Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that lava flows on Fernandina’s SSE flank continued to advance during 26 March-2 April. The flows were fed from a circumferential fissure that had opened high on the SE flank, just below the crater rim. Sulfur dioxide emissions detected by satellite fluctuated between about 200 and 1,300 tons per day and drifted W and SW on at least a few of the days. Daily thermal anomalies variable in both number and intensity over the lava flow continued to be detected. By 31 March the most distal part of the lava flow was about 1.5 km wide and about 2.4 km from the coastline.

Geological Summary. 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.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)