Volcanos

Roundup of Global Volcanic Activity – New Activity for the Week 16 December 2020 – 22 December 2020

Cerro Hudson – Chile : SERNAGEOMIN reported that a notable change in seismicity at Cerro Hudson was characterized by an increase in the frequency and magnitude of volcano-tectonic (VT), hybrid (HB), and long-period (LP) signals during 1-15 December. Two swarms of VT earthquakes were recorded during 10-11 December, with the largest event, a local M 2.9, located 4.7 km ESE of the caldera’s center at a depth of 4.6 km. The largest of five HB signals was a local M 3.1, located 4 km ESE at a depth of 4.3 km. The earthquake locations suggested a relatively shallow source SE of the caldera. No deformation or surficial changes were observed. The Alert Level was raised to Yellow (second highest level on a four-colour scale) on 22 December, based on the increased seismicity. ONEMI warned the communities of Aysén and Río Ibáñez, declaring a status of “Preventive Early Warning”, a level in between Green and Yellow.

Kilauea – Hawaiian Islands (USA) : HVO reported that a new eruption at Kilauea began on 20 December, after almost a month of pre-eruptive activity that included a dike intrusion. An earthquake swarm on 30 November centered in the middle of the caldera was recorded followed by periods of increased seismicity in the upper East Rift Zone. Spikes in seismicity began on 2 December; at 1745 earthquakes intensified beneath the S part of the caldera; tiltmeters simultaneously recorded accelerated deformation, resulting in about 8 cm of caldera floor uplift. The data suggested that a small intrusion had a volume equivalent to the amount of lava erupted in just 1-2 hours from Fissure 8 during the 2018 eruption. On 3 December seismcity and deformation decreased to pre-intrusion levels.

Lewotolo – Lomblen Island (Indonesia) : PVMBG reported that the eruption at Lewotolo continued during 16-22 December. Gray-and-white ash plumes were visible daily, rising as high as 800 m above the summit. Strombolian explosions were visible most nights ejecting material 100-200 m above the summit crater. Rumbling was heard most days. The Alert Level was remained at 3 (on a scale of 1-4) and the public was warned to stay 4 km away from the summer crater.

Merapi – Central Java (Indonesia) : BPPTKG reported that during 12-17 December white emissions from Merapi rose as high as 150 m above the summit. Rock avalanches traveled as far as 1.5 km down the Senowo drainage on the NW flank on 14 December. A comparison of photos taken on 11 and 15 December showed minor morphological changes in the summit area; drone video from 14 December revealed no new lava dome material in the summit crater. Seismic activity was less intense than the previous week. Electronic Distance Measurement (EDM) data continued to measure a distance shortening between points in the NW at a rate of 9 cm per day. The Alert Level remained at 3 (on a scale of 1-4).

Ruapehu – North Island (New Zealand) : GeoNet reported a warming trend of the crater lake water at Ruapehu, with a high temperature of 43 degrees Celsius. During an overflight to measure gas emissions the previous week, scientists observed that the lake was a uniform gray colour (suggesting it is well mixed) and some water overflow at the lake’s outlet. Gas output had increased in response to the heating cycle; the amounts of carbon dioxide (CO2) and sulfur gases (SO2 and H2S) in the plume were the largest measured in the past two decades. Short-lived pulses of volcanic tremor were coincident with gas emissions. The Volcanic Alert Level was raised to 2 and the Aviation colour Code was raised to Yellow on 21 December.

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