1. Chapter 10 Weathering and Mass Wasting
Visualizing Physical Geography by Alan Strahler and Zeeya Merali
Chapter 10 Weathering and Mass Wasting
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

2. Processes and Landforms of Arctic and Alpine Tundra
Chapter Overview
Weathering
Mass Wasting
Processes and Landforms of Arctic and Alpine Tundra
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

3. Describe permafrost and its effects, such as pingos and ice wedges.
Objectives
Explain the chemical and physical differences between those two types of weathering.
Show how soil creep, earthflow, mudflows, and landslides are all forms of mass wasting.
Describe permafrost and its effects, such as pingos and ice wedges.
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

4. Weathering
Weathering: all the processes that physically disrupt or chemically decompose a rock at or near the Earth’s surface
Two types of weathering:
1. Physical weathering
2. Chemical weathering
Weathering produces regolith
Physical weathering: breakup of massive rock (bedrock) by physical forces at or near the Earth’s surface
Regolith: layer of mineral particles that lies above bedrock
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

5. Weathering Physical Weathering
Physical weathering (mechanical weathering) fractures bedrock
Frost Action: water expands when it freezes, and fractures rock
Dominant process in arctic and high-mountain environments
Talus: fragments of rock at the base of a cliff
Joints: fractures in bedrock
Granular disintegration: rocks break up grain by grain
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

6. Weathering
Physical Weathering Salt-crystal growth: Water evaporates from sandstone pores, leaving salt crystals behind. Crystals grow and disintegrate rock.
Occurs in arid and semiarid regions
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

7. Weathering Physical Weathering
Unloading: rock is exposed at the surface, releasing pressure, so rock expands slightly
Sheeting structure: rock joints in layers parallel to surface, forming exfoliation domes
Other possible processes of physical weathering:
Temperature change
Plant roots
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

8. Chemical Weathering and its Landforms
Chemical Weathering: chemical change in rock minerals through exposure to the atmosphere and water
Most effective in warm, moist climates
Hydrolysis
Oxidation
Carbonic acid action
Dissolves limestone, creating caverns
Weathers buildings, tombstones
Soil acids weather basalt
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

9. Mass Wasting
Mass Wasting: spontaneous downhill movement of soil, regolith, and bedrock under the influence of gravity
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

10. Mass Wasting
Slopes
Bedrock: solid rock layer under soil and regolith, which is relatively unchanged by weathering
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

11. Mass Wasting
Slopes
Soil Creep: extremely slow downhill movement of soil and regolith
Earthflow: moderately rapid downhill flow of water-saturated soil, regolith, or weak shale
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

12. Mudflow and Debris Flood
Mass Wasting
Mudflow and Debris Flood
Mudflow: flowing mixture of water and soil or regolith that flows rapidly downhill
Lahar: volcanic mudflow
Debris flood or debris flow: very watery mudflow
Alpine debris avalanche: debris flow on steep slopes in mountainous regions
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

13. Mass Wasting Landslide
Landslide: rapid sliding of large masses of bedrock on steep mountain slopes or from high cliffs
Set off by:
earthquakes
sudden rock failures
oversteepening of slope
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

14. Mass Wasting Induced Mass Wasting
Mass wasting can be induced by human activities: excavation, adding water to slopes, extracting mineral resources, many other earth-moving activities
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

15. Mass Wasting—After the Deluge
Hurricanes can bring huge volumes of water on to the landscape, leading to debris avalanches and mudslides
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

16. Processes and Landforms of Arctic and Alpine Tundra Permafrost
Permafrost: soil, regolith, and bedrock at a temperature below 0º C, found in cold climates
Periglacial: environment near glacial ice
Permafrost reaches a depth of 300 to 450 m near 70º N
Ground ice: water frozen in pore spaces
Active layer: freezes and thaws with the seasons
Permafrost table: upper surface of the permanently frozen zone
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

17. Processes and Landforms of Arctic and Alpine Tundra
Environmental Problems of Permafrost
Human activities degrade the permafrost environment
Thermal erosion: surface layer removed, so the thaw extends deeper into the ground
Thermokarst: natural surface removed over large areas of tundraground subsidence results in depressions and lakes
Ground may subside
Buildings may collapse
Buildings must be insulated
Pipelines must be placed aboveground
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

18. Processes and Landforms of Arctic and Alpine Tundra
Patterned Ground and Solifluction
Annual freezing and thawing sorts particles by size, producing rings of coarse fragments
Stone polygons
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

19. Processes and Landforms of Arctic and Alpine Tundra
Patterned Ground and Solifluction
Solifluction: a type of earthflow found in arctic permafrost regions caused by soil that is saturated with water and then deformed into terraces
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

20. Processes and Landforms of Arctic and Alpine Tundra
Most periglacial processes and form of arctic tundra are also found in high alpine tundra
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

21. Processes and Landforms of Arctic and Alpine Tundra
Climate Change in the Arctic
By 2100, arctic temperatures may rise by 4º C to 8º C
Annual precipitation may increase by 20%
Active layer of permafrost will deepen over broad areas
Roads and pipelines disrupted
Populations of animals fluctuate
Hunting season shorter for native peoples
Boreal forest will migrate poleward
Forest productivity will decline from drought, insects, disease, fire
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.