Report on Fernandina (Ecuador) — 6 September-12 September 2017
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 September-12 September 2017
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2017. Report on Fernandina (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 6 September-12 September 2017. Smithsonian Institution and US Geological Survey.
0.37°S, 91.55°W; summit elev. 1476 m
All times are local (unless otherwise noted)
IG reported that activity at Fernandina began on 4 September with the detection of hybrid earthquakes followed by long-period events, and finally the onset of tremor at 1225 which heralded the beginning of the eruption. Lava emerged from a circumferential fissure near the SSW rim of the caldera and flowed down the S and SW flanks (with no evidence of the flows reaching the sea). A gas plume with low ash content rose 4 km above the crater rim and drifted W. Flows continued to be active on 5 September but by the evening the intensity had weakened. An eruptive plume rose about 2.5 km. Activity decreased significantly by 6 September.
Geologic Background. Fernandina, the most active of Galápagos volcanoes and the one closest to the Galápagos mantle plume, is a basaltic shield volcano with a deep 5 x 6.5 km summit caldera. The volcano displays the classic "overturned soup bowl" profile of Galápagos shield volcanoes. Its caldera is elongated in a NW-SE direction and formed during several episodes of collapse. Circumferential fissures surround the caldera and were instrumental in growth of the volcano. Reporting has been poor in this uninhabited western end of the archipelago, and even a 1981 eruption was not witnessed at the time. In 1968 the caldera floor dropped 350 m following a major explosive eruption. Subsequent eruptions, mostly from vents located on or near the caldera boundary faults, have produced lava flows inside the caldera as well as those in 1995 that reached the coast from a SW-flank vent. Collapse of a nearly 1 km3 section of the east caldera wall during an eruption in 1988 produced a debris-avalanche deposit that covered much of the caldera floor and absorbed the caldera lake.