Erebus, located on Ross Island, Antarctica, is one of the few volcanoes in the world with a persistent lava lake in its summit crater. Since 1972, and probably well before, minor explosions, punctuated by occasional larger Strombolian explosions, have been associated with the active lava lake. Since the Mt. Erebus Volcano Observatory suspended their seismic and infrasonic monitoring program in 2016, the volcano has been primarily monitored by satellite. This report documents activity during 2021.

Sentinel-2 satellite images during 2021 showed a single lava lake, except a much smaller second one on 30 October (figure 30). Occasionally, a white gas plume was visible. Based on MODIS infrared detectors aboard the Terra and Aqua satellites and analyzed using the MODVOLC algorithm, thermal activity during 2021 was much greater than the 2020 level (76) but much less than the 2018 and 2019 levels (774 and 624, respectively) (table 7).

Figure 30. Sentinel-2 infrared satellite images showing the active lava lake in the summit crater of Erebus during 2021. The image on 23 January 2021 (left) shows a single lava lake, while the image on 30 October 2021 (right) shows a larger lake at least one smaller thermal area immediately SW. Images use False Color rendering (bands 12, 11, 4). Courtesy of Sentinel Hub Playground.

Table 7. Number of monthly MODIS-MODVOLC thermal alert pixels recorded at Erebus during 2017-2021. See BGVN 42:06 for data from 2000 through 2016. The table was compiled using data provided by the HIGP - MODVOLC Thermal Alerts System.

Geological Summary. Mount Erebus, the world's southernmost historically active volcano, overlooks the McMurdo research station on Ross Island. It is the largest of three major volcanoes forming the crudely triangular Ross Island. The summit of the dominantly phonolitic volcano has been modified by one or two generations of caldera formation. A summit plateau at about 3,200 m elevation marks the rim of the youngest caldera, which formed during the late-Pleistocene and within which the modern cone was constructed. An elliptical 500 x 600 m wide, 110-m-deep crater truncates the summit and contains an active lava lake within a 250-m-wide, 100-m-deep inner crater; other lava lakes are sometimes present. The glacier-covered volcano was erupting when first sighted by Captain James Ross in 1841. Continuous lava-lake activity with minor explosions, punctuated by occasional larger Strombolian explosions that eject bombs onto the crater rim, has been documented since 1972, but has probably been occurring for much of the volcano's recent history.

Information Contacts: Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).