#vei-6

[volcanofandom]

So Mionian and Avellino eruptions occurred togheter. The two eruptions are indirectly mentioned in the Bible.

Time ago I read something about how often volcanoes are mentioned in religions, usually as positive presence, and Christianity has it’s own volcanoes aswell, though they’re mentioned only indirectly. It turned out that the mentioned volcanoes are Santorini and Vesuvius. Vesuvius caused the seven plague of Egypt, while Santorini was the one that helped the Jews to escape from the Egyptian slavery (also because Vesuvius is on the other side. It’s tsunami go in France, not toward Egypt).

Vesuvius Avellino eruption was a VEI-6 that ejected about 10 up to 26 km3 of volcanic material. Santorini eruption ejected 40 to up to 100 km3 of volcanic material, rating VEI-6 to VEI-7 (Santorini is very similar to Krakatau. Her only difference is the fact that Santorini is a shield, and most of her eruptions are effusive, while Krakatau is a caldera, and most of it’s eruptions are vulcanian. Santorini is also treacherous. she won’t advice you if she is going to burst. On the other hand Vesuvius, despite being a very violent volcano (It’s eruptions are never below VEI-3), will give you clear advice about it’s incoming eruptions.

On Wikipedia I’ve read that once it was though that Avellino eruption occurred about 200 years before Mionian eruption. But recent researces with Carbon14 show that the two eruption occurred in the same period, probably less than 10 years apart (most likely Vesuvius eruption occurring first) Maybe the two volcanoes erupted the same year, maybe even the same month or the same day. A full VEI-6 and a minor VEI-7 the same period is a super bad new.

I don’t know if in “ The Prince of Egypt “ the Bible was faithfully followed, however climate disturbance started to occur before the Jews escaping, and bad things already happening to the Egyptians. That was the effect of Vesuvius eruption. Then Moses and the Jews left the Egypt, and when they reached Israel, the sea closed on the Egyptians that were chasing the Jews. The moment when Santorini erupted. That shows that most easily, Vesuvius and Santorini erupted few weeks apart.

I’ve read recenty that volcanologist discover new things about the volcanoes they’re studying also with the help of religious texts. Now I don’t remember what volcano was (one of the Hawaii, Mauna Loa or Kilauea?), but they found evidences of an eruption thanks to the religious texts of Hawaiyan local beliefs. It does not matter if you’re a believer or an atheist, the religious texts revealed helpful, regardless your beliefs. This text describled exactly the eruption of a volcano, and it was pretty accurate.

[volcanofandom]

Pompei Eruption a lower end VEI-6. Most likely!

This is what a VEI 5 looks like

And here a VEI-6

The one above is Santa Maria. The volcano is still visible because the eruption was from the flank. The eruption didn’t damage the volcanic edifice, despite being a VEI 6.

The VEI-5 eruption looks rather small. I don’t perceive anything incredible from the pictures. The ash colum goes high in the sky, but people still went near to the volcano (well, this happened even during krakatau eruption, a major VEI-6 but people during the early phases of eruption, still went under the volcano, took pictures and went away. Some plinian eruption aren’t dangerous during the early phase.

Tiny Krakatau was a dwarf even back then, but it is capable of VEI-7. We can say ‘tiny yet powerful’

In Pliny descriptions, the first day the eruption ov Vesuvius wasn’t that bad. Yes it reached VEI-5 by the 24 august, the first day (10 hours are enough to reach a VEI of 5). The description suggest me it looked like something like St Helens, but more there was only a tall plinian column. People just went away from the volcano because of ash rain, that cowered the streets of Pompeii under some 2/3 meters of material.

But the day later it went all dark. Pliny was in a safe area at Misenum (Campi Flegrei). And he describle a dark sky, ash rain and lightinghs. at 30 km away from Vesuvius. The column was tall and even large. Vesuvius disappeared because of collapsing on itself. That sounds more like being near a volcano erupting at VEI-6. To reach VEI-6, a volcano needs little less than 48 hours.

Vesuvius had two legit VEI-5 eruption later (Pollena and Costantinopolee-1631 eruptions). Both were considered sub-plinian, and both, in the description, sounds something like the one of St.Helens, with the difference it lasted weeks rather than days.

I’m not the only one that believe Pompeii was a VEI-6, and certainly not the one that came out with this. There are experts that suggest that. also because paterial ejected from explosive eruptions get eroded easily and in short time. Mount Vulture in Italy was also capable of plinian eruptions, but the ejecta disappeared totally. We know it was an explosive volcano only because of it’s St.Helens shape. But we can’t know how high it’s VEI was (I’ve read only on a document that it was most likely half of the strenght of Vesuvius, so possibly a VEI-5 volcano or a lower end VEI-6

[volcanofandom]

Some reconstruction of Pompeii Eruption

[volcanofandom]

Why VEI matters (to me)

VEI (volcanic explosivity index) is a fixation I have. I’m not normally a number inclined autistic, but sometimes this occur. VEI is simple because it only has a scale of 9 (0 to 8) and don’t require complex math skills. In short, a VEI-6= 10 VEI-5, a VEI-7 = 10 VEI-6, 100 VEI-5 etc...

In general, a respecful volcano is, to me, at least VEI-6. VEI-6 is average. Most volcanoes can do VEI-6 eruptions, and those volcanoes can make feel their presence on whole Earth even when they aren’t dangerous because of geographic reasons. VEI 5 eruptions are highly dangerous (for those around the volcano) but if you live on the other part of the world, you don’t realize what’s goning on. The eruption will not influence you.

But VEI-6 eruptions create worldwide short term climatic effect. Normal VEI-6 eruptions are of normal intensity and last in 5/10 days. They generate a 30 km tall column and cover the soil of at least 6 meters of volcanic material. Often they leave the volcano scarred. The worst VEI-6 eruptions are low intensity eruptions like the ones of Laki. It was a Strombolian (effusive) eruption, so there were no high volcanic deposits, no 30 km tall Plinian colums, but ejecta stay on troposphere instead of going in the stratosphere. Those eruptions might turn Earth in a gas chamber, and you die poisoned, or anyway have long life health problems. Of course it also cause famine.

If an harmless, isolated volcano like Mount Erebus, will do a regular (Plinian) VEI-6, you’ll notice it. Even if you live far far away from it. Even if Erebus will not do any victim. Erebus is in Antarctica, and like Etna, is a shield-stratovolcano and it’s average VEI is 0. It also has a lava lake. The most peculiar part of this volcano is that the base is a shield, the middle part is a stratovolcano and the top is a shield again.

Mount Erebus.

Let’s talk now about VEI-5 volcanoes, like Bezymjannyj. It has the same characterisatic of Erebus, it is an isolated volcano and it is harmless because of this. Bezymjannyj is a stratovolcano and has about the same morphology as St.Helens, the two can be easily mistaken. Bezymjanny not only has a VEI of 5, but is also a violent volcano that tend ho have higly explosive eruptions, always. An ill tempered volcano. But it’s eruptions can’t be felt by people. VEI-5 eruptions don’t alter climate. They can be easily missed if you aren’t around.

Bezymjannyj, not St.Helens.

On English Wikipedia we have

6 - VEI-2 volcanoes 7 - VEI-3 volcanoes 26 - VEI-4 volcanoes (Of those Mount Rainier, and probably Vulcano, belongs to VEI-5 category) 37 - VEI-5 volcanoes (Of those St.Helens belongs to VEI-6 Category) 52 - VEI-6 volcanoes (Of those Krakatau belongs to VEI-7 Category) 31 - VEI-7 volcanoes 14 - VEI-8 volcanoes

I personally consider volcanoes that are below VEI-6 ‘weakling volcanoes’. I would not stay, not even around, a VEI-2 volcano if this one is ready to burst, because eruptions are always dangerous, but on worldwide scale, weakling volcanoes don’t matter. I’m in general disappointed or not impressed when I read "this volcano has a VEI of 5″. For most “VEI-5″ volcanoes, however, there is hope, as many of them are, in reality, understimated VEI-6 volcanoes. There is not much difference between a VEI-5 and a VEI-6 eruption after all, especially if the intensity of eruption is the same (Eruptions of St.Helens and Pinatubo had the same intensity, but Pinatubo eruption lasted longer. Even the Tambora eruption was as intense as the one of Mt.St.Helens, but it lasted three months. Vesuvius eruptions instead were highly intense, as they lasted only 12 hours - Avellino - and two days - Pompeii - and were VEI-6. Rinjani also had intense eruptions. VEI-7, 12 hours.

VEI-7 and VEI-8 volcanoes are on another league (though VEI-8 eruptions are extremely rare). VEI 7 volcanoes are ALWAYS dangerous when they do such eruptions. Even if they are placed in South Pole. VEI-7 eruption cause volcanic winters that last at least three years, and famine. Luckily normally even such eruptions are rare. Some countries have several VEI-7 volcanoes on their land, such as Italy, Greece, Indonesia, Japan and USA.

Alban Hills, a large stratovolcano, completely destroyed by VEI-7 eruptions that ejected about 300 km3 of material and covered Latium under 80 meters of ash. Twice. Alban Hills also had a high number of VEI-6+ eruptions.

Tambora, a massive shield volcano. In 1815 it evolved from a VEI-4 volcano to a VEI-7 volcano, leaving a 7 km wide crater. Inside the crater there is a high mountain landscape, with a lake, a river of fresh water, animals and traces of lava shields and effusive eruptions. The average VEI of Tambora is 0.

The beautiful Mt. Mazama, known as Crater Lake. It was a small shield volcano. It had a VEI-6 eruption first, and shortly later a VEI-7 eruption that formed a crater lake. Powerful eruptions one following the other are rare.

Paektu mountain, China/North Korea. a VEI-7 stratovolcano with an unusual small caldera.

VEI-7 volcanoes are scary because of the destructive capacity. However, VEI-7 eruptions also tend to leave beautiful and unusual landscapes on and around the volcanoes. VEI-7 volcanoes thend to have massive lakes, a peaceful look or to be luxuriant. Most VEI-7 volcanoes have a peculiar morphology that makes their VEI really obvious, except when they are highly active, like Teide and Merapi. In that case, they grow fast and look like regular volcanoes.

Not all VEI-7 volcanoes are violent on average. In fact,, the list of decades volcanoes only has three VEI 7 volcanoes: Merapi, Teide and Santorini. Merapi is violent, Santorini is in the middle of the sea, and water can accidentally go into the magma chamber, increasing the strenght of the eruption. And then Teide, normally not so violent, but people live near the volcano and even a VEI.2 can turn hazardous.

[volcanofandom]

The Enigma of the 79 AD Eruption of Vesuvius

By Henrik Posted 12/08/2016 on Volcano Cafe

(One of my favourite topics.)

Artist’s impression of the 79 AD eruption as seen from Pompeii. Image is probably a screen-grab from the movie “Last Days of Pompeii”.

The August 24th eruption of Vesuvius in 79 AD is the most famous and well-known volcanic eruption of all time. By now, volcanologists have pieced together the sequence of events to form a coherent and comprehensive picture and the only official dilemma is the actual date with meteorological evidence arguing a date towards the middle or end of September. Be that as it may, this is the history of the 79 AD eruption as it stands today.

Seventeen years before the eruption, the Neapolis (literally New City) area was struck by a powerful earthquake which seems to have had its epicentre close to Pompeii as the destruction was heaviest there. There are reports of hundreds of sheep dying from tainted air, probably carbon dioxide poisoning, which argues that the 62 AD earthquake was a precursor of the 79 AD eruption. In 64 AD, the emperor Nero visited Neapolis and performed at the theatre. During his performance, another earthquake struck but legend has it that the emperor concluded his performance after which the theatre was evacuated and then collapsed.

Map showing the major locations such as Misenum from where Pliny the Younger observed the AD 79 eruption. Please note that at the time, Pompeii was situated on the coast and that one probable reason it was not rebuilt was that after the eruption, the location was inland! (Wikimedia Commons)

On August 20th, 79 AD, the area was struck by a series of small earthquakes which increased in number over the next four days but according to Pliny the Younger, people were not alarmed as they were used to it. From the distance of Misenium where he was staying, the morning of August 24th seemed to be normal but around 1 p.m., the volcano erupted. A messenger from a friend of Pliny the Elder, one Rectina of Stabiae south of Pompeii, reached Pliny just as the first eruption occurred with reports of earlier and smaller eruptions not seen from Misenium. Modern research, primarily by Haraldur Sigurdsson (1982 and 2002) paints the following picture of the event:

Possible profile of Vesuvius prior to the 79 AD eruption 

The initial eruption was phreatomagmatic in nature, i.e. “throat-clearing”, and resulted in a column of pulverised, old material at least 15 km high. The column eventually collapsed and later, during the night, pyroclastic flows began. The first one is believed to have been about 550C hot and engulfed Herculaneum, killing some 5,000 inhabitants including those who had sought shelter in the boathouses. Mercifully death was quick as their brains quickly boiled and their skulls exploded.

According to Sigurdsson & associates, the eruption altered between plinian and peléan no less than six times. The main eruption when the eruption column is believed to have reached an altitude of 33 km and the peléan surges 4 and 5 that followed are believed to have been responsible for the destruction of Pompeii. Because of the greater distance from Vesuvius, about 11 km, the pyroclastic surges were not as hot at about 300C but hot enough to instantly cook the skin of its victims, effectively leaving them with third-degree burns covering 100% of their bodies, causing almost instantaneous death from heat shock. In the evening of August 25th, the eruption was over after some 30 hours.

Google Earth(?) image of Vesuvius clearly showing the scarp of the pre-eruption volcano named Monte Somma.

The 79 AD eruption has been assigned an “official” VEI of 5 but there are several reasons to doubt this. First of all, let us compare with the 1991 eruption of Mount Pinatubo! On July 16th 1990, the central Luzon was struck by a magnitude 7.7 earthquake which may have been a precursor to the eruption. On March 15th, earthquakes were felt by inhabitants close to the volcano and on April 2nd, phreatic explosions began and continued for several weeks. On June 7th, the first magmatic explosion occurred with an ash column some 7 km high. On June 12th, the large explosions began with a 30 min eruption which produced a 19 km high column and pyroclastic flows up to 4 km from the volcano. The next day, a 15 min explosion sent an ash column some 24 km high, then another eruption occurred lasting five minutes that produced a 24 km high column. The next day, June 14th, a three minute eruption resulted in a 21 km high column. On June 15th, Pinatubo was shattered by a cataclysmic eruption that lasted three hours and sent a 34 km high ash column skywards.

From this description, it is clear that Vesuvius eruption was comparable to that of Pinatubo, especially if one considers the brevity of the several Pinatubo eruptions in comparison to those of Vesuvius. The main Pinatubo eruption on June 15thlasted for three hours and produced an ash column 34 km high against the at least six hours long Vesuvius main eruption that resulted in a column 33 km high. The figure given for the Plinian phase of Vesuvius 79 AD eruption is eighteen hours. The depth of the pumice and pyroclastic flow deposits, 20 metres at Herculaneum and 2.8 m pumice plus several metres of pyroclastics at Pompeii, 11 km from the volcano, are comparable.

But the best evidence that volcanologists have (most likely) gotten it wrong comes from linguistics. Just to the north of the modern cone of Vesuvius lies a scarp or ridge of a much larger volcano named Monte Somma, which is sometimes claimed to be the result of the VEI 6 Avellino eruption dated to approximately 1800-1650 BC even if other sources suggest an eruption 17,000 BP as the originator. A study of the Avellino eruption reconstructs a minimum eruption time of 3 hours in which an initial explosion raised a column of 23 km which deposited about 0.32 km3 of white pumice while a second, more intense explosion, raised a column of 31 km depositing 1.25 km3 of grey pumice with pyroclastic deposits up to 50 cm thick at Avellino. As can be inferred from this reconstruction, the VEI 6 Avellino eruption was less explosive and the deposits were far less extensive and thick as those of the VEI 5 eruption of 79 AD.

Vesuvius as it appeared prior to the 79 AD eruption as depicted in a mural discovered in Pompeii.

But let us return to the linguistic evidence! Somma is Latin for summit and can only be the result of a situation where the scarp at 1,132 m a.s.l. is higher than the cone of Vesuvius, i.e. after the 79 AD eruption! At the time of the Avellino eruption, the tribe that was to become the Romans had not yet arrived in Italy, therefore it is impossible that the name is derived from a feature left by that or an earlier eruption. Furthermore, “somma” is not Etruscan in origin. Also, paintings of Vesuvius prior to 79 AD found at Pompeii show no signs of this “Monte Somma”. They appear to show a single cone about 1,900 metres high, although some claim it may have been as high as 2,500 m. It was also where Spartacus had his lair during the Third Servile War (73–71 BC)

From this evidence it is clear that the 79 AD eruption was, not a VEI 5, but a VEI 6 eruption that resulted in a collapse of Vesuvius where the volcano lost over a km in height and created the caldera whose highest point was afterwards named Monte Somma. The linguistic evidence provided by the name Monte Somma is so strong that any reconstruction of Vesuvius 79 AD eruption must account for this. The gauntlet has been thrown

Henrik

What I have to say about this, now?

Last year I didn't know much about Avellino. It was a new to me knowing about strong eruptions of Vesuvius before Pompeii (the most famous one), and I was just starting to explore the VEI classification. I ended in this page exactly by searching about the supposely 'VEI-5' of Pompeii.

What Henrik wrote made sense, indeed. Volcanic deposit on Pompeii are too thick for a VEI-5. Before Pompeii excavation, deposits were 7 meters thick - so I read on my science book at school, years ago. VEI-5 deposits are normally one or two meters thick, three meters if we consider a major VEI-5 eruption like the last eruption of Mt.Fuji, however 7 meters is already too thick. Somewhere (including Wikipedia) I've read that 6 meters is the minimum deposits thickness for a VEI-6.

The assigned 'VEI 5' to that eruption is precisely a 'VEI-5?' with a question mark, and some expert already increased the classification to a full VEI-6. The deposits that are found south of Naples (They say 4 to 8 km3, it depends from the site) are just a percentage of what came out from Vesuvius. In fact, in reality, most of ejecta ended in the sea and on mountains, and for geographical reason, deposits in the sea and on mountains went quickly eroded by rain and water. This would means that Vesuvius, most likely erupted about 10 km3 of material (I found that the total ejecta was about 12,5 km3). Deposit from an explosive eruption, unlike lava, don't last long in time. The concave flank of stratovolcanoes (such as Vesuvius) look that way exactly for that reason. Tephra needs time to cement and meanwhile mere wind and especially water scratch it away from volcanoes flanks. Pumice float and went lost.

The graphic above is from IGNV Osservatorio Vesuviano. Pompeii is classified as VEI-6.

From Volcanism and associated hazards: the Andean perspective, those are the most well know eruptions of the last 2000 years.  

It is not true that Avellino Eruption was less intense than Pompeii eruption. They are right to say it was actually stronger. Avellino is more than 30 km away from Vesuvius, and from Avellino, you can't see Vesuvius. It is hidden behind two mountains, as tall as Vesuvius. And at more than 30 km away from the volcano, behind two mountains, there were full 50 cm of deposits. Avellino eruption is also known to have altered the climate, however Vesuvius survived better back then, with a less damaged edifice.

Pompeii was a minor VEI-6, while Avellino was a full VEI-6.

Above, the distance between Vesuvius and Avellino.

As full power, Vesuvius is an average volcano (Most of well known volcanoes you can name had at least one VEI-6 eruption in the past), overall, Vesuvius is among the most violent volcanoes in the world, in good company with la Peleé and Merapi, worth deserving it's title as 'one of the most dangerous volcanoes on Earth'.

I forgot: the real date of Pompeii eruption is in late October, and not in August.

[volcanofandom]

A little revenge on the English Wikipedia

Two months ago I did several corrections on many volcanoes page on wikipedia, in Italian and English version. The Italian version accepted alll my corrections with no problems (except the one on Larderello).

But the english wikipedia, though accepthing most of my edits, suspended me for one month for ‘vandalilsm’.

I must mention that i’m not subscribed and that my IP is dinamic, so maybe it is another person that was suspended.

I discovered the suspension only the last day of my punishement. I must admit it took it personally. My edits weren’t mistakes, but I learned them from actual sites of volcanology.

Now, few days ago, I edited Etna page. I moved mount Etna from categoy ‘VEI-5 volcanoes to  categoy ‘VEI-6 volcanoes, as, by studying about volcanoes (I add: for my personal enjoyment) I learned that Etna is actually a VEI-6+ volcano (It does means that a single eruption of Mt.Etna might be 30 times or more explosive than the eruption of Mt.St.Helens in 1980, so very massive, and can alter climate). I could show the proofs, so the edit was accepted.

I was tempted to move Mt.St.Helens too among the VEI-6 volcanoes, but I discovered that somebody already moved ST.Helens in the VEI-5 category from VEI-6, claiming that there are no recorded strong eruption before 1980. Instead there are plenty sources about the ancient eruptions of St-Helens, including a VEI-6 that occurred 3000 years ago, and that destroyed the whole mountain. Someday I will fix that.

Another understimated volcano is Krakatau, but I didn’t took much interests in that yet. Krakatau is a caldera and I think it is one of the ugliest volcanoes in the world, maybe because is barren for geographic reasons. I’m more interested to stratovolcanoes and unusual shield volcanoes like Mt. Etna, Mt. Tambora and Mt. Erebus).

Other two volcanoes that usually are wrongly valued are Vesuvius and Pinatubo (the first is often understimated, the latter is often overstimated), but luckily on wikipedia they’re both placed in the right place.

Pinatubo is a lava dome, or somewhat a shield volcano. Though is officially classified as stratovolcano, It is very flat and large, it looks like an omelette (look on google Earth). Before 1991 it was a craterless volcano. Now I see why they realize it was a volcano few days before eruption. Luckily that has been enough to save most lives from an Avellino-like eruption.