Geology Reference
In-Depth Information
Blowouts occur in areas where vegetation has been removed, leaving loose sediments
susceptible to wind erosion. Because particles must be dry for wind transport, the
boundaries of blowout features are defined by the surrounding groundwater. When the
blowout is deflated low enough that the sediments are moistened by groundwater, defla-
tion stops because the particles can no longer be easily removed by wind.
Scratching the surface
After a wind current has picked up some sediment particles, it brushes these particles
against other objects. You may have experienced this process if you've ever felt sand
stinging your legs at the beach. The stinging feeling is the brushing of suspended and
saltating sediment particles against your legs.
The blasting of sediments against another object by wind creates features of
wind abra-
sion.
Abrading by wind appears to polish some surfaces, making them a little shiny and
very smooth.
Rocks that are subjected to wind abrasion have recognizable features and are called
ven-
tifacts.
Ventifacts have multiple surfaces eroded by wind abrasion. Figure 14-2 illustrates
how a ventifact is created.
Figure 14-2:
Creation of a venti-
fact by abrasion.
First the wind abrades one side of the rock, creating a smooth, flat surface in the direc-
tion of wind flow. If the rock's position changes or the direction of the wind flow
changes, another flat, smooth surface is created by abrasion.
Just Add Wind: Dunes and Other Deposi-
tional Wind Features
Geologic features created by wind depositing (leaving behind) sediments are usually one
of two types:
dunes
and
loess.
The distinguishing characteristic of these two features is
the size of the particles that build them. Due to the limited ability of wind to keep
