Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that moderate eruptive activity continued at Fernandina during 20-26 March. Daily thermal anomalies were detected in satellite images. Sulfur dioxide (SO2) emissions identified in TROPOMI satellite data totaled 158 tons on 20 March, 720 tons on 24 March, and 790 tons during 25-26 March. Secretaría de Gestión de Riesgos (SGR) maintained the Alert Level at White (the lowest level on a four-color scale).

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.

Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN), Secretaría de Gestión de Riesgos (SGR)