Wednesday, February 29, 2012

South by West of Center: Monitor Valley Salt Flat or Dry Lake

We were driving up Monitor Valley towards Potts Ranch Hot Springs (yes, up is north in this case), when we both spotted a strange whiteness on some hills located just north of the playa in the center of the valley. I had noticed this phenomenon at this site once before, but had attributed the light coloring of the hills to white beds of sediment, poorly welded ash-flow tuff, or air-fall tuff in the Tertiary volcanic section, and hence, had just driven on. This time, it looked as though dust or salt had blown northward off the playa.

We decided to check it out. We turned right on the decent side road that crosses the valley, drove to the closest whitish hill, and stopped amidst some white to very pale green bushes. The unnamed playa is located about 23 to 24 miles south by west of The Geographic Center of Nevada. (MSRMaps location).
I'm assuming the bushes are fourwing saltbush, or Atriplex canescens, in its wintry, somewhat non-leafy form.
Yes, they are covered by a thin coating of a white salt, an encrustation that flaked off easily into my hands.
To investigate this phenomenon further, we walked out onto the playa, a soft playa characterized by crusts. The photo (above) shows how the bushes gradually lose their salt crust going away from us along the northeastern playa edge, and shows part of the Monitor Range in the distance.
The crusty, soft surface is partially covered by windblown detritus.
The wind direction while we were out there was from south to north (right to left in the photo), which explains the salt coating on the bushes, unless the salt coating developed when winds from the south were blowing across a playa covered or partially covered with water.
When the playa surface is examined closely, circular features can be seen in the crusts. These circular patches will come up as blocks if prodded, and are (I hypothesize) most likely some form of biotic or cryptobiotic crust.
Looking back to the north toward my truck: the salt on the bushes is somewhat variable in distribution, apparently thinning away from playa's edge.
Now I turn and look down the five-mile length of the Monitor Valley playa. Monitor Valley continues another 25 miles beyond the south end of the playa, ending in the faint turquoise mountains in the far distance: the southern part of the Monitor Range. There is water on the playa in the far distance on the left (hard to see in this shot), and we have spotted a couple unknowns on the ground in the middle distance.
We decide to walk across the soft, crusty surface to see what's out there.
It's an old, salt-encrusted wooden post, fallen from its previously upright position, along with some other stuff of unknown origin or purpose. Picking the post off the playa floor pulls up the salt crust, revealing white to pinkish crystals on the bottom of the crust. I didn't try a taste test.
Salt crusts (possibly partly biogenic) out near the wooden post.
Salt encrusted wood, looking for all the world like driftwood.
And now, for the cold walk back to the truck.

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