Download - Chapter18 wind erosion and deposition
![Page 1: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/1.jpg)
Chapter 18: Arid Region Landforms and Eolian Processes
Physical Physical GeographyGeographyNinth EditionNinth Edition
Robert E. Gabler
James. F. Petersen
L. Michael Trapasso
Dorothy Sack
![Page 2: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/2.jpg)
Arid Region Landforms and Eolian Processes
![Page 3: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/3.jpg)
Arid Region Landforms and Eolian Processes
• Running water does more geomorphic work than wind– Eolian geomorphic processes are those caused
by wind– Arid regions provide a unique opportunity to
study geomorphology as there is little vegetation
![Page 4: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/4.jpg)
18.1 Surface Runoff in the Desert
• Desert Characteristics– Lack of precipitation– High evaporation rates– Sparse vegetation– Low weathering rates and
insufficient vegetation result in little moisture-retention soil
– Running water very effective in shaping land
Q: Why do you think the drainage density is so high here?
![Page 5: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/5.jpg)
18.1 Surface Runoff in the Desert
• Paleogeography– Most deserts have
not always been arid– Evidence:
• Deposits• Wave-cut shorelines
of extinct lakes• Immense canyons
occupied by streams far too small to have eroded such a large valley
![Page 6: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/6.jpg)
18.1 Surface Runoff in the Desert
• Running Water in Deserts– Ephemeral channels– Lose water through
infiltration– Abundance of coarse
sediments– Braided channels– Discharge rates
• Downstream decrease:– Infiltration– Evaporation
![Page 7: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/7.jpg)
18.1 Surface Runoff in the Desert
• Many desert streams terminate before sea– Cause
• Diminishing discharge• Mountains block
stream– Terminate in
depressions and form shallow, ephemeral lakes
– Interior drainage
![Page 8: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/8.jpg)
18.1 Surface Runoff in the Desert
• Regional base level– Stream that terminates in interior– Tectonic Activity can change regional base level
• Floors below sea level– Death Valley, CA– Dead Sea, Middle East– Turfan Basin, China– Lake Eyre, Australia
![Page 9: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/9.jpg)
18.1 Surface Runoff in the Desert
• Many desert streams terminate before sea– Streams that
originate in humid climates
• Humboldt River, Nevada
Q: Was the gorge eroded by the streams with this amount of flow?
![Page 10: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/10.jpg)
18.1 Surface Runoff in the Desert
• Exotic Streams– Rivers that successfully
traverse the desert and make it to the sea
• Nile (Egypt and Sudan)• Tigris-Euphrates (Iraq)• Indus (Pakistan)• Murray (Australia)
– Colorado River• Usually does not make
due to human use
![Page 11: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/11.jpg)
18.2 Water as a Geomorphic Agent in Arid Lands
• Arid Region Landforms of Fluvial Erosion– Channels of ephemeral
streams• Washes (arroyos)• Barrancas (Latin America)• Wadis (N. Africa and SE
Asia)– Braided channels– Prone to flash floods
![Page 12: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/12.jpg)
18.2 Water as a Geomorphic Agent in Arid Lands
• Arid Region Landforms of Fluvial Erosion– Dense network of
barren slopes (Badlands)
• High drainage density• Dakotas• Death Valley, CA• Big Bend, TX• S. Alberta
![Page 13: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/13.jpg)
18.2 Water as a Geomorphic Agent in Arid Lands
• Arid Region Landforms of Fluvial Erosion– Plateau
• Extensive, elevated region with fairly flat top
• Horizontal rock layers• Colorado Plateau
– Grand Canyon • Exposes the horizontal
rock layers• Rim of Grand Canyon
called caprock
![Page 14: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/14.jpg)
18.2 Water as a Geomorphic Agent in Arid Lands
• Arid Region Landforms of Fluvial Erosion– Mesas– Buttes– Monument Valley (Utah
and Arizona)
![Page 15: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/15.jpg)
18.2 Water as a Geomorphic Agent in Arid Lands
• Arid Region Landforms of Fluvial Erosion– Pediment
• Gentle retreat of steep mountain front
– Inselbergs
![Page 16: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/16.jpg)
18.2 Water as a Geomorphic Agent in Arid Lands
• Arid Region Landforms of Fluvial Deposition– As flow of stream
decreases, capacity decreases, which increases deposition
– Alluvial Fans• Channels may flare out
onto open plains• Sediment deposited
along base of highlands• Fan apex
![Page 17: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/17.jpg)
18.2 Water as a Geomorphic Agent in Arid Lands
• Arid Region Landforms of Fluvial Erosion– Alluvial fan
• Course sediment (boulders and cobbles) near fan apex
• Steepness decreases downslope
• Debris flow fans
![Page 18: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/18.jpg)
18.2 Water as a Geomorphic Agent in Arid Lands
• Arid Region Landforms of Fluvial Erosion– Bajada
• Alluvial fans joined together
Q: Why would a series of alluvial fans have a tendency to eventually join to form a bajada?
– Piedmont alluvial plain
![Page 19: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/19.jpg)
18.2 Water as a Geomorphic Agent in Arid Lands
• Playas– Bolsons
• Desert basins of interior drainage surrounded by mountains
– Playa• Lowest part of bolson• Fine-grained bed of
ephemeral lake• Pan
![Page 20: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/20.jpg)
18.2 Water as a Geomorphic Agent in Arid Lands
• Playas– Salt crust playas (salt flats or salinas)– Bonneville Salt Flat, UT
• Speed record– Edwards Air Force Base, CA
• Space shuttle landings
![Page 21: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/21.jpg)
18.3 Wind as a Geomorphic Agent
• Eolian– Landform created by
wind– Less effective than water– Wind Erosion and
Transportation• Deflation• Suspension• Surface creep• Ripples
![Page 22: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/22.jpg)
18.3 Wind as a Geomorphic Agent
• Wind Erosion & Transportation– Deflation– Surface creep– Ripples– Abrasion
![Page 23: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/23.jpg)
18.3 Wind as a Geomorphic Agent
• Wind Erosion & Transportation– Dust Storms– Sandstorms– Deflation hollows
Q: Can you suggest a continent that might be a source of major dust storms today?
![Page 24: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/24.jpg)
18.3 Wind as a Geomorphic Agent
• Wind Erosion & Transportation– Desert pavement (gibber)
Q: Is desert pavement a surface indestructible by human activities? Why?
– Ventifacts• Individual wind-fashioned
rocks
![Page 25: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/25.jpg)
18.3 Wind as a Geomorphic Agent
• Wind Erosion & Transportation– Pedestaled, or balanced
rock• Forms as a result of
physical and chemical weathering
Q: What other processes or rock factors could account for such an unusual shape?
![Page 26: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/26.jpg)
18.3 Wind as a Geomorphic Agent
• Wind Erosion & Transportation– Yardang
• Wind sculpted remnant ridge, often of easily eroded rock
Q: Which is the upwind side of the yardang?
![Page 27: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/27.jpg)
18.3 Wind as a Geomorphic Agent
• Wind Deposition– Sand dunes– Loess
• Fine grained sediment (e.g. silt) can be transported in suspension long distances before blanketing and modifying the existing topography
![Page 28: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/28.jpg)
18.3 Wind as a Geomorphic Agent
• Sand Dunes– Result of wind deposition– Sand seas
• Seemingly endless dune regions
– Small dune fields (coast)– Dune topography
• Sand sheets
Q: Why are coastlines such good locations for dune formation?
![Page 29: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/29.jpg)
18.3 Wind as a Geomorphic Agent
• Sand Dune Classification– Active
• Slip face• Angle of repose (35o)
– Stabilized
Q: These stabilized dunes are crossed by vehicle trails. How might these trails affect the stabilized dunes?
![Page 30: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/30.jpg)
18.3 Wind as a Geomorphic Agent
• Sand Dune– When wind and velocity
are constant, a dune can move forward by downward transfer of sediment
– Blowout
![Page 31: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/31.jpg)
18.3 Wind as a Geomorphic Agent
Q: Explain how plants can stabilize dunes.
![Page 32: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/32.jpg)
18.3 Wind as a Geomorphic Agent
• Types of Sand Dunes– Classified according to
shape and relationship to the wind
– Barchans (crescent-shaped dune)
![Page 33: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/33.jpg)
18.3 Wind as a Geomorphic Agent
• Types of Sand Dunes– Parabolic dunes– Transverse dunes– Longitudinal dunes– Star dunes
![Page 34: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/34.jpg)
18.3 Wind as a Geomorphic Agent
• Longitudinal Dune, Sahara DesertQ: Estimate the ground length of the dunes in this satellite image.
![Page 35: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/35.jpg)
18.3 Wind as a Geomorphic Agent
• Dune Protection– Recreation– Fragile environment
• White Sands, NM• Great Sand Dunes, CO• Cape Cod, MA
Q: Why should some dune driving need to be protected from human activities such as driving dune buggies and other recreational vehicles?
![Page 36: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/36.jpg)
18.3 Wind as a Geomorphic Agent
• Loess Deposits– Wind can carry in
suspension dust-sized particles for thousands of km before depositing them
• Gobi Desert, China (30-90m thick)
• American Midwest
• Q: Where is the origins of these loess deposits?
![Page 37: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/37.jpg)
18.3 Wind as a Geomorphic Agent
• Loess Deposits
Q: Why might the instability of loess cliffs be a problem?
![Page 38: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/38.jpg)
18.4 Landscape Development in Deserts
• Geomorphic differences between arid and humid climates– Expanse of bedrock– Lack of continuous water flow– Eolian process plays a greater role– Fault-block mountains in the Great Basin range
• Orographic• Warner mountains• Panamint range
![Page 39: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/39.jpg)
18.4 Landscape Development in Deserts
• A False-color satellite image of Death Valley, CA
• Panamint range to SW
Q: Why do you think the white areas are in the center of the valley?
![Page 40: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/40.jpg)
18.4 Landscape Development in Deserts
• Alluvial fans and playas (interior drainage)• Pediments and inselbergs (tectonically stable since a
distant period of mountain formation
![Page 41: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/41.jpg)
18.4 Landscape Development in Deserts
• Inselbergs– Erosional
remnant– Uluru (Ayers
Rock), Australia
![Page 42: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/42.jpg)
18.4 Landscape Development in Deserts
• Green River Overlook, Utah• Q: What aspects of this environment make this an
attractive landscape?
![Page 43: Chapter18 wind erosion and deposition](https://reader033.vdocuments.net/reader033/viewer/2022061103/540583758d7f729b768b4d75/html5/thumbnails/43.jpg)
Physical Geography
End of Chapter 18: Arid Region Landforms and Eolian Processes