Monturaqui crater

Monturaqui is circular, about 455 metres (1,493 ft) wide and 31 metres (102 ft) deep[2] and is surrounded by a rim[5] whose height varies between 48–16 metres (157–52 ft) owing probably to pre-existent topography.[6] The crater lies at an elevation of 3,500 metres (11,500 ft); about half ot he mass of Earth's atmosphere is concentrated below this altitude, meaning that the meteorite that created Monturaqui experienced less ablation during its passage through the atmosphere and could create a larger crater.[2] Alluvial material has covered the deepest part of the crater.,[7] which contains a small salt pan that supports several brushes.[8]

The basement in which the crater lies is formed by a 0–5 metres (0–16 ft) thick Tertiary-Pleistocene ignimbrite and underlying dyke-containing granites of Jurassic age; both of which crop out in the crater.[9] The terrain on which the crater lies is a tectonic block that was uplifted by 0.6 kilometres (0.37 mi) relative to the Salar de Atacama[2] and which is incised by watercourses that were diverted by the formation of Monturaqui crater.[9]

Impactites have been found around the crater.[9] These include glasses,[7] granitic rocks with evidence of shock metamorphosis as well as metallic iron and nickel but no remnants of the original meteorite.[9] The rocks show evidence of having been exposed to intense heat and pressure during the impact; reconstructed temperatures reached 1,500–3,000 °C (2,730–5,430 °F) with pressures of 50,000,000,000–65,000,000,000 pascals (7,300,000–9,400,000 psi).[10] Based on the chemistry of the impactite, Monturaqui was formed by an iron meteorite.[11]