September 07 , 2017 . Fernandina , Fuego , Nishinoshima , Poas , Turrialba .
September 07 , 2017 .
Fernandina , Galápagos , Ecuador :
ERUPTION CONTINUES, HIS INTENSITY DECREASED .
The volcano Fernandina, located in Galapagos province 90 km north of Puerto Villamil and 140 km from WNW Puerto Ayora, has a new eruptive phase since September 4, 2017, after 8 years without major surface activity. Between March 2015 and September 2017, there was an inflation of 17 cm centered on the caldera of the volcano associated with the injection of a new magma. Seismic activity began on September 4th with hybrid earthquakes (fractures with fluid movements) followed by earthquakes of Long Period type (fluid movements). The onset of the eruption is associated with a volcanic tremor that began at 12:25 local time. The lava flows apparently originate from a circumferential crack near the crack of the 2005 eruption south-southwest of the caldera. The lava flows on the South and South-West flanks, but so far there is no evidence that they have reached the sea. According to seismic and satellite data, the intensity of the eruption has considerably decreased from its beginning on 4 September, but until the night of 5 September, active lava flows could be observed. Generally, eruptions on the Galapagos have durations of a few days to a few weeks with pulsating variations in activity. It is important to note that there is also the possibility of other phenomena on the volcano, such as the collapse of the bottom of the caldera associated with explosive eruptions (1968 eruption) or the sliding of the walls of the caldera (eruption of 1988). For the time being, it is recommended not to approach the caldera or the eruptive crack.
Figure 1. Incandescence on the Fernandina volcano (source: Alex Medina, 04/09/2017).
Fernandina (0.37 ° S, 91.55 ° W, 1476 m), also called Cerro la Cumbre, is a large shield volcano with a summit caldera (6.5 km NW-SE, 4.8 km NE-SW, 900 m deep ) composed of basalt that built the island of Fernandina (34 km NW-SE, 30 km NE-SW) at the western end of the Galapagos archipelago.
With at least 25 eruptions reported between 1813 and 2009, Fernandina is considered one of the most active volcanoes in Ecuador. According to Kurz et al. (2014), the surface of Fernandina is less than 4,300 years old according to the age of exposure. It is estimated that Fernandina had an eruptive rate of 0.0044 km³ / year for the last 1000 years (Kurz et al., 2014) and that, according to its current volume, the island would have an emergence age of 32,000 years .
The most important historical event took place in June 1968 when, after an effusive eruption in May of the same year (estimated volume of 0.1 km³), the floor of the caldera collapsed to 300 meters in the southeastern part, in a period of 12 days increasing the area of the caldera from 1 to 2 km³ (Simkin and Howard, 1970). The collapse of the caldera was preceded by an explosive eruption which produced a column of emission of 24 km high, small ash falls in Puerto Villamil (90 km SE of the volcano) and pyroclastic waves at the » inside the caldera. It is estimated that the explosive activity emitted ~ 0.1 km³ of magma. The difference between the volume of collapse and the volume of eruptive products emitted (lava + ashes) suggests that much of the magma has retreated deep (Simkin and Howard, 1970, Bagnardi and Amelung, 2012).
The previous eruption of Fernandina occurred between April 10 and 28, 2009 with the emission of lava flow through a radial crack on the southwest flank of the volcano at a height of ~ 550 m reaching the sea and covering ~ 6.7 km² for an estimated volume of 0.09 km³ (Ramón et al., 2011).
According to Paula Tagle’s report, a « strange » cloud was observed on Fernandina on 4 September around 12:30 (local time TL, UTC-6). A column of gas with a low ash content of ~ 4 km (~ 2.5 km above the vent) was clearly observed later with a westerly direction. On the night of 4 to 5 September, incandescent lava flows were probably observed on the southwest flank by a circumferential crack near the top of the volcano up to a height of 400 m. On 5 September, the intensity of the eruption decreased with a ~ 2.5 km eruptive column (~ 1 km above the vent). According to the images of Alex Medina, the lava field was still active, but with less intensity on the night of September 5th.
Figure 2. Incandescence and lava flows on the Fernandina volcano (source: Alex Medina, 09/09/2017).
Seismic activity in the Fernandina region has shown low levels in recent weeks. Two earthquakes occurred near Fernandina on September 2: 1) at 12:36 UTC (TL + 6) a long-term earthquake with a magnitude Mw of 4.0, a depth of 5.6 km, located on the edge West Fernandina Island (Figure 3); 2) the other at 13:58 UTC, type VT, located southwest of Fernandina, for which it was not possible to calculate the size.
Figure 3. Seismograms of the 12:36 UTC earthquake of September 2, 2017 recorded in the seismic stations of the Galapagos network.
Seismic crisis of 4 September.
The seismic activity on the volcano began on September 4th at 11.34 UTC (05h34 TL) with a small hybrid earthquake (fluid fracturing). Then, hybrid earthquakes of maximum amplitude occurred between 15:56 and 16:21 UTC (09h56 and 10h21 TL) (Figure 4).
Figure 4. Hybrid earthquake recorded at 09:56 (TL) at the station of FER2, VCH1 and ALCE. No signal is visible on the infrared sensor.
From 17h25 UTC (11h25 TL), a change in seismicity occurs with events of long period (LP) associated with the movement of fluids (Figure 5).
Figure 5. Distribution of the Fernandina volcano earthquakes according to its size in c / o. The blue symbols represent earthquakes type hybrid and red to seismic type LP.
The beginning of the eruption is associated with a tremor seismic signal (vibration of the ducts) which starts at 6:25 (12:25 TL) (Figure 6). Thereafter, there is a marked decrease in the amplitude of the tremor (FIG. 7). On 6 September, the median amplitude of the seismic signal reached the noise level.
Observations by satellite.
According to the InSAR data processing carried out by Yu Zhou (Oxford) and Mike Stock (Cambridge), Fernandina showed a distortion of 17 cm between March 2015 and September 2017 (Figure 8), 5 cm of which occurred the last two months the eruption. This deformation would be associated with the intrusion of new magma under the caldera before the eruption.
Figure 8. Interferogram between 19 March 2015 and 4 September 2017 with a deformation of the caldera of 17 cm (Source: Yu Zhou and Mike Stock).
Clouds of ash
The Washington volcanic ash warning center (VAAC) reports the appearance of a column of eruption without ash content, on September 4 at 12:30 pm TL, originating from the Fernandina volcano, reaching a height of 2400 m above the to the west. On the same day at 19:52 TL, the same agency reported the appearance of a column of eruption with a possible ash content, reaching a height of 7000 m towards the Southwest (Figure 9). On September 5, at 01:15 TL, the appearance of a column of eruption, mainly of gas and water vapor, reaching a height of 2400 m and moving towards the southwest (FIG. reported.
Figure 9. Location and extension of emission columns reported by VAAC on September 4 and 5. (Source VAAC / NOAA).
The first satellite evidence of a hot spot on the Fernandina volcano was reported by HGIP of the University of Hawaii on September 4 at 12:58 TL, located south of the volcano’s caldera (Figure 10). Towards 15:58 TL, the same system showed that an emission originated from the volcano and was moving towards the West-North-West. During the following hours and during days 5 and 6, the infrared images continue to show the presence of hot spots in the same locations.
On the same day, the MIROVA satellite system exhibited an extreme thermal anomaly (19697 MW) at 13:25 TL, located south-southwest at the edge of the caldera (Figure 11). Subsequently, at 22:55 and 01:50 TL on 5 September, other low-intensity thermal anomalies (2384 MW and 5287 MW) were noted. Until 6 September, very high thermal anomalies continue to be recorded in the same area of the volcano.
The FIRMS system also reports the presence of hot areas on the Fernandina volcano since the afternoon of 4 September, in which case the location of these areas suggests that the eruptive activity originates from a circumferential fissure at the south- Southwest of the caldera and where the 2005 eruption occurred (Figure 12). Similar thermal alerts continue to occur on day 5 and on day 6 they decrease in number but remain present.
Figure 12. The thermal anomalies recorded by FIRMS on 5 September are grouped to the S and SW of the boiler edge of the Fernandina volcano (Source: FIRMS).
The IMO satellite system for the detection of SO2 gas shows the presence of a column of this gas from Fernandina Island and moves westward (Figure 13), on September 4 at 13:37 Galápagos). On September 5, the GOME-2 satellite sensor detects a gas cloud of about 800 km in length directed towards the West.
Figure 13. IMO (left) and GOME-2 instruments detect the presence of SO2 gas in an emission column moving west of Fernandina (Source: NOAA).
Visual observations, seismic and satellite data confirm the occurrence of an eruption on the Fernandina volcano. Deformation data indicate that this eruption could be associated with the intrusion of new magma under the caldera during the period March 2015 (or earlier) – September 2017. According to the seismic data, it is estimated that the eruption started towards 12h25 TL on 4th September and that its activity has decreased considerably since 15h00 on September 4th. However, satellite data and direct observations indicate that the eruption continued until at least the evening of 5 September.
Under these conditions, it is possible that the eruption is about to end. However, at other times on Fernandina (ei 2009) and other volcanoes in the Galapagos (ei Wolf 2015), there have been breaks during an eruption, so we can not rule out a further increase of the » eruptive activity in the next few days or weeks. It is important to note that there is also the possibility of other phenomena on the volcano, such as the collapse of the caldera bottom, associated with explosive eruptions (1968 eruption) or the sliding of the walls of the caldera (eruption of 1988). For the time being, it is recommended not to approach the caldera or the eruptive crack.
The IGEPN is aware of any changes in the conditions presented by the volcano.
Source : IGEPN
Fuego , Guatemala :
Lahars moderated on the volcano.
Due to the constant rainfall that is mostly generated in the volcanic zone, seismic station FG3 records moderate descent of lahars in the last few minutes, mainly from the ravines: Las Lajas, El Jute, Cenizas, Seca (Santa Teresa) and of the Mineral ravine. These lahars carry volcanic materials of different sizes, trunks and branches.
This is due to the activity carried out by the Fuego volcano.
Lahars descent into the lower ravines can cause damage to the road infrastructure, mainly in passing vehicles between Siquinalá and San Andrés Osuna, San Pedro Yepocaya and Sangre de Cristo, Rodeo in Guadalupe and on Las Lajas Bridge , among others so it is necessary to take precautions and not to stay in the ravines
Source : Insivumeh
Nishinoshima , Japan :
Elevation 25 m
The Japan Coast Guard reported that visual observations of Nishinoshima from an aircraft during the afternoon of 11 August suggested that the eruption was continuing; a high temperature area at the ocean entry on the W flank and a steam plume indicated flowing lava. Lava in the central crater could not be confirmed; a small fumarolic emission rose from the crater’s edge. Observations on the afternoon of 24 August suggested no lava flowing into the ocean.
Source: Japan Coast Guard.
Poas , Turrialba , Costa Rica :
Activity report of the volcanoes Poás, Turrialba: 6 September 2017, Updated at 11:00 p.m.
Volcano Poas: activity over the last 24 hours:
In the last 24 hours, the Poas continues its persistent degassing with a column of water vapor, magmatic gas and aerosols. A number of LP events have been recorded with a small amplitude, but these are sporadic.
The plume rises about 300 meters from the bottom of the crater and is scattered by winds near the surface, mostly to the west and southwest of the volcano.
There was no report of ash fall or sulfur odor.
Volcan Turrialba: activity over the last 24 hours:
During the last 24 hours, a small amplitude variable tremor was observed. A number of LP events with a small amplitude and sporadic VT events were recorded.
The camera showed a persistent degassing of variable force with a column of water vapor, magmatic gas, aerosols and sometimes ash, at a height of 1000 meters from the active crater since last night.
Last night, falls from the ashes were reported at San Isidro de Heredia and Moravia; and this morning at Guadalupe. An odor of sulfur is recorded at Sabanilla.
At the time of this report, the winds at the top of the volcano are variable, but are mainly directed southwest and west, with speeds of up to 29 km / h.
Source : Ovsicori
Photos : Archives Ovsicori/Rsn .