Internal activity level of the Nevado del Ruiz volcano.
Activity level 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 through the OBSERVATORIO VULCANOLÓGICO Y SISMOLÓGICO OF MANIZALES, reports that:
During the last week, the volcanic system continued to present instability in his behavior. The recorded seismic activity was mainly due to the fracturing of the rock in the volcanic structure. This type of seismicity was located in the North East areas, South-West and near the Arenas crater, and to a lesser extent in areas of the North West and South East of the volcano. The depths were recorded from 0.6 to 7.0 km. The maximum magnitude recorded during the week was 1.4 ML (local magnitude), corresponding to an earthquake on October 4 at 1:38 (local time) at a depth of 4.3 kilometers. It showed a slight increase on 3 and 4 October in the northeast section of Arenas crater and in the Azufrado River Canyon area.
Regarding the seismic activity associated with fluid dynamics in volcanic conduits, it was characterized by the recording of seismic activity type LP (long period) and shorts episodes of volcanic tremor , they showed a slight decrease regarding the final weeks evaluated. These episodes were associated with emissions of gases and ash in the atmosphere, which could be verified by web cameras installed in the volcano area, officials and technical staff during field work in the area of influence of the volcano. Combined with the reduction in tremor signal, it was noted the decrease in the amount of ash emitted into the atmosphere.
Seismicity related to fluid circulation is situated mainly in the Southeast sector and near the Arenas crater. The above processes mentioned were usually accompanied by thermal anomalies (another typical feature of active volcanoes), which can be tracked using satellite images provided by different agencies such as the portal Mírová, from Italian universities of Turin and Florence . During this week were reported on 28 and 30 September, two thermal anomalies in the Arenas crater of minor nature. The volcanic deformation measured from electronic inclinometers, GNSS stations and satellite images, which record changes in tilt, position and shape of the volcano during the last evaluation period showed stable performance.
The volcano continues to emit into the atmosphere a significant amounts of water vapor and gases, including sulfur dioxide (SO2). The column of gas, steam and ash reached a height of 2000 meters above the summit of the volcano on September 29, 2015. The direction of the dispersion of the column was in harmony with the wind regime, which showed during the week a variable but tended toward the northwest area of the volcano.
October 08, 2015. Nevado del Ruiz , Colombie :
Photo : Ingeominas ( 2011)