Tungurahua volcano news & eruption updates:
Tungurahua volcano (Ecuador): activity update & eruption warning
Sunday Aug 26, 2012 16:04 PM | BY: T
Map of the areas recently affected by ash fall
The Instituto Geofísico published a very informative and detailed summary of the current eruption of Tungurahua:
Current tremor signal from Tungurahua, showing a brief episode of weak tremor (IG)
(freely translated and abbreviated)
The current eruption of Tungurahua which began earlier this month has shown 2 distinct phases:
During the first from 14 to 21 August, the eruption was characterized by intense seismic tremor accompanied by strong roaring noises audible throughout the area, high SO2 emission and ash venting, drifted predominantly towards the West.
Between Friday night of 17 Aug and Tuesday August 21, the intensity of ash emissions and the roars reached their highest level, having also produced 5 pyroclastic flows on the northwestern flank of the volcano with a maximum length of 2.5 km from the crater rim. None reached cultivated or populated areas.
The lava flow originally suspected (from infrared images) to have issued from a point above the Cusu canyon was later discarded as scientists could not find any evidence of it during an overflight. What had caused this observation were ejected icandescent blocks landing in large numbers in this area and rolling down.
The total volume of ash deposited in the proximal area is estimated 400,000 to 500,000 cubic meters. Mmaximum thicknesses were 3 mm in Yuibug, 2 mm in Pillate, and 1.5 mm in Choglontús Chontapamba, 1 mm and 0.5 mm in Cahuají Puela. The ash falls particularly affected areas located to the west and to a lesser extent south-west, at a distance of no more than 15 km.
A second phase started approximately at noon on Tuesday, August 21 and continues until now, when the activity of the volcano can be considered moderate to low. The intense seismic tremor and strong roaring noises ceased and were replaced by short pulses of tremor lasting some minutes.
Instead, during this phase, some more sporadic and violent explosions occurred, especially during the afternoon of August 21.
Gas emissions also decreased to 20% of what was emitted during the previous stage. Ash emissions have been reduced to a few pulses with low to moderate ash content reaching heights of up to 2 km above the crater. Despite this lesser activity, pyroclastic flows of similar size to those of the first stage have occurred during certain explosions, such as one yesterday, August 24, at 15:33 on local time.
2 parameters apparently do not agree with the apparent present condition of decreased activity: positive strain values recorded by inclinometers, especially in the area of the Refuge, which would indicate magma pressurization near the surface. The second is a deep seismic signal, called VLP, which would be indicative of upward movement of magma from depth.
In conclusion we can state that there is a change in the eruptive behavior of the volcano, which has gone from generating constant tremor signals and columns of steam emission, associated gases and ash venting (16-21 Aug), to discrete moderate to large explosions (especially on the afternoon of August 21 to the afternoon of August 22), and - currently, and pulses of tremor interspersed with sporadic bursts of small to moderate size as the one registered in the afternoon yesterday.
The seismic signals of deep magma upward motion and deformation at the top of the volcano do not permit the conclusion that the volcanic parameters have returned to normal, so it is necessary to continue to monitor closely its developments.
While ash emissions are not abundant at the moment, the areas shown in the attached figure are those most likely to be impacted when activity resumes in the near future.
The continuing occurrence of pyroclastic flows in the past days makes it likely that more could occur and it is stressed out that higher areas around the volcano are at high risk, as well as the headwaters of the streams of the volcano.
Links / Sources:
Links / Sources:
Saturday, Aug 25, 2012
Activity has further calmed down over the past day. Only small explosions occurred and the maximum height of the steam and ash plume above the volcano has decreased to 2 km. ... [more]
Tungurahua volcano (Ecuador) activity update: occasional explosions with plumes rising up to 4 km height, constant steaming, moderate tremor
Friday, Aug 24, 2012
Activity remains at similar moderate levels as yesterday. Explosions every few hours are accompanied by strong cannon-shot noises and eject glowing bombs to up to 500 m height. Steam and ash plumes rise up to 4 km above the crater. Light ash fall was reported to the W and NW in the sectors of Chacauco, Cotaló and El ... [more]
Thursday, Aug 23, 2012
Tungurahua's activity has been decreasing since yesterday, which is also visible on the seismograms. Weak explosions could be heard occasionally, but visual observations were impossible due to cloud cover. [more]
Wednesday, Aug 22, 2012
IG reported that on 15 August three small explosions from Tungurahua were detected along with continuous tremor. An ash plume rose 1 km above the crater and drifted W, producing ashfall in El Manzano (8 km SW) and Pillate (7 km W). Activity increased the next day, characterized by increased tremor, roaring sounds, and instances of vibrating windows. An ash plume again rose 1 km, drifted W, and produced ashfall in El Manzano and Pillate. On 17 August two long periods of tremor associated with emissions were detected; 10 explosions were also recorded. Periodic clear views of the crater showed continuous steam-and-ash plumes rising 1.5-3 km above the crater and drifting WNW. Ash fell in Pillate and Bilbao (8 km W). Activity significantly increased at 2100, and strong explosions were detected. Cloud cover prevented visual observations. ... [more]