Supra and Englacial Processes II: the glacier terminus

1
Supra- and Englacial Processes IIthe glacier
terminus
2
Sources of Glacial Debris

• Supraglacial
• Rockfall
• Englacial
• Crevasse fill
• Thrusting
• Subglacial
• Plucking

3
Rockfall

• Penny Ice Cap (Canada) outlet glacier
• Rock walls
• Marginaldebris
• Lateral/medial moraines

4
Trimlines

• Big Timber Creek
• Moraines

and Trimline
5
2002 M7.9 Denali

• Black Rapids Glacier panorama
• Rock avalanches Effects?

By USGS from AK DNR - http//wwwdggs.dnr.state.ak
.us/earthquake.html
6
Debris in/on Ice

• Tulsequah Glacier (BC)
• Surface area
• Debris introduction to ice.

7
Glacial Transport

• Mooneshine Gl. (Canada)
• Estimate shear strength?
• Rock wall source - angular
• Note fines in foreground and meltwater

8
Medial Moraines

• Mooneshine Glacier (Canada)
• Ridge 3 m tall how much is debris?

9
Multiple Medial Moraines

• Muldrow Glacier (Alaska Range)

10
Medial Moraine Evolution

• Penny Ice Cap
• Outlet glacier
• Concentration of debris
• Supraglacial drainage
• Debris-covered terminus

11
The Glacier Terminus

• Black Rapids Glacier
• Active ice
• Stagnant ice
• (surges)
• Local reworking

12
Ablation Zone

• Chugach Mountains
• Debris accumulation
• Surplus of water and debris
• Dynamics of flow of ice and debris
• Evolution of local topography

13
Sources of Terminal Debris
14
Ice-cored Moraines

• Melt-out of ice over time
• f(climate)
• Last for decades to centuries (?)

15
Melt-out Tills

• Surface melt
• supraglacial
• Character of till?
• Basal melt
• subglacial
• Character of till?

16
Flowtills

• Redistribution of supraglacial debris
• Character?

17
Character of Glacial Debris

• Pangnirtung Pass (Canada)
• Note figure (63 Pete Birkeland) for scale
• No real limit to debris caliber

18
Till we meet again