2. Glaciers
Glaciers are a part of both the hydrologic cycle and rock cycle
Glacier – a thick mass of ice that forms over land from the compaction and recrystallization of snow and shows evidence of past or present flow

3. Glaciers Types of glaciers
Valley, or alpine glaciers – form in mountainous areas
Kennicott Glacier

4. Glaciers Types of glaciers Ice sheets or continental glaciers
Large scale
e.g., Over Greenland and Antarctica
Other types
Ice caps and piedmont glaciers

5. Glacier Movement Types of glacial movements Zone of fracture
Plastic flow
Slipping along the ground
Zone of fracture
Uppermost 50 meters
Crevasses form in brittle ice

6. Crevasses

7. Glacier Movement Zone of accumulation – the area where a glacier forms
Zone of wastage – the area where there is a net loss due to melting

8. Glacial Erosion Glaciers erode by Plucking – lifting of rock blocks
Abrasion
Rock flour (pulverized rock)
Striations (grooves in the bedrock)

9. Glacial Erosion Landforms created by glacial erosion Glacial trough
Hanging valley
Cirque
Arête
Horn
Fiord

10. Erosional Landforms Created by Alpine Glaciers

11. The Matterhorn in the Swiss Alps

12. Glacial Deposits Glacial drift All sediments of glacial origin
Types of glacial drift
Till – material that is deposited directly by ice
Stratified drift – sediment deposited by meltwater

13. Glacial Deposits Depositional features
Moraines – layers or ridges of till
Types of moraines
Lateral
Medial
End
Ground

14. End Moraines of the Great Lakes Region

15. Glacial Deposits Depositional features Outwash plain or valley train
Kettles
Drumlins
Eskers
Kames

16. Glacial Depositional Features

17. Ice Age Glaciers Glaciers of the past Ice Age
Began 2 to 3 million years ago
Division of geological time is called the Pleistocene epoch
Ice covered 30 percent of Earth’s land area

18. Extent of Ice Age Glaciation

19. Ice Age Glaciers Effects of Ice Age glaciers
Migration of animals and plants
Rebounding upward of the crust
Worldwide change in sea level
Climatic changes

20. Ice Age Sea Level

21. Causes of Ice Ages Successful theory must account for
Cooling of Earth, as well as
Short-term climatic changes
Proposed possible causes
Plate tectonics
Continents were arranged differently
Changes in oceanic circulation

22. Late Paleozoic Ice Age

23. Causes of Ice Ages Variations in Earth’s orbit Milankovitch hypothesis
Shape (eccentricity) of Earth’s orbit varies
Angle of Earth’s axis (obliquity) changes
Axis wobbles (precession)
Changes in climate over the past several hundred thousand years are closely associated with variations in Earth’s orbit

24. Orbital Variations

25. Deserts Any situation with a water deficiency
Distribution and causes of dry lands
Global distribution of air pressure and winds
Deep interiors of landmasses
Presence of high mountains

26. Global Dry Climate Distribution

27. Deserts Geologic processes in arid climates Weathering
Not as effective as in humid regions
Mechanical weathering forms unaltered rock and mineral fragments
Some chemical weathering does occur
Clay forms
Thin soil forms

28. Deserts Geologic processes in arid climates
Role of water in arid climates
Streams are dry most of the time
Desert streams are said to be ephemeral
Flow only during periods of rainfall
Different names are used for desert streams including wash, arroyo, wadi, donga, and nullah

29. Deserts Geologic processes in arid climates
Role of water in arid climates
Desert rainfall
Rain often occurs as heavy showers
Causes flash floods
Poorly integrated drainage
Most erosional work in a desert is done by running water

30. Desert Stream Channel

31. Deserts Basin and range: the evolution of a desert landscape
Uplifted crustal blocks
Interior drainage into basins produces
Alluvial fans and bajadas
Playas and playa lakes

32. Deserts Basin and range: the evolution of a desert landscape
Erosion of mountain mass causes local relief to continually diminish
Eventually mountains are reduced to a few large bedrock knobs called inselbergs projecting above a sediment-filled basin

33. Landscape Evolution in a Basin and Range Region

34. Deserts Wind erosion Deflation Abrasion Lifting of loose material
Produces
Blowouts
Desert pavement
Abrasion

35. Formation of Desert Pavement

36. Deserts Types of wind deposits Loess Deposits of windblown silt
Extensive blanket deposits
Primary sources are deserts and glacial stratified drift

37. Deserts Types of wind deposits Sand dunes
Mounds and ridges of sand formed from the wind’s bed load
Characteristic features
Slip face – the leeward slope of the dune
Cross beds – sloping layers of sand in the dune

38. Formation of Sand Dunes

39. Deserts Types of wind deposits Sand dunes Types of sand dunes
Barchan dunes
Transverse dunes
Longitudinal dunes
Parabolic dunes
Star dunes

40. Sand Dune Types