Photographer's Note

Peter Boehringer and I had a mini-TE meeting in Death Valley last month. The full moon enabled us to take nighttime shots of the famous Racetrack, where rocks mysteriously move across a dry lakebed in a high valley that branches off from Death Valley. There seem to be two competing theories about how this movement happens. One theory is that when it rains and the Racetrack becomes very slippery, wind alone is enough to push the rocks. Another theory is that occasionally, it rains enough that a few inches (maybe 10 cm) of water collect on the lakebed, and it may then freeze. (It can be cold, as Peter and I learned, since the Racetrack is at about 3700 feet, or 1130 m, elevation.) When the rocks become locked into a sheet of ice, the wind can push the entire sheet and drag the rocks along. You can read about such things at these web sites:

Information written for the general public

An abstract of a more technical scientific paper

This shot is lit entirely by moonlight. It's a 3-4 minute exposure at f9, ISO 100.

The rock in the picture is a little bigger than a basketball, as I recall. They vary from not much bigger than a grapefruit, up to the size of two watermelons.

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Additional Photos by Ken Alexander (kensimage) Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 1087 W: 39 N: 1167] (8563)
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