Subject: internal activity level of the Nevado del Ruiz volcano.
The level of activity continues: level of activity Yellow or (III): changes in the behavior of volcanic activity.
Regarding the monitoring of the activity of the Nevado del Ruiz volcano, the SERVICIO Geologico COLOMBIANO reports:
During the last week, the volcanic system continued to show unstable behavior. The recorded seismic activity was mainly associated with fluid dynamics in volcanic conduits. This type of seismicity, was characterized by a continuous recording of tremors short and long-term and kind of long period earthquakes (LP), located mainly in the vicinity of Arenas Crater and south of this sector. Continuous volcanic tremors episode were produced from December 20, 2015 at 12:47 (local time) and were reported in the extraordinary bulletin of the same day.
This volcanic tremor seismic signal, which recorded continuously up to the date of issue of this newsletter, presented different energy levels in its initial phase and has been associated with the significant release of gas and ash in the atmosphere, which were confirmed by reports and photos of Los Nevados National Park officials (NNNP), personnel of ASDEGUIAS, workers of Cerro El Recreo and nearby residents, both of the volcano and in the city of Manizales, and officials of the Colombian Geological Service.
As for seismic activity related to the fracturing of the rock in the volcanic structure, this type of seismicity was located mainly in the North East and North West areas distals on Arenas crater, and to a lesser extent in the Southeast sector of the volcano. The depths of the earthquakes are between 1.4 and 8.5 kilometers. The maximum magnitude recorded during the week was 1.1 ml (local magnitude), corresponding to two earthquakes, one of which took place on December 15 at 3:54 p.m. (local time) in the northeastern sector of Arenas crater at a depth of 4.10 km, the other recorded on December 20 at 1:47 in the North-West sector of the crater, at a depth of 4.73 km.
The volcanic deformation measured from electronic inclinometers, satellite navigation systems (GNSS) and satellite images, which record changes in tilt, position and shape of the volcano (respectively) during the last period evaluation showed some changes correlate with other monitoring parameters.
The volcano continues to emit into the atmosphere a significant amounts of water vapor and gases, including sulfur dioxide (SO2). During this week, permanent DOAS stations installed in the volcano area, recorded significant measured values of SO2. Many reports of strong smell of sulfur were received and demonstrate the high concentration of volcanic gas in the region.
The column of gas, steam and ash reached a height of 1300 meters above the summit of the volcano on December 16. The direction of the dispersion of the column is in line with the regime of prevailing winds in the region, who, during the week showed a predominant direction between the Northwest and the Southwest over the volcano.
It is considered that the volcanic system continues to evolve. New events can indicate an acceleration of the process, involving greater system instability. It is essential to pay attention to official information to be published by the Colombian Geological Service and to consider the recommendations for such events, including the use of masks.
December 26, 2015. Nevado del Ruiz, Colombia :
Source : SGC