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Racetrack Playa

Coordinates: 36°40′53″N 117°33′46″W / 36.6813°N 117.5627°W / 36.6813; -117.5627
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Racetrack Playa
LocationDeath Valley National Park
Inyo County, California
Coordinates36°40′53″N 117°33′46″W / 36.6813°N 117.5627°W / 36.6813; -117.5627
Lake typeEndorheic basin
Primary outflowsTerminal (evaporation)
Basin countriesUnited States
Max. length4.5 km (2.8 mi)
Max. width2 km (1.2 mi)
Surface area7 km2 (2.7 sq mi)
Shore length112 km (7.5 mi)
Surface elevation1,132 m (3,714 ft)
ReferencesU.S. Geological Survey Geographic Names Information System: The Racetrack
1 Shore length is not a well-defined measure.

The Racetrack Playa, or The Racetrack, is a scenic dry lake feature with "sailing stones" that inscribe linear "racetrack" imprints. It is located above the northwestern side of Death Valley, in Death Valley National Park, Inyo County, California, U.S..

Geography

The Racetrack Playa is 3608 feet (1130 m) above sea level, and 2.8 mi (4.5 km) long (north-south) by 1.3 mi (2.1 km) wide (east-west). The playa is exceptionally flat and level with the northern end being only 1.5 inches (4 cm) higher than the southern. This occurrence is due to major influx of fine-grained sediment that accumulates at the north end. The highest point surrounding the Racetrack is the 5,678 feet (1731 m) high Ubehebe Peak, rising 1970 feet (571 m) above the lakebed 0.85 mile (1.37 km) to the west.

The playa is in the small Racetrack Valley endorheic basin between the Cottonwood Mountains on the east and Nelson Range to the west. During periods of heavy rain, water washes down from the Racetrack mountain area[1] draining into the playa, forming a shallow, short-lived endorheic lake. Under the hot desert sun, the thin veneer of water quickly evaporates leaving behind a surface layer of soft slick mud. As the mud dries, it shrinks and cracks into a mosaic pattern of interlocking polygons.

The shape of the shallow hydrocarbon lake Ontario Lacus on Saturn's moon Titan has been compared to that of Racetrack Playa.[2]

360° night-time panorama of the Racetrack Playa. The Milky Way is the visible arc in the center above a sailing stone and tracks from others.

Features

The Racetrack

Racetrack is dry for almost the entire year and has no vegetation. When dry, its surface is covered with small but firm hexagonal mud crack polygons that are typically 3 to 4 inches (7.5 to 10 cm) in diameter and about an inch (2.5 cm) thick. The polygons form in sets of three mud cracks at 120º to each other.[3] A few days after a precipitation event, small mud curls, otherwise known as “corn flakes” form on the playa surface. Absence of these indicates that wind or another object has scraped away the tiny mud curls.

During the bimodal rainy season (summer and especially winter) a shallow cover of water deposits a thin layer of fine mud on and between the polygons of Racetrack. Heavier winter precipitation temporarily erases them until spring when the dry conditions cause new mud cracks to form in the place of the old cracks. Sandblasting wind continually helps to round the edges of exposed polygons. Annual precipitation is 3 to 4 inches (75 to 100 mm) and ice cover can be 1 to 2.5 inches (2.5 to 6.5 cm) thick. Typically only part of the playa will flood in any given year.

Sailing stones

Main article: Sailing stones
Sailing stone in Racetrack Playa

The sailing stones are a geological phenomenon found in the Racetrack. Slabs of dolomite and syenite ranging from a few hundred grams to hundreds of kilograms inscribe visible tracks as they slide across the playa surface, without human or animal intervention. The tracks have been observed and studied since the early 1900s, yet no one has seen the stones 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, in the upwards of 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.[4][5]

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. Sheets of ice form on the surface as night temperatures fall below freezing. Wind then drives these floating ice floes, their aggregate inertia and large area providing the necessary force required to move both small and large 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."[6]

A more recent theory[7] 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.[8]

On 30 May 2013, the LA Times reported that park officials are looking in to the theft of several of the rocks.[9]

Islands

Two islands of bedrock outcrops rise dramatically above the playa's surface at its northern end. The larger landmark is The Grandstand, a 73 feet (22 m) high dark dolomite outcrop, rising in dramatic contrast from the bright white surface of the Racetrack. The second 'island' feature is a smaller carbonate outcrop.

Visiting

Access is via Racetrack Road, reached at the Grapevine Junction near Scotty's Castle. The 28 mile rough gravel road heading south-west from Ubehebe Crater is passable with non-4WD vehicles but requires high ground clearance. It rounds the western side of the playa to a parking area with descriptive signs by the National Park Service. A bench here, placed by the Mano Seca Group, has scenic views of The Racetrack, The Grandstand, and mountain scenery. Another access to Racetrack Playa is Lippincott pass road that enters the Racetrack valley from the south west, climbing up from Saline Valley. Lippincott Pass and the roads in Saline Valley are extremely rough and negotiable for high clearance 4WD vehicles with all-terrain tires only.

Camping, while not allowed on the playa, is available in "primitive campsite" areas to the north and south. Visiting remote areas of Death Valley bears considerable risk. Summer temperatures can surpass 120°F (49°C), large areas are without cellphone reception, roads are treacherous and the closest gas station is in Furnace Creek.

The Grandstand in the northwest area of the playa

See also

See also the categories Death Valley and Protected areas of the Mojave Desert

References

  1. ^ Kletetschka Gunther, Roger LeB. Hooke, Andrew Ryan, George Fercana, Emerald McKinney, Kristopher P. Schwebler, (August 2013), Sliding stones of Racetrack Playa, Death Valley, USA: The roles of rock thermal conductivity and fluctuating water levels, Source: Geomorphology Volume: 195 Issue: 1 Pages: 110-117 DOI: 10.1016/j.geomorph.2013.04.032
  2. ^ Lorenz, R. D., B. Jackson and A. Hayes, Racetrack and Bonnie Claire : Southwestern US Playa Lakes as Analogs for Ontario Lacus, Titan, Planetary and Space Science, 58, 723-731, 2010
  3. ^ Sharp, Robert P. and Allen F. Glazner, Geology Underfoot In Death Valley and Owens Valley, 161-173, 1997
  4. ^ http://geosun.sjsu.edu/paula/rtp/images/map.gif
  5. ^ Messina, P.; Stoffer, P., and Clarke, K.C. (1997). "Mapping Death Valley's Wandering Rocks". GPS World (April, 1997): 34–44.
  6. ^ Brian Dunning (2007-01-15). "Living Stones of Death Valley - An examination of the mysterious stones that move by themselves across the desert floor". Skeptoid: Critical Analysis of Pop Phenomena. Retrieved 2011-11-04.
  7. ^ Lorenz, Ralph (01/2011). "Ice rafts not sails: Floating the rocks at Racetrack Playa" (PDF). American Journal of Physics. 79 (1): 37–42. doi:10.1119/1.3490645. Retrieved 24 June 2011. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)CS1 maint: date and year (link)
  8. ^ Schewe, Phillip. "Ice offers possible explanation for Death Valley's mysterious 'self-moving' rocks". PhysOrg.com. Retrieved 2011-06-24.
  9. ^ Sahagun, Louis. "Mysterious rocks stolen from Death Valley National Park".
  • Messina, P. (1997). "Mapping Death Valley's Wandering Rocks". GPS World (April, 1997): 34–44. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  • Reid, J.B. (1995). "Sliding rocks at the Racetrack, Death Valley: What makes them move". Geology. 23 (9): 819–822. doi:10.1130/0091-7613(1995)023<0819:SRATRD>2.3.CO;2. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  • Sharp, R.P. (1976). "Sliding stones, Racetrack Playa, California". Bulletin of the Geological Society of America. 87 (12): 1704–1717. doi:10.1130/0016-7606(1976)87<1704:SSRPC>2.0.CO;2. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  • Sharp, R.P. (1996). "Sliding rocks at the Racetrack, Death Valley: What makes them move? Discussion and Reply". Geology. 25: 766–767. doi:10.1130/0091-7613(1996)024<0766:SRATRD>2.3.CO;2. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  • Sharp, R.P. (1997). Geology Underfoot in Death Valley and Owens Valley. Missoula: Mountain Press Publishing Company. ISBN 0-87842-362-1. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  • Shelton, J.S. (1953). Can Wind Move Rocks on Racetrack Playa. Vol. 117. The American Association for the Advancement of Science. pp. 438–439.
  • Stanley, G.M. (1955). "Origin of playa stone tracks, Racetrack Playa, Inyo County, California". Bulletin of the Geological Society of America. 66 (11): 1329–1350. doi:10.1130/0016-7606(1955)66[1329:OOPSTR]2.0.CO;2.
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