[OM] Re: (OM) OT Yosemite Park

Subject: [OM] Re: (OM) OT Yosemite Park
From: "Scott Gomez" <scott@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Sat, 18 Feb 2006 13:23:09 -0800
What Moose said. :-)

The Sierra are most easily visualized as a large, rectangular "block".
If one thinks of that block as having originally been horizontal, it
would have been hundreds of miles long from northwest to southeast,
about 100 miles wide (roughly east to west), and some 3 miles thick (at
least, as far as is exposed). Now push down the western edge, relatively
evenly all along its northwest-southeast length, so that it pivots the
entire block, raising the eastern edge. The result is much like you
actually find... Relatively gradual slopes on the western side as one
leaves the central valley (traveling up what was once the flat upper
surface of the block), and very steep slopes on the eastern face where
the "originally vertical" edge of the block that had been hidden
subsurface rose up from the basin-and-range province to the east.

One can get an idea of how abrupt the slope on the eastern face of the
Sierra by comparing the altitude of Lone Pine, CA airport with Mt.
Whitney. Lone Pine airport is almost due east of Mt. Whitney, the
airport altitude is 3680 feet (1122m). Mt. Whitney is 14,505 feet
(4421m). Straight-line distance between the two is just over 13 miles,
yet in traversing the first half of that distance, one gains only about
3000 feet in altitude.

Virtually the whole of the Sierra has been glaciated as was mentioned by
Moose and Winsor. On the trails west of Lake Tahoe, the scored and
polished surface is plainly visible, as are lots of (sometimes very
large) erratics. Towards the south and east there is lots of evidence of
volcanism, with many areas where geologically recent outflows are
visible on the surface. The whole of the Mammoth Lakes region is a large
caldera (running roughly east-west from Lake Crowley in the east to
Mammoth Lakes in the west) that's been the subject of some concern in
recent years.


If you use Google Earth to view the area around Lone Pine, CA, you can
get a decent feel for the Eastern Sierra terrain. In my opinion, the
drive up US395 from Victorville, CA, north towards Lake Tahoe is one of
the more interesting drives one can make in California. Everything from
the high desert (about 4000 feet) in the Mojave at its south end to the
high peaks of the Sierra, with lots of cool stuff to see along the way.

I'd also recommend John McPhee's book, "Assembling California" for a
decent perspective on CA geology/geography, written by a layman. McPhee
has been a writer on many subjects for "The New Yorker" magazine for
many years. Or, if one is really interested in this stuff, his "Annals
of the Former World" (which includes "Assembling California") and
constitutes the results of some 20 years of traveling, meeting
geologists and learning about the geologic make-up of the USA along a
track that follows US Interstate 80 from NYC to San Francisco.

-----Original Message-----
From: olympus-owner@xxxxxxxxxx [mailto:olympus-owner@xxxxxxxxxx] On
Behalf Of Brian Swale
Sent: Saturday, February 18, 2006 1:04 AM
To: olympus@xxxxxxxxxx
Subject: [OM] (OM) OT Yosemite Park

Hi all

Another aspect of the Yosemite photos in that book by Ansel Adams that I
mentioned, is that many of the shots were taken away above the valley

Classic Adams sites such as Half Dome, El Capitan etc are placed in
perspective in relation to the surrounding landscape, and surprise,
surprise, with the slight exception of Half Dome, they hardly poke above
the general level.

The huge landscape above is characterised by extreme barren-ness. Smooth
rock surfaces and no soil..  I do not know the geological background, or
the rock types, but I'd take a guess at the rock being something very
hard such as granite, (but some columnar rock sites give the lie to that
assertion) so that an extremely long time is needed for soil to form
through normal erosion 
processes.   Secondly, if looks as though the area was covered by a
ice sheet within maybe the last 50,000 years, and anything not araldited
into place was shifted a long way..

A hostile environment up there, most times, I'd guess.


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