An eruption occurred at Rinjani on 1 October at 1730 following an increase in seismicity that began on 5 September (0-7 earthquakes occurred per day). DVGHM raised the Alert Level to 3 (on a scale of 1-4) or Orange. During 2-4 October, explosions produced thick gray ash plumes to heights of ~300-800 m above the post-caldera cone, Barujari. The explosions occurred on the NE slope of Barujari cone every 5 to 160 minutes. Seismicity was dominated by explosion earthquakes.

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

Following a steam-and-ash emission at St. Helens on 5 October, seismicity dropped to low levels and CVO reduced the warning from Volcano Alert (Alert Level 3: aviation color code Red), to Volcano Advisory (Alert Level 2: aviation color code Orange). During 6-12 October, seismicity was at low-to-moderate levels, with the highest magnitude earthquakes (M 2.4) occurring at a rate of one every 2 minutes on 8 October.

On 6 October only weak steam puffs were emitted from the volcano and CVO scientists confirmed that the top of the area of intense uplift was at or slightly above the highest point on the lava dome, which suggested that some uplift occurred during the period of low seismicity. Scientists also confirmed that small lahars spilled out of the crater and onto the Pumice Plain during a rainstorm the evening of 5 October. Lahars traveled a short distance toward Spirit Lake and the North Fork Toutle River. CVO received reports that a light dusting of ash from the emission on 5 October affected the eastern part of Mount Rainier National Park, ~110 km NNE of St. Helens. A new steam vent opened during the evening of 6 October, joining two that had been present for several days.

Measurements from recent photographs and LIDAR (LIght Detection And Ranging) showed that as of 7 October the intensely deformed and uplifted area on the S side of the 1980-86 lava dome was ~400 m (N-S) by ~490 m (E-W) with a maximum uplift of about 90-120 m. Additional analysis revealed that the total volume change represented by the deformation between late September and 6 October was ~16 million cubic meters. The average rate of change was ~2 million cubic meters per day. On 11 October, thermal imaging of the western part of the uplifting area revealed temperatures of 500 to 600 degrees C on a large pinkish-gray fin of rock and in nearby fumaroles and cracks. These observations are consistent with new lava having reached the surface of the uplift. A gas-sensing flight on 11 October measured fluxes of sulfur dioxide and carbon dioxide that were similar to, or slightly smaller than, those measured on 7 October.

CVO reported on 13 October, "As a result of the intense unrest of the past two and one-half weeks and recent observations, we infer that magma is at a very shallow level and is extruding onto the surface. Incandescence from hot rock or gases reflects off steam clouds and is visible from north of the volcano. During times of unrest, Mount St. Helens and similar volcanoes elsewhere typically go through episodic changes in level of unrest over periods of days to weeks, or even months. Such changes are in part driven by variations in the rate of magma movement. We expect fluctuations in the level of unrest to continue during coming days. Escalation in the degree of unrest could occur suddenly or with very little warning. There may be little time to raise the alert level before a hazardous event occurs."

Source: US Geological Survey Cascades Volcano Observatory (CVO)

Based on information from JMA, the Tokyo VAAC reported that an eruption at Asama at 2310 on 10 October produced a plume to an unknown height.

Source: Tokyo Volcanic Ash Advisory Center (VAAC)

During 6-11 October, block-lava flows continued to travel down Colima's N, NW, W, and S flanks as they have since 30 September. On 6 October, the block-lava flows on the N flank reached a length of ~600 m and a width of 150 m, and on the WNW flank the block-lava reached a length of ~250 m. About 32 explosions occurred that day, producing plumes to ~400 m above the volcano. On 11 October, a block-lava flow on the N flank reached a length of ~900 m and a width of ~150 m, and on the WNW flank the block-lava flow reached a length of ~300 m and a width of ~200 m. About 27 small explosions again produced plumes to a height of ~400 m above the volcano. During the report period, block-and-ash flows spilling from the fronts of the advancing block-lava flows reached ~ 2 km from the summit.

Source: Centro Universitario de Estudios Vulcanológicos (CUEV) - Universidad de Colima

According the Etna Volcan Sicilen website, lava emission continued at Etna during 6-11 October from vents around 2,620 m and 2,350 m elevations. Lava emission from the 2,620-m-elevation vent flowed in several arms down Valle del Bove. At the 2,350-m-elevation vent, lava flowed in tunnels for tens of meters.

Source: Etna Volcan Sicilien (Charles Rivière)

During the evening of 9 October, a narrow lava flow traveled ~800 m down Fuego's SSW flank towards the head of the Taniluyá River. A small sustained lava fountain reached ~75 m above the volcano during the evening of 10 October. On 12 October, a narrow lava flow traveled ~400 m from an area about 20 m below the S edge of the crater. Small avalanches occurred from the lava-flow fronts. Six explosions produced plumes to ~600 m above the volcano's summit. A small lahar traveled towards the Zanjón Barranca Seca Ravine.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)

During 8-11 October, emissions of gas and fine ash continued at Galeras. Plumes rose to a maximum height of ~1.5 km above the volcano. Small-amplitude tremor associated with gas-and-ash emissions was recorded.

Source: Servicio Geológico Colombiano (SGC)

On 11 and 12 October, patches of incandescent lava were visible on the PKK lava flow on the Pulama Pali fault scarp and all vents in the crater of Puʻu ʻŌʻō were incandescent. Tremor was at moderate levels at Puʻu ʻŌʻō. Essentially no tremor was recorded at Kīlauea's summit. A M 4.0 earthquake occurred at Kīlauea's summit at a depth of ~32 km on 11 October at 1030 that affected tilt meters. Taking earthquake- and rainfall-induced tilts into account, the volcanic tilt was minor.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)

According to HVO, since early July 2004 an increased number of earthquakes had been recorded from beneath Mauna Loa. From week to week, the numbers fluctuated but remained well above the norm. Through September, more than 580 earthquakes were centered beneath Mauna Loa's summit caldera and the adjacent part of the southwest rift zone. Most of these earthquakes were quite deep, from 35 to 50 km below the ground surface and small, less than M 3. They were "long-period" (LP) earthquakes, which means that their signals gradually rise out of the background rather than appearing abruptly. Such a concentrated number of deep LP earthquakes from this part of Mauna Loa is unprecedented, at least in the modern earthquake record dating back to the 1960s. During about 4-11 October, however, only 23 earthquakes were located under the summit.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)

On 11 October, a partial lava-dome collapse to the SW at Santa Maria's Santiaguito lava-dome complex produced a pyroclastic flow that traveled toward the Nimá Segundo River. An ash cloud formed that rose to a height of ~500 m and covered most of the dome complex. The collapse was preceded by an explosion that produced an ash-and-gas cloud to ~1.5 km above the volcano. Small explosions on 12 October produced small lava-dome collapses to the SW that generated avalanches of lava blocks and ash.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)

Volcanic and seismic activity at Soufrière Hills remained at slightly elevated levels during 1-8 October. The seismic network recorded one rockfall, two long-period earthquakes, and eight hybrid earthquakes. The sulfur-dioxide flux ranged between 187 and 1,144 metric tons per day, with a weekly average of 462 metric tons per day.

Source: Montserrat Volcano Observatory (MVO)

Volcanic and seismic activity at Tungurahua during 11-12 October were at relatively low levels, characterized by a few long-period earthquakes and small explosions. Emissions mainly consisted of steam and gas, with small amounts of ash.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)