Elusive, but ecologically vital, Namibia’s Ugab River only flows above ground for a few days each year. The subterranean waters underlying this ephemeral river, however, are shallow enough in places to fill hollows and sustain a wildlife population that includes the rare desert elephant.
In the image shown here, the river passes through nearly vertical layers of thinly bedded limestone, sandstone, and siltstone.

Image taken September 10, 2002, by Landsat 7.

Credit: NASA/GSFC/USGS EROS Data Center

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