Serpentine Post Updated

I just updated my Serpentine: A Group of Minerals post from last summer with some new geoblogosphere links relating to fibrous and asbestiform minerals, including erionite, a zeolite group of minerals that can occur in acicular to fibrous mineral habits. The reason for the update is that the Mineralogical Society of America recently released their Proposed Position Statement on Asbestos, as reported on more thoroughly by Chuck Magee at Lounge of the Lab Lemming and Steven Schimmrich at Hudson Valley Geologist (links below).

• Erionite and Cancer in Cappadocia, Turkey (Olelog, November 5, 2010)


• Guest Post - Naturally Harmful Metals and Minerals (The Geology P.A.G.E., December 29, 2010)


• Concerns over erionite dust as cancer source (Arizona Geology, January 5, 2011)


• Mineralogical Society of America proposes a position statement on Asbestos (Lounge of the Lab Lemming, March 1, 2011)


• Asbestos (Hudson Valley Geologist, March 9, 2011)

I'm particularly amazed that any regulatory agency would use a length:width ratio of 3:1 to describe a mineral as fibrous. Plagioclase would therefore be fibrous much of the time (though certainly not asbestiform), as would these huge cave crystals of selenite.

Where in the West: Half Dome from Olmsted Point

Yes, it's Half Dome, as Cole Kingsbury of Chaotically Flow-Banded so astutely (and quickly) noted. I figured this month's WITW would be easy, but thought perhaps Half Dome would be overlooked for a while longer, off there in the distance down the upper reaches of the Merced River drainage basin, beyond a hanging valley above Tenaya Canyon. Half Dome is a classic exfoliation dome, one that has been partly cut away along a regional joint system by the glaciations that formed Yosemite Valley. See this excellent picture of the exfoliation of Half Dome at EPOD.

It's a good thing that Ron Schott came up with the location from which the photo was taken — that location being Olmsted Point or, more likely, somewhere near the Olmsted Point pullout on Highway 120, the Tioga Pass Road. I'm sure I would have eventually found the point using Google Earth, but Google Street View just shows fog. Unhelpful.
I don't see a name for the particular side canyon or creek below Olmsted Point, but both the side canyon and main canyon are U-shaped drainages carved by glaciers. The topo map is from MSRMaps, courtesy of the USGS. It's a little messed up as far as the splicing goes, but the north-south dividing line between Sections 31 and 32 is about a mile.

View Olmsted Point in a larger map

Besides the glacial pavement, glacial polish, glacial striations, and glacial erratics (lower left of the WITW photo) already noted in the comments of WITW: March 2011, there is a nice criss-crossing of joint sets, sets that are roughly orthogonal. One joint set, as seen in my photo, is parallel or sub-parallel to the direction of glacier movement indicated by the striations. Larger, more regional fracture patterns can be seen in the Google Map view above. The regional fracture pattern at N30E is parallel to the hanging valley below Olmsted Point.

Too bad I didn't have my Brunton with me while on this summer, 2000, roadtrip. It mostly wasn't that kind of a trip, more of a family thing with roadtripping and geology added. The particular family involved (mine) has difficulty dissociating roadtripping from geology, and indeed, why should we?!

Roadside Geology of Yosemite Valley by Garry Hayes of Geotripper.
Roadside Geology of Yosemite Valley at Geotripper Images.

Two Years Ago Today: Circle Around the Sun at the Iditarod

Two years ago today, on a Saturday, I was in downtown Anchorage for the ceremonial start of the Iditarod, and this sun halo (22° halo) and associated sun dog (parhelion) was visible to the east over the Chugach Mountains.
As for this year, the ceremonial start was March 5th, and the official re-start in Willow was yesterday, March 6th. The race is now underway; current standings can be accessed here.

I love Alaska in the winter, at least in short doses, though I didn't make it up there this year.

A more recent (and more colorful) sun dog at EXPLICITLY UNEXPLICIT.

Light and Color on a Cozy Indoor Day

It's cloudy and threatening snow outside, and I'm staying indoors, pretending we have a warm stove radiating heat, drinking coffee mixed with cocoa. This one corner of our little house usually looks fairly uncluttered, and sometimes the plants even get a bit of light. Not today. The upper shelves are stacked with various books, mostly geology or travel related, though not entirely. Titles I can read from here include A Garden of Bristlecones, Blue Highways, Alaska: Saga of a Bold Land, Topo! for Nevada, and Nevada Off the Beaten Path. I recommend all these books, though I can't comment about the Topo! program, as I haven't used it.

I'd say that it's probably cabin fever that's keeping me indoors, but that's not right: surely cabin fever would send me outside despite the dreary weather. It must be something else.
Over near the front door, a door used only to retrieve mail, the plants look bright and cheery, even as if the sun were shining through the clouds, but their color has as much to do with the camera setting as anything else.
Um, maybe it's time for more coffee.

Where in the West: March 2011

The Where in the West series has become an erratic, semi-quarterly to semi-annual feature on this blog, with March being a favored month. The March, 2011, edition of WITW should be fairly easy, so I'm expecting the name of the obvious geologic and geographic feature, and would also like the approximate location from which I took the picture along with the identification of some geologic features. I can see or infer at least four; but then, I know where it is. :)

Photo was digitized from a 2000 print
© 2011 Looking for Detachment
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