Report for Piton de la Fournaise
OVPF reported that after several hours of increased seismicity at Piton de la Fournaise a seismic crisis began at 0145 on 15 September, accompanied by rapid deformation. Tremor began at 0425, contemporaneous with the opening of fissures on the S flank near Rivals Crater. Around 1000 an estimate of the lava flow rate, based on satellite data, was 30 cubic meters per second. During an overflight about an hour later observers noted five fissures. The central fissure was the most active, producing lava fountains 30 m high; two lava flows that merged downstream had already flowed more than 2 km towards the wall of the Enclos Fouqué. By the afternoon of 16 September the estimated flow rate was between 2.5 and 7 cubic meters per second. Only three vents were active and a cone had started to form. Lava flows continued to advance during 16-18 September.

Report for Krakatau
Based on satellite data, the Darwin VAAC reported that during 11-13 and 17-18 September ash plumes from Anak Krakatau rose to altitudes of 1.5-1.8 km (5,000-6,000 ft) a.s.l. and drifted NW, W, and SW. The Alert Level remained at 2 (on a scale of 1-4); residents and visitors were warned not to approach the volcano within 2 km of the crater.

Report for Merapi
PVMBG reported that during 10-16 September the new lava dome in Merapi’s summit crater continued to slowly grow. By 16 September the volume of the lava dome was an estimated 112,000 cubic meters, and the growth rate was 1,600 cubic meters per day. White emissions of variable density rose 20 m above the summit. The Alert Level remained at 2 (on a scale of 1-4), and resident were warned to remain outside of the 3-km exclusion zone.

Report for Dukono
Based on satellite data, wind model data, and notices from PVMBG, the Darwin VAAC reported that during 12-18 September ash plumes from Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted in multiple directions.

Report for Suwanosejima
JMA reported that during 12-13 September eruptive events at Suwanosejima’s Ontake Crater generated plumes that rose 1.1 km above the crater rim. Tremor increased, and nighttime crater incandescence was also visible. The Alert Level remained at 2 (on a 5-level scale).

Report for Aira
JMA reported that there were 13 events and also 13 explosions at Minamidake crater (at Aira Caldera’s Sakurajima volcano) during 10-18 September, with ash plumes rising as high as 1.8 km above the crater rim and material ejected as far as 1.1 km. Crater incandescence was visible at night. The Alert Level remained at 3 (on a 5-level scale).

Report for Ioto
During an overflight of Ioto (Iwo-jima) on 12 September the Japan Maritime Self Defense Force observed seawater jetting 5-10 m above the sea surface on the S coast, suggestive of a submarine eruption.

Report for Sarychev Peak
SVERT and KVERT reported increased activity and ash emissions at Sarychev Peak in mid-September. A thermal anomaly had been periodically visible since 7 May 2018, though more recently anomalies were detected during 8 and 11-12 September. Explosions sometimes occurred during 11 and 13-15 September, and ash emissions rose 3-4 km (10,000-13,100 ft) a.s.l. On 14 September ash plumes drifted as far as 120 km. On 14 September KVERT stated that the Aviation Color Code was raised to Orange, though on 17 September SVERT noted that the Aviation Color Code was at Yellow. KVERT reported that explosions at 0910 on 17 September generated ash plumes that rose as high as 4.5 km (14,800 ft) a.s.l. and drifted 21 km NE.

Report for Ebeko
KVERT reported that a thermal anomaly over Ebeko was identified in satellite images during 7, 9, and 12-13 September. Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E, observed explosions that sent ash plumes to 3.4 km (11,200 ft) a.s.l. and occasional incandescence during 10-13 September; ash plumes visible in satellite data drifted 113 km SE and NE. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Report for Karymsky
KVERT reported that a thermal anomaly over Karymsky was identified in satellite images on 7 September. Dense and continuous ash emissions from the crater were visible on 10 September. Explosions during 10-11 September generated ash plumes identified in satellite images rising 5-6 km (16,400-19,700 ft) a.s.l. and drifting about 860 km NE. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Report for Klyuchevskoy
On 12 September KVERT reported that activity at Klyuchevskoy had continued to decrease, with the last ash plume visible on 14 July. A weak thermal anomaly was occasionally visible though the temperature of the anomaly had steadily decreased. Gas-and-steam emissions continued. The Aviation Color Code was lowered to Green (the lowest level on a four-color scale).

Report for Sheveluch
KVERT reported that a thermal anomaly over Sheveluch was identified in satellite data during 7-8 and 12-13 September. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Report for Semisopochnoi
On 16 September AVO raised the Aviation Color Code (ACC) for Semisopochnoi to Yellow and Volcano Alert Level (VAL) to Advisory after increased seismicity was detected at 0831. Retrospective analysis of satellite data acquired on 10 September revealed small ash deposits on the N flank of Mount Cerberus, possibly associated with two bursts of tremor recorded on 8 September. This new information coupled with intensifying seismicity and a strong tremor signal recorded at 1249 on 17 September prompted AVO to raise the ACC to Orange and the VAL to Watch. Seismicity remained elevated on 18 September with nearly constant tremor being recorded by local sensors.

Report for Veniaminof
AVO reported that the eruption at Veniaminof continued during 12-18 September. A lava flow had traveled 800 m down the S flank of the summit cone by 14 September, remaining confined to the ice-filled summit caldera. A webcam in Perryville (35 km S) recorded nighttime incandescence, and sporadic gas emissions in the day during clear conditions. Elevated surface temperatures were identified in satellite images, and seismicity remained elevated. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Report for Kilauea
HVO reported minor incandescence from a collapse pit in the central part of Kilauea’s Fissure 8 cone during 12-15 September, and that small amounts of fuming rose from a small spatter cone located towards the back of the Fissure 8 cone during 12-18 September. Seismicity and ground deformation remain low at the summit, and aftershocks from the M 6.9 earthquake in early May were located along faults on the south flank. The combined rate of sulfur dioxide emission from the summit and the LERZ (less than 1,000 tonnes/day) were lower than any time since late 2007. Small collapses at Pu'u 'O'o Crater during 12-14 September generated visible dust plumes. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange.

Report for Popocatepetl
CENAPRED reported that each day during 12-17 September there were 64-189 steam-and-gas emissions from Popocatépetl, some of which contained minor amounts of ash. Nighttime crater incandescence was sometimes visible. Explosions were detected almost every day: eight on 12 September; one on 14 September; five on 15 September; three on 16 September. A series of emissions and explosions accompanied by tremor began at 0425 on 17 September and lasted for 365 minutes; incandescent tephra was ejected. The Alert Level remained at Yellow, Phase Two.

Report for Turrialba
OVSICORI-UNA reported that passive gas-and-ash emissions from Turrialba were continuous in September through the 13th. Events during 17-18 September produced plumes that rose 300 m above the crater and drifted SW and NW.

Report for Sangay
Based on satellite images and wind model data, the Washington VAAC reported that on 11, 13, 15, and 17 September ash emissions from Sangay rose to 5.8-6.4 km (19,000-21,000 ft) a.s.l. and drifted SW and W. A thermal anomaly was visible each day, and also on 16 September.

Report for Sabancaya
Observatorio Vulcanológico del Sur del IGP (OVS-IGP) and Observatorio Vulcanológico del INGEMMET (OVI) reported that explosions at Sabancaya averaged 13 per day during 10-16 September. Hybrid earthquakes were infrequent and of low magnitude. Gas-and-ash plumes rose as high as 2.5 km above the crater rim and drifted 30 km N, NE, and SE. The MIROVA system detected seven thermal anomalies, and on 12 September the sulfur dioxide gas flux was high at 2,060 tons/day. The report noted that the public should not approach the crater within a 12-km radius.

Report for Nevados de Chillan
Servicio Nacional de Geología and Minería (SERNAGEOMIN) Observatorio Volcanológico de Los Andes del Sur (OVDAS) and ONEMI reported the continuing, slow growth of the lava dome in Nevados de Chillán’s Nicanor Crater during 11-17 September. Gas emissions persisted, and sometimes contained ash. Periodic explosions sometimes ejected material that was deposited around the crater. Notably, at 0057 on 12 September, an explosion associated with a partial dome-collapse event ejected incandescent material 700 m above the crater rim and onto the flanks. An explosion at 2224 on 13 September generated ash plumes that rose 2.5 km above the crater rim. The event also ejected incandescent material to the SE, and generated a pyroclastic flow that traveled as most 400 m E. The Alert Level remained at Orange, the second highest level on a four-color scale, and residents were reminded not to approach the crater within 3 km. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the communities of Pinto, Coihueco, and San Fabián.