Erosion

 


Erosion:

  Detachment (picked up)

    Transportation (moved)

      Deposition (deposited/dropped)


Erosion Shuffle: Picked up and moved (Opens in YouTube)
Water erosion simulation (erosion pans)

   

dust storm

Black Sunday: April 14, 1935, Pampa, TX. Wind erosion was a terrible problem in the Great Plains of the United States in the 1930's during the Dust Bowl, and again in the drought of the 1950's. These "Black Blizzards" are the result of tiny soil particles (silts and clays) suspended high into the atmosphere. Sometimes soil particles are carried in the global jet stream currents.
 
These were taken in various places in the Texas and Oklahoma Panhandles from1994 to 2005.
Wind erosion is still a problem at times in some areas in the Great Plains, as can be seen in these photos. These were taken near Olney, TX circa 1998. (These trees did not grow with their roots out of the ground!) This result of erosion detaching and removing soil is called pedestaling.
tree roots without soil...sand and soil blown out from under tree

 
visibility obscured by wind erosion wind erosion on bare field wind erosion before a thunderstorm wind erosion on bare, sandy field
Wind erosion limits visibility. Wind erosion can begin with windspeeds as low as 5.8 m/s  (13 mph) at the soil surface. Downdrafts before thunderstorms often generate wind erosion. Sandy soils are particularly susceptible to wind erosion
Though wind erosion will always occur, it will probably never be as bad in the United States as it was during the Dust Bowl because farmers are using better technology to protect the soil. Even a small amount of residues (leftover plant parts) on the soil surface helps reduce erosion by decreasing detachment and transportation, and encouraging deposition. Wind erosion was not as severe in the "Filthy Fifties" due to the use of irrigation and better management practices.

However, wind erosion like this is currently a problem in Western China, and in the Sahel and Sahara regions of Africa.
Link to story about April 2001 China dust storm

Water erosion simulation (erosion pans)

(Click on following images for larger picture. Opens in new window.)


Water can detach and transport (wash away) soil, leaving rills (the small finger-like areas just larger than the pen), or it can create gullies that may be deeper and wider than a car.
(More on rills)

Water can also remove (detach and transport) a thin layer from the soil surface. This type of erosion is called "sheet erosion" and is difficult to detect.

rills
Water erosion and deposition left a sand bar in a field When water washes soil out of one place, it leaves it somewhere else (deposition). The sand bar in this field was deposited after a thunderstorm that created runoff and erosion upslope. 
Soil that has no vegetation (plants) to protect it is the most vulnerable to both wind and water erosion. Soil was eroded out of the field on the left, and carried into the ditch beside the road. Some of the soil was left in the ditch after the runoff subsided.
 
ditch filled with deposited sediments after soil was eroded from the field
soil under parking lot washing out   Erosion is not just an agricultural problem. The drainage area for this parking lot was poorly designed, resulting in this gully, severe damage to the pavement, some exposed pipe. Such problems are expensive to repair.
 
  In urban areas, the most severe erosion problems occur during construction of new buildings, factories, parking lots, etc. The land is cleared of all vegetation, so it is unprotected from wind or water (rain). Often, contractors are required to take measures to limit soil loss from the site. The hay bales were placed in this ditch to slow the movement of water. When the water slows down, it loses energy, which decreases detachment and transportation, and increases sediment deposition.
 
hay bales in ditch to slow water
cloth barrier fence, often called a silt fence   This cloth barrier, or silt fence, slows the movement of water off this construction site. You can see places where the soil has accumulated on the left side of the cloth barrier (near the chain link fence). If not for this barrier, the soil would have been transported off the construction site.
 
TEKS: conservation
   Grade 3: 112.5.b11A
   Grade 4: 112.6.b1B
     Actually, the b1B in most grade levels addresses conservation
     Renewable/nonrenewable/inexhaustible resources – some address
     conservation and human impacts
   Grade 1: 112.3.b10 A-C
   Grade 3: 112.5.b11A
   Grade 5: 112.7.b11C
   Grade 7: 112.23.b14C (desertification, deforestation, urban
     sprawl/development, ...)
   Grade 8: 112.24.b14C (desertification, deforestation, urban
     sprawl/development, ...)
   Env Sys: 112.44c4E (desertification, deforestation, urban
     sprawl/development, ...), 5C
TEKS: erosion takes time:
   Grade 4: 112.6.b10A
   Grade 5: 112.7.b11A&C
   Grade 5: 112.7.b12A
   Grade 6: 112.22.b14A
   Grade 7: 112.23.b8A (kinetic energy related to erosion)
   Grade 7: 112.23.b14 A-C
   Grade 8: 112.24.b12A rock cycle
   Grade 8: 112.24.b14 A&C
   Int Phys Chem: 112.42c8A

 

Updated 05-03-2013. Copyright 2005. Clay Robinson, Ph.D., as to all resources: Materials may not be reproduced without Dr. Robinson's written consent. Students are prohibited from selling (or being paid for taking) notes or webpages during this course to or by any person or commercial firm without the express written permission of the developer of these pages.