Tarso Toh is a volcanic field located in Chad, north of Tarso Toussidé volcano. It fills valleys and plains over an area of 80 km in east-west direction and 20–30 km in north-south direction. It contains 150scoria cones and two maars. Tarso Toh is a volcanic plateau and has lateral dimensions of, resulting in a surface area of about. It rises to elevations of above sea level and above the surroundingterrain. The plateau encompasses about 150 separate volcanoes, some of which are found in remnants. Some lava flows at Tarso Toh have reached large distances. Part of the field is the Begour crater. It is about wide and is mostly dry with the exception of several small ponds and a ring of diatom- and mollusc-containing sediments which forms a ring terrace inside the crater. Radiocarbon dating has yielded ages of 8,300 ± 300 years ago on sediments within Begour, and Tarso Toh is considered to be a Holocene volcano. The Tibesti features several different rock formations. A crystalline basement cis covered by Mesozoic sandstones. These were subject to deformation and later overprinted by volcanic rocks. This basement is about 500-600 million years old. The recent volcanism has been explained with the existence of a mantle plumebeneath Tibesti.
Climate and biota
The climate of the region is arid but in general there is more precipitation than in the surrounding desert, which results in the formation of wadis. Temperatures at Zouar range from in winter to in summer; at high altitudes freezing temperatures may be common. Vegetation is scarce; in the proximity of waters some acacias and grasses can be found. A number of mollusc shells have been found in the Begour sediments, such as Anisus costulatus, Anisus dallonii, Biomphalaria pfeifferi, Bulinus truncatus, Gastrocopta klunzingeri,Lymnaea natalensis, Melanoides tuberculata, Pisidium sp.Segmentina angusta, Succinea sp., Thapsia vesti and Zootecus insularis, although their identification is now always clear.
