26/04/2015. Piton de la Fournaise, Ngauruhoe, Popocatepetl .
Piton de la Fournaise, La Réunion :
Since the end of the eruption of 4 February, which had lasted twelve days, the Piton de la Fournaise has not eased the pressure: in two months, the volcano observatory has recorded 168 deep earthquakes, between 1 and 7 kilometers below the level of the sea.
The situation is unusual at Piton de la Fournaise and these events “quite rare” emphasizes the scientific team of Bourg-Murat: while less than 600 deep earthquakes were recorded in ten years (since 2004), or 4 per month on average, we counted 80 per month between February 16 and April 22, exactly 168. At the same time, however, the superficial earthquakes can be counted on the fingers of both hands.
“We know that something is happening, says Nicolas Villeneuve, director of the observatory. And they are located mainly to – 5 km. “The comparison is tempting to the situation that preceded the memorable eruption of Piton Kapor (termed” eruption of the century “), because these earthquakes are distributed” along the 1998 leads “year of the eruption. But these earthquakes are much more lower than those that preceded the eruptive crisis of 1998. Scientists are wondering about the meaning of these events that may suggest the beginning of filling of a fairly deep magma chamber, while no classic sign of filling of a chamber located towards – 2 km is observed.
The scientists scrutinized the signs of a possible migration of magma in the volcanic edifice, being careful not to predict a new eruption, because there is no clear signal in the current state, even if the actual events may contribute to pressurize the storage areas of the more superficial magma.
Other indicators are there however, as the “continuous inflation of the summit cone” and “presence of magmatic gases.” These two sources that confirm seismological observations: SO2 (sulfur dioxide) is deep origin (-5 km) while H2S (hydrogen sulfide) is more superficial. The increase of the latter “could result from a disruption of the hydrothermal system. This process could contribute to the source of pressure detected at shallow depth below the top. “
Finally, the flow of CO2 (carbon dioxide) tend to increase since April 15, on the northern rift zone 120 (zone of “weakness” and identified and constituted by the volcanic axis between the top of the Piton de la Fournaise and the Piton des Neiges, facing north-west).
Source : François Martel-Asselin – clicanoo.re
Photos : Fournaise info , Iloha.fr
Ngauruhoe, Nouvelle Zélande :
Volcanic unrest at Ngauruhoe has declined to representative background levels over the past three weeks. The number of volcanic earthquakes recorded near the volcano is now at typical background numbers. No other indicator of unrest has been detected. GeoNet lowered the Volcanic Alert Level to 0 (no volcanic unrest) from Level 1 (minor unrest).
It is now three weeks since GeoNet last recorded a slightly unusual number of shallow volcanic earthquakes at Ngauruhoe, indicating volcanic unrest. Furthermore, no anomalous ground temperature or unusual level of gas emission were detected at the summit, during visits, indicating that the minor unrest recently occurring at Ngauruhoe has now ceased. GeoNet accordingly lowered the Volcanic Alert Level to 0 from Level 1. GNS Science continues to closely monitor Ngauruhoe and our other active volcanoes through the GeoNet project
The Volcanic Alert Level was raised to Level 1 from Level 0 on March 20 in response to the changes in volcanic earthquake activity. In March, the number of events per day has ranged from 1 to 67, which was similar to previous minor episodes of unrest between 2006 and 2010.
The Aviation Colour Code for Ngauruhoe remains at Green.
Source : geonet.org.nz
Photo : Geo.
Popocatepetl, Mexique :
April 25, 11:00 h (April 25, 16:00 GMT)
In the last 24 hours the monitoring system at Popocatepetl volcano registered 57 exhalations of low intensity, accompanied mainly by steam and gas emissions. The most important occurred yesterday at 13:35, 15:07 and 15:38 h, this morning at 03:16 , 03:43 and 08:00 h .
Additionally, two volcanotectonic earthquakes of less tan 2 magnitude occurred yesterday at 22:51 and 22:52 h.
Most of the time covered by this report the volcano maintained a tenuous plume of gases and steam headed northwards . During the night, incandescence could be seen above the crater, which increased during the exhalations.
At the time of this report there is no visibility towards the volcano, but earlier this morning it could be seen with a continuous tenuous plume of gases and steam headed to the northeast .
The level of volcanic alert of Popocatepetl is located in Amarillo Phase 2.
Source : Cenapred .
Photo : Erik Gomez Tochimani