1

Chapter 17

Alpine & Continental GlaciersGlacial Mass BalanceGlacial Ice Formation

Glacial Movement & ErosionErosional and Depositional Landforms

The Pleistocene EpochGeomorphology of SW Manitoba

1

What is a Glacier?Mass of snow and ice:

existing throughout the yearevidence of movement

Grows:

Shrinks:

Moves:

2

Types of GlaciersTwo basic types:Alpine and Continental

Differ in terms of:1.

2.

3.

4.

3

2

Rivers and Sheets of Ice

4ALPINE CONTINENTAL

Glacial Ice in Canada

5

Alpine Glaciers

• Located in mountainous regions

• Form at elevation above the snowline

• Movement is:_______________

6

3

Columbia Icefield,

B.C.-Alberta

Valley Glaciers

7

Cirque Glacier

8

Cirque Basin

9

4

Valley and Tidal Glacierswest coast B.C., Alaska

10

Piedmont Glacier location unknown

11

Continental Glaciers• Large continuous mass of glacial

ice, regardless of location, is referred to as a continental glacier

• Come in different sizes: • Largest - ice sheet (>50,000 km2)• Smaller - ice cap (<50,000 km2)

• If mountain tops are visible called ice field

• Movement controlled by:____________________________

12

5

Ice Sheets, Caps, and Fields

13

Outlet Glacier

14

Glacial Ice FormationAccumulation of snow and ice, thick layersWeight → increased pressure at depthPressure melting point at depth is reduced

Snow → Gr. Snow → Firn → Imp.GIce → Tr. GIce

Behaves as a plastic under pressure - flows

Process takes from a few yrs to thousands of yrs

15

6

16

Glacial Mass Balance

Accumulation = Precip. (all forms), snow avalanches17

18

7

Glacial Mass Balance

Ablation = snowmelt, sublimation, deflation, and calving19

20

Glacial Advance or Retreat?

Glaciers advance/grow when:Precip. ↑ and/or temperatures ↓Causing ↑ accumulation and/or ↓ ablation Equilibrium line shifts towards terminus;the glacier advances

Glaciers retreat/shrink when:Precip. ↓ and/or temperatures ↑Causing ↓ accumulation and/or ↑ ablation Equilibrium line shifts towards accumulation zone;the glacier retreats 21

8

Advance or

Retreat?

Movement of glacial ice is NOT necessarily coincident with advance or retreat of the terminus.

Ice may be moving even when the terminus is stationary, advancing, or retreating

22

Glacial MovementRate of movement depends on:1. Rate of _____2. Slope of _____3. Slope of _____4. Temperature of ______ 5. Presence of _____ at base

Rate varies - metres/day to cm/yearFaster near _____, along _____Slowest near _____and _____due to ____________________

23

Glacial MovementThree mechanisms of movement:

1) Basal Sliding

2) Plastic Flow

3) Shearing

24

9

Ice Regelation and Plucking

Due to pressure changes at base of glacier 25

26

Glacial ErosionThree processes account for the majority of glacial erosion:1) Plucking

w/ ice regelation

2) Abrasion polishing, scouring, striations, grooves

3) Bulldozingglaciotectonic features

27

10

28

29

30

11

31

32

Erosional Landforms

Createdby Alpine Glaciation

Glaciation typically removes soil and regolith, eroding down to bedrock33

12

Postglacial Alpine

Landscape& Resulting Erosional

Landforms

Identify and describe cirque basins, cols, horns, aretes, tarns, hanging and u-shaped valleys, paternoster lakes, fjords 34

35

36

13

37

Depositional Landforms Created by Alpine or

Continental Glaciation

drift

till outwash

diamict?

by ice by water

38

MorainesAccumulations of till (unsorted material)Terminal or end moraines; advance = ablationSequence of end moraines referred to as washboard or recessional morainesLateral vs. Medial Moraines (alpine)

Depositional Landforms Created by Alpine or Continental Glaciation

Animation –Terminal and Recessional Moraines

39

14

40

41

42

15

43

44

Glaciofluvial deposits (sorted material)Glaciers develop extensive drainage systems in the ablation zoneon = _______________within = _____________and beneath = _____________Sediment laden runoff deposits an _______ _________ in a process analogous to the development of a delta or alluvial fan

Depositional Landforms Created by Alpine or Continental Glaciation

Animation – Outwash

45

16

46

47

48

17

49

50

Ablation of stagnant ice; = till plainDeposition of glaciofluvial seds; = inverted topography after ice melts

Subglacial fluvial deposits result in long sinuous ridges called _______________Supraglacial lake deposits result in hills called _____________________Blocks of clean ice result in subsidence and depressions called ____________________

Depositional Landforms Created by Continental Glaciation

51

18

Two general types of streamlined features:Roche Moutonnee – __________________

gentle intercepting slope, steep leeward slopeDrumlins - _______________________

steep intercepting slope, gentle leeward slope

Erosional and Depositional Landforms Created by Continental Glaciation

52

Deposition by Continental

Glaciers

53

54

19

55

Pleistocene Glaciation

56

Mechanisms of Climate

Fluctuation

57

20

58

59

Glacial Lakes and Spillways

60

21

61