QUICK FACTSWhere is it? Toussid volcano, Chad [21.03731548, 16.47357325]What's in the photo? The petrified remains of ancient lava and a skull-like calderaWho took the photo? An unnamed astronaut on board the International Space StationWhen was it taken? Sept. 23, 2019This eye-catching satellite snap shows off a sprawling mass of petrified lava surrounding the jet-black slopes of a potentially dangerous volcano in the heart of the Sahara. A smaller volcanic "skull" lurks near the shadowy peak's base.Toussid (also known as Tarso Toussid) is a "potentially active" stratovolcano located within the Tibesti Mountains, which cover around 40,000 square miles (100,000 square kilometers) of northern Chad and southern Libya. The dark peak stands 10,712 feet (3,265 meters) above sea level, making it the second-tallest mountain in the Tibesti region.The name Toussid roughly translates to "which killed the local people with fire" in the language of the nearby Indigenous people, hinting at a destructive and deadly history. However, according to the Smithsonian Institution's Global Volcanism Program, there is no evidence that the volcano has erupted during the Holocene the current geological epoch, which began around 12,000 years ago. It is unclear if it has actually killed anyone. The dark blob surrounding the volcano is known as a massif. It is made up of layers of overlapping magmatic rock left by multiple ancient lava flows that effusively erupted, or slowly poured from, the volcano's summit.The shadowy structure, which is up to 20 miles (32 kilometers) across at its widest point, stands out against the surrounding sand-covered plateau, which has been carved into a network of crisscrossing canyons by eons of wind blasting, according to NASA's Earth Observatory.The massif surrounding Toussid is made of overlapping lava flows. If you look closely at this image, you can see how they criss-cross over one another. The Trou au Natron caldera is also more clearly visible in this photo, which was captured by the European Space Agency's Copernicus satellite in September 2021. (Image credit: ESA/Copernicus)Just southeast of the massif (in the upper right of the photo), there is a small, white circle containing several dark patches. This is Trou au Natron a roughly 3,300-foot-deep (1,000 m) volcanic crater, or caldera, which looks eerily like a giant skull when viewed directly from above.The cranium-like caldera likely formed during an explosive eruption more than 120,000 years ago. It was once filled with a giant salt lake that was home to ancient algae and other microorganisms. When the lake dried out, around the start of the Holocene, the receding water left behind a thick layer of white salt surrounding a pair of eyelike volcanic cones. Toussid is one of the youngest mountains in the Tibesti range, which formed by similar effusive eruptions long before the stratovolcano was born. The entire region likely once matched the massif's dark hue before being relentlessly bombarded by sand and wind. In another 100,000 years or so, the massif may blend in with the surrounding plateau, according to the Earth Observatory.Trou au Natron's salty white floor and volcanic cones make it look eerily like a skull when viewed from above. The dark slopes of Toussid can also be seen in the background of this image. (Image credit: Gerhard Holub/Wikimedia)While the shadowy volcano has remained dormant for several millennia, it occasionally puffs out steam from small vents, or fumaroles, near its summit, suggesting that it is still technically active, according to the European Space Agency. However, geologists have not properly assessed its eruptive potential. Indonesia's 'Twin Peaks' volcanoes A 2021 astronaut photo shows the surprising similarities between Mount Sundoro and Mount Sumbing, which lie at the heart of Java, Indonesia. Volcanic 'googly eyes' stare into space A 2014 astronaut photo shows a pair of volcanic lakes appearing to stare up into space from the Chiltepe Peninsula of Nicaragua's Lake Managua. These "eyes" and "skull" were created by violent eruptions thousands of years ago. Pair of 'glowing' lava lakes in Africa This false-color satellite photo from 2014 shows the immense heat emanating from lava lakes at the summits of a pair of simultaneously erupting volcanoes in Congo.