Glacial deposition creates distinctive landforms and contributes to glaciated landscapes

Glacial Deposition and Landforms

2.8 Glacial deposition
creates distinctive
landforms and
contributes to glaciated
landscapes
Specification link: c. The assemblage of landforms can be used to
reconstruct former ice extent and movement and for provenance
(erratics, moraines, crag and tail, drumlin orientation).

Reconstructing Past Glaciation Using Relict Glacial Landscapes

. Glacial landforms can be used to reconstruct the extent of ice cover in
the past, and the direction ice masses move in. For example, we can
determine ice extent by studying the distribution of ground moraine
and mapping the position of the terminal moraines.
. A number of erosional and depositional landforms can be mapped to
indicate the direction of ice movement, including striations, roche
moutonnees, crag and tail and drumlins. Furthermore, the elongation
ratio of drumlins can be calculated to indicate the rate of ice
movement.
https://timeforgeography.co.uk/videos-list/glaciation/evidence-
uk-glaciation-deglaciation/

Factors Making Landform Identification Difficult

• Landforms may be modified
• Several glaciations
• Post-glacial weathering and erosion
• Human activities

. Therefore several landforms must be studied for accurate
reconstruction. Till fabric analysis is a valuable fieldwork technique for
studying both the origin and the route of former glaciers using glacial
deposits.

Glacial Landform Indicators

A) Very useful for proving that ice
flowed from location to another
Erratic
D) Mark the forward edge of an
ice mass so can used to
reconstruct its outer limit, but
are vulnerable to subsequent
erosion
Terminal moraine
B) The long axes are aligned in the
direction of flow, so can be used to
show patterns of ice movement
Drumlin
E)Both landforms have an
upstream end, so are good
indicators of ice flow direction
Crag and tail/roche moutonnee
C) Most fluvio-glacial action happened
at the edge of ice masses so these can
indicate areas that were not ice-
covered or were at the ice margin
Fluvio-glacial
F)May indicate ice extent, but
only for warm based ice. These
deposits can be difficult to date
accurately
Till plain

Till Fabric Analysis

. As a glacier moves, it turns the larger till rock fragments (clasts) to
point in the direction of the ice movement. Therefore it is possible to
study the orientation of the clasts to understand the former ice
movement.

Till Fabric Analysis Rose Diagrams

Rose diagrams can be used to present data on clast orientation. The raw data in has been sorted into
15° intervals, as shown in the table.

Clast Orientation Frequency

Clast orientation (°)
frequency
0-15
0
16-30
0
31-45
0
46-60
0
61-75
11
76-90
18
91-105
12
106-120
16
121-135
6
136-150
3
151-175
0
175-180
0

Task: Complete a Rose Diagram Using Till Fabric Data

N
Wind Speed
(m/s)
15.50 (1.6%)
10.80 (6.1%)
W
3.6%
E
8.23 (27.6%)
4%
6%
5.14 (35.0%)
8%
10%
3.09 (22.6%)
12%
1.54 (0.0%)
Calm->
0.00 (3.6%)
S
Made with BREEZE MetView - www.breeze-software.com

Till Fabric Analysis Rose Diagrams (Continued)

Rose diagrams can be used to present data on clast orientation. The raw data in has been sorted into
15° intervals, as shown in the table.

Clast Orientation Frequency Data

Clast orientation (°)
frequency
0-15
0
16-30
0
0
31-45
46-60
0
61-75
11
76-90
18
91-105
12
106-120
16
121-135
6
136-150
3
151-175
0
175-180
0

Clast Orientation Intervals

0-15
16-30
20
31-45
46-60
15
-
61-75
10
76-90
5
91-105
106-120
121-135
136-150
151-175
176-180