As
you embark or continue your journey to discover and explore
beautiful and historic rocks, waterfalls, peaks, creeks and other
wonders, please keep in mind that these places need to remain wild
and protected so that they may be enjoyed by others for generations
to come. Please be diligent in respecting these sites by doing the
following:
- Please keep trash with you at all times, do not leave it behind
in these pristine places.
- Bury human waste 6 inches deep, make certain you are at least
50 paces away from any water source and PLEASE bring your toilet
paper and sanitary items back out with you.
- Keep food and all scented items on your person at all
times.
- Support wildlife by allowing them to find their own food, do
not feed them.
- Allow plants to grow and water to stay clean by staying on
trails, bike paths and roads.
Thank you, Yosemite Wilderness Management
The coordinates are a hike from the nearest parking and includes
a few river crossings. Stay on the trail even if it is muddy. The
final coordinates take you along a granite outcrop a short way away
from the trail. Look south up the valley to get the overall picture
of a glacially cut 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. The glacial ice puts the most erosion on the lower
portion of the valley sides, so it widens out the V shape into a U.
Additionally, the flowing ice erodes the insides of meanders,
straightening out once sinuous river channels. Unlike water where
the inertia of the water causes erosion on the outside of a curve
as the water collides with the bank in order to change direction
(see Merced Meander EarthCache), flowing ice moves slow enough that
the same inertial forces are not at play. The erosion of flowing
ice is greatest where the ice moves fastest, and that is where the
slope of the valley is greatest. The inside of the bends is where
the topography drops faster than the outside of a bend. The end
result is the straightening and widening of the valley.
At this high elevation, the Lyell Fork was completely filled
with glacial ice multiple times during the most recent set of
glaciations including the Tahoe and Tioga glaciations which did not
fill much of Yosemite valley. In fact, one of the few remaining
glaciers in the Sierra Nevada (the Lyell Glacier) is located at the
head of the valley.
While steep walled, almost vertical walled valleys such as
Yosemite are often portrayed as typical of glacial valleys, they
are actually at one extreme of the range of glacial valley
profiles. In addition, Yosemite Valley has been filled in by up to
2000 feet of sediment. The Lyell Fork, having been scoured by a
glacier only 20,000 years ago has retained much of the
geomorphology of a glacial valley. This valley’s smooth, open
U-shaped profile is actually more typical of glacial valleys. The
valley is also quite straight extending southeastward
Logging questions:
- The text "GCGC2M295 Tuolumne River Glacial Valley Geomorphology
" on the first line
- The number of people in your group (put in the log as
well).
- Describe the symmetry of the valley and compare it to a U
shape.
- What are the downstream coordinates where the Lyell Valley
changes course from its glacially cut straight northwest
orientation?
The following sources were used to generate this
cache:
- Matthes, Francois. 1930 USGS. Geological Survey
Professional Paper 160 Geologic History of the Yosemite Valley.
http://www.nps.gov/history/history/online_books/geology/publications/pp/160/index.htm
Last Updated: 28-Nov-2006
- Kiver, Eugene and David Harris. 1999. Geology
of U.S. Parklands Fifth Edition, John Wiley & Sons,
Inc.