Volcanos

Roundup of Global Volcanic Activity - New Activity for the week of 4 December - 10 December 2019

Nishinoshima | Japan : A thermal anomaly at Nishinoshima was identified in satellite images on 5 December, prompting JMA to expand the marine exclusion zone around the island to 1.5 km. The Japan Coast Guard (JCG) conducted an overflight the next day and observed Strombolian explosions ejecting blocks as high as 200 m above a crater on the E side of the central pyroclastic cone. Lava flows had traveled to within 200 m of the coastline. Light gray eruption plumes drifted E. During an overflight on 7 December observers confirmed continuing Strombolian activity and saw lava entering the sea.

Semisopochnoi | United States : Strong tremor at Semisopochnoi was recorded by local seismic and regional infrasound networks beginning at 0026 on 7 December, heralding the start of an eruption and prompting AVO to raise the Aviation colour Code to Orange and the Volcano Alert Level to Watch. The meteorological cloud deck over the volcano was at around 3 km (10,000 ft) a.s.l.; no ash signals were detected above this altitude. A period of intermittent explosions was detected, and afterwards seismicity remained elevated at least through 9 December.

White Island | North Island (New Zealand) : A deadly and short-lived (1-2 minutes) eruption at White Island began around 1411 on 9 December, prompting GeoNet to raise the Alert Level to 4 and the Aviation colour Code to Orange. The eruption originated from the crater floor and generated an ash plume that rose 3.7 km (12,000 ft) above the vent. Ashfall was confined to the island and covered the crater floor based on webcam views. Activity waned after the event and within a few hours the Alert Level was lowered to 3. An exclusion zone extending just under 10 km around the island was emplaced for all (non-police) vessels.

The New Zealand Police stated that 47 local and international people in a tour group were on the island at the time of the eruption. A majority of the people in the group were seriously injured and taken to area hospitals; six were confirmed dead. On 10 December the police concluded that there likely were no additional survivors after several reconnaissance flights conducted post-eruption; nine people remained missing and assumed to be on the island.

On 10 December GeoNet reported that although seismic activity had dropped to low levels after the eruption, localized steaming and mud jetting continued from the active vents. Tremor significantly increased starting around 0400 on 11 December. Results from an overflight to collect gas emission data, along with other monitoring data collected over time, suggested that a shallow magma source was driving the tremor, gas emissions, and jetting activity.