Chaitén bulletin no. 83 (9 March 2009) 11 March 2009

Bulletin no. 83 on the eruption of Chaitén volcano, covering the period 4 to 9 March 2009 , has been released by the Chilean geological service SERNAGEOMIN. The original document (PDF) can be found on Werner Luis’s Chaitén site. Translation as follows.

ERUPTION OF CHAITÉN VOLCANO
TECHNICAL BULLETIN NO. 83
4 TO 9 MARCH 2009
OVDAS-SERNAGEOMIN

1. Visual monitoring

During this period the growth of the dome complex has continued, concentrated particularly in the central-southern sector, where the central pinnacle and a significant remaining portion of Dome 1 are located. The images taken by the DGAC camera have shown frequent collapses that have occurred especially on the unstable sides of the central pinnacle and the south wall of Dome 1. All the gravitational collapses have produced block-and-ash flows and some of these have been channelled towards the headwaters of the Chaitén river. The fine particulate material of pulverized rock from the block-and-ash flows (the ‘ash’) has risen with the volcanic gases and water vapour, forming plumes of light brown colouring, which have tended to disperse in a south-eastern direction towards Futaleufú. Today [i.e. 9 March 2009], collapses have been produced towards the south with winds predominantly from the north, which has dispersed the particulate material in the direction of Chaitén (Fig. 1).

Figure 1. Gravitational collapse of the south flank of Dome 1 recorded at 16:10 on 9 March 2009 by the DGAC camera, in which the dispersal of the plume of fine material towards Chaitén can be clearly seen.

2. Seismic activity

The analysis of the data obtained by the Chaitén volcano monitoring stations reveals that the seismic activity has slightly declined in the number of HB-type [Hybrid] earthquakes occurring, with 1 earthquake every 2-3 hours, with a magnitude over 3.5, some of which reached a magnitude 4.0 (Fig. 2).

With regard to the VT-type [volcano-tectonic] earthquakes, these have practically disappeared, with only 2 earthquakes of very low magnitude of less than 1 being recorded.

In general, the HB-type earthquakes are located to the south of the Chaitén caldera (Fig. 3), with depths of around 5.0km.

Figure 2. Seismogram recorded at STAB station for 7 March between 00:00 and 11:59 GMT. The average occurrence of HB-type earthquakes with magnitudes between 3.5 and 4.0 is 1 earthquake every 2-3 hours (red ellipse).

Figure 3. Location of earthquakes on 7-8 March. They are located to the south of the Chaitén caldera. [Click on picture for enlarged version.]

3. Conclusions and interpretations

The seismic activity of Chaitén volcano continues to decline slightly in the number of larger HB-type earthquakes, that is, those with magnitudes between 3.5 and 4.0. The earthquakes that have been recorded have principally been of HB-type, which indicates the continuing feeding of magma into the dome complex, principally in the central-southern sector.

With regard to possible scenarios, these remain as outlined in the previous report, that is to say, total or partial gravitational collapses of the remaining section of Dome 1 towards the south and/or major collapses during periods of intense rainfall, the block-and-ash flows could produce hot lahars in the directon of Chaitén, while the large quantity of volcanic material and tree trunks in the valley of the Chaitén river could subsequently be removed towards the town of Chaitén producing new lahars.

Taking into account the continuing seismic activity with HB-type earthquakes of up to magnitude 4.0, the continuing growth of the dome complex and the frequent gravitational collapses from the southern part of Dome 1 and from the central pinnacle, associated with explosions and pyroclastic flows, along with the high probability of the occurrence of new lahars during periods of intense rainfall, SERNAGEOMIN maintains Volcanic Red Alert.

[End of SERNAGEOMIN bulletin.]

For all our Chaitén coverage: Chaitén « The Volcanism Blog.

Information
Global Volcanism Program: Chaitén – summary information for Chaitén (1508-41)
SERNAGEOMIN – Servicio Nacional de Geología y Minería (Spanish)
Erupción del Volcán Chaitén – extensive coverage of the Chaitén eruption

Chaitén bulletin no. 82 (28 February to 1 March 2009) 4 March 2009

Bulletin no. 82 on the eruption of Chaitén volcano, covering the period 28 February to 1 March 2009 , has been released by the Chilean geological service SERNAGEOMIN. It is available from the OVDAS website (PDF) and from Werner Luis’s Chaitén site (PDF). Translation as follows.

ERUPTION OF CHAITÉN VOLCANO
TECHNICAL BULLETIN NO. 82
28 FEBRUARY TO 3 MARCH 2009
OVDAS-SERNAGEOMIN

1. Visual monitoring

Through ground and aerial observations from 28 February to 3 March it has been possible to assess the evolution of the Chaitén volcano dome complex, its large central pinnacle and the volcanic gases with a predominance of water vapour that it continually emits (Fig. 1).

Figure 1. View of the large central pinnacle and the southern slope of a segment of Dome 1 from Chaitén on 1 March. The steep and unstable sides can be clearly seen. Photograph C. Gallegos.

During this period it has been possible to observe that the growth of the dome complex continues, particularly in the central-southern sector, where the central pinnacle and a substantial remaining portion of Dome 1 are located. This can clearly be inferred from the frequent collapses that occur on the unstable slopes, particularly in the central pinnacle and in the southern wall of Dome 1 (Figs. 2 and 3). All the gravitational collapses have produced block-and-ash flows and the majority of these have added to the large depositional cone in the south-west sector of the domes and, in part, have been channelled towards the headwaters of the tributary of the río Chaitén. The fine particulate material of pulverized rock (the so-called ‘ash’) of the block-and-ash flows has risen with the volcanic gases and water vapour, forming plumes of light brown colouring, which have tended to disperse in a south-east direction towards Futaleufú. During the night of 1-2 March, some fine ash material was also deposited in Santa Bárbara and Chaitén.

Fig. 2. Gravitational collapse in the south wall of the remnant of Dome 1 on 1 March. These collapses, generating pyroclastic flows (of block-and-ash type), reveal both the growth of this area and the great instability of the south wall at the headwaters of the tributary of the río Chaitén. Photograph C. Gallegos.

Fig. 3. Another view of a somewhat larger gravitational collapse in the south slope of the remnant of Dome 1 on 2 March. The pyroclastic flows of block-and-ash flow type accumulated in the headwaters of the tributary of the río Chaitén. Photograph C. Gallegos.

On 3 March during an overflight co-ordinated with the Regional Office of ONEMI it was possible to verify that the deposits of the block-and-ash flow that descended through the río Chaitén on 19 February still maintaind high temperatures in some areas, with emanations of water vapour and even burning of trees where they had come into contact with lava blocks from the domes, with high temperatures (over 300ºC). In addition it was observed that a gas column had condensed to form a dense steam column of up to 1km altitude (due to high atmospheric humidity) with a dispersion plume towards the south that contained traces of fine particulate material of light brown colouring.

During this period, the collapses have occurred at a frequency of 2-3 per hour, of varying magnitudes. In the afternoon of 3 March they took place every 40 minutes.

2. Seismic activity

The data provided by the Chaitén volcano monitoring network shows an average of 2-3 HB-type [hybrid] earthquakes per hour, with magnitudes of between 1.3 and 3.6. Among these, some earthquakes of greater magnitudes stand out (between 3.2 and 3.6), which occurred at a rate of 1 earthquake per hour, on average, on 28 February. This later declined to 1 earthquake every 2 hours in the first days of March.

In relation to the VT-type [volcano-tectonic] earthquakes, these have occurred in a very isolated form and with magnitudes not exceeding 0.8.

In preliminary form, the HB-type earthquakes have continued to be located principally in the southern area of the Chaitén caldera, with a depth calculated at between 5 and 10km. On the other hand, the Seismological Service of the University of Chile has reported much deeper earthquakes, located between 17 and 24km.

Figure 1 [should be 4]. Seismogram recorded by the station STAB [Santa Bárbara] for 1 March between 12:00 and 23:59 GMT. The HB-type earthquakes of greater magnitude decline to a rate of 1 earthquake every 2 hours (red ellipse).

3. Conclusions and interpretation

The seismicity of Chaitén volcano has declined slightly in the number of larger HB-type earthquakes, that is to say, with magnitudes of between 3.2 and 3.6, in comparison to previous days. The earthquakes that have been recorded are principally of HB-type, which indicates the continuing supply of magma to the dome complex.

Some processes that may occur in view of the current situation of the volcano:

• Total or partial gravitational collapse of the remaining segment of Dome 1 towards the south.
• Gravitational collapse of the central pinnacle (possibly towards the south-west).
• If major collapses take place during periods of intense rain, the block-and-ash flows will produced hot lahars in the direction of Chaitén.
• The large quantity of loose volcanic material and tree trunks in the valley of the Chaitén river may easily be dislodged towards the town of Chaitén during intense rain, producing further lahars.

Taking into account the continuation of seismic activity with HB-type earthquakes of up to magnitude 3.6, that the growth of the dome complex and the occurrence of collapses of part of Dome 1 and of the central pinnacle continues, associated with explosions and pyroclastic flows (block-and-ash flows), along with the high probability of the occurrence of further lahars during periods of intense rain, SERNAGEOMIN maintains Volcanic Red Alert.

[End of SERNAGEOMIN bulletin.]

For all our Chaitén coverage: Chaitén « The Volcanism Blog.

Information
Global Volcanism Program: Chaitén – summary information for Chaitén (1508-41)
SERNAGEOMIN – Servicio Nacional de Geología y Minería (Spanish)
Erupción del Volcán Chaitén – extensive coverage of the Chaitén eruption

Chaitén bulletin no. 81 (27 February 2009) 3 March 2009

With the recent upsurge in activity at Chaitén volcano, SERNAGEOMIN has been issuing bulletins on an almost daily basis. All Chaitén reports are archived (as PDF files) on the ‘informes’ page at the website of the Observatorio Volcanológico de los Andes del Sur (OVDAS). The latest to be made available is bulletin no. 81, which reports activity for 27 February 2009. The original document (PDF) is available from the OVDAS website. Translation as follows.

ERUPTION OF CHAITÉN VOLCANO
TECHNICAL BULLETIN NO. 81
27 FEBRUARY 2009
OVDAS-SERNAGEOMIN

Visual monitoring

During an overflight co-ordinated with the Regional Office of ONEMI, in which the National Director of SERNAGEOMIN took part, it was confirmed that the south sector of dome 1 continues to be active, with relatively rapid growth and an increase in fracturing and instability of its flanks, with numerous collapse fans of rock and ash flows on the south slope (Fig. 1). During observations by SERNAGEOMIN personnel in the area, it was estimated that relatively significant collapses of the central spine (needle or pinnacle) and/or from the south sector of dome 1, both of which are growing, occur in the range of 4-5 per day, making the emissions much wider and irregular and changing their colouring to clear brown, because of their greater ash content (for example, at approximately 18:20 today, Fig. 2). Meanwhile minor collapses are observed periodically from the spine towards the interior of the 19 February collapse scar. There is a continual growth of the volume of material in the fan located in the south-eastern sector of the ring that surrounds the domes, which is formed by deposits of rock and ash flows associated with partial collapses of the central spine.

Thermal measurements

Preliminary reports and results confirm that the central spine has temperatures varying between 400ºC and 200ºC. In addition there are north-south [thermal] alignments on the south slope of dome 1, and in this same dome a zone has been detected with temperatures of up to 300ºC, located immediately to the east of the central spine. Finally, in the centre of dome 2 an area with temperatures of up to 270ºC has been observed, and the steam fumaroles in this dome vary between 130ºC and 180ºC. The foregoing confirms the data provided in the bulletin of 25 February for this dome complex and the observations reported in the bulletin before that. Also, it confirms the data contained in the bulletin of 25 February regarding the temperatures in the waters and the deposits in the middle course of the rió Chaitén.

Seismic activity

During the day, the seismicity has maintained the characteristics of the preceding days, with 2-3 HB-type earthquakes per hour with magnitudes of between 3.2 and 3.6, at relatively shallow depths.

Figure 1. Detail of the south sector of dome 1, in which the steep, unstable sides can be seen, strongly fractured and with rock and ash flows on the southern slope caused by partial collapses. In the foreground can be seen part of the apex of the fan of rock and ash deposits which is continually augmented by partial collapses of the steep sides of the western part of the central spine (needle or pinnacle). Photograph P. Duhart.

Figure 2. Partial collapse, of relatively small dimensions compared with that of 19 February 2009, of part of the central spine or of the southern slope of dome 1, generating an irregular cloud of ash and gas which turns to a clear brown colouring and appears to move towards the upper course of the drainage channel of the ring that surrounds the domes. Photograph by C. Gallegos, taken at 18:30 on 27 February from Chaitén.

Conclusions and interpretation

The growth and the partial collapses of the central spine and the south sector of dome 1 are continuing. The principal danger is focused in the growth and probable collapse of significant portions of the central spine and of the south sector of dome 1, along with the generation of renewed lahars during intense and prolonged rains, which will transport the volcanic deposits in the fan of accumulated rock and ash flows in the ring that surrounds the domes and in the middle course of the Chaitén (or Blanco) river, towards the town of Chaitén. The seismic activity continues without significant variations compared to that reported in the previous bulletin.

Taking into account the registering of earthquakes at relatively superficial levels and at depth, the continuing probability of the occurrence of further large collapses of significant parts of dome 1 and the spine, with associated explosions and pyroclastic and ash flows, along with the probability of the occurrence of renewed lahars during periods of prolonged and intense rain, SERNAGEOMIN maintains Volcanic Red Alert.

[End of SERNAGEOMIN bulletin.]

For all our Chaitén coverage: Chaitén « The Volcanism Blog.

Information
Global Volcanism Program: Chaitén – summary information for Chaitén (1508-41)
SERNAGEOMIN – Servicio Nacional de Geología y Minería
Erupción del Volcán Chaitén – extensive coverage of the Chaitén eruption
Chaitén bulletins archive – at OVDAS, Observatorio Volcanológico de los Andes del Sur

Chaitén bulletin no. 80 (26 February 2009) 2 March 2009

SERNAGEOMIN bulletin no. 80 on the eruption of Chaitén volcano was issued on 26 February 2009. The original text can be found at the OVDAS website (PDF) and a slightly edited version is also available on the SERNAGEOMIN site. Translation as follows.

ERUPTION OF CHAITÉN VOLCANO
TECHNICAL BULLETIN NO. 80
26 FEBRUARY 2009
OVDAS-SERNAGEOMIN

Visual monitoring

Reports from SERNAGEOMIN personnel in the Chaitén area indicate that the eruptive activity is remaining relatively stable, with an altitude of the column of less than 2km. During the day some small collapses have occurred on the slopes of the pinnacle. On each occasion, there have been temporary changes in the eruption column, which has become wider and irregular and has turned clear brown in colour, because of the greater ash content. Small collapses were observed, for example, at 17:39, 18:44, 18:59 and 19:35, this last of greater magnitude (Fig. 1). Also, continuing eruptive activity with emission of ash and gases, with the growth of the dome, has been observed in the southern sector of dome 1. The columns are irregular and spasmodic, with a predominance of gas and ash over water vapour, along with numerous small fumaroles formed principally of water vapour.

Figure 1. Partial collapse, of relatively small dimensions, of part of the pinnacle towards the upper part of the scar left by the collapse of 19.02.09, generating an irregular cloud of ash and gases which turns a clear brown colour (photograph by C. Gallegos, taken at 19:40 from Chaitén).

Seismic activity

The seismic activity presents no significant changes compared to that reported in yesterday’s bulletin, with 1-2 HB-type earthquakes with magnitudes within 2.5 and 3.6. The Seismological Service of the University of Chile reports, in addition, 2 earthquakes with depths of 15.1km and 14.4km, respectively.

Conclusions and interpretation

Growth and partial collapses continue at the pinnacle and the south sector of dome 1. The seismic activity continues without significant changes in comparison to the previous bulletin.

Taking into account the seismicity of the area of the volcano, the continuing probability of the occurrence of new major collapses of important parts of dome 1 and the pinnacle, generating explosions and associated pyroclastic and ash flows, along with the probability of the occurrence of new lahars during periods of prolonged and intense rainfall, SERNAGEOMIN maintains Volcanic Red Alert.

[End of SERNAGEOMIN bulletin.]

For all our Chaitén coverage: Chaitén « The Volcanism Blog.

Information
Global Volcanism Program: Chaitén – summary information for Chaitén (1508-41)
SERNAGEOMIN – Servicio Nacional de Geología y Minería (Spanish)
Erupción del Volcán Chaitén – extensive coverage of the Chaitén eruption

Chaitén bulletin no. 79 (25 February 2009) 1 March 2009

SERNAGEOMIN bulletin no. 79 on the eruption of Chaitén volcano was issued on 25 February 2009 and essentially reports the findings of the overflight carried out on that day. The original text can be found at the OVDAS website (PDF) and a slightly edited version is also available on the SERNAGEOMIN site. Translation as follows.

ERUPTION OF CHAITÉN VOLCANO
TECHNICAL BULLETIN NO. 79
25 FEBRUARY 2009
OVDAS-SERNAGEOMIN

Visual monitoring

On an overflight carried out today, 25 February, in a Chilean Air Force helicopter, with specialists contracted by ONEMI to perform thermal measurements, it was confirmed that the eruptive activity described in the previous bulletin has been maintained, that the remnant of dome 1 in the southern sector is found to be active and growing, as is the pinnacle, which presents very steep and unstable slopes (Fig. 1). On the other hand, volcanic material, the product of partial collapses of the pinnacle and dome 1, continues to accumulate upon the extensive fan of blocks and ash located at the foot of the collapse escarpment.

In addition, it was observed that dome 1, in the south-eastern quadrant, is very unstable (Fig. 2), making it highly likely to collapse, generating pyroclastic flows towards the east and towards the drainage channel of the basal ring of the dome complex.

New estimates today confirm the dimensions of the escarpment of the major collapse last Thursday. The north-eastern axis is 500m, the north-western axis is 300m with an average depth of 300m, in a wedge shape.

Thermal measurements

The preliminary data (A. Pávez, oral communication) indicate temperatures in the order of 270ºC at the pinnacle, 200ºC at the south remnant of dome 1 and lower temperatures at dome 2, in the north sector. This suggests that the current magmatic activity is concentrated in the southern sector of dome 1 and at the pinnacle. In addition, the water of the río Chaitén in the portion affected by the pyroclastic flows and rocks and ashes is about 50ºC in the middle to lower portion of the channel, which rises to 70ºC in the middle part, where the flow deposits, associated with the partial collapse (19.02.09) reached temperatures of 130ºC. Additionally, there are thermal alignments with an approximately north-south orientation in the south slope of the currently active remnant of dome 1. It should be noted that this sector of the dome did not present a notable thermal anomaly during the measurements taken in the month of January of the present year, which occurred at the pinnacle. The final detailed figures and interpretations of this study will be contained in the respective report which will be issued by the expert and promptly delivered to ONEMI and SERNAGEOMIN.

Figure 1. Geometry and dimensions of collapse, of pinnacle and of domes 1 and 2 (photograph P. Duhart). [N.B. In this image, English translations of terms are pasted directly over the Spanish originals. The term 'H2O(g)>Pyroclasts' indicates that in this area of emissions, water vapour predominates over pyroclastic material; the reversal of the '>' indicates that the relative proportions are reversed.]

Figure 2. South-eastern slope of the south remnant of dome 1, which displays instability, abundant emissions of steam, gases and ash, with in addition numerous partial collapses generating block and ash flows on its slopes (photograph P. Duhart).

Seismic activity

The seismicity recorded by the Chaitén volcano seismic network presents no major changes in comparison to that reported in the previous bulletin no. 78, with 1-2 HB-type earthquakes with magnitudes less than 3.6, located beneath the volcano. The University of Chile Seismological Service reports today a very shallow earthquake with a magnitude of 2.7 at 10:30.

Conclusions

The eruptive activity remains unchanged and confirms the activity and growth of the pinnacle and the south remnant of dome 1. In addition there is instability of significant sectors of the dome complex (for example, south-eastern slope), the pinnacle and the steep sides of the limits of the collapse. The seismic activity recorded maintains the characteristics that have been present during the last few weeks.

Taking into account the characteristics of the seismicity recorded in the area of the volcano, the continuing probability of the occurrence of new large collapses of significant portions of dome 1 and of the pinnacle, generating explosions and associated pyroclastic and ash flows , along with the probability of further lahars during periods of prolonged and intense rainfall, SERNAGEOMIN maintains Volcanic Red Alert.

[End of SERNAGEOMIN bulletin.]

For all our Chaitén coverage: Chaitén « The Volcanism Blog.

Information
Global Volcanism Program: Chaitén – summary information for Chaitén (1508-41)
SERNAGEOMIN – Servicio Nacional de Geología y Minería (Spanish)
Erupción del Volcán Chaitén – extensive coverage of the Chaitén eruption

Chaitén in action, 27-28 February 2009 28 February 2009

Images from the Tele13 Chaitén webcam, 27 February 2009. The left image was taken at 16:50 local time, the right image at 21:34 local time.

The Tele13 webcam (direct link here, link that opens in your default media player here) has been providing some of the most remarkable images of the Chaitén eruption that we have yet seen. The camera is located just south of  Chaitén town and looks north. The images below were captured yesterday evening and overnight, and show partial collapses, debris flows and, in the images from after dark, the dome glowing and flickering with incandescence. There is a total of 19 images in this post: click on ‘more’ below to view the entire series.

The first sequence runs from 17:16 to 17:24 (all times are local) and shows a small collapse, ashen plumes and debris flows. Note the small debris flow descending the south flank of the dome in the image timed at 17:19.

17:16

17:17

17:19

17:23

17:24

(more…)