Posted by: Alan Pitts | April 18, 2011

Split Rock, Wyoming

As the weather is getting warmer I’m getting really excited to break loose for some summer field studies and to see new rocks and regions.  So in the spirit of exploring new geology outside  my home region I decided to revisit some of last summer’s stock of geology photos I took while driving cross country from Virginia to California, and somehow failed to blog about them.

Here is my trusty copilot and BFF Becka setting up for a righteous handstand in front of Split Rock,  along the Sweetwater River Valley in Wyoming

The rock being hand-stood upon is granite, or ( for the sake of finishing this blog tonight) lets call them granitic, which began as a magma pluton and very slowly crystallized at depth from molten magma to a solid rock body.

This slow cooling process allowed the growth of these impressive euhedral feldspar crystals, with a finger for scale (and another finger to establish the proper scale on fingers).

And these:

I like to think the rocks in my home region as pretty darn old, the Grenville rocks of the Blue Ridge Province in Virginia are about 1,200 million years old,  a much greater amount of time than I can comprehend with out breaking it down.  These rocks are easily twice that old, from the Archean and somewhere around 2,500 million years ago ( I’m trying to break myself of the habit of using Billions since it is not used the same in all places, so from now on will be in thousands of millions or Ga, giga annum)

Here is a Google image to get an aerial look. The photos and handstands were preformed on the small fish-shaped rock outcrop at the bottom of the picture looking north towards the larger exposed rock body.

Here is a closer view of the outcrop we were on:

The whole outcrop is sliced by a series of more or less parallel joints.  Here is an annotated version of the above image to show the jointing, for those having trouble seeing them.

And this for those who might be having a hard time seeing the blatant  “fish-shapedness” of this hunk of granite.

Ha ha, always good to have multiple working hypotheses right ? Ok, but seriously, back to the joints…

Granite forms at depth in the earth, under great pressure.  As the rock cools and is eventually exposed it experiences less pressure and expands and contracts, forming joints.

These joints offered some protection from the wind where we found some resilient plant life trying to make a living for themselves on the unforgiving granitic uplands.

Or maybe it is dead…. interesting nonetheless.

As well as this cactus:

I give these joints a big two thumbs sideways !

Split Rock served as a natural landmark for pioneers along the Oregon Trail making the long and grueling journey west.  This image is from the Wyoming Historic Preservation Office looking at Split Rock from the proper angle, which I think is NE from our location and looking N/NW.

If you went to elementary school in the mid 80’s to early 90’s you might remember this stop from the incredibly popular and now classic computer game Oregon trail.   Back when I was a little kid on the Oregon Trail (computer game), I never took the opportunity to stop and enjoy sites like these.  Normally by this point on the journey I had lost several family members to dysentery and had barely enough rations to make it to the next outpost.

Here is a picture of me in front of Split Rock with the Oregon Trail  in the valley below crossing my body at the waist.

Or maybe its the trail crossing my body at the shins, I’m not sure, but its one of those, we didn’t stick around long enough to find out.  Because like the early pioneers we too were on a journey west and still had many miles of new rocks and regions ahead of us.

Above is our Chevy great white whale of a cross-continental vehicle.  The ‘Burban as we liked to call her, was like a modern day diesel-powered equivalent to the covered wagons traversing this country a hundred years earlier.  The Burban carried us more than 2000 miles over the Appalachian Mountains, across Mississippi and through the Great Plains in two days, all with out a single broken axle or failed river crossing.

I really love Wyoming, and cant wait to return.

I still have a few more from Wyoming and the journey west that I want to get out before this summer starts, which is the official deadline I’m giving myself on last season’s material.

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