Trou au Natron (French: "hole of natron") or Doon Orei ( Teda: "big hole") [1] is a volcanic caldera of the Tibesti Massif in the nation of Chad in Northern Africa. [2] [3] The volcano is extinct. It is unknown when it last erupted. [4] [5] Its volcano number is 0205–01. [6] Trou au Natron is located just south-east of Toussidé, the westernmost volcano of the Tibesti Mountains. Its edge cuts into the nearby Yirrigue caldera.
The caldera sits at an elevation of 2,450 m (8,040 ft). [7] It has an irregular diameter of approximately 6–8 km (4–5 mi) and is up to 1,000 m (3,300 ft) deep. [2] Four smaller volcanic cones, made of scoria or andesitic tuff sit on the floor of the caldera. [2] [8] Numerous smaller vents and hot springs on the caldera's floor emit hot steam and mineral water. [2]
Because of its irregular shape, it has been theorized that the caldera was formed as a result of multiple massive explosions, each of which deepened the enormous pit. [2] During these explosions, chunks of debris up to 5 m3 (180 cu ft) in size may have been hurled up to 10 km (6.2 mi) from the crater. [2] Its exact period of formation is unconfirmed, although a Pleistocene formation has been suggested. [6] It is known to be one of the youngest formations on the Tibesti Massif. [4]
Much of the surface of the caldera is lined with a white crust of carbonate salts such as sodium carbonite and natrolite. [8] This substance is also known as natron, leading to the French name for the site. This crust is sometimes known as the Tibesti Soda Lake. [2] [9] The crusts are formed when mineral-rich steam is emitted from small vents on the crater's floor. When this water evaporates in the desert heat, the minerals remain behind as part of the crust. [2]
Both the slopes and the floor of the caldera contain thick layers of fossilized aquatic gastropods and diatoms, indicating that the caldera was once home to a deep lake. During the Last Glacial Maximum, the lake may have been up to 500 m (1,600 ft) deep. Radiocarbon dating on some of these samples indicates an age of approximately 14,500–15,000 years Before Present. [10]
The Trou au Natron has a caldera diameter of six to eight km...
Trou au Natron (French: "hole of natron") or Doon Orei ( Teda: "big hole") [1] is a volcanic caldera of the Tibesti Massif in the nation of Chad in Northern Africa. [2] [3] The volcano is extinct. It is unknown when it last erupted. [4] [5] Its volcano number is 0205–01. [6] Trou au Natron is located just south-east of Toussidé, the westernmost volcano of the Tibesti Mountains. Its edge cuts into the nearby Yirrigue caldera.
The caldera sits at an elevation of 2,450 m (8,040 ft). [7] It has an irregular diameter of approximately 6–8 km (4–5 mi) and is up to 1,000 m (3,300 ft) deep. [2] Four smaller volcanic cones, made of scoria or andesitic tuff sit on the floor of the caldera. [2] [8] Numerous smaller vents and hot springs on the caldera's floor emit hot steam and mineral water. [2]
Because of its irregular shape, it has been theorized that the caldera was formed as a result of multiple massive explosions, each of which deepened the enormous pit. [2] During these explosions, chunks of debris up to 5 m3 (180 cu ft) in size may have been hurled up to 10 km (6.2 mi) from the crater. [2] Its exact period of formation is unconfirmed, although a Pleistocene formation has been suggested. [6] It is known to be one of the youngest formations on the Tibesti Massif. [4]
Much of the surface of the caldera is lined with a white crust of carbonate salts such as sodium carbonite and natrolite. [8] This substance is also known as natron, leading to the French name for the site. This crust is sometimes known as the Tibesti Soda Lake. [2] [9] The crusts are formed when mineral-rich steam is emitted from small vents on the crater's floor. When this water evaporates in the desert heat, the minerals remain behind as part of the crust. [2]
Both the slopes and the floor of the caldera contain thick layers of fossilized aquatic gastropods and diatoms, indicating that the caldera was once home to a deep lake. During the Last Glacial Maximum, the lake may have been up to 500 m (1,600 ft) deep. Radiocarbon dating on some of these samples indicates an age of approximately 14,500–15,000 years Before Present. [10]
The Trou au Natron has a caldera diameter of six to eight km...