Abstract
During July 10th–11th 2015, Volcán de Colima, Mexico, underwent its most intense eruptive phase since its Subplinian–Plinian 1913AD eruption. Production of scoria coincident with elevated fumarolic activity and SO2 flux indicate a significant switch of upper-conduit dynamics compared with the preceding decades of dome building and vulcanian explosions. A marked increase in rockfall events and degassing activity was observed on the 8th and 9th of July. On the 10th at 20:16h (Local time=UTM−6h) a partial collapse of the dome generated a series of pyroclastic density currents (PDCs) that lasted 52min and reached 9.1km to the south of the volcano. The PDCs were mostly channelized by the Montegrande and San Antonio ravines, and produced a deposit with an estimated volume of 2.4×106m3. Nearly 16h after the first collapse, a second and larger collapse occurred which lasted 1h 47min. This second collapse produced a series of PDCs along the same ravines, reaching a distance of 10.3km. The total volume calculated for the PDCs of the second event is 8.0×106m3. Including associated ashfall deposits, the two episodes produced a total of 14.2×106m3 of fragmentary material. The collapses formed an amphitheater-shaped crater open towards the south. We propose that the dome collapse was triggered by arrival of gas-rich magma to the upper conduit, which then boiled-over and sustained the PDCs. A juvenile scoria sample selected from the second partial dome collapse contains hornblende, yet at an order of magnitude less abundant (0.2%) than that of 1913, and exhibits reaction rims, whereas the 1913 hornblende is unreacted. At present there is no compelling petrologic evidence for imminent end-cycle activity observed at Volcán de Colima.
Highlights
The andesitic stratovolcano Volcán de Colima in western México (19.51N, 103.62W, height 3860 m) is one of the most active volcanoes in North America and is currently in a highly active phase
These large collapses and resulting pyroclastic density currents (PDCs) represent a significant and sudden increase in intensity above background in all monitoring systems. These events are a departure from the dome-building and explosions style of activity. Together this set of observations appears to correlate with the Luhr and Carmichael (1990) model, which by extension indicates that end-cycle activity is likely to occur imminently, and could be considered to have commenced with these events
We favor a boiling-over mechanism to explain the anomalous eruptions of July 2015 at Volcán de Colima
Summary
The andesitic stratovolcano Volcán de Colima in western México (19.51N, 103.62W, height 3860 m) is one of the most active volcanoes in North America and is currently in a highly active phase. In our particular case we focus upon rapidly estimating vesicle and crystal content
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