UNIVERSITY OF SOUTH ALABAMA
Last Time
Total Station Project
GY 301: Geomorphology
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Computer Software
Schedule a help session if needed
3 maps due tomorrow by 5 pm
Lecture 17:
Arid Landforms
http://www1.sulekha.com/mstore/blizzard/albums/default/100_4344.JPG
Arid and Semi-Arid Regions
• Arid and semi-arid regions are distinguished on the basis of their
annual precipitation sums and include:
Arid and Semi-Arid Regions
Deserts with an annual precipitation sum <50 mm/year and
devoid of vegetation (Hot arid regions occur at 30 degrees latitude or in rain
shadows)
Arid and Semi-Arid Regions
Arid regions with 50-250 mm/year precipitation and sparse
vegetation, and
Arid and Semi-Arid Regions
Semi-arid regions with a precipitation sum of 250 to 500 mm
per annum and a steppe savannah/prairie/pampa vegetation
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Arid and Semi-Arid Regions
Important geomorphic processes in the dry regions of the
world differ from those in more humid environments:
•streams are intermittent or ephemeral (and have very irregular discharges),
•mass-wasting processes and unconfined sheet floods are prominent,
•many rivers do not flow into the sea but end in inland depressions without
outlet,
•salt lakes are a common landscape feature,
•aeolian processes play an important role, particularly in areas receiving less
than 150 mm/year of precipitation
•physical weathering processes are prominent whereas hydrolysis of minerals is
subdued.
Cycle of Landform Development
• Initiated by tectonics: Normal Faulting resulting from
lateral extension of lithosphere
• Alluvial
Fans
• Playa Lakes
• Inselbergs
• Bajada
• Pediment
(Bajada)
(Inselbergs)
Arid Landform Stages of Development
Alluvial
Fan
• High relief (early)
– Alluvial Fans
(Early Stage)
• Middle
– Rounded Divides
– Bajada
– Playa Lakes
• Low Relief (late)
– Inselbergs
– Pediment
http://media-2.web.britannica.com/eb-media/65/58765-004-83C0D7F1.jpg
Arid Landform Stages of Development
Arid Landform Stages of Development
• High relief (early)
• High relief (early)
– Alluvial Fans
– Alluvial Fans
• Middle
• Middle
– Bajada (merged alluvial fans)
– Playa Lakes
– Bajada
– Playa Lakes
• Low Relief (late)
• Low Relief (late)
– Inselbergs
– Pediment
– Inselbergs
– Pediment
Playa Lakes
http://3dparks.wr.usgs.gov/carrizo/html/a023.htm
Bajada
http://www.c4g.lsu.edu/moj_gis_dir/bajada_tm.jpeg
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Middle Stage Arid
Arid Landform Stages of Development
• High relief (early)
Inselbergs
– Alluvial Fans
• Middle
– Bajada
– Playa Lakes
• Low Relief (late)
– Inselbergs
– Pediment
http://www.agc.army.mil/research/products/desert_guide/images/i511.gif
Arid Landform Stages of Development
Arid Landform Stages of Development
• High relief (early)
• High relief (early)
– Alluvial Fans
– Alluvial Fans
• Middle
• Middle
– Bajada
– Playa Lakes
– Bajada
– Playa Lakes
• Low Relief (late)
– Inselbergs
– Pediment
Reg
• Low Relief (late)
Pediment
http://www.schweich.com/images/IMG10611sm.jpg
Late
Stage
Arid
– Inselbergs
– Pediment
– Reg
http://www.soton.ac.uk/~imw/jpg-Sabkhas/6SBK-reg-distant.jpg
Upcoming Stuff
Homework
Finish Total Station Project (due Friday)
Next Lecture:
Karst Geomorphology
Friday’s Lab:
Map interpretation (arid landforms)
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