THE OUARKZIZ IMPACT CRATER is located in northwestern Algeria, close to the border with Morocco. The crater was formed by a meteor impact less than 70 million years ago, during the late Cretaceous Period of the Mesozoic Era, or “Age of Dinosaurs.”
Originally called Tindouf, the 3.5-kilometre wide crater has been heavily eroded since its formation; however, its circular shape is highlighted by exposures of older sedimentary rock layers that form ridgelines trending roughly northwest to southeast. From the vantage point of an astronaut on the International Space Station, the impact crater is clearly visible with a magnifying camera lens.
A geologist interpreting this image to build a geological history of the region would conclude that the Ouarkziz crater is younger than the sedimentary rocks, as the rock layers had to be already present for the meteor to hit them. Likewise, a stream channel can be seen cutting across the centre of the crater, indicating that the channel formed after the impact had occurred. This Principal of Cross-Cutting Relationships, usually attributed to the 19th century geologist Charles Lyell, is a basic logic tool used by geologists to build relative sequence and history of events when investigating a region.
Astronaut photograph provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Centre. The image was taken by the Expedition 30 crew. Text adapted from information issued by William L. Stefanov, Jacobs/ESCG at NASA-JSC.
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