Geomorphological Features of the Galeras Volcanic Complex



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The Galeras volcanic complex, near the city of Pasto, was formed in several steps. At similar to 560 ka, BP a major caldera (the Coba Negra Caldera) appeared with its center similar to 5 km west of the present-day active volcano top. This caldera was 5 km in diameter and elongated in the E-W direction. The wall of the subsequent Jenoy caldera is covered by glacial morphology indicating a pre-glacial (<ca. 20 ka) age. These data suggest that the location of the eruptive main centers changed several times, moving eastward. Another 4-km-diameter caldera was formed during the Jenoy stage. The E-W migration trend of the volcanic centers can be seen in the Coba Negra caldera. Between 12.8 and 5 ka, the summit portion of the cone collapsed toward WSW and formed the youngest avalanche debris deposits. The collapse scar has a horseshoe shape and the sliding surface almost certainly cut across the main magma conduit. The presence of other, older avalanche debris deposits suggests previous lateral collapses, the scars of which can be recognized on the upper southern slope of the volcano. The active cone lies in the uppermost part of the sector collapse depression. Most of the surroundings are covered by pyroclastic deposits from the Galeras and neighboring volcanoes. The Galeras volcano is still active and constitutes a real hazard for the surrounding inhabitants.


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Active volcanism, Volcanic landforms, Glacial landforms