A2 Glacial Deposition
Glacial Deposition
TODAY
LAST GLACIAL MAXIMUM
Further compaction squeezes all the air spaces out.
The firn changes to a blue-green glacial ice.
Once it reaches a thickness of 30 - 40 metres, the ice
cannot support its own weight and yields to plastic
flow.
It now moves downslope under its own weight.
Fluvio-glacial environment
WATER - SORTED
Terminal
ICE
UNSORTED
Glaciers:
ERODE
TRANSPORT
DEPOSIT
Processes of Transportation:
1. Supra-glacially- on the glacier surface
2. Englacially - inside the glacier
3. Subglacially - at the base of the glacier
Why does Deposition Occur?
Ice Melting - due to:
1. Pressure Generated Heat
2. Geothermal Heat
3. Daytime Warming - Insolation
4. Warmer temperatures at lower altitudes
5. Prolonged insolation in Polar summers
Processes of Deposition
Landforms
1. Melt-Out (TILL)
Moraines
Till Plains
Erratics
2a. Fluvioglacial
(CONSOLIDATED)
2b. Ice Contact
Sandurs
Varves
Drumlins
Eskers
Kames
Landforms
1. Melt-Out (TILL)
Moraines
Till Plains
Erratics
Medial Moraine
Medial Moraine
Lateral Moraine
Supraglacial Moraine
Supraglacial Moraine
Recessional Moraine
Till - unconsolidated - eg Cromer
Erratic - eg Norwegian erratics found in East Anglia
Landforms
2 Fluvioglacial (CONSOLIDATED)
Sandurs
Varves
Outwash plains / Sandurs.
•Kames and kettle lakes may be part of this environment.
As the ice melts, a hole, or kettle, forms in the debris. This is
similar to burying an ice cube in fine sand; when the ice cube
melts, a pit develops.
Views from Storadimon
A small delta
VARVES
Thick Varves =
•Warm Temperatures
•Lots of melting - Ablation
•Increased Deposition
Landforms
1b. Ice Contact
Eskers
Kames
Drumlins
Sediment deposited
Esker - a sinuous ridge of sands and gravels
Valley
Side
Valley
Side
ICE
NB supraglacial channels flow to side of glacier (as glacier is slightly
higher in the middle. The lateral stream channels are trapped by the
valley sides. They carry sediment - hence SORTED deposits - and are
different to lateral moraines - which are UNSORTED.
Once the ice has melted away (I.e in an interglacial period)
a terrace is left perched up on the valley wall - SORTED
deposits
Drumlins
The situation is further complicated by
subsequent re-working of the sediments for example by climatic cooling and a
subsequent ice re-advance.This can make
it difficult to establish what a drumlin
actually is as the evidence can been
bulldozed by ice
•Example Bangor, North Wales
Rock Flour
As rock flour enters this lake in Alberta, Canada, it turns the
water milky.
An iceberg containing glacial debris.
What are these landforms of glacial
deposition?
A2 REVISION
GLACIAL
DEPOSITION