Name: Marty G.
What causes the "slicks" that sometimes form on a large,
irregular body of water with flow (river or estuary, for example)? The
slick appears under certain wind conditions as a linear, with-the-current
calm region on an otherwise more ripply surface.
(I'm guessing that a very thin layer of oil or oil-like material is
stretched along the surface, decreasing the wind's purchase on the water.)
Your guess is probably correct. The "slicks" are visible because of light
interference because the film thickness is of the order of the wavelength of
visible light -- 400-700 nanometers. The source could be from agricultural
runoff, oil contamination or even a "natural" source such as the sap from
evergreens. The colors of the slick will move and swirl with the current as
the moving water changes the thickness of the film.
Click here to return to the Environmental and Earth Science Archives
Update: June 2012