Médano Blanco

Position of center of photo (Lat/Long): [-38.662/-59.13]

Narrow cordons of coastal dunes stretch for hundreds of kilometers along this part of Argentina’s coast. The Médano Blanco is not far from the arid and windy borderlands with Patagonia - one of the windiest places on Earth.

The effects of strong westerly winds (blowing from bottom to top in this image) can be seen everywhere in this astronaut photograph. Dune-ridge crests are oriented at right angles to the prevailing wind. Geologists suspect that erosion by wind has excavated numerous hollows, which now dot the farmland as small shallow lakes. A stand of dark green trees has been planted on the upwind side of a health spa - the white dot is the roof of a stately building - as a protective barrier against the wind.

The white fringe along the seashore is formed by lines of breaking waves. Crossing swell trains appear offshore in the Atlantic, and the curvature of the swell shows the effect of the westerly wind. Winds tend to drive the sea currents in this area, though some prominent onshore swells also approach the coast from the southeast. The light brown tinted seawater near the shore is rich with fine mud that is stirred up out of coastal sediments by wave action, then washed seaward and east by currents.