|
Ninety percent of all avalanches occur on moderate slopes with an angle
of 30° to 45° (snow tends not to accumulate on steeper slopes). Avalanches
occur when the gravity pushing the collection of snow at the top of the
slope is greater than the strength of the snow itself. A change in temperature,
a loud noise, or vibrations are all that are necessary to trigger one of
these snowfalls that begin at a "starting zone." The avalanche continues
down slope along the "track" and ultimately the avalanche fans out and settles
in the "runout zone." Avalanche prevention and mitigation involves a variety of methods. Snow fences are built to prevent the buildup of snow in starting zones, structures are built to stabilize snow. deflecting walls are built to divert avalanche flows away from buildings and even entire towns. Sheds build across roadways that pass through persistent avalanche paths can help to protect motorists from avalanches. Additionally, the reforestation of slopes with trees helps to prevent avalanches. |
References:
http://geography.about.com/library/weekly/aa022299. Free Web site. Last Visited February 2004
Images:
Heading from Flaming Text, http://www.flamingtext.com/net-fu/example.html Last Visited February 2004 Free Web site
Background from Flaming Text, http://www.flamingtext.com/backgrounds Last Visited February 2004 Free Web site
Button from Flaming Text, http://www.flamingtext.com/buttons Last Visited February 2004 Free Web site