Who knew so much geography could be crammed into such a beautiful image as this one.
Taken by ESA’s ENVISAT satellite, this image shows the mountains of Tibesti on the borders of Chad and Libya.
First of all, the dominant blue smudge are the mountains themselves – the highest range in the Saraha. Most have been created by now-dormant volcanoes, but some are still active in the region. Lava flows can just be seen on the western edge, flowing to the left. The highest peak – Emi Koussi can be seen as a darker circle in the lower right part of the dark area. Emi Koussi is a really interesting volcano, as scientists believe it is a good analogue Elysium Mons – one of the largest volcano on Mars.
The white area at the top of the image is a depression in the landscape, caused by accumulating carbonate salts blown off the surrounding regions. When these carbonates dissolve in water they produce what is known as a soda lake. Incredibly alkaline and incredibly salty means that only the hardiest of animals and bacteria can live there. It doens’t mean though that they are unproductive. Many soda lakes produce large quantities of cyanobacteria, which in turn supports a huge number of flamingos.
Finally, the sweeps of orange and yellow in this impressionist canvas is really made up of Saharan sands. Since Envisat is roughly 785km up in the air, thats obviously a hell of a lot of sand. Noone has yet counted how many grains there are in the Sahara. We’d love to know your best guess. Make sure to show your working in the comments below.