Miniature Sand Devils

September 08, 2012

Sanddevils 092n

: Mila Zinkova; Mila’s Web site
Summary Authors: Mila Zinkova; Jim Foster

The photo above shows a string of sand devils I noticed on a visit to Ocean Beach in San Francisco this past summer. I was hoping to photograph the sunset, but it was so windy at the beach that only a few brave souls dared to leave the safety of a car. I opted to remain in my vehicle. Besides, the force of the beach sand being flung about would have surely damaged my camera. Suddenly I noticed a few miniature fountains of sand swirling around. I hadn’t seen anything like this on any of my many previous beach trips. The beach sand confined to a space wide enough to allow for a sidewalk between the two barricades was being lifted by the howling wind above the top of the smaller barricade (perhaps about 18 in or 0.5 m in height). Like tiny eddies spinning up in a courtyard, these sand devils were caused by microscale wind shear. However, unlike dust devils, which typically form in calm conditions, these whirlwinds occurred during strong winds. They were fascinating to watch -- I wasn’t sorry I drove to the beach after all. Photo taken on June 12, 2012.

Photo details: Camera Maker: Canon; Camera Model: Canon PowerShot SX40 HS; Focal Length: 22.9mm; Aperture: f/4.5; Exposure Time: 0.013 s (1/80); ISO equiv: 160; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB; Software: Adobe Photoshop CS3 Windows.