Next time you're passing above North Africa at an altitude of 440 miles, check out the Haruj volcanic field in central Libya. From space, the volcanic plateau looks like a giant oil spill.
This week, NASA released a stunning image of the expansive Haruj. The image is the amalgamation of hundreds of photographs collected by NASA's Landsat 8 satellite and its Operational Land Imager between July 24, 2013 and April 13, 2016.
Scientists used an algorithm to scan the images for the best and clearest pixels -- those unobscured by dust or clouds. Together, the best pixels form a crystal clear mosaic.
Over the course of 5 million years during the early Pliocene, more than 120 volcanic vents leaked lava across the 17,000-square-mile plateau known as the Haruj. As the lava hardened, layer upon layer of basalt formed.
A closeup image of the eastern edge of the volcanic field reveals depressions in the ancient basalt, many of which have been filled with sand blown by the desert winds. Some sandy pockets of older basalt -- those that are surrounded but not covered by younger lava flows -- are called kipuka.