Page 559 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

16.2
DUNE FORMS (continued)
Parabolic:
Crescent-shaped dune with opening end facing upwind; U-shaped “blowout” and arms anchored by vegetation, which stabilizes dune form.
Barchanoid ridge:
Wavy, asymmetrical dune formed from coalesced barchans with ridges aligned transverse to effective winds; resembles connected crescents in rows with open areas between.
Star dune:
Pyramidal-shaped structure with three or more sinuous, radiating arms extending outward from a central peak; results from effective winds shifting in all directions.
Reversing:
Dune with asymmetrical ridge, intermediate between star dune and transverse dune; wind variability can alter shape between these forms.
Longitudinal:
Linear, slightly sinuous, ridge-shaped dune, aligned parallel with the wind direction. Averages 100 m high and 100 km long but can reach to 400 m high.
Dome:
Circular or elliptical dune with no slipface; sometimes modified into barchanoid forms, and sometimes stabilized by vegetation.
Compare: How are barchan and parabolic dunes similar? How are they different?
The Sahara Desert in Libya
[Denis Burdin/Shutterstock.]
GEOquiz
1. Summarize: Describe the growth, structure, and migration of a 2. Infer: Give one reason that star dunes and longitudinal sand dune beginning with a small obstacle that intercepts sand dunes are often higher than other types of dunes. particles and assuming a relatively constant wind direction.
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geosystems in action 16 WIND-BLOWN DUNE FORMS