Study Guides
GLS210 Geomorphology

Section A: Introduction

Section B: Glaciers

Section C: Tectonism

Section D: Tectonic Landforms and Volcanism

Section E: Weathering, Mass Wasting and Karst

Section F: Fluvial Systems

Section G:  Desert and Periglacial environments


Atlas of Landforms

GLS 210 Website

 

Section B: Glacial Processes and Landforms

Readings Bloom Recommended Internet sites
    1. NSICD All About Glaciers > Glacial Gallery
    2. Swisseduch.ch Glaciers online
    3. Lemke Illustrated Glossary of Alpine Glacial Landforms
    4. Geomorphology From Space Chapter 13: Glacial Landforms
    5. North American Glacial Varve Project

Classification of Glaciers

A. Based on morphology and relationship with topography

B. Based on thermal regime

C. Based on Activity (related to mass balance)



Zones of a Glacier

Glacier mass balance (glacial budget: accounting of input and ouput; accumulation and ablation)

How do glaciers flow?

  1. Creep (ductile/plastic deformation) occurs at depths > 60m
  2. Brittle deformation (typically occurs at depths < 60 m)
  3. Basal sliding (requires basal water)
  4. Regelation slip (subglacial meting and refreezing)
  5. Subglacial flow (deformable bed)
    Rate of creep
    • Glen's flow law (Flow rate = kT3): strain rate is proportional to the cube of shear stress and increased with rising Temp. K is a constant related to temperature and T is shear stress.
    • Shear stress (T) = pghsinƟ where p is the density of ice, g is gravity and  Ɵ is the slope of the ice surface

Internal flow variations

Internal stress - internal variation in flow and transport directions

  • Longitudinal (compressive and extensive)
  • Lateral (converging and diverging)
  • Extending flow causes ice to flow toward the bed compressive flow causes ice to flow towards the surface.



Glacial Erosion

Processes

Features created by erosion (bedrock)

Large-scale features of erosion

  • Troughs/U-shaped valleys  (alpine and continental) and related features
    • Fjords, trough lakes and paternoster lakes
    • hanging valleys
    • ice-faceted spurs
  • Cirques (alpine)
    • tarn
  • Aretes (alpine)
  • col (alpine)
  • Horn (alpine)
  • stoss and lee topography (alpine and continental)
  • Knock and lochan topography (continental)

Intermediate

  • roche moutonnee (asymmetrical)
  • whalebacks (symmetrical)
  • flybergs

Small scale features of erosion (good directional indicators)

  • striations(striae) and grooves
  • Craig and tail
  • chattermarks,crescent gouges, etc.

Characteristic glacial products

  • rock flour and erratics


Glacial Deposition

Settings: glacial, ice-contact, proglacial
(glacial fluvial, glacial lacustrine/marine, eolian)

Environments and Processes

1. Glacial - formed by the ice

  • Subglacial release (shearing and/or melting)
  • Ablation
  • dumping
  • pushing (glaciotectonic)
  • mass-wasting (? - closs enough)

2. Glacial fluvial - deposited by braided glacial meltwater

3. Glacial marine/lacustrine  - sediment carried by meltwater and deposited in a marine or lake environment

4. Eolian - windblown and deposited sediment (e.g. loess)

Glacial Depositional Landforms

Glacial  Deposits - deposited directly from glacial ice

Subglacial Deposits

  • Ground moraine: blanket of lodgment and ablation till
  • Drumlins :These are formed both by erosion and deposition
    • Composition: till and/or glaciofluvial sediments
    • Shaped like and inverted spoon; steep side faces up-ice

Marginal Moraines

  • Form: ridge parallel (lateral) or perpendiclar (end) to flow
  • Composition: till and or glaciofluvial sediments
  • process: dumping during a still stand, push during minor or major re-advance
  • Types:
    • End moraines: terminal and recessional
    • lateral (alpine) or interlobate (continental)

(See also the classification of moraines in Table 17-1 p. 384)

Meltwater Deposits and related featurs (sorted and washed)

Morphosequence

  • Series of contemporaneous sedimentary facies formed within, along, and beyond the margin of a glacier
  • Morphosequences in New England are used to map ice marginal positions where typical end moraines are lacking.

Concepts, processes and terminology


Questions

      1. How do you distinguish proglacial sediments from glacial or ice-contact sediments.
      2. Explain how glaciers flow and discuss the influencing factors.
      3. What positive feedback mechanisms contribute to the growth of continental ice sheets? The deterioration?
      4.  List and discuss the processes of subglacial weathering and erosion?
      5. Describe the various ways diamicton is deposited from a glacier.
      6. How does the concept of equifinality apply to drumlins?
      7. Compare and contrast the modification of landscape by continental and alpine glaciers.
      8. Explain why the relative load in an alpine glacier is far greater than a continental glacier.
      9. Describe how unglaciated regions were altered during the last ice age. Give two examples.
      10. Describe and explain the character of till.
      11. What factors influence the glacial erosion of a bedrock terrain.
      12. How are paleolake elevations determined and why are they tilted?
      13. If you were hired to find a high yield well field for a municipality where would you look?
      14. What effect did glaciation have on the landscape of the Northshore?
      15. Discuss the economic value of glacial deposits in NewEngland.
      16. Which components of the local landscape would you consider relict? Which would you not?
      17. Describe the Presumscott Fm and explain why its is found up to 130 m above present sea level in inland Maine.
      18. Explain why the large lobate moraines, which form the principle topography in the Midwest are largely     lacking in New England.
      19. Explain the effect of glaciation on drainage systems in the Midwest?
      20. Discuss the formation of the following lakes: Bonneville, Aggasiz, Hitchcock, Cape Cod.