Thursday, April 08, 2021

Soufriere volcano updates

 Updates on the volcano

7th May 2021 21.00 PM local

There is no change in the state of the volcano. I hope the downgrade of the alert to orange is just in time to prevent a massive Covid-19 outbreak. From now on, I will keep updating the Covid dashboard, but not this volcano topic.

6th May 2021 11.00 AM local

As I mentioned yesterday, the alert level has been changed to orange. Here is the full press release, and below that the infographic with what this entails.

The UWI St. Augustine, Trinidad & Tobago. Thursday, May 6, 2021. 
— The Government of Saint Vincent and the Grenadines has lowered the volcanic alert level at La Soufrière to ORANGE based on a recommendation from The University of the West Indies Seismic Research Centre (UWI-SRC).    

UWI-SRC/MVO Volcano-seismologist and current Scientific Team Lead Roderick Stewart made the recommendation to the cabinet on Tuesday, May 4, during his update on the recent activity at the volcano.  Mr. Stewart indicated that the recommendation was being made given that there have been no explosions at the volcano since April 22, and the number of volcanic earthquakes recorded has also decreased significantly. At alert level ORANGE the volcano may resume explosions with less than twenty-four hours of notice.

Lahars (mudflows) continue to pose a dangerous threat to the river valleys surrounding the volcano, including Wallibou and Rabacca. Mudflows observed over the past several days have contained boulders up to 5m (15 feet) in diameter. Scientists also observed steaming flows, which are likely due to contact with and incorporation of hot volcanic deposits. Lahars can cause damage to property and severe injury to persons in their path.  Access to the RED volcanic hazard zone should be limited to government-approved essential work only. Conditions remain hazardous, and the potential for injury also remains.

5th May 2021 21.00 PM local

And the update tonight is that the seismic team will give updates Mondays, Wednesdays, and Fridays from now on.

5th May 2021 10.00 AM local

Possibly back to orange alert very soon!

The volcano is still keeping quiet, and with the rainy or hurricane season starting soon, the danger of lahars will only increase for months, maybe even years to come.
Today in the cabinet meeting there will be a discussion, and there may soon be a decision to lower the alert level to orange.
This would mean that persons evacuated from the orange zone can move back to their homes, and the government can start cleaning up in the red zone.
With the threat of lahars, it will also be time to rethink locations and building requirements in the red zone.
This is good news and maybe just in time to prevent an outbreak of Covid-19 in the shelters.

3rd May 2021 21.00 PM local

The seismic pattern is still the same. This morning Dr. Stewart, the seismologist monitoring the volcano, said that it should be reasonably safe to return to the orange zone as long as the government knows of the return so they could quickly assist with evacuation if necessary.
Multiple lahars were recorded again.
SO2 flux was measured and came at 1036 tons per day; I have no idea if that is a lot or not.

1st May 2021 21.00 PM local

The seismic pattern is still the same, with only a few long period, volcano-tectonic and hybrid earthquakes. A few small lahars were recorded. And another beautiful time-lapse video from today, the volcano is still venting.

30th April 2021 21.00 PM local

The seismic pattern is still the same, with only a few long period, volcano-tectonic and hybrid earthquakes. A few small lahars were recorded. 
The question I asked last Wednesday has been answered by UWI seismic; here it is:
Question: How does the current seismic activity at la Soufriere compare with that of other active volcanos that are not erupting, like Mt Pelee, for example? When can you say an eruption has ended, does the seismic activity need to go to non-existent, or can there still be a low level of activity?
Answer: Current seismic activity is comparable to volcanoes that aren’t erupting. To say an eruption has ended we would need low seismic activity but not necessarily zero. The decision on it being over is not based solely on seismic activity. Also depends on ground deformation and gas.
And here is a beautiful timelapse video of today, taken from the Belmont observatory, credit Richard Robertson, UWI-SRC

29th April 2021 21.00 PM local

No change in the seismic pattern. It is still raining, the lahars continue on the flanks of La Soufriere> Some of the lahars are steaming, having passed through hot volcanic deposits. Many of them carry trees, which are now forming a hazard at sea.
29th April 2021 15.30 PM local

It has been raining heavily for part of the night and all day so far, causing multiple lahars, flooding, and mudslides. Several houses have collapsed.

28th April 2021 21.30 PM local

Still quiet,  only a few long period, volcano-tectonic and hybrid earthquakes have been recorded. Something is causing these though, the question is, does this always occur at active volcanoes even when there is no eruption taking place?

28th April 2021 11.45 AM local

Still quiet inside the volcano. The main danger at the moment is the lahars.

27th April 2021 20.45 PM local

No change in the seismic pattern. Some lahars have been recorded this morning after rain. A lahar is a rapidly moving flow of ash, volcanic deposits, mud, and anything it meets. When these lahars met hot volcanic deposits, clouds of steam were seen. Being anywhere near these mudflows is not safe. This is one of the reasons the alert level is still red.

27th April 2021 11.35 AM local

No change; the volcano is keeping quiet. One issue at the moment is that a comparison with the situation before the effusive eruption started is not possible. The seismic measurement station near the top of the volcano has been destroyed by the explosive eruption. The other stations have been placed after the effusive eruption started.
This morning's advice was that cleanup could start in the orange zones and as far north as Georgetown, but the alert level remains red.

26th April 2021 21.15 PM local

No change in the seismic pattern. The seismic team flew in a plane near the volcano today; it was too cloudy to see everything inside the crater. Near continuous steam venting was observed out of several places in the crater. Here is a picture they took:

25th April 2021 21.00 PM local

No changes in the seismic pattern. The team monitoring the volcano published a radar/satellite image of the crater as it looks now; this is their comment: "satellite radar imagery acquired on 24th April indicates probable continued growth or formation of a lava dome following the explosions on 18 and 22 April". And here is the picture:

25th April 2021 12.15 PM local

No changes in the seismic pattern so far. The scientific team has made a presentation explaining the various types of earthquakes that occur at La Soufrière. I have copied this here.

24th April 2021 21.15 PM local

The volcano is keeping quiet, with only a few long-period, volcano-tectonic and hybrid earthquakes.

23d April 2021 21.15 PM local

The update today says there were a few long-period, volcano-tectonic and hybrid earthquakes. Nothing to report really. Last night a few lahars were recorded around 9 PM, location unknown.

23d April 2021 16.15 PM local

No update was provided as yet today. Professor Robertson did indicate this morning that there seems to be an interval of a few days between eruptions, so as soon as there is any update, I will publish it.

22nd April 2021 20.15 PM local

The eruption this morning at 11.09 AM generated a high-level seismic tremor which continued for 20 minutes. After that low-level seismic tremor occurred, which lasted for about 2 hours while the volcano continued ash venting. The first ash plume rose about 8km high. There was also a PDC (pyroclastic flow) moving down the western flank of the volcano. Time-lapse of the explosion below:

22nd April 2021 11.30 AM local

Right now there is an explosive event. The ash cloud does not look as spectacular from my porch, I was even wondering if it was an eruption or a cloud.
Before the eruption, the long period earthquakes have been increasing. I will update the exact time of the eruption; in Bequia Admiralty Bay we see it a bit later than the actual occurrence.
This is a picture taken from the observatory by the scientists at 11.08AM:

21st April 2021 21.00 PM local

Hardly any change, except that the long period earthquakes are increasing in rate and some rockfalls and volcano-tectonic earthquakes have been recorded. Below is a photo of the seismic plot. Sorry for the alignment and the ad; I try to make the picture as large as possible.

21st April 2021 12.30 PM local

No change; there might be a dome building: the long period earthquakes are associated with the movement of magma. If there is not enough gas in the magma, a dome will build. This dome then functions as a cork, and if there still is gas present in the magma, pressure will build up, and the cork will pop, which we will see as an explosive eruption.
The gas measurements done so far do not give sufficient information yet to calculate anything about timing. According to the scientists, the expectation is that at least one or two eruptions could still occur.

20th April 2021 21.30 PM local

No change in the seismic pattern. In addition to the long period earthquakes some rockfalls were recorded and some volcano-tectonic earthquakes.

20th April 2021 11.30 AM local

No change in the seismic pattern during the night. One of the seismic stations recorded the signal typical of a mudflow (lahar) that may have come down on the south-eastern side of the volcano.

19th April 2021 19.00 PM local

The volcano is still at the long-period and hybrid earthquakes. The periods between eruptions seem to be getting longer, so I hope we will have nothing to report for the next 36 hours at least!

19th April 2021 11.00 AM local

Seismic tremor continued until 21.00 PM yesterday. After that, the long-period earthquakes started back until 1 AM, after which their rate dropped.
The GPS positions keep changing, probably corresponding to inflation and deflation of the mountain.

18th April 2021 21.00 PM local

At 16.49, an explosive eruption occurred. The ash plume went up about 8km and drifted to the west southwest. It generated some interesting cloud formations and sunset!
The same long period earthquakes are continuing, the explosion generated a  seismic tremor.
The scientific team says this kind of activity is an indication of build-up and subsequent destruction of a lava dome.

18th April 2021 16.00 PM local

Near continuous long period and occasional volcano-tectonic earthquakes are still reported by the scientific team. The long period earthquakes usually are associated with the movement of magma and could mean that a lava dome is building.

17th April 2021 16.00 PM local

For the time being, the long period earthquakes have continued at a low level, and there were no tremors. So it is nice to have nothing to report about the volcano!

16th April 2021 21.00 AM local

The seismic pattern continues with nearly constant long-period earthquakes and low-level tremors. At. At 6.15 AM, there was a high-level tremor associated with an explosive eruption and ash venting. 
More gas measurements were done and this time measured 460 tons a day.
Two GPS stations are still standing, one in Belmont and one in Georgetown. They are moving slightly in a Northeasterly and Northwesterly direction respectively, towards La Soufrière, indicating that the mountain is "shrinking" or deflating, caused by depletion of the magma chamber, at least let's hope so.

16th April 2021 11.00 AM local

Another explosive eruption occurred this morning at 6.15 AM. The eruption column was quite energetic and was about km high. The ash cloud went to the west of St. Vincent this time. The period between explosions now is about 40 hours, but we are not nearing the end yet...
Yesterday the scientists measured and calculated the amount of SO2 gas vented by the volcano and came to an amount of 809 tons a day. 
I wonder if this will have an effect on the next hurricane season, which is starting soon. If the SO2 gas reaches high enough, it will be in the form of aerosols reflecting sunlight and thus generating a cooling effect on earth. In this case, the cooling effect would be on the Atlantic Ocean. The seawater temperature plays a significant role in the formation of tropical storms and hurricanes. If it is too cold, there will be no hurricane.
15th April 2021 21.00 PM local

The seismic pattern has changed, there is now a nearly continuous long period earthquake, and there were three brief periods of low-level tremor. No explosive eruptions occurred, but there is still some venting. A new dome may be building. Could this eruption of La Soufrière 2021 be nearing its end?

15th April 2021 11.00 AM local

The same seismic pattern continued into the night, with bands of tremor separated by long-period earthquakes. From what I understand, these long-period earthquakes are associated with magma moving inside the volcano but with not enough energy to cause an eruption. Banded tremors started at around 2.30AM, and venting was observed around 4 AM. This venting did not go very high and consisted of ash and gases that went up about 4000 feet. Most of it blew westward, offshore. On satellite imagery, it looks like there was some more venting at about 10 AM this morning.
The periods between eruptions are getting a bit longer now, about 14 hours, while venting continues.
A lot of aid is arriving for displaced persons, the distribution is posing some logistical challenges, especially for those housed in private homes.

14th April 2021 21.00 PM local

The same pattern of tremor and earthquakes continued today. The last two eruptions were about 13 hours apart. They seem less energetic and contain a lot of gas. Below is an animation of the entire explosive eruption stage of the volcano so far which perfectly depicts the tremors and the periods between eruptions.

14th April 2021 12.00 AM local

There has just been another explosion seen from my porch in Bequia. Update to follow.

14th April 2021 11.00 AM local

The same pattern of seismic tremor and  Long Period earthquakes (LP) increasing in strength continued yesterday evening, until an explosion at 22.48 PM. This explosion caused a pyroclastic flow (PDC) towards the east. Lahar's were also reported in Sandy Bay.
Professor Robertson said that the columns of gas and debris now have less energy causing them to collapse and generating these PDC's.

13th April 2021 21.00 PM local

This morning's eruption was a Vulcanian explosion, which is an explosion consisting of small to moderate explosive eruptions lasting seconds to minutes. PDC's can be generated, and ash columns can reach heights of 20 km. A large seismic tremor was registered during this explosion. After that, a smaller seismic tremor continued for 3 hours.
Before the explosion, there was an increasing number of Long Period earthquakes, and after the 3-hour seismic tremor, LP earthquakes are again increasing. These are smaller till now.
PDC's were again observed on the west coast.
There were several cruise ships in Kingstown to take persons displaced by the eruption to islands near St. Vincent. The majority of evacuated persons prefer to stay and go home as soon as possible. The ships have left.

13th April 2021 16.30 PM local

Two spectacular pictures of the eruption this morning, one from the South of St. Vincent and one from St. Lucia with the Pitons in the foreground. As you see, the air is clear, no ash, and the visibility is excellent except in the North of St. Vincent.

Update 13th April 2021 11.00 AM local.

The pattern of short bands of seismic tremors interspersed with long-period earthquakes continued into last night. Associated with these tremors and earthquakes was audible venting.
After 01.30 AM, the earthquakes became more frequent, and there was an explosion at 6.30 AM. According to professor Robertson, the lead scientist, this was more like a classic volcanian explosion with less ash and mainly gases. I am waiting for an official report, but on the radio, he said that there may be capping of the crater happening, and when there is enough pressure built up, it explodes.
This is a fast timelapse video of the eruption this morning:

Update 12th April 2021 21.00 PM local

After 6 am this morning, 3 tremors have been recorded, associated with explosive eruptions or increased ash venting. The episodes of tremors were 2-8 hours apart. Pyroclastics flows have been observed on the Southern and Western flanks of the volcano. They reached the sea at three locations. Extensive damage to vegetation has been observed. The East experienced heavy ashfall, no PDC's. Though Rabacca river is still steaming, it seems some lahars are making their way down on that side. These can be dangerous and destructive as well.
A picture is of a village on the Western coast of St. Vincent.

Update 12th April 2021 11.00 AM local.

At 4.15AM, there was a large explosive eruption of the volcano. Tremors were recorded with larger intervals between them than before, 5-8 hours, associated with ash venting.
Satellite imagery indicates that both the old and the new dome are gone. The eruptions now come straight out of the crater, which has an estimated depth of 800 meters. At this latest eruption, much larger and hotter fragments were ejected in the form of a column of gases and material that collapsed on the volcano's flanks.
This is the most dangerous part of the volcanic eruption. The collapsed column has become a pyroclastic flow or density current, also called a PDC. This flow of debris and ash is very hot (200-700 C or more) and moves with great speed and force, destroying and burning everything in its path.
A last rescue attempt will be made for anyone still in the Red Zone today.

Update 11th April 2021 21.00 PM local

Seismic tremors have been recorded throughout the day, coinciding with episodes of venting or explosive activity. Steaming in the upper parts of the Rabacca valley was observed at about midday. The cause of this phenomenon is was investigated, and the last I heard about it was that the scientific team thinks it was a lahar, hot material mixed with rain flowing down the river valley.
In Bequia, the ashfall is less than yesterday; it rained again at about 17.00 local time, which seems to clear the air.

Update 11th April 2021 11.45 AM local.

It rained last night in Bequia, and the air is much cleaner now. Ashfall is reported in Barbados, Saint Lucia, Grenada, and the Southern Grenadines.

Mainland St. Vincent had an island-wide electricity outage, some roofs in Sandy Bay have collapsed, and tree branches fall off under the weight of the ash.
Tremors have been recorded throughout the night every 1.5 to 3 hours, combined with eruptions or ash venting. I include a short video of the satellite imagery of last night.

Update 10th April 2021 20.45 PM local

We can't see anything to the North from Bequia, so I have been waiting for an update from the scientists in St. Vincent. Activity at the volcano declined somewhat last night, but this afternoon at about 15.30pm, banded tremors were observed, indicating that magma and gas were approaching the surface.
Each tremor episode lasted 20 to 30 minutes, with gaps between them of one to three hours, and at each episode, explosive eruptions or ash venting occurred.

I have been seeing these ash ventings on satellite imagery; I insert a zoomed-in image here. It was taken at 20.30PM local—a big blob of ash moving East.
This is the link to the satellite imagery, click on St. Vincent, and you will get the updated zoomed-in image.

Update 10th April 2021 15.00 PM local

Kingstown earlier today

Update 10th April 2021 11 AM local
Everything is covered in fine ash in Bequia. The lead scientist said this morning in a live update that the entire new dome of 13 million cubic meters may have blown off in the air yesterday. 
Update 9th April 2021 20.30PM local
A third eruption occurred; the volcano is very active with continuous tremors and venting. In the dark, lightning is observed in the ash plume.

    3rd eruption

Update 9th April 2021 16.15PM local
I am not sure if this is a third explosive eruption or still part of the second one. I just took this picture from the Belmont walkway in Bequia.

Update 9th April 2021 15.45PM local
A second eruption occurred at 14.45 and is either ongoing, or there may have been a third one just now.

    Second eruption

Update 9th April 2021 11.00AM local 
A short video of ashfall in Chateaubelair and one of the eruption itself, both shared on Facebook.

Update 9th April 2021 9.00AM local At 08.41 am, the expected explosive eruption of La Soufriere volcano began. The ash plumes reached a height of up to 8km. Ashfall has been observed as far South as the airport.
On infrared satellite images, the ash is observed traveling in a  Northeasterly direction.

Update 8th April 2021 21.00PM local An evacuation order has been issued for the North of St. Vincent. Picture from the monitoring equipment camera. Unfortunately, there is not enough bandwidth available for a live stream.

Update 8th April 2021 11.00 local: The volcano is emitting more gases and steam for the past few hours. Some images shared on Facebook:

From 3 am "banded tremors" have been recorded at one of the monitoring stations around the volcano. The lead scientist in charge of monitoring the volcano explained that a banded tremor is basically a continuous vibration of the ground and is often associated with magma moving towards the surface.

Update 5th April 2021: A new swarm of Volcano-Tectonic (VT) earthquakes began at the
La Soufrière Volcano at 6:38 am today. They occurred at a depth of about 6km. The largest so far had a magnitude of 3.9 and was felt by residents living in the volcano's vicinity.

Sunday, April 04, 2021

Covid dashboard for St. Vincent and the Grenadines

 Covid Dashboard

I find the official dashboard of the Ministry of Health somewhat chaotic, so I decided to make my own. Below is the draft; please comment if you have suggestions.
I personally would like to know the test backlog and/or the number of results pending, but that information is not provided. I wonder if there were no other Covid related deaths than the persons who died in hospital so far.

La Soufrière volcano St. Vincent

Soufrière in state of effusive eruption

The volcano in the north of St. Vincent has entered a state of effusive eruption since the 27th of December 2020. This was first noticed through satellite imagery used for tracking high temperatures (fires). In this case, the high temperature was caused by magma reaching the surface.
An effusive eruption means that magma (molten rock) reaches the surface producing a lava flow or dome. This generally occurs when there is a relatively low amount of gas. In an explosive eruption, pressurized gases are trapped within the magma, causing it to break apart violently.

The alert level is orange at the moment; no evacuation orders have been issued.

An extensive array of monitoring equipment has been put in place around the volcano, which should be sufficient for the scientists staffing it to notify the disaster management authorities on time.
Signals could include changes in gas chemistry, changes in the mountain shape, or volcanic earthquakes.

The new dome is hot: in the beginning, a red glow was observed. This turned out to be burning vegetation. Some of the smoke you see in the pictures is steam boiling the groundwater in the crater. From the 1st of February, sulfur dioxide gas was detected in the eruption. The scientific team thinks this is because the groundwater in which the SO2 was previously dissolving is now drying up.

The old dome is 130 meters high, the new one on 21st March is 105 meters high. Before the last explosive eruption of 1979, there was also a dome growth associated with an effusive eruption which started in 1971.

Starting at approximately 10:30 local time (14:30 UTC) on the 23rd of March 2021, the monitoring network recorded a swarm of small low-frequency seismic events, which lasted for about 45 minutes.  These events were different from previous activity in that they were also recorded on other stations.  
Starting at 16:53 local time (20:53 UTC) on 23 March 2021, the monitoring network started recording volcano-tectonic (VT) earthquakes. These earthquakes are normally associated with underground fractures of the rock mass and are commonly generated by magma pushing through an unyielding rock mass.  The volcano-tectonic earthquakes were located beneath the volcano, at depths down to 10 km below the summit.  The largest of these had a magnitude of 2.6.  Some of them have been reported felt by people living in communities close to the volcano, such as Fancy Owia and Sandy Bay.   It stopped again on the 26th.
The lead scientist monitoring the volcano, professor Robertson, says these volcano-tectonic earthquakes are associated with magma trying to push its way through, whereas the small tremors observed daily around the crater are associated with the growth of the dome.
Update 5th April 2021: A new swarm of Volcano-Tectonic (VT) earthquakes began at the
La Soufrière Volcano at 6:38 am today. They occurred at a depth of about 6km. The largest so far had a magnitude of 3.9 and was felt by residents living in the volcano's vicinity.

I include pictures, most taken by the monitoring scientists except the first one, of the development of the new dome. Please click to enlarge.

Picture posted on Facebook

    27th December

   January 6th dead vegetation


     1st February

12th February

  3rd of March

24th March
     1st of April