Report on Fernandina (Ecuador) — 25 May-31 May 2005
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 May-31 May 2005
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2005. Report on Fernandina (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 25 May-31 May 2005. Smithsonian Institution and US Geological Survey.
0.37°S, 91.55°W; summit elev. 1476 m
All times are local (unless otherwise noted)
According to the Washington VAAC, a weak hotspot was visible at Fernandina on 29 May at 2045 and a very short narrow plume of ash and gas was visible around 2215. There were no local reports confirming an eruption. By 30 May at 0615 the emission had dissipated and only the hotspot remained visible on satellite imagery.
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.