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In Scandinavian Mythology, Valhalla
literally translates to, "Hall of the Slain". According
to the myth, an enormous Hall was located at Asgard, ruled over by
the supreme God Odin. It was said that those that died in
battle were led to Asgard by the Valkyrie.
No less majestic is the small hanging valley of Valhalla,
located some 15 miles from trailhead along the High Sierra
Trail. Standing at the head of the valley, like the crest
from the helmet of one of the famous Valkyrie, stands the 2,000
foot monolith, Angel Wings. The South face of which, is the
largest granite wall in Sequoia National Park.
Like it's closely related relatives in other parts of the Sierra
Nevada, the story of Angel Wing's formation is one of powerful
geologic forces, and glaciation.
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Mountain Building
The earliest granite of the Sierra Nevada formed some 200
million years ago, when much of the area was covered with an ocean.
Plate tectonics, the movement of the plates that form the
earth’s crust, played an important role in the formation of
the Sierra Nevada, and is also responsible for the volcanic and
seismic activity we experience today. Picture the earth’s
crust as being made up of puzzle pieces that glide over a layer of
molten magma.
In a process described as subduction, the Pacific Plate dropped
under the North American plate in a process that still persists to
this day. The resulting friction between the two plates
resulted in molten plumes of plutonic rock to form beneath the
surface. The hotter, and relatively lighter, plutonic
material, "floated" towards the surface and joined to become the
massive batholith that makes up the Sierra Nevada mountain
range.
As the subduction continued, uplift was also shaping the
mountain range. Some 80 million years of erosion, scraped
away the marine sediment layer that rested on the Sierra batholith,
but there was still much work to be done to shape the landscape
that is familiar to us today.
Glaciation
The story of how glaciation shaped the Sierra Nevada is a
familiar story to most students of California Geology, dating back
to John Muir and his speculations on how Yosemite Valley was
formed. While plate tectonics, plutons and batholiths could
be described as forming the large scale features of the Sierra
Nevada, it was glaciers that sculpted and formed much of the
scenery we are familiar with afterwards. Glaciers work on the
landscape can be evident in several ways. The first is, and
the most obvious, is the changing of V shaped valleys to U shaped
valleys. An excellent example of this is the Hamilton Lake
basin where you will be standing at the cache page coordinates.
Landscapes that are not completely buried by the ice are
"sharpened" by glaciers. Angel Wings is a good example of
this process. As glaciers descended the valleys on either
side of the formation, rocks would be "plucked" from the sides, and
like a course grade of sandpaper, sharpen the knife edge ridges
into what are commonly called "aretes". At higher elevations,
glaciers would sculpt peaks with wide cirques with steep headwalls,
much like what you will see at the far end of Hamilton
Lake.
Now with those formalities out of the way....
Geology and Rock Climbing
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Few recreational activities are so dependent on
Geology as Rock Climbing. Visible from the coordinates above
is one of the largest granite faces in the Sierra Nevada, Angel
Wings. Due to it's remote location, it's understandable that
there are currently only half a dozen or so recorded routes that
scale the main South Face (denoted with red lines on the picture to
the left). Most of the routes take a minimum of two days to
ascend, requiring, what is usually, an uncomfortable night on the
sheer face. The following are some of the features that
rock climbers utilize, not only for upward ascent, but also for
placing protection (usually in the way of camming devices, "nuts" ,
and pitons): |
Splitters:
Gazing up at the 2,000 foot wall, one of the most obvious
feature are cracks, that run both vertically and
horizontally. Cracks, or sometimes called splitters, are due
in large part to a process called exfoliation, which is the process
in which shells of rock detach from the main rock mass along
exfoliation joints. These cracks can range from thin insipid
seams, to massive and cavernous "chimneys". As layers of the
rock are cast off, like an onion, the underlying rock expands
slightly, producing vertical or curving cracks that split the rock
perpendicular to the rock face.
Flakes:
Flakes are slabs of rock that are in the process of exfoliation
from a cliff.
Dihedrals:
Dihedrals are places where two adjacent rock walls come together
to form a right angled corner (or something closely approximating
it). Dihedrals usually have their origins in rockfalls.
When a slab of rock from from a cliff face, often detaching
along a splitter and an exfoliation joint, the resulting fresh
faces form the dihedral.
Dikes:
Dikes are sheet like bodies of rock that form when magma is
injected into a crack in older rock. Dikes are common
throughout the Sierra, and can reach bands as thick as a foot in
width. For reasons having to do with mineral size and
composition, dikes tend to be more resistant to weathering and
erosion than the granitic rock they intrude. In some
instances, dikes can appear to protrude out, providing edges and
knobs that are perfect for climbing.
Logging Requirements:
From a vantage point between the cache page coordinates and
where the photo above is taken (probably the first clear view of
the face where the trail crosses Hamilton Creek), choose one of the
five routes that I have traced in the picture above. For
simplicity sake, we will arbitrarily number them from left to
right, 1 through 5:
- Please include in your email, the GC Code and Listing Title in
the subject line.
- How many people are in your party.
- From the route you have chosen, please count the number of
instances of the features listed above you can see from your
vantage point, that the route either crosses or follows (e.g. 2
dihedrals, 4 splitters, 1 dike, etc)
- For a brief minute, let's suspend reality and say you are a
world class rock climber, intent on ascending Angel Wings by the
route you have chosen. Since ascending the route will more
than likely take two to three days, please describe where you will
be spending the night on the wall (distance from the base,
estimated size of ledge if there is one).
- Suspending reality for one more brief moment, lets say that you
are caught in some unseasonably bad weather and are forced to
retreat the following day. How many rappels will it take from
your bivouac spot to reach the ground (assuming a 150 foot
rope)?
- For the sake of verifying the visit to the cache page
coordinates, there is a signed cutoff from the main trail
just West of Hamilton Lake, to an aging and decrepit structure that
is a short distance from the trail. What does it appear that
this structure has been used for and does it still appear to be in
use at the present?
References:
Geology Underfoot in Yosemite National Park by Allen F. Glazner
and Greg M. Stock, 2010
Sequoia and Kings Canyon National Park Geology Overview
Scandinavian
Mythology from Wikipedia
Geology of
the Sierra Nevadas by Mary Ann Resendes
The High Sierra: Peaks, Passes, Trails, R.J. Secor