August 20 , 2016. EN. Etna , Katla , Nevados De Chillan , Bagana .
August 20 , 2016.
Etna , Sicily :
The Etna is an active volcano that everyone knows. He reminds us with the persistence of its gas plume emitted from its summit that goes up to kilometers in the bright sky of Sicilian summer. But maybe everyone does not know that Etna is one of the most active volcanoes and « Transformiste » of all the earth. New craters appear, old valleys are filled with lava, and it happens so that, year after year, it is difficult to recognize the profile of our mountain « of fire. »
Figure 1 – The craters of the summit today (in brackets, the opening year). In the early twentieth century, there was only one active mouth, the central crater (yellow shading). All craters are aligned along a structure (dashed gray) lining the side of the volcano that moves eastward (black arrow).
The Etna’s summit is the most « transformational » area: there is a little over a hundred years, there was only one crater at the top, the central crater. Today, we look at five, two (Voragine and Bocca Nuova) in the « old » Central Crater, while the three other mouths are open to the northeast and the southeast (Fig. 1).
But why these changes on Etna? And what makes « unstable » this volcano? An answer can be found in the study conducted by a group of researchers from the Institute of Geophysics and Volcanology from the University of Roma Tre, which traces the history of the New Southeast Crater, which is built there are less than ten years.
The causes of this important event in the recent history of Etna have been identified in the instability that characterizes the entire eastern flank of the volcano, about a slow but continuous steady movement towards the East (from several centimeters to several decimeter per year). The unstable region interested the region of the summit craters, which divide into « holes« along alignments oriented in the North-South, North East–South West and North West–South East. Which are in fact structural guidelines which have arisen new vents at the top of the volcano.
Figure 2 – fracture system (black arrows, « graben« ) that connects the Northeast with the Voragine crater. The new mouth of August 7 opens where the graben intersects the semicircular fractures placed inside the Voragine.
The latest events confirm this volcano-tectonic setting. The most recent eruption, which took place in May 2016 in La Voragine, was accompanied by a visible fracturing of the ground, which affected the entire summit area. One side of the North East crater collapsed inside, blocking its duct. A structural depression in steps (technically called « graben ») opened between the Crater Northeast and the Voragine, also cracking the cones of the Southeast Crater and the New Southeast Crater (Fig. 2). The entire field of fracture was 300 meters wide and almost 2 km long, and « opens » the summit area in a compatible geometry with the movements of the East flank of the volcano.
Figure 3 – Glowing gas is continuously emitted by the new little mouth that opened on August 7 in the Voragine, near its eastern edge.
The new degassing mouth, which opened on 7 August near the eastern edge of the Voragine, fits perfectly into this structural framework. It is located in the area where the « graben » intercepts the edge of La Voragine, in an area subject to open both by the « pull » induced by the movements of the side of the volcano, that by deepening (subsidence ) currently affecting the center of La Voragine. A combination of critical factors, which caused the opening of this new little mouth, characterized by the emission of abundant hot gases (Fig. 3).
Source : Marco Neri , Primo Ricercatore, Istituto Nazionale di Geofisica e Vulcanologia – Sezione di Catania, Osservatorio Etneo , lagazzettasiracusana.it
Katla , Iceland :
Today (19-August-2016) a magnitude 3,5 earthquake took place in Katla volcano. It was followed by several earthquakes, both before the strongest earthquakes and after it.
The earthquake activity in Katla volcano. The green star shows the location of the magnitude 3,5 earthquake.
This doesn’t seems to be an activity connected directly to magma movements. This might however be a gas under pressure breaking rock, since clues this summer suggests that heat is now increasing in the caldera. At least for now, it might cool down again in coming months. The most common months for Katla volcano to erupt are from July until November, eruptions in other months are less common, they do happen every few hundred years.
Source : Jón Frimann / jonfr.com
Carte : Islande Met Office.
Photo : Futura sciences
Nevados De Chillan , Chile :
Volcanic Activity of the Complex Nevados de Chillan.
The level of activity of the volcanic complex is at :
LEVEL YELLOW: changes in the behavior of volcanic activity – likely time for an eruption weeks / months.
The volcano near the southern border of Mendoza, recorded 1,211 seismic events including 42 earthquakes associated with rock fracturing process, called volcano-tectonic earthquakes.
In addition, there were 14 explosions in the area of craters formed in 2016, characterized by a high concentration of particulate matter.
The most energetic explosion took place on August 8 at 4:56 p.m. reaching an altitude of about 2 km above the emission center and having the greatest energy during this year.
The images obtained by the network of cameras in the area showed a pulsating surface activity generally characterized by the emission of a whitish plume associated with a high content of water vapor, sometimes interrupted by explosive activity with particulate matter emissions, a glow is sometimes observed by night mode cameras.
During this fortnight, the appearance of 14 explosions stands out in the area of craters formed in 2016, and were characterized by a high concentration of particulate matter and a generally poor vertical development. The record of low temperatures in the craters (<60 ° C), leads to the conclusion that the pulses had a phreatic / hydrothermal character. The most energetic explosion occurred on August 8 at 16:56 local time (8:56 p.m. GMT), which reached an altitude of about 2 km above the emission center level and having the highest energy recorded during the year.
According to data provided by the four (4) GNSS stations that control the deformation of the surface of the volcanic complex, some changes were observed in the horizontal and vertical components in the last 3 days. Furthermore, data from two (2) inclinometers installed around the complex, show variations which are not correlated with seismicity or episodes of adverse weather conditions, suggesting a direction of West – North – West inclination, about 6 prad in the northern part and 10 Prad in this component.
The sulfur dioxide emission (S02) recorded by the team DOAS (Differential Optical Absorption Spectrometry) Chillán Station, located 3 km east-northeast (ENE) of the active crater, recorded value average of 828 ± 442 td / day. due to the pulsatile nature of degassing, data show high variability. However, there was an increase in the number of valid measurements obtained during the first half of the month, which found an increase in sulfur dioxide emissions compared to previous months.
Monitoring parameters allow to deduct a greater dynamic in the magmatic system, although a low surface energy affects the hydrothermal system promoting the occurrence of phreatic explosions in the currently active craters. In this scenario, the emergence of new phreatic explosions and / or phreatomagmatic eruptions is possible. Therefore, the volcanic alert level remains at yellow. It is considered high risk area in the state, the area bounded within 3 km from the active craters and it is recommended to limit the access to this area.
Source : Sernageomin
Bagana , Papua New Guinea:
Volcanic eruption in Bougainville: the people called to shelter
19 AUGUST 2016. For several weeks, the Bagana volcano has been erupting in Bougainville, a Province of Papua New Guinea. For their safety, the inhabitants of the village of Torokina have been asked to leave their homes.
It is not lava flows that threaten the villagers living in the shadow of the volcano, but the ash that spread over the land, making it impossible for agriculture. Some details provided by Luke Pamsi, acting head of the region Torokina « It has an impact on the gardens and the sources and reserves of fresh water. The water is contaminated by ash. We have had several days of rains and it’s already causing some flooding on the coast.
Food and water were distributed to inhabitants – rice, mainly for the moment. But according to the authorities, this situation will continue at least three months, as further eruptions are expected.
As in 2014, the population was asked to leave the village and settle temporarily in a rescue center. But the temporary accommodaton could last, warns Luke Pamsi: « According to our calculations, it will be repeated every two years. In a few months we will meet with the International Organization for migrantions (IOM), they will help us develop a plan. At a meeting with residents, I have already mentioned a possible permanent move, but they are not in favor because of problems such as the issue of land ownership. »
The Bagana volcano is one of the most active in the world. Since its discovery in 1842, it has erupted several times, including in 1950, 1952 and 1966. Since 1972, the activity is almost constant.
Source : RADIO AUSTRALIE