La Soufriere St. Vincent volcano may erupt big time

[bjdeming]

It's the big crater I copied the URL of. Here's a before-after GIF from Sentinel Hub.

He also tweets that the sulfur cloud has reached Cabo Verde. And it is in the lower stratosphere.

The UWI-SRC director said that this degree of explosiveness and plume height are bigger than the last two big ones: 1979 and 1902.

 

[bjdeming]

Live cam (h/t to Dr. Klemetti, who advises to ignore the eruption prediction thing on the right):



However, NEMO tweets that the pyroclastic flows now happening are from column collapse as the vent pressures fluctuate.

And some amazing satellite imagery (source) tweeted yesterday showed no domes, rather, a series of new explosive craters. The power of this thing is just amazing.

 

[bjdeming]

What a pyroclastic flow apparently looks like on radar (Martinique is two islands up in the chain):




Source. (They decided later that it was column collapse, not a dome explosion.)

It's those enormous coignimbrite clouds.

That's about the area where, in 1902, no animal or human out in the open survived, and there were fatalities in many shelters and on boats offshore, too, per Andersen and Flett.

Today, that whole section has been evacuated since the 8th. Volcanology has come a long way! (This thread has many nerdy details about La Soufriere's history and how they worked out the hazards.)

But many people have lost everything. You can't evacuate property.

 

[bjdeming]

This UWI-SRC expert, Dr. Richard Robinson, is basically the "James Spann" of SVG right now -- trusted by the people and helping everyone with advice and information as the emergency unfolds. Here, he is being interviewed by the prime minister during the first half of the show (the live part starts around 3:50), giving background this morning on the pyroclastic flows and what to expect next. It's excellent science communication, too -- love that boiling milk analogy.

Robinson is in the Belmont Observatory, a few miles from the crater. That's probably the source of the live cam, too.

 

[bjdeming]

Hmm....

For example, a large eruption in the tropical regions of the Northern Hemisphere leads to a southward shift of the Intertropical Convergence Zone. This results in an increase in hurricane activity between the Equator and the 10°N line, and a decrease further north. The zone’s southward shift has further effects in the Southern Hemisphere, causing a decrease in activity on the coasts of Australia, Indonesia, and Tanzania, while Madagascar and Mozambique experience an increase. These changes can last for up to four years following the eruption.

Source

Found that while wondering if this volcano's copious ashfall into the tropical Atlantic might cause a plankton bloom and, at this time of year, affect tropical system formation. That question -- a bloom, possible effects -- goes unanswered.

 

[bjdeming]

The Smithsonian's Global Volcanism Program summed up things here. Plume heights got as high as 52,000 feet, so, yes, tropopause or close to it.

For instance,



It's still going on but less energetically and more episodically at the moment. I haven't seen any more estimates of SO2 output, but the sulfur cloud reportedly has reached as far east as Niger and the ash as far west as Ecuador and the Pacific Ocean.

The technology to look right down an erupting volcano's throat is amazing. To this layperson, it looks like the crater has enlarged, but in their scientific update tonight UWI-SRC tweeted that they would be reporting their analysis later.

 

[bjdeming]

This, too (second tweeted video). You can also see here the weather effect of the chain of mountains (extinct volcanoes) that forms the backbone of the island. In 1902, per Andersen and Flett, clouds kept people on the windward side from realizing Soufriere had erupted. They thought it was a thunderstorm until ash and rocks rained down instead of water.



The pyroclastic flows (PDC) are moving in all drainages, with some reaching the sea, but per UWI-SRC they seem to be heading more eastward over time. Today's update is the same as yesterday's -- episodic explosions and PDC's. With the recent rain, there has also been one lahar reported thus far; this hazard will turn ugly over the summer and beyond.

It's getting difficult, physically and emotionally, for folks in the green zone, per Twitter and some media articles.

 

[bjdeming]

Doing some reading for a blog post this Sunday on Soufriere and the Atlantic hurricane season and realized that this is the largest SO2 output from a Caribbean eruption on record, and AFAIK it is the first large eruption observed in the Atlantic MDR. Granted it's early in the year still and also, compared to Pinatubo's caldera-forming eruption in 1991 (18 megatonnes of SO2 into the stratosphere), Soufriere SV's crater-forming eruption is tiny (just a fraction of the estimated 0.4 to 0.6 megatonnes of sulfur went into the stratosphere thus far, per satellite observations).

Still, it may count for something. And I hope that southward-shifting ITCZ hypothesis works out -- potentially fewer US landfalling storms is good news in an ENSO-neutral year.

I'm really looking forward to the official 2021 outlook in May!

Meanwhile, La Soufriere has calmed down a little recently and might even be trying to form a dome, per UWI-SRC. Hopefully, the worst has passed.

Two other Caribbean volcanoes are on alert - Pelee, on Martinique, and the submarine volcano Kick 'Em Jenny -- but it's low-level and there are no reports of increased activity.

 

[bjdeming]

Just a sulfur update:



If all the wildfire smoke in both hemispheres didn't affect TCs, it seems doubtful that this will. La Soufriere is just doing intermittent explosions now, but they are still carefully monitoring seismicity, GPS (deflating a bit), gas and other signs.

Interesting article this week in the Jamaica Observer:

Volcanologist, Professor Richard Robertson, is warning that while the explosions at La Soufriere volcano have been getting weaker and less frequent over the last two days, this does not mean that the eruption has ended.

“We are not convinced that the magma down here has all come up,” he said Wednesday evening on “Round Table Talk” on the state-owned VC3 cable channel.

“We are not sure how much [magma] it is and we are not convinced that it is completely up, that it is out, or that it has run out of steam,” he said, adding “It will take us a little while to be sure it is really ended”.

The volcanologist, the lead scientist from the Seismic Research Centre (SRC) of the University of the West Indies (UWI), monitoring the volcano, said that residents must remain on their guard, avoid the Red Zone and take steps to minimise the impact of the ash.

He said that the safe zones are expected to remain that way for the duration of the eruption.

The news comes even as Robertson and his team, as well as other professionals in the United Kingdom, had feared that the volcano had returned to “prehistoric” eruptions as occurred 15,000 years ago. Such an eruption had the potential to turn St Vincent into a “desert,” Robertson said.

I wondered about that, having read that Soufriere has had plinian and ultraplinian events in prehistotic times.

This screencap from a wonderful Streva Project playlist on La Soufriere (#3) shows the difference (volcanologist for scale).


The VEI 4 1902 and 1812 pyroclastic flow deposits are labeled. Per UWI-SRC, this current event might prove to be similar to the one in the 1700s, which isn't labeled with a date here.

But look at the pre-1700s deposit (NOT "deposits"). That's what this volcano can do, if circumstances are right. This doesn't seem to be the case now, although no one is letting their guard down yet.

Those cruise ships that were sent? They might have had to evacuate all of the island's roughly 100,000 residents quickly if it had turned out that last weekend's opening blasts were just throat clearing. I think two ships are still on standby, but hopefully the volcano will calm down and go back to sleep.

 

[bjdeming]

Total evacuation is apparently still on the table, but no moves toward it seem to be taken yet.

The volcano had a largish explosion yesterday, but that might have been a lava dome; that happens a lot at this type of volcano. Here is this morning's update from about five hours ago. (This open-access book on volcanic crisis communication might interest some people, tok.)

What is concerning is the UWI-SRC report a couple days ago that Soufriere's deflation has apparently reversed and new magma might be coming in.

 

[bjdeming]

Yesterday they summarized the eruption to date in a live Zoom press conference that later made its way to YouTube. It's worth listening to, if you're following events on St. Vincent, and not only for Rod Stewart's delightful Scottish-Caribbean accent. (The "U-wee" is apparently how they refer to the University of the West Indies [UWI].)

Dr. Robinson calls the early phase plinian or subplinian. Mr. Stewart explains very simply what they see in the seismograms (incidentally, y'know how he leaves it with the telltale signs of an explosion coming? La Soufriere blew within the past hour. At last report, about forty minutes ago, the plume was 8 km high and rising.)

Intermittent explosions like this, at lower intensity than the first blasts, are what can be expected now, and this could go on for weeks to months or even longer, they say. They hope that the volcano will settle down, build a dome, and go dormant, but they can't rule out new magma rising and the whole process, including the plinian-style beginning, happening all over.

Me: After all, this thing started with a dome.

We'll just have to wait and see, but given its location and the approaching hurricane season, mets probably are watching it closely, too.



Something else they have in common with volcanologists:

 

[bjdeming]

There is something bigger than La Soufriere on this island:

Far in the distance, warm air swirls off the African coast, and embryonic storms slowly mature into the hurricanes that will visit future transatlantic trauma upon us. The scientists forecast better (worse?) than even odds that we’ll be hit by a major storm this year.

...

Yet, here we are. Surviving. Learning. Recovering. Rebuilding. Our faith in God’s mercies and in the brotherhood of our fellow man is indeed seeing us through. We are neither bowed nor broken. Discouraged or defeated. What ever the future brings, it’s gonna have to come better than 30something cataclysmic detonations to stop us.

Even amidst heartbreaking individual stories of loss and pain, there is a palpable sense that things could have been much, much worse. There is a sense that things are slowly improving, and that we are going to be, collectively, good.

For the time.

-- Read the whole thing