November 15 , 2019.
Indonesia : Lamongan ,
The Centre for Volcanology and Geological Hazard Mitigation (PVMBG) has recorded hundreds of local tectonic shocks as a result of the increased volcanic activity of Mount Lemongan in Lumajang, East Java.
PVMBG reported that a total of 252 earthquakes rocked the area on Wednesday November 13. Tremors from 15 of them were felt with an amplitude of 10-30 mm at I-IV level on the MMI scale.
“Based on observations and visual and instrumental data analysis up to November 13, the activity level of Mount Lemongan is still at level I (normal),” PVMBG Head Kasbani remarked.
He further appealed to the community living west to southwest of Mount Lemongan, namely Sumber Petung Village, Tegal Randu, and Papringan, to remain calm and not to be provoked by baseless rumours related to the volcanic eruption that claim they are likely be affected by the earthquakes.
Hikers are also being asked to stay vigilant regarding any developments of Lemongan’s activities issued by the local PVMBG and Regional Disaster Mitigation Agency (BPBD).
Mount Lemongan is a unique volcano in the world, in that its eruptions do not happen at the summit, but on lands around the mountain. Hence, the eruption forms craters and small mountains known as bocha. There are around 60 points of eruption around the mountain.
The Gunung Anyar cinder cones were formed during an eruption in 1898 at 400 m elevation on the SW flank of Lamongan. The eruption began on February 5. Activity slowed by the 7th, but included the emission of two small lava flows, the largest of which traveled 300 m by the time it stopped on February 15.
Lamongan, a small stratovolcano located between the massive Tengger and Iyang-Argapura volcanic complexes, is surrounded by numerous maars and cinder cones. The currently active cone has been constructed 650 m SW of Gunung Tarub, the volcano’s high point. As many as 27 maars with diameters from 150 to 700 m, some containing crater lakes, surround the volcano, along with about 60 cinder cones and spatter cones. Lake-filled maars, including Ranu Pakis, Ranu Klakah, and Ranu Bedali, are located on the E and W flanks; dry maars are predominately located on the N flanks. None of the maars has erupted during historical time, although several of the youthful maars cut drainage channels from Gunung Tarub. The volcano was very active from the time of its first historical eruption in 1799 through the end of the 19th century, producing frequent explosive eruptions and lava flows from vents on the western side ranging from the summit to about 450 m elevation.
Source : indonesiaexpat.biz , GVP .
Photos : Anis Efizudin/kye/15 , Tom Casadevall, 1987 (U.S. Geological Survey).
Hawaii , Mauna Loa :
19°28’30 » N 155°36’29 » W,
Summit Elevation 13681 ft (4170 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW
Mauna Loa Volcano is not erupting. Rates of deformation and seismicity have not changed significantly over the past week and remain above long-term background levels.
HVO staff visited the summit of Mauna Loa on foot to repair the webcam on April 24. The weather was perfectly clear and views of the caldera floor showed nothing unusual.
During the past week, approximately 180 small-magnitude earthquakes (nearly all smaller than M2.0) were detected beneath the upper elevations of Mauna Loa. Most of the earthquakes occurred at shallow depths of less than 5 km (~3 miles) below sea level.
Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) measurements show continued summit inflation, consistent with magma supply to the volcano’s shallow storage system.
Readings of fumarole temperature and gas concentrations at the Sulphur Cone monitoring site on the Southwest Rift Zone remain stable.
Source : HVO.
Italy , Stromboli :
Weekly bulletin from 04 November 2019 to 10November 2019 (date of publication of 12 November 2019)
SUMMARY OF THE STATUS OF ACTIVITY
In light of the surveillance data, we highlight:
VOLCANOLOGICAL OBSERVATIONS: During this period, a normal explosive activity of strombolian type was observed accompanied by degassing activities. The hourly frequency of the explosions fluctuated between medium-high values (16 events / h on November 6 and 7) and high values (23 events / h on November 9). The intensity of the explosions was mainly low in the craters of the North zone and medium-high in the zone of the craters Center-South.
SISMOLOGY: The seismological parameters do not show any significant changes. It should be noted the occurrence at 3 h 11 UTC on November 12, 2019 of an earthquake of magnitude ML = 2.2, previously located near the east coast of the island at a depth of 5.2 ± 0.8 km.
DEFORMATIONS: There are no significant changes to the permanent GPS and Tilt networks.
GEOCHIMIE: The flow of SO2 is at an average level The isotopic ratios of helium dissolved in thermal groundwater remain unchanged at the average low values (data of 23/10/2019). The CO2 / SO2 ratio is between medium and high.
The analysis of the images recorded by the cameras located at an altitude of 400 m, at an altitude of 190 m, and at Punta dei Corvi, made it possible to characterize the eruptive activity of Stromboli. During the period under review, the explosive activity was generated primarily by at least three (3) eruptive vents located in the North crater area and by at least three (3) eruptive vents located in the Central South Crater Zone. All the mouths are placed inside the depression which occupies the terrace of the crater
In the northern zone, the explosions mainly involved low-intensity explosions (less than 80 m high) emitting coarse materials (lapilli and bombs). In many explosions, the falling products covered the outer slopes of the area facing the Sciara del Fuoco, and some blocks were rolled a few hundred meters before stopping. The average frequency of the explosions was variable between 4 and 10 events / h. The explosive activity of the three mouths in the Center-Sud region caused explosions emitting coarse materials mixed for purposes, of medium intensity (less than 150 m in height) and sometimes high (greater than 250 m in height) . In some explosions, the products fell back into the upper part of the Sciara. The frequency of explosions in the Center-Sud zone was variable between 10 and 14 events / h … / …
Source : INGV.
Photo : web cam skynet
Ecuador , Sangay :
Update of eruptive activity
The Sangay volcano continues its current eruptive phase that started on May 7th (190 days in total until the publication of this report). It should be noted that the activity occurs from two eruptive centers: the central crater and the Ñuñurco vent (South-East). The central crater has an explosive activity that generates small ash emissions up to 3.2 km above the crater, frequently directed to the west and southwest. Associated with these emissions, ash falls have been reported in recent days in the areas of Cebadas and Guarguallá (Chimborazo province). In addition, ballistic blocks are projected by explosions and are deposited on all the upper flanks of the volcano. On the other hand, the Ñuñurcu vent has an effusive activity that results in an almost continuous emission of lava flows that are deposited along the south-east flank. On the lava flow fronts, there are usually small rock falls that reach the Río Volcán basin and the upper channel.
Frequently, these deposits are remobilized by precipitation, forming mudslides and debris (lahars) in the Río Volcán. The presence of sediments in this river, which joins the downstream upstream of the Upano River, has been persistent in recent months (see Special Report No. 4). During a field inspection on October 19, deposits of a recent lahar were discovered on the shores of the Upano River. In addition, pH values of 7.91, a temperature of 17.9 ° C and a conductivity of 179 μS / cm2 were measured in the water of Río Volcán, normal values compared to other rivers in the region. Ecuador.
Visual observations and surface activity.
1. Central Crater:
In the central crater, there is a continuous emission of water vapor, gas and ash of moderate to high content. Satellite sensors have identified sulfur dioxide emissions of up to 1,300 t / d, typically ranging from 100 to 500 t / d (Fig. 1a). These are mainly directed west-southwest, in the predominant direction of the winds (Fig. 1b). The ash columns during the period 2019 reached 3 km altitude (Fig 1b), with an average of 1 km altitude. This activity has produced in recent days reports on ash falls mainly in the areas of Cebadas and Guarguallá (Chimborazo province). In addition, gas emissions were observed in the fumarole fields located in the Ñuñurco sector and along the southern flank crack under the central crater.
Figure 1. Comparison of geophysical monitoring parameters for the Sangay volcano during the 2019 period. A) Sulfur dioxide emissions recorded by the SENTINEL-SP5 satellite. b) Emission column height of ash, above the crater level, issued by the Washington VAAC and a pink chart showing wind direction and speed. c) Thermal emission power and cumulative volume estimated using the MODIS satellite sensor.
2. Event Ñuñurco:
The analysis of the thermal images indicates a temperature of at least ~ 480 ° C in the Ñuñurco vent, from which several lava flows were emitted (Fig. 2). Some of these flows have reached distances greater than 2 km. Several satellite automatic detection systems such as MIROVA, MODVOLC (Fig. 1c) and FIRMS have also reported these phenomena. From the front of these streams, hot blocks that reach the base of the cone, accumulate in the upper Volcan River. To date, approximately 50 to 25 million m3 of emitted materials have been estimated (blue lines in Figure 1c).
Figure 2. Photographs of the upper east and southeast flanks of the Sangay volcano. On the left, eruptive activity with vapor emission from the central crater and emission of a powerful lava flow from the Ñuñurco vent (May 2019 / Photo: M. Almeida, IGEPN). On the right, emission of low ash columns from the central crater and emission of a new lava flow in the area corresponding to the surface of the lava flow observed in May, delimited by the broken yellow lines (Photos P. Ramón , IG-EPN).
3. Río Volcán:
During the overflight of August 6, 2019, on the east flank, one could observe the upper basin of the Volcan River, which was filled with pale-colored sediments. Thermal images from this area also showed that deposits in some areas were hot even in the river bed (Fig. 3).
Figure 3. Left, photograph of the upper basin of the volcano, showing deposits of pyroclastic material associated with the most recent activity of the Sangay volcano (photo: P. Ramón, IG-EPN). Right, thermal analysis of the south-east flank of the volcano, at the top of the Volcan River. Several hot pyroclastic deposits associated with this eruption period are observed (Image: Silvia Vallejo IG-EPN).
The presence of sediments at the confluence of the Volcan and Upano rivers has been persistent in recent months (see Special Report No. 4). This accumulation is due to the fact that the material of the current eruption is remobilized by the rains in the area, which leads to the formation of mudslides. The deposit of a very recent lahar has been discovered near the confluence of rivers, which is rich in sand-like materials about 30 cm thick on the banks of the river (Fig. 4). In addition, during the on-site visit on October 19, the Volcán River had a pH of 7.91, a temperature of 17.9 ° C and a conductivity of 179 us / cm2, values similar to those of other rivers of Ecuador.
Figure 4. Deposit of lahar discovered near the confluence of Volcán río and Upano (Photo: Francisco Vasconez IG / EPN).
The Sangay volcano maintains its eruptive activity started on May 7 this year, characterized by explosive emissions from the central crater and effusive in the Ñuñurcu vent. The ash columns reached a maximum height of 3 km above the crater with an average of 1 km. Due to this activity, ash falls have recently been reported in the Cebadas and Guarguallá areas (Chimborazo province). The main volcanic hazards associated with this eruptive phase are as follows: ash drop, ballistic projectiles, lava flows and subsequent collapses of up to several kilometers. In addition, frequent rains cause the remobilization of volcanic material generating mudslides and lahars in Volcán River, which can affect the waters of the Upano River. Finally, it should be mentioned that the eruptive activity recorded during this year (2019) was greater than that recorded during previous eruptive processes (eruptions 2015, 2016, 2017 and 2018).
The Institute of Geophysics of the National Polytechnic School remains attentive to the current eruptive process of the Sangay volcano and will inform the moment of any change in its behavior.
Source : PR-FJV-FN-SV-ME-DA-BB-SH , Institut de géophysique , Ecole Polytechnique Nationale.
Photo : Galapagos Tours Nature Galapagos & Ecuador , sept 2018