MONTSERRAT

E-mail messages from MVO, August 7/11, 1997

---------- Forwarded message ----------
Date: Sun, 10 Aug 1997 15:21:47 -0400 (EDT)
From: Tony Glaser 
To: Montserrat E-mail group 
Subject: MVO Evening Report 8th August, 1997 (fwd)

MVO seem to me mis-labelling some of their reports - some of the evening
ones seems to be labelled as morning ones . . . TG

---------- Forwarded message ----------
Date: Sat, 9 Aug 1997 08:12:27 -0300
From: MVO 
Subject: MVO Morning Report 8th August, 1997


Montserrat Volcano Observatory
Montserrat, W.I.
Report for the period  4 pm 7 August to 4 pm 8 August 1997  

The cyclical pattern of activity at the volcano continued with explosive
eruptions occuring at intervals of 10 to 12 hours.  There were two events
in the last 24 hours at 09:55 pm on 7th August and 10:32 am 8th August. 

The earthquake count for the reporting period is 12 rockfall signals, 5
long period earthquakes and 136 hybrid earthquakes.  The hybrids were
largely concentrated in a swarm between 03:34 am and 12:35 pm, the
explosion at 09:55 pm last night was unique to date in that it was not
preceeded by a hybrid swarm. 

Violent explosions occured at 09:55 pm and 10:32 am with load rumblings
heard at the observatory.  At 10:32 am the explosion column rose
vertically to 1500 to 20000 feet.  Because the wind was in a northerly
direction heavy ashfall was experienced throughout the North of the island
with pieces of pumice 2-3 cm in diameter falling in St Johns.  Intense
pyroclastic flows were observed after this explosion.  A helicopter flight
at 11:55 showed that flows had reached down Mosquito Ghaut to Harris, down
Tuitts' to Farms and down White River to two bends below the Great Alp
Waterfall.  It was also observed from the helicopter that there had been
small flows in White Ghaut and Tar River Valley in the East.  From the
observatory flows were observed down Gages and in the Belham River Valley
but ash clouds stopped these being confirmed afterwards from the air.  It
is likely that pyroclastic flows also resulted from the explosion last
night but these were not observed.

All ghauts on the volcano are now filled with hot pyroclastic flow
deposits and under no circumstances should people venture into this area. 
It is expected that as the current elevated level of activity continues
further pyroclastic flows will occur on all flanks of the volcano.  This
makes Plymouth extremely dangerous.  The Belham River valley is also very
dangerous and should not be entered at all.  Access to the exclusion zone
is completely restricted, and people should stay away from the flanks of
the volcano.  The central zone is evacuated overnight and people should
not return to there homes until advised to do so.  After an explosive
event moderate ash fall can be expected throughout the island.  When this
occurs people in the northern zone should stay indoors until the fall is
over.  Ash is present in the atmosphere and dust masks should be worn
outdoors.  Everyone should continue to stay alert and listen to Radio
Montserrat for any announcements. 


. . . The Electronic Evergreen, courtesy of GEM Radio Network

============================================================================

---------- Forwarded message ----------
Date: Sun, 10 Aug 1997 15:16:00 -0400 (EDT)
From: Tony Glaser 
To: Montserrat E-mail group 
Subject: MVO Morning Report 9th August, 1997 (fwd)

Via MNI-INFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I've just got back on line after my weekend away. It doesn't appear anyone
else forwarded the MVO reports, so there they come . . 

Tony Glaser

---------- Forwarded message ----------
Date: Sat, 9 Aug 1997 07:54:53 -0300
From: MVO 

Montserrat Volcano Observatory
Montserrat, W.I.
Report for the period 4 pm 08 August to 7 am 09 August 1997

Activity at the volcano overnight has remained at a very high level with
continued explosive activity. An explosive eruption occurred at 09:11 pm.
This was preceded by a swarm of hybrid earthquakes which started at 1600
and ended at the time of the explosion and consisted of 44 discrete
events. A hybrid swarm started at approximately 04:00 this morning and was
still continuing at 07:00 am.

The explosion occurred at 0911 pm.  A loud rumble was heard at the MVO and
an incandescent column of material observed rising from the dome, together
with several intense bursts of glowing material. Heavy ash and fragmented
pumice fall was experienced in Old Towne for about 40 minutes after the
eruption. It is not yet known if there were associated pyroclastic flows. 

The activity is still generally following a cyclical pattern with regular
inflation and deflation of the volcano with explosive activity as the
cycle reaches its peak. The periodicity of the events is approximately 11
hours +/1 hour. However, pyroclastic flows have also occurred outside the
most probable time period, and so at no time is it safe to enter the
exclusion zone, including the Belham river valley. The risk of further
explosive eruptions remains high and the present pattern of activity is
expected to continue. 

There is ash in the air in the west of Montserrat and therefore dust masks
should always be worn in these areas. Drivers should also be considerate
whilst driving in ashy conditions. The Belham River valley is very
dangerous and should not be entered. Access to the exclusion zone is
completely restricted, and people should stay completely away from all the
flanks of the volcano. Everyone should continue to stay alert, and listen
to Radio Montserrat for any announcements. 

07:00, 09 August 1997


. . . The Electronic Evergreen, courtesy of GEM Radio Network

============================================================================

---------- Forwarded message ----------
Date: Sun, 10 Aug 1997 12:51:48 -0400
From: Peter Beadle 
To: mni-info@gemradio.com
Subject: MVO Report for 8 - 9th August

Via MNI-INFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Montserrat Volcano Observatory

Report for the period 4 PM 8 August to 4 PM 9 August 1997
Over the last 24 hours there has been a sudden change to the cyclical 
patterns of explosive activity previously observed over the past 5 days. 
There was an explosive eruption last night 2051. The explosion which was 
expected to occur this morning between 0700 and 0900 did not take place.

Yesterday evenings explosion was preceded by a swarm of hybrid 
earthquakes which consisted of 31 discrete events between 1600 to 2042. 
The explosive eruption occurred at 2051. A loud rumble was heard at the 
MVO and a red glow appeared over the vent. Incandescent material then 
showered down to the North and over Gages. Several intense bursts were 
also noted. Heavy ash and fragmented pumice fall was experienced in Old 
Towne for about 20 minutes after the eruption. It is not yet known if 
there were associated pyroclastic flows.

Precursory hybrid activity began again at 0506 today. The frequency of 
the individual events gradually increased until by 0800 the discrete 
events had merged in continuous high amplitude tremor. The tremor had 
identical spectral characteristics to individual hybrid events. This 
level of activity continued for around 2 hours then decayed until the 
swarm ended at 1320. Very similar activity preceded the catastrophic 
pyroclastic flows of the 25th June 1997, fortunately in this instance no 
collapse or explosion occurred. A second hybrid swarm of slightly lower 
intensity began at 1421 and ended at 1657, comprising of 31 events. 
These events were similar in character to those in the previous swarm.

The earthquake count for the reporting period is 4 rockfall signals, 14 
long period earthquakes and 158 hybrid earthquakes. However, the actual 
number of hybrid events is expected to be much larger as during 
continuous tremor periods events do not trigger the system.

All ghauts on the volcano are now filled with hot pyroclastic flow 
deposits and under no circumstances should people venture into this 
area. It is expected that as the current elevated level of activity 
continues further pyroclastic flows will occur on all flanks of the 
volcano.  This makes Plymouth extremely dangerous.  The Belham River 
valley is also very dangerous and should not be entered at all. Access 
to the exclusion zone is completely restricted, and people should stay 
away from the flanks of the volcano. The central zone is evacuated 
overnight and people should not return to there homes until advised to 
do so. After an explosive event moderate ash fall can be expected 
throughout the island.  When this occurs people in the northern zone 
should stay indoors until the fall is over. Ash is present in the 
atmosphere and dust masks should be worn outdoors.

Such changes in the pattern of activity further emphasize the inherent 
unpredictability in the volcanic system. The risk of further explosions 
remains high. People should remain vigilant and continue to listen to 
radio Montserrat for any announcements.

Montserrat Volcano Observatory
^Z

. . . The Electronic Evergreen, courtesy of GEM Radio Network

============================================================================

---------- Forwarded message ----------
Date: Sun, 10 Aug 1997 15:47:57 -0400 (EDT)
From: Tony Glaser 
To: Montserrat E-mail group 
Subject: MVO morning report, 10 August 1997 (fwd)

Via MNI-INFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


---------- Forwarded message ----------
Date: Sun, 10 Aug 1997 07:05:19 -0300

Montserrat Volcano Observatory
Montserrat, W.I.
Report for the period 4 pm 09 August to 7 am 10 August 1997

Activity at the volcano overnight has remained at a high level with
continued hybrid earthquake activity. 

Two hybrid swarms have occurred overnight. The first, between about 11 pm
and 3 am, was less intense than the swarms experienced yesterday. The
second started at 6 am and is still ongoing at the time of reporting. No
explosion occurred at the end of the earlier swarm. 

The activity of the volcano appears to be changing. The 12 hour
periodicity seen over the last few days seems to be broken, and although
no explosions have occurred for the past 24 hours, there is no guarantee
that further explosions will not take place, and these may be more intense
than those already experienced. Pyroclastic flows have also occurred
outside the most probable time period, and so at no time is it safe to
enter the exclusion zone, including the Belham river valley.

There is ash in the air in the west of Montserrat and therefore dust masks
should always be worn in these areas. Drivers should also be considerate
whilst driving in ashy conditions. The Belham River valley is very
dangerous and should not be entered. Access to the exclusion zone is
completely restricted, and people should stay completely away from all the
flanks of the volcano. Everyone should continue to stay alert, and listen
to Radio Montserrat for any announcements. 

07:00, 10 August 1997


. . . The Electronic Evergreen, courtesy of GEM Radio Network

============================================================================

---------- Forwarded message ----------
Date: Sun, 10 Aug 1997 22:27:07 -0400 (EDT)
From: Tony Glaser 
To: Montserrat E-mail group 
Subject: MVO evening report, 10 August / members / NY Times / London

Via MNI-INFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


New York Times
-------------
Montserrat will be featured in a front-page article in tomorrow's (Monday)
New York Times - it should also be on their website at
http://www.nytimes.com

Any more news from Montserrat? The MVO reports of rocks dropping all the
way to St John's, of incandescent stuff falling, are very concerning . .
please let's hear a few words from some of the other members in
Montserrat.

---------- Forwarded message ----------
Date: Sun, 10 Aug 1997 18:47:55 -0300
Subject: MVO evening report, 10 August 1997

Montserrat Volcano Observatory
Montserrat, W.I.

Report for the period 4 pm 9 August to 4 pm 10 August 1997

The activity of the volcano has continued at a high level during this
reporting period. Hybrid earthquakes have been the main seismic signals
recorded by the network. New dome growth was observed in the scar left by
the explosive activity of last week.

233 hybrid earthquakes, 23 long periods and 8 rockfalls were recorded by
the seismic network today. No volcano-tectonic earthquakes were recorded.
Most of the hybrids occurred in two swarms. The first, between about 11 pm
and 3 am, was less intense than the swarms experienced yesterday. The
second started at 6 am and continued until 11:12 am. This was at the same
intensity as the large swarm yesterday morning, and progressed into near
continuous high amplitude tremor at around 7 am. The number of hybrid
events is probably far higher than that recorded since many of the closely
spaced events will not trigger the seismic software.

A brief clear view of the summit of the volcano was obtained this morning.
A growth of new dome material was observed in the deep oval-shaped scar
formed by the explosive activity of the past few days. Thus it appears
that the hybrid earthquakes are associated with rapid extrusion of new
lava.

The activity of the volcano has changed over the last few days. The 12
hour periodicity seen previously seems to be broken and, although no
explosions have occurred for the past 36 hours, there is no guarantee that
further explosions will not take place. These may be more intense and
longer lived than those already experienced. If explosions do occur, the
central zone should be evacuated immediately, and people in the northern
zone should seek shelter under a strong roof as soon as possible. After an
explosive event, small rocks and ash can be expected to fall anywhere on
the island. Ash and falling rocks also make driving hazardous. Ash is
present in the atmosphere and dust masks should be worn outdoors. MVO are
currently assessing the levels of ash in the occupied zone using a hand
held dust monitor.

All ghauts on the volcano are now filled with hot pyroclastic flow
deposits. It is expected that as the current elevated level of activity
continues, further pyroclastic flows could occur on all flanks of the
volcano. This makes all of the exclusion zone extremely dangerous.
Pyroclastic flows could reach into the Belham river valley. Access to the
exclusion zone is completely restricted, and people should stay away from
the flanks of the volcano. The central zone is evacuated overnight and
people should not return to their homes until advised to do so.

Such changes in the pattern of activity further emphasize the inherent
unpredictability in the volcanic system. The risk of further explosions
remains high. People should remain vigilant and continue to listen to
Radio Montserrat for any announcements. 

16:00, 10 August 1997



. . . The Electronic Evergreen, courtesy of GEM Radio Network

============================================================================


---------- Forwarded message ----------
Date: Mon, 11 Aug 1997 21:58:41 -0400 (EDT)
From: Tony Glaser 
To: Montserrat E-mail group 
Subject: MVO Evening Report 11th August / welcome

Via MNI-INFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


Office of the Prime Minister (Kingston, Jamaica)    rreece@uwimona.edu.jm

I understand that as the Prime Minister of Jamaica, the Hon P.J.
Patterson, is currently Chairman of CARICOM, he wishes to be kept abreast
of developments in Montserrat.

Tony Glaser

---------- Forwarded message ----------
Date: Mon, 11 Aug 1997 20:43:39 -0300
Subject: MVO Evening Report 11th August, 1997

Montserrat Volcano Observatory
Montserrat, W.I.

Report for the period 4 pm 10 August to 4 pm 11 August 1997

Activity at the Soufriere Hills Volcano has continued at an elevated level
during the reporting period.  Hybrid earthquakes swarms remain the
dominant seismic signal. 

287 hybrid earthquakes, 28 rockfalls and 4 long periods earthquakes were
recorded by the seismic network today. No volcano-tectonic earthquakes
were recorded. Most of the hybrids occurred in three swarms.  The first,
between 4:18 pm and 9:11 pm yesterday contained 154 hybrids and was the
most intense of the period.  The second which included 58 events occurred
between 1:32 am and 4:17 am today.  The third swarm occurred between 8:31
am and 11:13 am and included 72 events.  The third swarm was followed by a
small explosion at about 11:38 am. No audible sound was heard from this
explosion but pyroclastic flows were generated in Mosquito Ghaut and Gages
valley.  The flows appeared diffuse with weakly convecting ash clouds. 
The ash plume produced by the event convected slowly to about 8000 ft. 

The summit of the volcano has been obscured for the entire day due to low
cloud and vigorous steaming from the area of the new crater.  A midday
observation flight allowed examination of the distribution of pumice flows
from last week's explosions.  Pumice flows have extended along the whole
of Tuitts Ghaut down to Farms village at the juncture of Farms and Pea
Ghauts.  In Mosquito Ghaut, the flows have extended to just south of
Harris village.  The upper Tar River valley is now covered with a thin
veneer of pumice flows and about 80 % of the new delta is now covered. 
The maximum run-out of pumice flows in the Galways area is about 600 m
from the sea.  In the Gages valley and Fort Ghaut the pumice flows have
reached about 500 m from the sea.  In Tyre's Ghaut (previously called the
unnamed ghaut), the flows appear to have extended just past the junction
with the Belham stream. 

Theodolite measurements of the new crater carried out during clear
conditions two days ago gave a volume of between 5 and 7 million cubic
metres for this feature.  The highest point measured on the dome at that
time was 981 metres or 3266 feet above sea level. 

The activity of the volcano has changed over the last three days. The 12
hour periodicity seen previously is now broken and appears to have been
replaced by hybrid earthquake swarms and dome growth.  The small explosion
which occurred today demonstrate the potential for explosions to occur
with little or no warning during this period.  Further explosions can
occur in the future and these may be more intense and longer lived than
those already experienced. If explosions do occur, the central zone should
be evacuated immediately, and people in the northern zone should seek
shelter under a strong roof as soon as possible. After an explosive event,
small rocks and ash can be expected to fall anywhere on the island. Ash
and falling rocks can make driving hazardous. Ash is present in the
atmosphere and dust masks should be worn outdoors. MVO are currently
assessing the levels of ash in the occupied zone using a hand held dust
monitor. 

All ghauts on the volcano are now filled with hot pyroclastic flow
deposits. It is expected that as the current elevated level of activity
continues, further pyroclastic flows could occur on all flanks of the
volcano. This makes all of the exclusion zone extremely dangerous.
Pyroclastic flows could reach into the Belham river valley. Access to the
exclusion zone is completely restricted, and people should stay away from
the flanks of the volcano. The central zone is evacuated overnight and
people should not return to their homes until advised to do so.

Such changes in the pattern of activity further emphasize the inherent
unpredictability in the volcanic system. The risk of further explosions
remains high. People should remain vigilant and continue to listen to
Radio Montserrat for any announcements. 

16:00, 11 August 1997



. . . The Electronic Evergreen, courtesy of GEM Radio Network

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