[BR-Crater] photos from Stratofox 4 trip to Black Rock

[Ian Kluft]

On Mon, Aug 20, 2007 at 11:20:51AM -0700, Ian Kluft wrote:
> I separated out the pictures of rocks from the general camping trip
> because each appeals to different audiences.
>    general: http://www.stratofox.org/pics/sf4-200708/ian/
>    rocks:   http://www.stratofox.org/pics/sf4-200708/ian/rocks/

Brad's photos from Stratofox 4 are up on the web site.  I split them up
the same way.
    general: http://www.stratofox.org/pics/sf4-200708/brad/
    rocks:   http://www.stratofox.org/pics/sf4-200708/brad/rocks/

This one was particularly interesting.
   http://www.stratofox.org/pics/sf4-200708/brad/rocks/CRW_6907.jpg

A different view of the same rock is shown in one of my photos.
   http://www.stratofox.org/pics/sf4-200708/ian/rocks/img_9949.jpg

The intrusive black rock in there is the same kind as we've found laying
among loose rocks in the area.  At first it looks like obsidian.  Brad
confirmed it isn't obsidian.  It's very hard, not brittle.  But seeing
it in that rock was yet another interesting observation because volcanic
obsidian wouldn't be found like this - it would be in a lava flow, not
in fractures of other rocks.

A quick summary of the areas where the photos are from...
   Friday 8/17 evening: N of Upper High Dry around 41.0014°N 118.9622°W
   Saturday 8/18 morning: SW of Upper High Dry around 40.9797°N 118.9731°W
   Saturday 8/18 afternoon: E of Upper High Dry around 40.9998°N 118.9386°W
   Saturday 8/18 evening: NNE of Upper High Dry around 41.0038°N 118.9616°W
(I got these coordinates by clicking on the approximate areas on TopoZone.
Sorry, GPS download plots won't be done before this weekend.)

Some of the areas we explored this time are as much as 2-3 miles apart.
In all places, breccias were easy to find.  Above a certain point the
rocks became all breccias.  Below that they were thoroughly fractured
rocks containing some breccia dikes.

The exception was the Saturday afternoon area at the overlook of the
east arm of the Black Rock Desert, where we found breccias everywhere,
and did not find the fractured rocks.  We didn't venture down the rougher
section of the 4x4 trail east of there since we only had 2 vehicles.