chapter 21: deserts and wind. a desert is a region that receives less than 25 cm of precipitation...
TRANSCRIPT
![Page 1: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/1.jpg)
CHAPTER 21:DESERTS AND WIND
![Page 2: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/2.jpg)
A desert is a region that receives less than 25 cm of precipitation per year.
What is the annual
precipitation in your region?
![Page 3: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/3.jpg)
Life Support
• Vegetation is so sparse, and water so rare, that a desert is unable to support significant populations of animals.
![Page 4: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/4.jpg)
Temperature
• Desert regions can have extreme temperatures ranges because the atmosphere contains little humidity to block the Sun's rays or retain heat at night.
![Page 5: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/5.jpg)
Natural Climate Change
• Climates can change naturally. The Sahara region was humid 5,000 to 10,000 years ago
![Page 6: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/6.jpg)
Deserts may be hot or cold, but low precipitation is a common trait
![Page 7: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/7.jpg)
Arctic circle
Some would argue that the “Arctic Desert” isn’t really a desert. Why do most cool dry areas have more vegetation than hot dry areas?
![Page 8: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/8.jpg)
Atmospheric moisture circulation determinesthe location of most deserts
Polar Cells
Ferrel Cells
Hadley Cells
![Page 9: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/9.jpg)
Formation
• Air warms and contracts as it sinks closer to Earth’s surface.
• Evaporation exceeds condensation.
• Deserts form, clustered around 30°N and 30°S latitudes.
![Page 10: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/10.jpg)
Other Factors Determining Desert Formation
• Not all deserts lie around 30° latitude• Several other factors contribute to desert locations:
– • orographic effect
![Page 11: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/11.jpg)
Other Factors Determining Desert Formation
– dry, cold air descending over polar regions
– the distance atmospheric moisture is transported
![Page 12: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/12.jpg)
Other Factors Determining Desert Formation
– cold ocean current adjacent to a tropical coast
![Page 13: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/13.jpg)
Other Factors Determining Desert Formation
– poor management of farmland
![Page 14: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/14.jpg)
Other Factors Determining Desert Formation
– deforestation
![Page 15: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/15.jpg)
Each desert has unique characteristics
• Trade Wind Deserts
![Page 16: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/16.jpg)
Each desert has unique characteristics
• Mid-latitude Deserts
![Page 17: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/17.jpg)
Each desert has unique characteristics
• Rain Shadow Deserts
![Page 18: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/18.jpg)
Coastal deserts
![Page 19: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/19.jpg)
Ripple and dune Terminology
• Wind is an important geological agent
![Page 20: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/20.jpg)
Ripple and dune Terminology
• Suspension: Silt carried in suspension produces well-sorted deposits of progressively smaller sediments with distance.
![Page 21: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/21.jpg)
Ripple and dune Terminology
• Loess: Eolian deposits of silt are left by continental glaciations
Mineralogically how does loess differ from typical wind-blown sand?
![Page 22: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/22.jpg)
Ripple and dune Terminology
Desert Pavement (lag deposit of coarse sediment left after fines blow away)
Yardang (rock outcrop sculpted by sand abrasion)
![Page 23: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/23.jpg)
Sand Dunes reflect sediment availability anddominant wind direction
• Abundant loose sediment (usually sand) • Energy to move sediment (usually wind)• An obstacle to trap sand (often a bush)• A dry climate
![Page 24: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/24.jpg)
Ripple and dune Terminology
• Barchan (Crescentic Dune)• Strong wind in one direction, small amounts of sand, limited
vegetation
• Transverse (Crescentic Dune)• Weak wind in one direction, large amounts of sand deposited
perpendicular to wind, limited vegetation
![Page 25: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/25.jpg)
Ripple and dune Terminology
• Parabolic Dune• Arms stabilized upwind by vegetation, often start as semi-circular blowouts
that elongate
• Longitudinal Dune• Winds flowing in opposing directions, two slip faces, aligned with wind
![Page 26: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/26.jpg)
Ripple and dune Terminology
• Star dune• Multidirectional winds, largest
dunes, grow tall instead of moving
• Sand seas • Large regions (>125 km2) of
windblown sand numerous, very large dunes, sand covers >20% of the ground surface
![Page 27: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/27.jpg)
Sand Dunes
What are the differences in shape and wind characteristics of Barchan and Parabolic dunes?
![Page 28: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/28.jpg)
Arid Landforms
• Arid landforms can be shaped by water• Flash floods are common• Streams tend to be ephemeral, flowing only after heavy rain.
![Page 29: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/29.jpg)
![Page 30: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/30.jpg)
Evolution of Desert Landscapes
![Page 31: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/31.jpg)
Playa Lakes
• Playa Lakes are products of rainfall and evaporation
What is the evidence that this area was recently
wet?
![Page 32: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/32.jpg)
Desertification
• Desertification is the process by which land loses its vegetation and turns into a desert
Both natural and anthropogenic factors lead to desertification. What are some of the factors?
![Page 33: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/33.jpg)
Environmental refugees
![Page 34: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/34.jpg)
Desertification
• Desertification threatens all six inhabited continents
![Page 35: CHAPTER 21: DESERTS AND WIND. A desert is a region that receives less than 25 cm of precipitation per year. What is the annual precipitation in your region?](https://reader030.vdocuments.us/reader030/viewer/2022032612/56649e0c5503460f94af525a/html5/thumbnails/35.jpg)
COPYRIGHT
Copyright © 2014 John Wiley & Sons Canada, Ltd. All rights reserved. Reproduction or translation of this work beyond that permitted by Access Copyright (The Canadian Copyright Licensing Agency) is unlawful. Requests for further information should be addressed to the Permissions Department, John Wiley & Sons Canada, Ltd. The purchaser may make back-up copies for his or her own use only and not for distribution or resale. The author and the publisher assume no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information contained herein.