Section 15: Eolian Processes and Arid Landscapes

SLOs: eolian processes and dunes, semi-arid regions and desertification, landscape features.


Lesson 1:

Instruction

The processes of wind that erode, transport, and deposit surface materials are called eolian processes.  The main wind-erosion processes are: deflation and abrasion.  Deflation is defined as the removal or lifting of particles, while abrasion is labeled as the grinding or sandblasting of surfaces with particles aloft.  The chief wind-transportation processes are: saltation and surface creep.  Saltation occurs when smaller particles are moved by bouncing windward, while surface creep arises when larger particles are moved by rolling windward.  The most important wind-deposit landforms are: dunes and loess deposits.  In Ventura County, sand dunes are the foremost landforms created by eolian processes.  Dunes come in multiple classes, including crescentic types (such as barchan, transverse, parabolic, and barchanoid shapes), linear types (like longitudinal and seif shapes), star types, and other types (exemplary dome and reversing shapes).   

Photos and Images

(star-shaped dunes)

(dome-shaped dunes) (deposits without dunes) (barchanoid-shaped dunes) (transverse-shaped dunes)

Quiz

Where are you most likely to find dunes in Ventura County?  Why?

 


Lesson 2:

Instruction

Eolian and fluvial processes create desert landscapes.  Most of the worlds dry places are located in arid or semi-arid regions.  Ventura County is within a semi-arid region, but none of the county landscape is considered a desert.  However, in the Los Padres National Forest, the north-eastern most terrain borders high desert to the east.  Desertification, or the changing of any landscape into a desert landscape, is a major problem globally.  Recent human-induced climate changes are exacerbating this phenomenon.  Although desertification is not occurring rapidly in Ventura County, this global trend is still a threat.           

Photos and Images

 
 (high desert in the Los Padres National Forest)

Quiz

Your assignment is to do one thing to prevent climate change and desertification in your everyday life.  Global warming, climate change, and desertification are all linked.  Therefore, if global warming is reduced then desertification is reduced as well.  Reduce your consumption or creation of greenhouse gases (such as carbon dioxide) in any way to complete this obligation.    

 


Lesson 3:

Instruction

There are many beautiful landscape features within Ventura County.  Eolian processes have the capability to create yardangs.  Yardangs are streamlined rock structures, which are ridged based on rock type layers and aligned parallel to wind direction.  Eolian and fluvial processes can also expose rocks that would otherwise never be visible on the surface.  Some rocks appear pitted and grooved because of eolian erosion; these are identified as ventifacts.  Ventifacts are literally artifacts of wind erosion.  It takes a long time for these landscape features to evolve into what we now see.  The ones shown below are all preserved in our local and national protected areas for the benefit of current and future generations.

Photos and Images
    (yardangs in the Los Padres National Forest)          (rocks exposed by eolian and fluvial processes)  (ventifacts near the Santa Monica National Recreation Area)    

Quiz

Using Google Earth, try to locate an interesting landscape feature created by eolian processes.  Where is it and what does it look like?     


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2006 Jessica Douglas