Astronaut's lens reveals Sahara's tallest peak and salty secrets
High above the vast African desert, an astronaut from the ISS captured a photo of the enormous extinct volcano Emi Koussi (Mount Koussi), with lava streams and dry riverbeds carved by water that once flowed there. At the summit, he discovered a white lake.
An astronaut on board the International Space Station (ISS), a member of Expedition 72, recently photographed Emi Koussi (Mount Koussi). This massive volcano, extinct for about 1.3 million years, rises in the heart of the Sahara in northern Chad. Standing 3,400 metres above sea level and spanning an impressive 69 kilometres, the wide volcanic cone is intersected by dark lava streams, which serve as reminders of its fiery past.
There is no trace of snow at the summit
The latest photo was published on NASA Earth Observatory. Emi Koussi, surrounded by sunlit expanses of bright desert sand, is the highest point in the Sahara. When we look closely at the photograph, we can spot something extraordinary: white layers, but not of snow, rather of salt. It is the bed of a salty lake that settled at the bottom of the caldera, notes NASA Earth Observatory.
It is certainly a striking contrast to the dark volcanic rock. The dry, salty lake is about 740 metres below the summit. Nearby, you can also notice several round volcanic vents that are remnants of past eruptions.
Hidden canyons and neighbouring volcanoes
Numerous dry riverbeds appear as thin lines on the volcano's slopes, radiating from the caldera, describes NASA Earth Observatory. Despite very low rainfall in the region, geologists believe such channels were formed through water erosion over thousands of years. A few channels on the lower slopes, including those in the lower part of the image, are marked by shadows.
A line of small, round cones and vents appears on the northern slope of the volcano. It runs towards the slopes of Tarso Ahon, another large volcanic mountain. The depression between Emi Koussi and Tarso Ahon is occupied by deep canyons, which cast the largest shadows. One of the canyons is 600 metres deep and channels water to the west, while another is 250 metres deep and channels water to the east. The canyons were formed in the depression due to the concentration of water flow from both Emi Koussi and Tarso Ahon.
This photograph, labelled ISS072-E-423041 and published by NASA Earth Observatory only now, was taken by an astronaut on board the International Space Station on 29 December 2024, using a Nikon Z9 digital camera with a 200 mm lens. It was captured during Expedition 72 and comes from the ISS Crew Earth Observations Facility and Earth Science and Remote Sensing Unit at NASA’s Johnson Space Center.
