Ghostly face peering out of Trou au Natron •

Ghostly face peering out of Trou au Natron

Today’s Image of the Day from NASA Earth Observatory features what appears to be a ghostly face peering out of Trou au Natron, a deep volcanic pit in northern Chad. 

Trou au Natron is a volcanic crater (or maar) located in the Sahara desert. It’s part of the Tibesti Mountains, a chain of volcanic formations. 

The crater is filled with natron, a naturally occurring mixture of sodium carbonate decahydrate (Na2CO3·10H2O) and around 17% sodium bicarbonate (also called baking soda) along with small quantities of sodium chloride (salt) and sodium sulfate. 

This mixture gives the crater its name, as “natron” refers to this type of salt, which was historically used in a variety of ways, including mummification by the ancient Egyptians. 

Trou au Natron is noteworthy for its stark and impressive landscape, with steep crater walls surrounding the salt flat inside. The photo was captured by an astronaut on the International Space Station on February 12, 2023.

“The edge of the ‘face’ is partly formed by shadows cast by the rim of a caldera – a type of volcanic crater formed after an explosive eruption or the collapse of the surface into a partially-emptied magma chamber,” said NASA.

“The ‘eyes’ and ‘nose’ are cinder cones – steep conical hills built around volcanic vents. The cinder cones are thought to be relatively young in geological terms, likely forming within the past few million years and possibly as recently as the past few thousand years.”

“The white area around the ‘mouth’ is a mineral crust made of a salt known as natron – a mixture of sodium carbonate, sodium bicarbonate, sodium chloride, and sodium sulfate. It forms as hot spring water pools on the surface and evaporates, and mineral-rich steam rises from the surface of the geothermally active area.”

Image Credit: NASA Earth Observatory 

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