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Richat Structure: the Eye of the Sahara
February 12, 2013 8:20 PM   Subscribe

First noticed by westerners in 1965, when the Gemini-4 spacecraft flew over northwest Africa (alternate source, with link to uncompressed TIF | in Earth photographs from Gemini III, IV, and V on, the Richat Structure in the Sahara desert of west–central Mauritania resembles an impact crater or a circular target (or a possible Atlantis, or Plato's circular city, or maybe an open-pit mine), but is a naturally occurring 40-50 km (25-30 mi) geologic dome that has eroded over time. It's large enough that, when seen in person, the scale of the geography is hard to capture. But it is quite impressive when seen from space (mentioned previously)
posted by filthy light thief (7 comments total) 30 users marked this as a favorite

It looks as though there is a sort of lake at the center. Is it weird that I kind of want to live a hermetic existence in a little floating house at the center of that lake?
posted by Scientist at 8:32 PM on February 12, 2013 [2 favorites]

Scrolling in on the google site shows names in and around the formation. El Kadim appears to be a village on the southeastern edge where the sand drift ends.

Scientist, Sebket el Guelb appears to be an intermittent lake.

Am too tired to search out more, but if anyone else finds some, please post.

Looking at the sand drifting in, I am wondering if we're not fortunate to be able to see this during a short period of time when it's uncovered, or has not yet been covered. If we hadn't sent up a camera for another five hundred years, would we still have been able to see this?
posted by BlueHorse at 9:38 PM on February 12, 2013

Looking at it in Topomapper, there's about 200m of elevation difference in the general area -- about the same as the deepest Saharan dunes. So possibly. But also keep in mind that the Sahara has only been a desert for about 3500 years or so (unless you go back into human prehistory). If the structure was at all perceptible as something other than changes in terrain, I wonder what some of the ancient civilizations in the region thought of it.
posted by dhartung at 9:55 PM on February 12, 2013 [1 favorite]

One of the fun things that geologists tend to speculate about (besides how Eurypterids would taste) is what exactly would happen in a modern Kimberlite eruption and what it would actually look like. These are deep deep mantle-derived features - do they just suddenly pop up one day like a pimple? Then as an afterthought, you tend to hope that it happens somewhere like the middle of the Sahara, rather than underneath a city.
posted by grajohnt at 11:57 PM on February 12, 2013

This reminds me of Upheaval Dome (what a name!) in Canyonlands.
posted by jessssse at 5:49 AM on February 13, 2013

Jinx, jessssse! But your map link is some other dome, here's Canyonlands' Upheaval Dome.

Also not very impressive from the ground.
posted by phliar at 6:25 PM on February 13, 2013

Speaking of the Sahara seen from space: Detailed satellite images reveal the web of connections that sustain life on Earth.
posted by homunculus at 9:03 PM on February 13, 2013 [2 favorites]

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