Rotational slumps are landslides that occur when a slumping block
slides on a curved failure surface, causing the upper surface to
tilt back.
Mudflows occur when unconsolidated materials become saturated
with water during snowmelt or rainstorms and flow downslope.
At times, combinations of both types of landslide occur together,
for example at the Wildwood slide site in north Calgary.
The Wildwood slide site in north Calgary (Photo: P. Wozniak)
The stage was set for failing slopes when large quantities of
glacial and lake sediments were deposited during the Ice Age in the
broad pre-glacial Bow and Elbow river valleys. The rivers cut down
through these sediments to create the steep slopes that we see
along the rivers today. These steep slopes are unstable and may
fail when the ground becomes saturated with water.
Human Factors:
Landslides are natural phenomena, but some slope failures of the
last several decades were caused in part by human activity. Removal
of material from the base of slopes, placing earthfill at the top
of slopes, and excessive lawn and garden irrigation on top of
bluffs contribute to slope failures.
To Log this EarthCache please email the answers to the follow
questions:
- Please estimate the dimensions (height and width) of the
Wildwood Failure surface.
- Please estimate the current height from the bow river to the
top of the Slump Debris field.
Also you will need to post a photo with your log of you or your GPS
with the Ridge in the background.
Sorry Folks, no photo and your log will be deleted.