The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Thursday, these notices are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of eruptions during the week, but rather a summary of activity that meet selected criteria. Carefully reviewed, detailed reports are published in the Bulletin of the Global Volcanism Network.

The US Geological Survey reported that small plumes of discolored water around the Ahyi Seamount had been intermittently identified in satellite images over the last few months, though recent ones had more discrete plume shapes suggesting more vigorous activity. Plumes on 1, 7, and 11 July drifted less than 500 m from the vent area. No signals were detected in data from underwater pressure sensors near Wake Island (about 2,270 km E of Ahyi). The plumes were likely the result of gas released into the water column and could reflect either vigorous hydrothermal degassing or be associated with an ongoing effusive eruption. At 1013 on 16 July the Aviation Color Code was raised to Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level was raised to Advisory (the second lowest level on a four-level scale).

Source: US Geological Survey

The Alaska Volcano Observatory (AVO) reported that a small phreatic explosion originating at Korovin?s summit crater lake within the Atka Volcanic Complex was detected in seismic and infrasound data at 0355 on 16 July. No emissions were identified in satellite images, but regional weather clouds obscured views below 3 km (10,000 ft) a.s.l.; an ash plume generated by a small explosion would be expected to be small and dissipate quickly. Elevated seismicity declined immediately after the event. The Volcano Alert Level was raised to Advisory (the second lowest level on a four-level scale) and the Aviation Color Code was raised to Yellow (the second lowest color on a four-color scale) at 0503. Typical elevated temperatures at the crater lake were seen in clear overnight satellite images during 18-19 July. Unrest declined; at 1208 on 21 July the Volcano Alert Level was lowered to Normal and the Aviation Color Code was lowered to Green.

Source: US Geological Survey Alaska Volcano Observatory (AVO)

The Sezione di Catania - Osservatorio Etneo (INGV) reported eruptive activity at Etna?s summit craters during 13-19 July characterized by gas emissions rising along the fissure between Voragine Crater (VOR) and Northeast Crater (NEC), gas emissions rising from Southeast Crater, and explosive activity at both NEC and Bocca Nuova Crater (BN). INGV staff conducted field surveys on 16 and 18 July and observed sporadic explosions at NEC and yellowish-brown ash emissions rising from the W vent in BN. Ash emissions at BN became nearly continuous during 18-19 July with grayish-brown plumes rising several hundred meters above the summit. A notably energetic event at 1807 on 19 July produced a gray ash cloud that rose 300 m above the vent. The Alert Level remained at Yellow (the second lowest level on a four-level scale) according to the Dipartimento della Protezione Civile.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that an eruption at Krakatau continued during 16-22 July. White, gray, and/or black ash plumes rose as high as 200 m above the summit and drifted in multiple directions during 16 and 19-20 July. Incandescence was visible at night on 11 July. White plumes rose up to 100 m above the summit on the other days. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3 km away from the active crater.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

The Japan Meteorological Agency (JMA) reported that further analysis of seismic data at Kuchinoerabujima from 9 July and results from field visits indicated that there likely was no increase in volcanic unrest. At 1550 on 17 July the Alert Level was lowered to 1 (on a scale of 1-5).

Source: Japan Meteorological Agency (JMA)

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera?s Sakurajima volcano) during 13-20 July. Volcanologists conducted a field survey on 13 July and measured high sulfur dioxide emissions, averaging 2,200 tons per day. That same day ash plumes rose as high as 1.7 km above the summit and drifted N and NE. Crater incandescence was visible in webcam images during 13-17 July. Very small eruptive events were recorded during 17-20 July. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to be cautious within 2 km of both the Minimadake and Showa craters.

Source: Japan Meteorological Agency (JMA)

The Wellington Volcanic Ash Advisory Center (VAAC) reported that ash-and-gas plumes at Ambae were identified in satellite and webcam views during 15 and 18-20 July rising 2.7-4.3 km (9,000-14,000 ft) a.s.l. and drifting SE, S, and SW. The plumes were brown on 19 July. The same day some flights were disrupted or canceled according to a government source. The Alert Level remained at 3 (on a scale of 0-5), and the public was warned to stay outside of Danger Zone B, defined as a 3-km radius around the active vents in Lake Voui, and to stay away from drainages during heavy rains.

Sources: Australian High Commission in Port Vila, Vanuatu,Vanuatu Meteorology and Geohazards Department (VMGD),Wellington Volcanic Ash Advisory Center (VAAC)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Dukono continued during 16-22 July. Daily white plumes rose as high as 200 m above the summit and drifted in multiple directions. At 0650 on 16 July a white-and-gray ash plume rose 2.1 km above the summit and drifted N. White-and-gray ash plumes rose 100-500 m above the summit and drifted NE and E during 17 and 20-22 July. The Alert Level remained at Level 2 (on a scale of 1-4) and the public was warned to stay 4 km away from the Malupang Warirang Crater.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

The Alaska Volcano Observatory (AVO) reported that slow lava effusion continued to feed a thick flow in Great Sitkin?s summit crater during 15-22 July. The flow advanced ESE based on radar satellite data. Seismicity was minor and likely associated with rockfalls on the growing dome. Elevated surface temperatures were identified on most days and webcam and satellite images showed minor steaming from the dome during 18-19 July. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale).

Source: US Geological Survey Alaska Volcano Observatory (AVO)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity at Ibu continued during 16-22 July, with daily eruptive events recorded by the seismic network. Daily gray or white-to-gray ash plumes rose 200-800 m above the summit and drifted E, NE, and NW. Incandescence at the summit was visible in some nighttime webcam images. The Alert Level remained at 2 (the second lowest level on a four-level scale) and the public was advised to stay 2 km away from the active crater and 3.5 km away from the N crater wall opening.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing eruptive activity at Kanlaon during 16-22 July. The seismic network recorded 8-36 daily volcanic earthquakes; the counts included 1-3 daily periods of tremor on most days, lasting 28 minutes to four hours and 43 minutes. Sulfur dioxide emissions ranged from 625 to 1,914 tonnes per day. Volcanic emissions rose 300-900 m above the summit and drifted in multiple directions. The Alert Level remained at 2 (on a scale of 0-5); the public was warned to stay out of the 4-km-radius Permanent Danger Zone (PDZ) and pilots were advised to avoid flying close to the summit.

Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

The Hawaiian Volcano Observatory (HVO) reported that the eruption within Kilauea?s Kaluapele summit caldera, characterized by episodic fountaining, incandescence, and intermittent spatter from craters along the SW margin of Halema?uma?u Crater, continued at variable levels during 15-22 July. Gas plumes rose from both the N and S vents and drifted SW though the week. Nighttime incandescence was persistent at both vents, though it was stronger at the S vent and intermittent at the N vent. Flames, likely caused by the ignition of volcanic gases, were visible at both vents during 15-18 July and only at the S vent during the rest of the week. The Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale) and the Aviation Color Code remained at Yellow (the second lowest color on a four-color scale).

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)