1. Glaciers and Glaciation

2. Glaciers and Glaciation
What is a Glacier?
Formation and Movement
Glacial Erosion
Erosional Landforms
Glacial Deposits
Causes of Ice Ages

3. GEOL131: Glaciers
What is a Glacier?

4. What is a Glacier? Mass of land-based ice In motion downslope
GEOL131: Glaciers
What is a Glacier?
Mass of land-based ice
In motion downslope
Part of two cycles
Hydrologic
Rock

5. What is a Glacier? Four kinds of glacier Alpine (or valley)
GEOL131: Glaciers
What is a Glacier?
Four kinds of glacier
Alpine (or valley)
Continental (or ice sheet)

6. What is a Glacier? Four kinds of glacier Ice cap Outlet
GEOL131: Glaciers
What is a Glacier?
Four kinds of glacier
Ice cap
Outlet

7. Locations of Modern Glaciers
GEOL131: Glaciers
Locations of Modern Glaciers
Glaciers are shrinking and disappearing worldwide
Glacier National Park, Montana:
1910: 150 glaciers
2010: 25 glaciers

8. Formation and Movement
GEOL131: Glaciers
Formation and Movement

9. Formation Accumulation of snow Snow recrystallizes into firn
GEOL131: Glaciers: Formation & Movement
Formation
Accumulation of snow
Snow recrystallizes into firn
Ice crystals with texture of sand
If depth of firn reaches 160 feet, crystals fuse together

10. Movement Plastic flow Basal sliding
GEOL131: Glaciers: Formation & Movement
Movement
Plastic flow
Most movement occurs this way
Flow in the solid state under high pressure
Basal sliding
Small amount of movement
Entire ice mass slides along base

11. Movement Glacier budget GEOL131: Glaciers: Formation & Movement
Balance between accumulation and loss of ice

12. Movement Glacier budget Ice accumulates via Snowfall
GEOL131: Glaciers: Formation & Movement
Movement
Glacier budget
Ice accumulates via
Snowfall
Tributary glaciers
Trunk and tributary glaciers, Greenland.

13. Movement Glacier budget Ice is lost via Melting Calving
GEOL131: Glaciers: Formation & Movement
Movement
Glacier budget
Ice is lost via
Melting
Creates meltwater rivers
Calving
Creates icebergs
Greenland calving event
A calving glacier

14. GEOL131: Glaciers
Glacial Erosion

15. Erosion Mechanisms Plucking Abrasion
GEOL131: Glaciers: Glacial Erosion
Erosion Mechanisms
Plucking
Chunks of rock pried loose from glacier’s bed
Abrasion
Scraping/scouring of underlying rock

16. GEOL131: Glaciers
Erosional Landforms

17. Glaciated Mountain Valleys
GEOL131: Glaciers: Erosional Landforms
Glaciated Mountain Valleys
Glacial troughs & hanging valleys

18. Glaciated Mountain Valleys
GEOL131: Glaciers: Erosional Landforms
Glaciated Mountain Valleys
Glacial troughs & hanging valleys

19. Horns, Cirques, and Aretes
GEOL131: Glaciers: Erosional Landforms
Horns, Cirques, and Aretes
Horn

20. GEOL131: Glaciers
Glacial Deposits

21. Types of Glacial Sediment
GEOL131: Glaciers: Glacial Deposits
Types of Glacial Sediment
Drift
General term for any sediment deposited by a glacier
Till
Deposited directly from melting ice
Unsorted

22. Terms Stratified drift Deposited by meltwater rivers Well-sorted
GEOL131: Glaciers: Glacial Deposits
Terms
Stratified drift
Deposited by meltwater rivers
Well-sorted

23. Moraines Made of till Four kinds: Lateral Medial End (terminal) Ground
GEOL131: Glaciers: Glacial Deposits
Moraines
Made of till
Four kinds:
Lateral
Medial
End (terminal)
Ground

24. Lateral and Medial Moraines
GEOL131: Glaciers: Glacial Deposits: Moraines
Lateral and Medial Moraines
Created by valley glaciers

25. End Moraines Created by all glaciers
GEOL131: Glaciers: Glacial Deposits: Moraines
End Moraines
Created by all glaciers
Ridge of till at end of glacier; left behind if ice retreats
End moraine

26. Ground Moraines Created by all glaciers
GEOL131: Glaciers: Glacial Deposits: Moraines
Ground Moraines
Created by all glaciers
Layer of till left as glacier retreats
Ground moraine

27. GEOL131: Glaciers: Glacial Deposits: Moraines
Moraines in Michigan

28. Possible Causes of Ice Ages
GEOL131: Glaciers
Possible Causes of Ice Ages

29. What is an Ice Age? Extended period of greatly expanded glaciation
GEOL131: Glaciers: Causes of Ice Ages
What is an Ice Age?
Extended period of greatly expanded glaciation
Most recent Ice Age:
Began about 2 million years ago
Ended about 10,000 years ago
Glaciers advanced and retreated many times
Michigan ice-covered until about 12,000 yrs ago

30. Maximum extent of ice during last Ice Age
GEOL131: Glaciers: Causes of Ice Ages
Maximum extent of ice during last Ice Age
Accumulation centers
Michigan

31. Possible Causes Plate tectonic movement Variations in Earth’s orbit
GEOL131: Glaciers: Causes of Ice Ages
Possible Causes
Plate tectonic movement
Variations in Earth’s orbit
Others
Changes in atmospheric composition
Changes in Earth’s reflectivity
Cooling of ocean currents

32. Plate Tectonic Movement
GEOL131: Glaciers: Causes of Ice Ages
Plate Tectonic Movement
Glaciers can only exist on land
To have Ice Age, large land masses must be in polar latitudes

33. Orbital variations Alter intensity of cold and warm seasons
GEOL131: Glaciers: Causes of Ice Ages
Orbital variations
Alter intensity of cold and warm seasons
Three kinds:
Precession
Obliquity
Eccentricity

34. Orbital variations: Precession
GEOL131: Glaciers: Causes of Ice Ages
Orbital variations: Precession
Wobble of rotational axis
26,000-year cycle

35. Orbital variations: Obliquity
GEOL131: Glaciers: Causes of Ice Ages
Orbital variations: Obliquity
Tilt angle of rotational axis
41,000-year cycle

36. Orbital variations: Eccentricity
GEOL131: Glaciers: Causes of Ice Ages
Orbital variations: Eccentricity
Shape of orbit
100,000-year cycle

37. Other factors: Atmospheric composition
GEOL131: Glaciers: Causes of Ice Ages
Other factors: Atmospheric composition
Greenhouse gases trap heat, keep Earth warm
Carbon dioxide, methane, water vapor
Lower concentrations = cooler global temps

38. Other factors: Earth’s reflectivity
GEOL131: Glaciers: Causes of Ice Ages
Other factors: Earth’s reflectivity
Earth’s surface either absorbs solar energy or reflects it
Depends on material
Lighter-colored material = more reflection = colder temps
Glaciers are light-colored, reflective

39. Other factors: Cooling ocean currents
GEOL131: Glaciers: Causes of Ice Ages
Other factors: Cooling ocean currents
Ocean currents move heat from tropics to higher latitudes
If warm currents become colder, average global temp drops

40. End of Chapter