Monday, August 13, 2012

Death Valley, the place of dead things, deadness, and also dying.

Death Valley 

As a part of my geomorphology class, we went on a trip to Death Valley California.  It is a great place to view many surficial features like alluvial fans, salt pans, losing streams, dunes, etc.  It is such a great place for this because everything is DEAD!  There are no plants to block the geologist's view of the rocks and sediments.  

View of Badwater Basin in Death Valley from the east, looking west-ish.

So why is Death Valley so low?  It is part of the Basin and Range Province which is a part of the Earth's crust that is being pulled apart.  Death Valley has experienced both extensional (pull apart) shear and transtensional (things moving past each other and rubbing against each other) shear.  Here is a picture:

The blue area has dropped relative to the red.  This is why Death Valley is so low, in part.

From: 4D analogue modelling of transtensional pull-apart basins, 
  • Jonathan E. Wu, 
  • Ken McClay, 
  • Paul Whitehouse, 
  • Tim Dooley 
  • Marine and Petroleum Geology Volume 26, Issue 8, September 2009, Pages 1608–1623.

    The lowest spot in North America!  How far is 282 ft. or 85.5 m below sea level?

    That far...wait, what does that sign say?

    The water in the bottom of the basin is hyper-saline.  As the water evaporates, salt comes out of solution and crystallizes.  This is a very common process in arid environments.

    After all water has evaporated, a salt crust remains.

    The ONLY life we saw the whole trip, ladybugs and a tarantula (later).  Why are there ladybugs in the salt pan?  I have no idea.  If anyone can tell me why I will be happy and say "thank you".

    Me at the Mesquite Flats Sand Dunes in Death Valley.  
    Desiccation between dunes that has been recently exposed by wind scour.  You can see different levels of interdunal surfaces that look like steps leading off the right edge of the photo.  Man for scale.

    This interdunal area can be seen on Google Earth. 

    Here it is.  There are some beautiful star dunes that are formed by variable wind directions.  

    How can you not bury someone with all this sand available?  Jason Luke is the victim.

    Ubehebe Crater.  This is the result of  magma and water getting together in the subsurface...BOOM!  The groundwater was flashed into steam when magma came close to the surface.  Ubehebe is very young geologically.  Just a couple thousand years old. 

    A sailing stone at Racetrack Playa

    How the heck do they get there?  

    "The sailing stones are a geological phenomenon found in the Racetrack. The stones slowly move across the surface of the playa, leaving a track as they go, without human or animal intervention. They have never been seen or filmed in motion. Racetrack stones only move once every two or three years and most tracks last for three or four years. Stones with rough bottoms leave straight striated tracks while those with smooth bottoms wander.
    The sailing stones are most likely moved by strong winter winds, reaching 90 mph, once it has rained enough to fill the playa with just enough water to make the clay slippery. The prevailing southwest winds across Racetrack playa blow to northeast. Most of the rock trails are parallel to this direction, lending support to this hypothesis.[2][3]
    An alternate hypothesis builds upon the first. As rain water accumulates, strong winds blow thin sheets of water quickly over the relatively flat surface of the playa. A layer of ice forms on the surface as night temperatures fall below freezing. Wind then drives these floating ice sheets, their aggregate inertia and large area providing the necessary force required to move the larger stones. Rock trails would again remain parallel to the southwest winds. According to investigator Brian Dunning, "Solid ice, moving with the surface of the lake and with the inertia of a whole surrounding ice sheet, would have no trouble pushing a rock along the slick muddy floor."[4]
    A more recent theory[5] is that ice collars form around rocks and when the local water level rises, the rocks are buoyantly floated off the soft bed. The minimal friction allows the rocks to be moved by arbitrarily light winds.[6]" From Wikipedia.

    Dendritic drainage patterns on Racetrack Playa.

    The other living thing.  But not for long.  Something was wrong with his leg.

    Well, I've got to be honest, Death Valley is most interesting while sitting at home if you are not a geologist or geomorphologist.  I had a blast, but, well, I am a geologist.  The pictures are cool.