Volcanos

Global Volcanic Activity - New Activity for the week of 14 August - 20 August 2019

Asamayama | Honshu (Japan) : JMA reported that, after a small phreatic eruption occurred at Asamayama on 7 August, both seismic activity and sulfur dioxide emissions temporarily increased and then decreased later that day. During 8-19 August white plumes generally rose 400 m above the crater rim; occasionally they rose as high as 800 m. Sulfur dioxide emissions were 70-300 tons per day. On 19 August the Alert Level was lowered to 2 (on a scale of 1-5).

Semisopochnoi | United States : AVO reported that during 14-17 August seismicity at Semisopochnoi remained elevated and was characterized by periods of continuous tremor and discrete low-frequency earthquakes; seismic data became unavailable starting sometime on 17 August. Cloudy weather often prevented satellite views of the volcano, however some recent clear views indicated that the N cone crater had a smooth featureless area, indicating water or tephra at an elevation several meters below the previous floor. The Volcano Alert Level remained at Watch and the Aviation colour Code remained at Orange.

Shishaldin | Fox Islands (USA) : AVO reported that during 14-20 August continuous, low-level tremor at Shishaldin was recorded by the seismic network and elevated surface temperatures were visible in infrared satellite images. The spatter cone in the crater had grown and partially filled the summit crater. The Aviation colour Code remained at Orange and the Volcano Alert Level remained at Watch.

Tangkubanparahu | Western Java (Indonesia) : PVMBG reported that during 12-18 August phreatic events at Tangkubanparahu's Ratu Crater continued to produce sometimes dense gray-to-white plumes that rose as high as 200 m above the vent, and dense black ash plumes that rose as high as 100 m. The emissions were accompanied by roaring. Ashfall was localized around Ratu Crater. The seismic network recorded continuous tremor. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to stay 1.5 km away from the active crater.

Ubinas | Peru : IGP reported that during 13-19 August blue-coloured gas plumes from Ubinas rose to heights of less than 1.5 km above the base of the crater. Seven thermal anomalies were recorded by the MIROVA system. The number of seismic events was 1,716 (all under M 2.4), a decrease in the total number recorded during the previous week. The Alert Level remained at Orange (the second highest level on a four-colour scale) and the public were warned to stay outside of a 15-km radius.

Tonga Islands : A submarine eruption in early August from an unnamed seamount about 50 km NW of Vava’u in Tonga created extensive areas of pumice rafts. Sailing crews encountered the pumice starting on 9 August about 40 km NNW of Late Island. Rachel Mackie described a pronounced odor of sulfur, and eventually being surrounded as far as she could see, with the surface pumice layer being 30 cm deep and containing pieces up to 80 cm in diameter. Sentinel-2 satellite imagery from 11 August showed the raft, averaging about 2.5 km across but strung out for 35 km NE-SW, located 70 km WNW of Late Island; another band of scattered rafts extended directly back from the main mass towards Late for 50 km. The raft continued drifting, and was at least another 60 km SW from its previous location as of 16 August. Eruptive activity at this location was previously reported in September-October 2001.