Report on Saunders (United Kingdom) — 25 December-31 December 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 December-31 December 2019
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2019. Report on Saunders (United Kingdom). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 25 December-31 December 2019. Smithsonian Institution and US Geological Survey.
57.8°S, 26.483°W; summit elev. 843 m
All times are local (unless otherwise noted)
Three distinct thermal anomalies in the summit crater of Michael on Saunders Island were identified in a satellite image acquired on 24 December. Satellite images from 29 November and 2 December showed similar anomalies.
Geologic Background. Saunders Island is a volcanic structure consisting of a large central edifice intersected by two seamount chains, as shown by bathymetric mapping (Leat et al., 2013). The young constructional Mount Michael stratovolcano dominates the glacier-covered island, while two submarine plateaus, Harpers Bank and Saunders Bank, extend north. The symmetrical Michael has a 500-m-wide summit crater and a remnant of a somma rim to the SE. Tephra layers visible in ice cliffs surrounding the island are evidence of recent eruptions. Ash clouds were reported from the summit crater in 1819, and an effusive eruption was inferred to have occurred from a N-flank fissure around the end of the 19th century and beginning of the 20th century. A low ice-free lava platform, Blackstone Plain, is located on the north coast, surrounding a group of former sea stacks. A cluster of parasitic cones on the SE flank, the Ashen Hills, appear to have been modified since 1820 (LeMasurier and Thomson, 1990). Analysis of satellite imagery available since 1989 (Gray et al., 2019; MODVOLC) suggests frequent eruptive activity (when weatehr conditions allow), volcanic clouds, steam plumes, and thermal anomalies indicative of a persistent, or at least frequently active, lava lake in the summit crater. Due to this observational bias, there has been a presumption when defining eruptive periods that activity has been ongoing unless there is no evidence for at least 10 months.