Over the last 24 hours, seismicity on the Shishaldin volcano has reached a similar level to that observed during other eruption periods in recent weeks, which corresponds to the resumption of eruptive activity on the volcano. This is further supported by the high surface temperatures observed on cloud satellite imagery. No ash plume has been detected. Seismicity dropped sharply around 3:40 am on November 20th and remains at a relatively low level. This suggests that the eruptive activity could be suspended again. No gas plume was seen this morning on a clear webcam.
A high resolution satellite radar image of the Shishaldin summit shows current morphological changes: the growing central slag cone filling most of the pre-eruptive summit crater. A new vent inside this cone and another in the south formed during a more recent explosive activity. Lava flows and lahars are also visible, radiating from the summit to the northwest, north and north-east. Some distortion is caused by the oblique angle of view of the satellite and the correction of the terrain. This image was provided by Simon Plank (German Aerospace Center, DLR) as part of a permanent collaboration with the Alaska Volcano Observatory on Remote Sensing of Volcanic Eruptions.
Shisahaldin - Radar image from 14.11.2019 showing the morphological changes of the crater - AVO / Dietterich, Hannah
The weekly report of the Colombian Geological Survey confirms the instability of Nevado del Ruiz, in alert yellow level.
Seismicity related to fluid dynamics in the volcanic system showed a decrease in the number and energy of registered earthquakes, compared to the previous week. It was characterized by the presence of continuous and sometimes harmonic volcanic tremor, as well as long-lived (LP) and very long-lived (VLP) earthquakes recorded individually or in conjunction with volcanic tremor pulses. of variable energy and were located mainly in the crater Arenas and its surroundings.
Some of these signals were associated with small gas and ash emissions, confirmed by cameras in the volcano area, as well as information from officials at Nevados National Park and VAAC (Current Volcanic Ash Advisories). . The recording of new seismic signals of this type, which may be associated with new emissions of gas and ash, which will be dispersed according to the wind regime at the time of emission, is not excluded.
Nevado del Ruiz - overview of 15.11.2019 - Doc. Cámara SGC-OVSM_1
The seismicity caused by rock fracturing has maintained similar levels, in number of earthquakes and released seismic energy, compared to the previous week. This type of seismicity was mainly located in the Arenas crater, in the western, south-southwest, southeast and northeast areas of the volcanic structure and, to a lesser extent, in the northern sector of the volcano. The depth of the earthquakes ranged from 0.3 to 7.1 km. A slight increase in this type of seismicity recorded on November 12 is 3.4 km west of the crater. The maximum magnitude recorded during the week and during the seismic increase was 1.0 ML (local magnitude), which corresponds to the earthquake recorded on November 12 at 20:48 (local time) at 4.2 km depth.
It is also worth noting the occurrence of two episodes of volcanotectonic earthquake type " drumbeat ", short-lived and very low energy, recorded November 18. This type of seismicity is linked to the processes of ascension and evolution of domes1 on the surface of a volcano.
The deformation of the volcanic surface measured from electronic inclinometers and GNSS (Global Navigation Satellite System) stations did not show any significant changes during the week.
The volcano continues to emit water vapor and high levels of gas, mainly sulfur dioxide (SO2). These levels are estimated from data obtained from SCANDOAS stations and the processing of satellite images. In tracking the information provided by the MIROVA and NASA FIRMS portals, low-energy thermal anomalies were recorded on November 14, 16, 17 and 19.
Nevado del Ruiz - activity of 17.11.2019 - animation of the SGC Cámara-Cisne-Ruiz
In Costa Rica, Turrialba does not erupt on November 20th; a small plume, rich in water vapor, allows a good view of the active crater.
The seismicity remains similar to that of the previous days.
In Karangetang, north of Sulawesi, activity remains stable.
Lava flows are present in two drainages over 1,000-1,500 meters from the summit; hot spots are observable in the two summit craters, which emit water vapor and gas.
The PVMBG reports, for this November 20, 136 eruptions of eruption, 14 earthquakes of blast, 2 hybrid earthquakes, 3 shallow volcanic earthquakes and continuous tremor of dominant to 2 mm.
The level of activity remains at 3 / siaga, with exclusion zones of 2.5 to 4 km.
Sources: PVMBG, Magma Indonesia and Sentinel2