|
Calabozos is a Holocene caldera in central Chile's Maule Region (7th Region). Part of the Chilean Andes' volcanic segment, it is considered a member of the Southern Volcanic Zone (SVZ), one of the three distinct volcanic belts of South America. This most active section of the Andes runs along central Chile's western edge, and includes more than 70 of Chile's stratovolcanoes and volcanic fields. Calabozos lies in an extremely remote area of poorly glaciated mountains. Calabozos and the majority of the Andean volcanoes formed from the subduction of the oceanic Nazca Plate under the continental South American continental lithosphere. The caldera is in a transitional region between thick and thin lithosphere, and is probably supplied by a pool of andesitic and rhyolitic magma. It sits on a historic bed of volcanic and plutonic sedimentary rock (rock formed within the Earth) that in turn sits on top of a layer of merged sedimentary and metamorphic rock. Calabozos is responsible for the huge Loma Seca Tuff, a body of material to in volume. It accumulated over at least three eruptive periods, beginning 800,000 years ago (0.8 mya) and lasting until 150,000 years ago (0.15 mya). The caldera's dimensions are by , and it has an elevation of . Activity from the caldera has produced many other stratovolcanoes to form a complex volcano.〔 == Geography and structure == Calabozos lies in central Chile's Maule Region, near Curicó and Talca, on the western Andes.〔Hildreth ''et al.'' (1984), p. 45.〕 This is an area of poorly glaciated mountains that is not permanently populated. There are no roads, and it is only accessible via horse or on foot.〔Hildreth ''et al.'' (1984), p. 47.〕 Calabozos is part of the South Volcanic Zone, which runs along the western edge of central Chile and extends south, jumping the border to continue its course in Argentina. This range includes at least nine caldera complexes, more than 70 of Chile's stratovolcanoes and volcanic fields that have been active in the Quaternary, and hundreds of minor eruptive centers. The South Volcanic Zone is the most volcanically active region in Chile, and produces around one eruption per year. Its largest historical eruption was at Quizapu Crater, located to from the north side of Cerro Azul's summit,〔 and its most active volcanoes are Llaima and Villarrica.〔Stern ''et al.'' (2007), pp. 154–156.〕 Calabozos is a ring-shaped caldera by wide,〔 with an elevation of .〔 Volcanoes have been formed by eruptions in the crater. The largest, which is on the southern rim of the caldera, is the Holocene Cerro del Medio complex with an elevation of . It is made mainly of andesite and dacite, and has a volume of to . On the southwestern edge several eruptions have created the Descabezado Chico volcano (elevation: )〔 which consists of four overlapping volcanic craters.〔 The last eruption occurred during Holocene time, and produced a dacitic lava flow ( in volume) that extends for .〔 Cerro Colorado, with an elevation of , forms another cone in the complex.〔 Towards the center of the caldera, hot springs including Cajon Loz Calabozos and Baños de Llolli〔 are present.〔 The springs are as old as 0.3 mya, and may have formed directly after Calabozos's second eruption〔 as a result of uplift caused by re-occurring activity in the caldera.〔 The vents occur in two clusters, Colorado and Puesto Calabozos, and are located along the margin of a fault at the southwestern edge of the caldera.〔Grunder ''et al''. (1987), p. 289.〕 Hildreth ''et al''. (1983) evaluated that Calabozos could potentially be useful for the harvesting of geothermal energy.〔Hildreth ''et al.'' (1984), p. 53.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Calabozos」の詳細全文を読む スポンサード リンク
|