Geography 111:
Introduction to Physical Geography and Environmental Studies

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Geog 111 Lecture Outline: Deserts and Glaciers and Related Landforms
Update: 10/8/05

Review

Karst and Hydrothermal Processes: underground water

1. Karst Processes and Landscapes

2. Hydrothermal Features


Next: Deserts and Glaciers: dry and ice...



Desert Landforms

McKnight 8.19: Dry climates

Regions of the world where water is scarce but water is still important and plays a large role in shaping landforms




Desert landforms: processes which shape them are related to those that shape landforms in more humid areas: but there are key differences




1. The Work of Water in Dry Regions: Fluvial Processes



1a. Surface Water in Deserts


McKnight 18.4: Nile River



Humid regions: characteristics of rivers?



Desert regions: characteristics of rivers?





McKnight 18.6: Dry Lake Beds in Australia




McKnight 18.8: Playas in Western US




The real effect on desert landforms is from fluvial processes: flowing water




1b. Fluvial Erosion in Arid Lands

Fluvial (flowing water) processes are most important way desert landforms are shaped



McKnight 18.10: Slope in Dry and Moist Areas



McKnight 18.11: Bornhardt


McKnight 18.12: Australian Bornhardt



McKnight 18.13: Pediments




1c. Fluvial Deposition in Arid Lands

McKnight 18.14: Piedmont

Generic term for the area at the foot of a mountain range

In desert areas: zone of fluvial deposition




Fluvial erosion and deposition create unique desert landforms



1d. Desert Fluvial Landforms: Basin and Range Terrain

Basin and range region: huge area, minimal external drainage


Raitz Landforms Map


McKnight 18.26: Basin and Range




McKnight 18.27: Alluvial Fan Image





1e. Desert Fluvial Landforms: Mesa and Scarp Terrain

Map: San Juan Pueblo, NM



McKnight 18.25: Basin and Range and Mesa and Scarp Landscapes

Four-corners area of the US Southwest


McKnight 18.29: Mesa and Scarp Photo




McKnight 18.30 Cross Section




McKnight 18.33: Pinnacles, Buttes, Mesas, Plateaus




Weathering and erosion: sapping




McKnight 18.34: Badlands





2. The Work of the Wind in Dry Regions: Aeolian Processes

Wind is closely associated with deserts but plays a somewhat limited role in shaping desert landforms with the exception of sand dunes

Aeolian processes: related to the movement of air over the earth's surface




2a. Aeolian Erosion and Transportation


McKnight 18.18: Aeolian Transportation

Deflation: movement of loose particles through the air or along the ground

Abrasion: natural 'sandblasting'




2b. Aeolian Deposition



Sand dunes: one of the most distinctive desert landforms

McKnight 18.19: Sand Dune Movement




McKnight 18.20: Common Dune Patterns

Barchan: usually mobile dunes on a stable (eg., non-sand) surface


McKnight 18.20: Common Dune Patterns

Traverse dunes: less uniform, linear dunes




Seifs: linear, parallel, ridges of sand





2c. Desert Aeolian Landforms

McKnight fig. 18.1: Erg

Ergs



McKnight 18.3: Reg

Regs


Hamada




Sum: Desert Landforms

1. The Work of Water in Dry Regions: Fluvial Processes

Key: despite its scarcity, water is the most important external landform shaping agent in dry regions of the world

1a. Surface Water in Deserts

1b. Fluvial Erosion in Arid Lands

1c. Fluvial Deposition in Arid Lands

1d. Desert Fluvial Landforms: Basin and Range Terrain

1e. Desert Fluvial Landforms: Mesa and Scarp Terrain


2. The Work of the Wind in Dry Regions: Aeolian Processes

Aeolian processes: related to the movement of air over the earth's surface

Most effective where surface material is fine, dry and not held in place by vegetation

2a. Aeolian Erosion and Transportation

2b. Aeolian Deposition

2c. Desert Aeolian Landforms






Glaciers and Glacial Landforms

McKnight 9.5: The Hydro Cycle




McKnight 19.1a: Pleistocene Glaciation



McKnight 19.1b: Pleistocene Glaciation: US Detail


McKnight 19.1c: Pleistocene Glaciation: Europe Detail



McKnight 19.2: Contemporary Glaciation



McKnight 19.3: Contemporary Glaciation in N. America



Focus on the effects of ice and glaciers which directly affect landforms


Periglacial processes: zone beyond the extent of glaciers and ice



Sea level changes: if more water is stored as ice, there is less water in oceans



Crustal depression: weight of ice caused earth's crust to sink: up to 4000 feet



Precipitation changes: increase in precipitation particularly during glacial retreat




1. Glaciers Formation and Flow

Glaciers form when there is a year to year accumulation of snow



McKnight 19.8: Snow to Ice



Glacial flow




McKnight 19.10: Glacial Flow vs Glacial Advance

Glacial ice is always flowing, even though the glacier itself may not be advancing




McKnight 19.9: Glacier Cross Section



Overall result of glacial flow is a form of erosion by water




Glacial erosion accounts for only about 7% of erosion (now)





2. Mountain Glaciers

McKnight 19.5: Mountain Glaciers



McKnight 19.6: Alpine Glaciers



McKnight 19.28: Landforms shaped by Mountain Glaciers



3. Continental Ice Sheets and Glaciers

McKnight 19.1a: Pleistocene Glaciation



3a. Development and Flow of Pleistocene Glaciation




3b. Erosion by Ice Sheets

Glacial movement tends to smooth out the land beneath it


Effectiveness of erosion by glaciers



McKnight 19.16: Plucking



McKnight 19.11: Glacial Abrasion



WWW): Finger Lakes in NY




Results: a smooth but not flat terrain




Transportation by Glaciers




3c. Deposition by Ice Sheets and Glaciers during Pleistocene

Pleistocene glaciers


Drift: any material moved by glaciers


Many glacial deposits are unstratified and amorphous (not particular shape)


McKnight 19.13: Till Photo

Till: material deposited directly by moving or melting ice, with no meltwater flow or redeposition involved; usually occurs at the edge of a glacier

Till plain:



McKnight 19.14: Erratic Photo

Erratics: huge fragments of rock, carried and deposited by glacier




Other glacial deposits do have particular patterns: stratified

Moraine: irregular rolling hills and ridges; concentrations of glacially deposited materials

McKnight 19.20: Terminal Moraine

Terminal moraine:




McKnight 19.18: Glacial and Glaciofluvial Features

Recessional moraine:




WWW) Terminal and Recessional Moraines in US Midwest

Usually shaped in concave arcs bulging outward in the direction of ice movement




McKnight 19.18: Glacial and Glaciofluvial Features

Ground moraine:




Drumlins: ridges aligned parallel with the direction of the ice movement




Glaciofluvial Features




McKnight 19.18: Glacial and Glaciofluvial Features

Outwash plains:


Eskers: long sinuous ridges of stratified drift



McKnight 19.23: Kame

Kame: small, steep mounds or conical hills




McKnight 19.19: Kettles

Kettle: chunks of ice left behind as glacier melts






Sum: Glaciers and Glacial Landforms


1. Glaciers Formation and Flow

Overall result of glacial flow is a form of erosion by water


2. Mountain Glaciers


3. Continental Ice Sheets and Glaciers

3a. Development and Flow of Pleistocene Glaciation

3b. Erosion by Ice Sheets


...transportation by glaciers...

3c. Deposition by Ice Sheets and Glaciers during Pleistocene




E-mail: jbkrygier@owu.edu

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