Report for Etna
INGV reported that Strombolian activity at Etna’s Northeast Crater (NEC) likely began on 8 September. Continuous Strombolian activity recorded between 2000 on 9 September and 0700 on 10 September produced diffuse ash emissions which quickly dissipated. The most intense part of the eruptive period occurred during 2000-2200. Minor ashfall was reported in Piedimonte Etneo, Giarre-Riposto, and Rifugio Citelli. Incandescence from the activity had significantly subsided by 0300 on 10 September, coincident with the ejection of lava fragments outside of the crater. Dilute ash puffs were continuously observed at dawn the next day. Strombolian activity ceased around 0540 and then resumed around 0800. Weather conditions hindered observations at times on 11 September but clear observations after 2000 allowed for the confirmation of continuing explosive activity at varying intensity at NEC.

Ash emission from Voragine Crater began during the morning of 12 September and gradually increased in frequency. Activity further intensified at 1200 as Strombolian activity commenced and tephra ejected out of the crater was deposited at the base of Bocca Nuova Crater. Strong Strombolian explosions were felt in Zafferana Etnea, Aci S. Antonio, Pedara, and neighboring areas.

Webcam and field observations on 13 September confirmed continuing activity at NEC and Voragine craters. Diffuse ash plumes rose from NEC and dispersed near the summit area. Strombolian activity at Voragine Crater ejected coarse tephra as high as 20 m above the crater rim and produced diffuse ash emissions. Impact craters from the ejected tephra were distributed mostly in the W part of the area between Bocca Nuova and Voragine craters down to 3,000 m elevation. Activity continued on 14 September. During an overflight on 15 September observers noted that a scoria cone had formed in Voragine Crater, and diffuse ash emissions continued to rise from NEC.

Report for Krakatau
PVMBG reported that Anak Krakatau’s seismic network recorded five eruptive events during 9-15 September. A webcam at the summit recorded diffuse white plumes rising 150 m from the bottom of the crater, and dense gray-and-white ash plumes rising 300 m. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km-radius hazard zone from the crater.

Report for Tangkubanparahu
PVMBG reported that phreatic events, accompanied by roaring, continued at Tangkubanparahu's Ratu Crater during 9-15 September, though no larger eruptions were recorded. Ash-and-steam emissions rose as high as 20 m above the vent and steam plumes rose as high as 200 m. 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.

Report for Merapi
PVMBG reported that during 9-15 September the lava-dome volume at Merapi did not change and was an estimated 461,000 cubic meters, based on analyses of drone images on 8 August. Extruded lava fell into the upper parts of the SE flank, generating block-and-ash flows that traveled as far as 1.1 km down the Gendol drainage. Diffuse white plumes rose as high as 100 m above the summit. The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to stay outside of the 3-km exclusion zone.

Report for Sangeang Api
The Darwin VAAC reported that on 11 September a diffuse ash plume from Sangeang Api was identified in satellite images rising to 3 km (10,000 ft) a.s.l. and drifting N. The Alert Level remained at 2 (on a scale of 1-4).

Report for Karangetang
PVMBG reported that during 9-15 September lava continued to effuse from Karangetang’s Main Crater (S) and Dua Crater (N), traveling as far as 1.5 km down the Nanitu, Pangi, and Sense drainages on the SW flank. Sometimes dense white plumes rose to 100 m above the summit. According to the Darwin VAAC an ash plume rose almost 650 m above the summit and drifted E on 11 September. The Alert Level remained at 2 (on a scale of 1-4).

Report for Dukono
Based on satellite and wind model data, and information from PVMBG, the Darwin VAAC reported that during 11-17 September ash plumes from Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted N, NNE, and NE. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

Report for Aira
JMA reported that inflation at Minamidake crater (at Aira Caldera’s Sakurajima volcano) began to be detected on 9 September and was similar to the deformation recorded just before a notable eruption on 16 June 2018. An eruption recorded at 0746 on 16 September produced an ash plume that rose 2.8 km above the crater rim and drifted SW. A series of eruptive events were recorded during 0830-1110. Deformation ceased after the events. An explosion at 0927 on 17 September generated an ash plume that rose 1 km and ejected blocks as far as 1.1 km. Two eruptive events later than day produced ash plumes that rose 1.6 km. The Alert Level remained at 3 (on a 5-level scale).

Report for Asosan
JMA reported that during 10-13 September ash plumes rose 1.6 km above Asosan’s summit crater rim. The sulfur dioxide emission rate was 1,600 tons per day on 11 September. The Alert Level remained at 2 (on a scale of 1-5).

Report for Ebeko
Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 7-13 September that sent ash plumes up to 3 km (10,000 ft) a.s.l. and drifted S, SE, and N. Ash fell in Severo-Kurilsk on 6 September. A thermal anomaly was identified in satellite images on 8 September. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Report for Alaid
The Tokyo VAAC reported that on 11 September an ash plume from Alaid identified in satellite images rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted SE.

Report for Karymsky
KVERT reported that a thermal anomaly over Karymsky was visible in satellite images on 10 September. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Report for Sheveluch
KVERT reported that a thermal anomaly over Sheveluch’s lava dome was identified daily in satellite images during 6-9 and 12 September. Resuspended ash formed plumes that drifted 250 km ESE during 11-12 September. Satellite and webcam data recorded ash emissions and a gas-and-steam plume with some ash drifting 50 km ESE on 12 September. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Report for Shishaldin
Low-level lava fountaining and minor explosive activity within Shishaldin’s summit crater was last observed on 17 August and likely continued during 11-17 September; continuous tremor was recorded by the seismic network and elevated surface temperatures were visible in satellite images. The webcam possibly recorded a steam emission on 16 September. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Report for Pacaya
A special report from INSIVUMEH noted that seismic activity at Pacaya had increased on 8 September, with RSAM values reaching 7,000 units by 13 September, coincident with increased explosive activity at Mackenney Crater. Explosions from a growing cone in the crater ejected material as high as 75 m above the cone. Lava effusion increased; lava flows advancing on the N and NW flank towards Cerro Chino were about 500 m long. Avalanches of blocks up to 1 m in diameter were produced by the flow front. Similar activity was observed during 15-16 September.

Report for Ubinas
During 10-15 September the number of seismic events at Ubinas totaled 4,093, with volcano-tectonic (VT) signals being the most numerous, averaging 572 events per day, and all having magnitudes under M 2.5. Hybrid events averaged 299 events per day. Continuous emissions of blueish gas and water vapor were recorded by the webcam rising to heights less than 1.5 km above the summit. Two thermal anomalies were recorded by the MIROVA system. An explosion at 0725 on 12 September produced a gas-and-ash plume that rose 1.5 km and affected several districts S and SE in the Moquegua region. The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of a 10-km radius.

Report for Nevados de Chillan
ONEMI and SERNAGEOMIN reported that during 10-17 September white-to-gray gas plumes from Nevados de Chillán’s Nicanor Crater rose 400-800 m above the rim and drifted NE, E, and SE. Explosions sometimes ejected incandescent material onto the E and SE flanks. A lava flow on the NNE flank was 100 m wide, 5 m thick, and had advanced 600 m by 14 September. The Alert Level remained at Orange, the second highest level on a four-color scale. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the communities of Pinto, Coihueco, and San Fabián, and stated that the public should stay at least 3 km away from the crater on the SW flank and 5 km away on the ENE flank.

Report for Copahue
OVDAS-SERNAGEOMIN reported that a long-period (LP) earthquake at Copahue recorded at 1657 on 11 September correlated with an infrasound signal from an explosion; a gas-and-ash emission rose to low heights. A larger explosion, recorded at 2245 along with an LP earthquake, produced a plume that rose 250 m above the crater rim. Incandescent deposits around the vent were visible at night, and a 3-km-long ash deposit, covering an area of 3.4 square kilometers, was visible on the ESE flank. The Alert Level remained at Yellow (second lowest level on a four-color scale); SERNAGEOMIN recommended no entry into a restricted area within 500 m of the crater. ONEMI maintained the Alert Level at Yellow (the middle level on a three-color scale) for the municipality of Alto Biobío.

Report for Villarrica
Video from an 11 September overflight of Villarrica, conducted by the Carabineros Región de La Araucanía, showed an active cone on the crater floor. ONEMI and SERNAGEOMIN noted that the activity was consistent with the elevated seismicity detected by the seismic network during the previous few days. Seismicity and explosive activity in the crater both began decreasing on 12 September and continued a downward trend at least through 16 September. Discrete tremor signals disappeared during 15-16 September, with moderate levels of continuous tremor dominating the signal. No explosions were detected. SERNAGEOMIN lowered the Alert Level to Yellow, the second lowest level on a four-color scale. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the municipalities of Villarrica, Pucón (16 km N), Curarrehue, and the commune of Panguipulli, and changed the exclusion zone for the public to a radius of 1 km around the crater.