
flowing over it
They are usually found in groups or swarms
Kettle Holes
• These were formed by isolated blocks of ice melting more
slowly than the rest of the ice-sheet
• The melted ice leaves behind boulder clay
• When the block of ice finally melts, the meltwater is trapped
by the boulder clay surrounding it
• This leaves small, round kettle holes
Task 1:
Using the information that you have just heard and your notes,
answer the following question;
Select one feature of glacial deposition
and explain the processes involved in the
formation of this feature.
Annotated diagrams may be used.
3 marks