Gour de Tazenat 2.63

The Gour de Tazenat is a volcanic lake in the French department of Puy-de-Dôme. It was formed by a phreatomagmatic eruption about 29,000 years ago.TopographyThe lake marks the northern limit of the Chaîne des Puys. It is located in Charbonnières-les-Vieilles, near Manzat in the French department of Puy-de-Dôme. It is 20km northwest of Riom, 5 kilometres northeast of Manzat and 2.5 kilometres south of Charbonnières-les-Vieilles.The lake has a depth of 66m. Its banks, except in the north and northeast, are wooded and have a height of 50m.The crater of this volcano is on average 80m deep and 700m wide. A 2.8 km trail can be used to walk around it. Navigation on the lake is prohibited.GeologyGour de Tazenat is a volcanic crater formed by a phreatomagmatic eruption. The banks of the lake have a volcanic crescent moon shape (north, east and south) formed by projections arranged in layers. In the stratum at the base, the basaltic volcanic projections, released as blocks, volcanic bombs and pozzolana are mixed with boulders (granite, granulite metamorphic rocks) from the base torn out by violent explosions. The bombs have a cauliflower shape, typical of phreatomagmatic eruptions due to fissures created by contact with water. The setting up of these initial projections corresponds to the beginning of the eruption when magma rises to the surface in contact with continental water. It causes heavy explosions capable of breaking fragments of crystalline basement, and the appearance of volcanic bombs in cauliflower shapes. Thereafter, water is removed and activity becomes more magmatic than phreatic. After cessation of eruptive activity, the Gour de Tazenat gradually filled with rainwater.