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Lastarria
Lastarria, also known as Azufre, is a stratovolcano along the border of Argentina (border of the Catamarca and Salta provinces) and Chile (Antofagasta region). The volcano is part of the Lazufre volcanic system and is noted for the presence of molten sulfur lava flows as well as a debris avalanche. There is no recorded activity in historical times, but ground inflation has been observed.
==Geology==
Lastarria is constructed on a Miocene-Pleistocene basement and contains the 0.6±0.3 million year-old andesitic-dacitic Negriales de Lastarria or Big Joe lava field with a volume of 5.4 km3 to the southwest and the Espòlon Sur (Southern Spur) edifice that is attached to the main edifice at the latter's summit. The main edifice itself contains five summit craters. The volcano was constructed in five stages. The Southern Spur developed first, followed by the Negriales lava flows. The craters 1 and 2 were followed by 3 and 4 and 5 are the youngest. The activity of the craters involved mainly pyroclastic flows, followed by lava domes and lava flows in craters 4 and 5.〔 The youngest Holocene manifestation of volcanism is a lava dome on the northernmost crater rim. Lastarria's Holocene activity has been mainly explosive, unlike preceding stages involving effusive activity.〔
Magnetotelluric analysis has evidenced the presence of various high-conductivity layers. The first layer lies beneath the summit and is related to both the fumarolic activity as well as to neighbouring Laguna Azufrera lake. The second layer extends to the south of the edifice, into the Negriales area, and appears to be magmatic in origin, possibly a magma chamber. The third deep layer is most likely a magmatic sill, and there is evidence for a pluton beneath the volcano.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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