From the Lamar Valley Ranger Station you can look up and
down valley to see glacial U-shaped valley. This valley does
not look exactly like the classic outline of a U valley
because landslides and erosion have worn down the sides of the
valley.
Glaciers tend to follow the preexisting drainage. They take the
V-shaped valleys that flowing waters carve and widen out the bottom
of the valley into a U. This leaves steep sides that are supported
as long as the ice remains in the valley.
Once the glacier melts, the valley walls no longer have support.
Where the bedrock is solid such as Yosemite, the valley walls
remain steep. However, in this valley the bedrock is made up of a
conglomerate that does not have the internal strength to maintain
the steep walls.
The hillside behind the ranger station to the northeast is
evidence that the bedrock is unable to maintain a steep slope. The
landslide can be recognized by the bumpy, (hummocky) area with a
crescent shaped steep slope at the top that is typically less
vegetated than above and below. The steep sloped area is called the
head of the slide and the bottom of the slide is the toe. You may
need to go a short way east on the road to get a more sidelong view
of the head to easily recognize it.
Logging requirements:
Send me a note with :
- The text "GC14YV8 Lamar Valley – A Glacial Cut Valley" on the
first line
- The number of people in your group.
- Look on the opposite side of the valley and identify how many
more slides are visible.
The above information was compiled from the
following sources:
- NPS informational Pannel
- Fritz, William J., Roadside Geology of the
Yellowstone Country, Mountain Press Publishing Company, May
1989.
Placement approved by the
Yellowstone National Park