Geology Rocks! Racetrack Revelations

We arrived at Death Valley all set up to solve the mystery of the Racetrack Playa’s incredible sailing stones.  But things don’t always turn out the way you expect them to…

DSC_1778This remote, dry-mud area of one of America’s youngest national parks is strewn with small rocks and larger boulders of dolomite, all of which have long tracks trailing behind them in the hard pancake-flat surface, clear evidence that these seemingly stationary objects traverse, often significant distances, across the park’s dry lake.  This phenomenon has been scientific conundrum since the 1940s, and I have always found this particular geological mystery a particularly fascinating one.  Are these rocks moved by hurricane strength winds, rain, dust devils or other natural forces, perhaps? Everyone had his or her own hypothesis.  

And so, when we had the opportunity to visit Death Valley on our latest US road trip, we made sure we had booked a tour of the legendary racetrack!

DSC_1703As luck would have it, however, we started our tour in the knowledge that scientists had only the day before our trip announced that they had observed the rocks in motion earlier in the year, thus drawing a line under decades of speculation and establishing a new scientific theory. The theory was made public across the United States on the morning of Thursday the 28th August. What timing?! 

First Observation of Rocks in Motion

The scientists we need to thank for unraveling this enigma are Richard and James Norris, who published their findings in PLOS One (details below).  To conduct their experiments, they used a weather station together with GPS instrumented rocks to track their movement, but they were also fortunate enough to capture on camera the rocks in motion one morning in December 2013.  Whilst they have succeeded where many have failed for 60 years, their revelations tell of a form of “Goldilocks” scenario, where conditions have to be “just right” for is phenomenon to unfold.

DSC_1743One of the essential elements was rain, and in one of the driest places on Earth, rain is not present in the valley very often. Indeed the report notes that the movement in the rocks could be as sporadic as over years and decades, due to the extreme lack of rainfall in the area.  To trigger the event, rain would need to fall in the area to create a pond to a depth that would leave part of the rocks exposed above the surface, and the temperature would then need to plummet sufficiently to freeze the pond.  The rocks were observed moving on sunny, clear days, when steady but light winds would cause floating ice to break-up and push rocks easily along the wet and slick mud of the playa.  The tracks themselves were only visible when the water subsided from the plain. DSC_1775DSC_1752DSC_1723DSC_1769And there you have it: the unexplained finally explained! (You can read the full publication at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0105948)

DSC_1734

Reflection

Whilst some part of me was sad that we finally knew how these rocks glide through the mud, it was exciting to observe these marvels and understand and appreciate what we were seeing in their natural surroundings. The journey to the playa is in itself worth doing.  A thirty mile off road track heading South-West from Ubehebe Crater and takes you through a myriad of different landscapes including volcanic areas and a Joshua Tree forest.DSC_1682DSC_1796DSC_1673DSC_1806

Recommendations

We would, however, recommend hiring a guide as the journey is treacherous and being stranded in the remote desert would be fatal, with Summer temperatures reaching the 120 degrees Fahrenheit and no cell-reception to call for help. We had a fantastic guide Gerry, from Farabee’s Jeep hire! 

Farabee’s Jeep Rentals – http://www.farabeesjeeprentals.com

Furnace creek – http://www.furnacecreekresort.com

Death Valley National Park – http://www.nps.gov/deva/index.htmDSC_1791

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