March 22 , 2017. EN. Cerro Azul , Bulusan , Turrialba , Popocatepetl .
March 22 , 2017.
Cerro Azul , Galapagos , Ecuador :
Increased activity of the Cerro Azul volcano.
The Cerro Azul volcano is a basaltic volcano located in the southwest tip of Isabela Island in the province of Galapagos. This volcano is located southwest of the volcano Sierra Negra, 47 km west of Puerto Villamil. Since 1932, there have been 11 eruptions of the Cerro Azul volcano, the last occurred in May-June 2008.
Geology of Cerro Azul.
The summary of geological and historical eruptive activity is mainly based on the work of Naumann and Geist (2000).
The Cerro Azul volcano is the second highest volcano (1,640 meters behind the Wolf volcano with 1,710 meters) of the Galapagos Islands (Figure 1). This volcano has a total surface area of 34 x 22 km and has a compound shape with sides inclined at ~ 25 ° near the caldera, forming the top of the volcano, and flanks with a low inclination (~ 4 °), forming the outermost parts. The contact between the high and low slopes occurs at a radial distance of 4.5 km from the crater and at a height of 600 m. The eruptive activity of the last 1000 years is mainly concentrated in the West, North and East of the volcano. Over the past 5,000 years, its intense eruptive activity has covered lava flows most of its surface. In its caldera, lavas of more than 50,000 years have been found.
The caldera of the Cerro Azul volcano has a depth of 450 m and an area of 4.2 km (NW-SE) x 2.2 km (NE-SW). Its area is small compared to other volcanoes on the current Isabela Island (for example, Caldera of the Sierra Negra volcano: 9.3 x 7.4 km). The Cerro Azul volcano has circumferential fractures of lava emission (parallel to the caldera), which occur mainly in the upper part of the volcano, and radial fractures (perpendicular to the caldera) in its lower part. This bimodality of the fractures is related to the shape of the volcano and affect their eruptive dynamics. Thus voluminous lava flows are formed in the bottom of the volcano or on its flanks which have little inclination; And less bulky streams in its upper part. The maximum distance traveled by these flows is 12 km from the point of emission (which is not necessarily the caldera, but may be the flanks) and are 1 to 4 m thick (Figure 2).
The presence of the Sierra Negra volcano in the northeast of the volcano of the Cerro Azul volcano represents a change of slope in the morphology. Lava flows that move in this direction will change course northwest or south-east to the Sierra Negra-Cerro Azul contact.
Fig. 2. Geological map of the Cerro Azul volcano. The lava flows of the last eruption of this volcano in 2008 (Naumann and Geist, 2000) are noted.
Historical eruptive activity.
The historic eruptive activity of the Cerro Azul volcano took place in its caldera and on its flanks with an average eruptive episode every 7 years (1932 to 2008). The largest volcanic eruption described in the Cerro Azul volcano occurred in 1943 with a volcanic explosion index of 3 (> 10 million m3 of pyroclastic flows). The most recent eruptions (1979 and 1998) have occurred since the radial fractures of the east flank and inside the caldera. A large number of eruptions reported in the last century have located the emission centers on the eastern flank of the volcano because it is visible from Puerto Villamil, located south of Isabela Island. Several eruptions may have occurred during this period on the western and northern flanks and have not been reported due to their remoteness from population centers.
Cerro Azul volcanic eruption, 2008 [Excerpt from the Geophysical Institute (2008a, b, c)]
The eruption of the Cerro Azul volcano began at 21:43 (TL) on 29 May 2008 following an increase in seismic activity. During this eruptive episode, which lasted until June 11, two eruptive phases were distinguished. The first phase took place between 29 May and 1 June, consisting of a rapid emission of lava flows from the top of the cone along concentric and radial fractures (Figure 3). This activity generated a small eruptive column of ash that turned to the northwest and lava flows emitted from the summit that entered the caldera of the volcano. During this phase, the largest earthquake (M 3.7, 30 May) in the northern part of the volcano with SO2 emissions of 10,597 kt was recorded. The largest SO2 emissions were observed by the IMO instrument on 31 Mi, with 21820 kt.
On the other hand, during the second eruptive phase, the lava flows were emitted from a radial slot in the lower part of the building. These flows descended by 10 km on the east and south-eastern flanks of the volcano with an average width of 2.3 km. The eruptive activity decreased considerably between 16 and 17 June.
Fig. 3. The lava flows emitted during the eruption of the Cerro Azul volcano in 2008.
Increased seismicity of Sierra Negra and Cerro Azul in 2017.
From 15 February this year, an increase in seismicity, which was characterized by the presence of rock fracture events (VT) was observed. On the 16th, a swarm of about 1 hour occurred, then a decline in activity sporadic events was noted. These events were located and some of them were under the Sierra Negra volcano. The presence of sporadic earthquakes with different energy continued and could be found a little more, between 8 and 13 March, under the Sierra Negra volcano.
However, on March 18, a new swarm that lasted about 30 minutes, was observed. On March 19, it is observed that earthquakes are more frequent and of greater magnitude (3.4 ML). On the 20th, from about 7:00 am to 6:00 pm, a swarm was observed. It should be noted that the earthquakes that took place between 19 and 20 March are located south-east of the Cerro Azul volcano, contrary to that observed on the previous days (Figure 4).
It is clear that there is a migration of the activity of the Sierra Negra volcano to Cerro Azul.
Fig. 4. Location of the earthquakes since February between the volcano Sierra Negra and Cerro Azul. Most of these events are very small for them to be localized.
Conclusions – probable eruptive scenarios.
From what has been observed in recent months, the most likely is an eruption on the Cerro Azul volcano of the same type as in 2008, either through different radial or circumferential cracks that are activated at different times. This activity generally lasts from a few days to a few weeks. In the event of an eruption in the caldera, the occurrence of hydromagmatic explosions due to the presence of small lakes is possible.
Note that there are no human activities near the volcano that could be affected by lava flows. However, in the event of explosive activity, small ash falls can occur in Puerto Villamil depending on the speed and direction of the winds.
Moreover, the increase in seismic activity recorded on 19 may not necessarily be an eruptive precursor, if this was generated by a small intrusion, unable to generate a surface eruption. This is monitored and changes will be reported.
Source : DN/MC/ET/MA/SH/AA/VL/AO
Escuela Politécnica Nacional
Bulusan , Philippines :
BULUSAN VOLCANO BULLETIN 21 March 2017 8:00 A.M.
Bulusan Volcano’s seismic monitoring network recorded six (6) volcanic earthquakes during the past 24 hours. Degassing at the active vents could not be observed due to thick clouds covering the summit. S ulfur dioxide (SO2) emission was measured at an average of 11 tonnes per day on March 17, 2017. Precise leveling data obtained on January 29, 2017 – February 03, 2017 indicated deflationary changes since October 2016. This is consistent with data from continuous GPS measurements that indicated short-term deflation of the edifice since January 2017. However, the edifice remains generally inflated with respect to July 2016, based on continuous GPS data.
Alert Level 1 (abnormal) status remains in effect over Bulusan Volcano, which means that it is currently in a state of unrest probably driven by hydrothermal processes that could generate steam driven or phreatic eruptions. Local government units and the public are reminded that entry into the 4-kilometer radius Permanent Danger Zone (PDZ) is strictly prohibited and that vigilance in the Extended Danger Zone (EDZ) must be exercised due to the increased possibilities of sudden and hazardous phreatic eruptions.
Source : Phivolcs
Photo : Wikipedia
Turrialba , Costa Rica :
Activity report of the Turrialba volcano,
March 21, 2017, updated at 11:00 AM
Over the last 24 hours, the Turrialba volcano has emitted a plume of gases, aerosols, and small amounts of sporadic ash. The flow of gases and ash is low, the plume has a blue-white color, and its height reaches about 100 meters above the top of the volcano. The seismographs of the seismic network record medium volcanic tremor signals of varying amplitude, and few low frequency earthquakes (LP).
The gases, aerosols and ashes are dispersed mainly southwest over the region including Finca La Central, El Tajo, La Pastora and Cartago areas such as Cot, Tierra Blanca, Llano Grande, Chicua, San Rafael de Oreamuno, Pacayas, according to the meteorological data of the National Institute, IMN and the numerical model of calculation AERMOD. There are no reports of ash falls.
The OVSICORI-A remains vigilant on volcanic and seismic activity.
Source : Ovsicori
Popocatepetl , Mexico :
21 March 11:00 h (21 March 17:00 GMT)
Over the past 24 hours, by the monitoring systems of the Popocatepetl volcano, 52 low intensity exhalations, accompanied by volcanic gases, have been identified. A volcano-tectonic earthquake, today at 9:01 am with an amplitude of M 1.8 was also recorded.
During the night, an incandescence above the crater was observed.
At the time of this report, the volcano is observed with a constant emission of volcanic gases south-south-east.
CENAPRED asks not to approach the volcano and in particular the crater.
The volcanic alert level of the volcano Popocatepetl is located in Amarillo Phase 2.
Source : Cenapred .
Photo : Karel Del Angel