Monday, April 13, 2009

The Etosha Pan

Today's NASA Earth Observatory image of the day is of a place that is near and dear to my heart, the Etosha Pan of Namibia:

In late 1996, my father and I took a trip to Namibia to study termite mound gas exchange as part of an Earthwatch expedition, and afterwards we rented a car and went off on a little safari. Up in Etosha National Park, the wildlife was pretty amazing. Here's a leopard that crossed the road in front of us, immediately followed by a second leopard:

An oryx (or gemsbok):

...And an elephant, drinking from one of the watering holes that fringe the main salt flats:

Namibia has been getting a lot of water lately, as evidenced in compare/contrast images like these, also from NASA's Earth Observatory:

June 2007:

Last week:

And that brings us back to the first image:

In this picture, you can see a new package of river water coming south into the Etosha Pan from the Oshigambo River of Angola. This is "fresh" water, but it has a dissolved load of sediments in it. As the water hits the hot, baking expanse of the Etosha Pan, it evaporates, but the dissolved ions within don't have that option. So they become more and more concentrated, and settle out in a chemical precipitate. This is where all the salt comes from: even freshwater is a little bit salty, and when you evaporate it repeatedly in an enclosed drainage basin, evaporite minerals accumulate there.

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