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Sangay
Sangay (also known as Macas, Sanagay, or Sangai) is an active stratovolcano in central Ecuador. It is the most active volcano in Ecuador, having erupted three times in recorded history. It exhibits mostly strombolian activity; the most recent eruption, which started in 1934, is still ongoing. Geologically, Sangay marks the southern boundary of the Northern Volcanic Zone, and its position straddling two major pieces of crust accounts for its high level of activity. Sangay's approximately 500,000-year-old history is one of instability; two previous versions of the mountain were destroyed in massive flank collapses, evidence of which still litters its surroundings today.
Because of its remoteness, Sangay hosts a significant biological community with fauna such as mountain tapirs, giant otters, cocks-of-the-rock, and king vultures. Since 1983, its ecological community has been protected as part of the Sangay National Park. Although climbing the mountain is hampered by its remoteness, poor weather conditions, river flooding, and the danger of falling ejecta, the volcano is regularly surmounted, a feat first achieved by Robert T. Moore in 1929.
== Geological setting ==
Lying at the eastern edge of the Andean cordillera, Sangay was formed by volcanic processes associated with the subduction of the Nazca Plate under the South American Plate at the Peru–Chile Trench. It is the southernmost volcano in the Northern Volcanic Zone, a subgroup of Andean volcanoes whose northern limit is Nevado del Ruiz in Colombia.
The next active volcano in the chain, Sabancaya, is in Peru, a distant to the south. Sangay lies above a seismogenic tectonic slab located about beneath Sabancaya, reflecting a sharp difference in the thermal character of the subducted oceanic crust, between older rock beneath southern Ecuador and Peru (dated more than 32 million years old), and younger rock under northern Ecuador and Colombia (dated less than 22 million years old). The older southern rock is more thermally stable than the northern crust, and to this is attributed the long break in volcanic activity in the Andes; Sangay occupies a position at the boundary between these two bodies, accounting for its high level of activity.〔
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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