Thermal anomaly on Mount Michael, possible strombolian activity

Thermal anomaly on Mount Michael, possible strombolian activity

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A satellite image captured by NASA/USGS Landsat-8 on January 31, 2018 show a thermal anomaly present in the summit crater of Mount Michael volcano on Saunders Island, South Atlantic Ocean.

"The anomaly is clearly an indicator that some elevated activity has been taking place inside Mount Michael's crater," South Sandwich Islands Volcano Monitoring Blog reports.

"In my opinion, I believe some low-level strombolian activity has been occurring or at least a lava pool is present on the crater floor."

Thermal anomaly inside Mount Michael summit crater on January 31, 2018

Thermal anomaly inside Mount Michael summit crater on January 31, 2018. Credit: NASA/USGS Landsat-8

Thermal anomaly inside Mount Michael summit crater on January 31, 2018

Thermal anomaly inside Mount Michael summit crater on January 31, 2018. Credit: NASA/USGS Landsat-8

Satellite images acquired August 10 and 18 as well as October 4, 5 and 15, 2017 show what appear to be gas emissions originating from the volcano, but no eruption was confirmed.

Gas plume emanating from Mount Michael, Sounders volcano, South Sandwich Islands

Gas plume emanating from Mount Michael, Sounders volcano, the South Sandwich Islands on October 15, 2017. Credit: NASA Aqua/MODIS

The last entry in Smithsonian/USGS Global Volcanism Program's Weekly Reports database for this volcano was in October 2015. The MODVOLC thermal alert system detected thermal anomalies over Michael's summit crater during September 30 - October 7. Thermal alerts, however, started on August 28.

The previous entry was in October 2005. "The first MODVOLC alerts at Mount Michael since May 2003 recently began, indicating an increased level of activity in the island's summit crater (and presumed lava lake). The alerts occurred on October 3, 5, and 6."

Geological summary

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 (1 640 feet) 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). Vapor emission is frequently reported from the summit crater. Recent AVHRR and MODIS satellite imagery has revealed evidence for lava lake activity in the summit crater. (GVP)

Featured image: Thermal anomaly inside Mount Michael summit crater on January 31, 2018. Credit: NASA/USGS Landsat-8

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