Death Valley 

I have always wanted to visit the hottest, driest spot in North America - Death Valley.  The theme of water, lack of water and extremes in temperature, altitude, and geologic activities can all be found in Death Valley.    Sitting on top of a remarkably symmetrical alluvial fan lies Furnace Creek, the hub of Death Valley National Park. The visitor center is in this location as well as the very few sources of water in the valley.  In the photo below you can see the desert surrounding the small space of water and vegetation.   I wondered what caused this situation to happen, how could the geologic history evolve such that no springs, a river of the more considerable preponderance of springs appeared?  The entire valley has very little water (less than 2 inches) year round. The scarce springs and surrounding lush oases support thriving plant communities and attract a wide variety of animals. They are one of the Mojave desert's most biologically diverse environments.  According to research on USGS, Much of the water drawn aquifer was charged many thousands of years ago, during the Pleistocene ice ages, when the climate was colder and wetter.   Today's drier climate does not provide enough precipitation to recharge the aquifer at the rate at which water is being withdrawn. (USGS, retrieved from Web Site).

Furnace Creek Inn, near the site of the original spring. 

Photo by M. Moreno, USGS.

Sticking with the lack of water theme: Our second stop at in Death Valley was Bad-water and the salty remains of a wetter time.  In looking up research, I was able to find during the Holocene (about 2000-4000 years ago), the climate used to be wet, so wet that streams running from nearby mountains gradually filled Death Valley to a depth of almost 30 feet.   What could cause this collection of salt?  How thick is it and what is underneath the salt - I might expect a sedimentary base because of supposed water on top.   The minerals left behind as shown in the photo below by earlier Death Valley lakes dissolved in the shallow water, creating a briny solution, today this is represented as a salty floor of 95% salt about 3-5 feet thick.   This is the lowest spot in the Western Hemisphere at -282 feet below sea level.   Based on the fact of this being so far below sea level, I was very intrigued, and I think that a geologic map might help me understand this area. 

Photo of Polygonal cracks in a salt pan. 

Photo by Tom Bean, NPS.

In addition to lack of water, below sea level altitude, there is also a volcano.   At the edge of Ubehebe Crater, we a time that seemed just over two thousand years ago... You can see the enormous crater of the volcano in the picture below.   

A look into the depths of Ubehebe Crater, the most significant and youngest volcanic feature at this stop. Photo by W.R. Jones, NPS.

Why did this volcano occur?   Where are the fault lines that forced the volcanic activity and why did it get cut off.  Clearly a geologic map would help me understand this further.  According the the USGS research, some of Ubehebe Crater field's most dramatic eruptions occurred when magma met water-soaked bedrock and alluvial fan sediments. In an instant, water flashed to steam, and a violent release of steam-powered energy blasted away the confining rock above. (This is called a hydrovolcanic eruption.) It produced a dense, ground-hugging cloud of rocky debris which surged out from the base at up to 100 miles/hour, decimating the landscape. A fiery fountain of lava erupted with a roar, forming a vent to the south of what is now Ubehebe Crater. Liquid rock was thrown into the air, then fell to the ground as solidified cinders or partially-molten lava blocks and bombs. A ring of black volcanic material soon builds around the central vent. The first of the Ubehebe Crater complex is born. (USGS, retrieved from Web)