Discover the Rarest Sand Dunes: How Paleozoic ‘Black Mesas’ Shape the Sahara from Space

Check out this stunning photo taken from the International Space Station (ISS). It captures three ancient black mesas in the Sahara Desert, located near the town of Guérou in southern Mauritania. These natural formations create a striking visual with their dark hues and surrounding sand dunes.

The mesas rise steeply, reaching heights between 1,000 and 1,300 feet. The largest is about 6 miles wide. Interestingly, they create a “dune-free zone” to the west, where no sand accumulates. This is due to a phenomenon called “wind scour,” where fast-moving winds sweep sand away from that area.

The black color of these mesas comes from a layer called “rock varnish.” This coating, a mix of manganese and iron oxides, forms over thousands of years. It’s often made up of very thin layers, and scientists believe microorganisms play a role in its formation. For more on this, check out NASA’s Earth Observatory.

The photo shows two main types of dunes: climbing dunes and barchan dunes. The climbing dunes pile up along the eastern sides of the mesas, while the barchan dunes look like rippled tails, stretching away from the black rocks, glowing with reddish-yellow tones.

With winds usually blowing from the east, sand collects on the eastern slopes. But to the west, it’s a completely different story due to those fast winds that clear sand away. Another photo from an astronaut in 2014 shows this unusual effect over a larger area, illustrating how the dunes extend further away.

Looking back into history, during the Paleozoic era, these mesas were likely part of a larger rock formation. Erosion from water and wind over millions of years broke them apart, similar to how other geological structures, like the Richat Structure, formed. The Richat Structure, also known as the “Eye of the Sahara,” is located about 285 miles north of Guérou.

You can find mesas in many parts of the world, particularly in the Sahara and regions of the United States like Colorado and New Mexico. Interestingly, mesas also exist on Mars, carved by the planet’s winds over billions of years, showcasing a fascinating connection between geological processes on Earth and beyond.

Photos like these provide a glimpse into the intricate and beautiful patterns of our planet’s geology. For more remarkable images from space, check out the NASA Earth Gallery.

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