The Icelandic Hotspot Hypervolcano™ – Why old traps won’t erupt again

Photograph by Jeff Shea. A range of north Greenland shield volcanoes eroded by glacier ice so that they more remind of a range of strato-volcanoes.

Earlier today commenter Lucas Wilson asked me about volcanism in Greenland. So, I thought I should write a short piece on what once used to drive the volcanism there.

But let us start with what we today call the Icelandic hotspot. In here we have a tendency to talk about large volcanoes now and then, and sometimes about what is called “super volcanoes” in the media. But, the fact is that Iceland is both the largest volcanic structure on the planet, and also by far the oldest active one.

Let us start with largest. Iceland stands for between one third and half of all the magma on the planet during the last 250 million years. The rate of lava produced is fairly prodigious. Also, few know how long this has been going on. The answer is that it all started far before Iceland was born. Time for a history lesson.

Iceland was born as the Icelandic Hotspot moved close to the Mid Atlantic Rift; Iceland was born from the mid parts to the west and the east. This is as a function of the hotspot giving extra magma to the normal volcanism of the MAR, and thusly building the volcanic edifice known as Iceland as the MAR rifts apart.

Photograph by Ansgar Walk. Trap formation eroded by Glaciers, Ice age glaciation, and coastal erotion. Baffin Island.

Okay, now to the age thing. The Icelandic Hotspot is one of the really few surface expressions on the planet that is stationary. I know, the hotspot per see is not visible, but its effects are. So, as the continents and plates have fun surfing around bumping in to each other they slide over the poor hotspot.

A few tens of millions of years ago it was a part of the North American plate that slid over the Hotspot, and as that broke apart magma pushed through and created Greenland. As the now archipelago of Greenland slid away it lost its capacity to have eruptions pretty permanently.

Before that it was Newfoundland that popped up as it slid over the hotspot. And before that we had the same hotspot creating the largest Large Igneous Province on the planet, the North Arctic Igneous Province (NAIP). Before that Labrador and Baffin Island slid over the NAIP, and that put us at about 95 million years ago. And 130 million years ago it created the Alpha Ridge. Any  super volcano will have an inferiority complex to that eruption.

Before that and even further down in time it was known as the Siberian Traps, the largest on land eruption. And now we are back 250 million years in time. Before that things get a bit harder to track.

Photograph by Jxandreani, wikimedia commons. This is a part of the Putorana-Norilsk Deposit.

Here comes an interesting thing. What is today known as the Icelandic Hotspot has been conveying about the same amount of magma since the Siberian Traps. Give or take the eruptive rate has constantly been around 0,5 to 1,5 cubic kilometer per year since day one. And as we all know the average erupted material is only 1 in 20 of the magma that comes up. The rest stays as intrusions or inside magma chambers. So, on an average year the Icelandic Hotspot will loft up 20 cubic kilometers of material.

Now some of you will say something like “Hey dude, it never erupted continuously, so it can not be the same. And dude, the Siberian Traps erupted more material than Iceland”.

The reason for it not having erupted constantly is that it need either pressure enough to crack a continental plate, or the magma had to wait for a spot that was weakened that it could crack. The Siberian Trap was a momentous episode, but the largest separate eruption was “only” 3000 cubic kilometers of lava erupted (Norilsk Deposit). In the end the Siberian Traps is only standing for a slight elevation in erupted material even though a lot of magma had accumulated under the Eurasian plate before onset of eruption. Average erupted material during the Siberian Traps was only twice what Iceland is popping out on average.

The Siberian traps carved by a river into a kilometer high cliff.

We should also remember that eruptions happen in cycles. The Norilsk Deposit is probably a hundred million year event, or in other word, it would take on average 100 000 000 years in between every eruption of that size. It is estimated that it took about a hundred years to erupt that amount. So, on average 30 cubic kilometers per eruption year and that is not a nice thing to be around, but far from what it takes to produce a mass extinction.

We know that there are about 2 to 4 eruptions on the scale of above 10 cubic kilometers in Iceland today per every thousand years. They tend to happen on a 270 year cycle. We also know that every few thousand years we get them in the 30 to 50 cubic kilometers. Most likely those come in about 1000 year cycles, but in various places over Iceland, and on average over time.

About once every 10 000 years we get one upwards to a 100 cubic kilometers. I do not know of any eruption in Iceland significantly larger than that, and would be surprised if anyone finding one. The reason of course is that the MAR creates a fairly open passageway for the magma. Norilsk was happening due to the dense rock of the Eurasian plate storing up magma under it until it cracked, so the necessary magmatic pressure can most likely not build like that in Iceland.

So, now we know that old huge volcanoes cannot erupt again due to the magma-hose being disconnected as the plates slide away from the “gas-station”, and we also know how persistant the hotspot is.

Super volcanoes, well all is relative…

Bonus Riddle from Alan

Many of you might have missed that we tend to have volcanic and geologic riddles every friday in here. Lately we did not have that due to El Hierro taking center stage. But we do know that there are many that love them, so here is bonus riddle. Remember, it should end up in something rocky.

Huh! Last week, I went into a nice bakers – they only had this rock-cake!

CARL

The pain filled issue with Ischia

Photograph by Giovanni Mattera. Castle Aragonese seen from Ischia. The castle is sitting ontop of a resurgent dome plug from a flanking vent.

The World’s most ill begotten piece of real estate – Part III

The Chinese have a saying, “May you live in interesting times”. And it is in no way a friendly thing to say; on the contrary it is a rather magnificent curse. In Naples people live all their lives in interesting times. If it was not enough with being the poorest city in Italy, they also have to contend with the Camorra (local mafia), drug-wars, corrupt politicians, strikes and general civil unrest. To top it off even further they have built their city on top, or around, no less than 3 active super volcanoes. Could the times get more interesting than that? Well you could add large earthquakes and tsunamis to the list.

Ischia, or more correctly Monte Epomeo, started it’s activity about 350 000 years ago. Technically it is of the complex volcano type. During the first 300 000 years it grew and developed a large edifice paired with an over-sized volcanic sub-structure.

56 000 years ago the volcano had reached the critical level where the edifice was too large and heavy to be sustained on top of the very large magma chamber. The eruption probably started as a very large VEI-6 eruption that emptied out the magma chamber sufficiently for the roof to collapse. And since Ischia is an Island it then got messy as the ocean roared down into the open magma chamber. The ensuing VEI-7 explosion created the Green Tuff Ignimbrite. This Green Tuff Ignimbrite should not be confused with the even larger Pantelleria Green Tuff (Italy is rather interesting…) that covers most of the Mediterranean area.

Photograph showing Sant Angelo D’Ischia, another resurgent dome from a flanking vent.

After the eruption the Island was completely gone. As far as is known a 23 000 year long period of dormancy followed, but there might have been minor subsurface eruptions that helped to start healing the roof of the volcanic chamber system.

33 000 (Ar/K-dating) years ago a new phase started where the volcano had frequent effusive eruptions that helped to weld the tuff together healing the roof of the magma chamber along the entire 10 kilometer wide caldera.

28 000 years ago things started to get really interesting. By then the roof above the chamber was sufficiently structurally sound to hold for the increasing pressure inside the chamber. That caused the entire roof to be pushed upwards.

Most of the readers in here are familiar with the concept of resurgent lava domes. We have all seen them being pushed out of craters like odd plugs. For those interested in seeing the phenomenon I recommend Soufriere Hills at Montserrat. Thing is though that it is normally smaller craters that suffer from this rather dangerous condition.

The island of Ischia photographed from Castle Aragonese. The mountain area in the background on the island is Monte Epomeo, a resurgent dome formed as the caldera floor is lifted up above the caldera rim. Here be Dragons.

Problem here is that Monte Epomeo is a super volcano, and as such does things in super-size. And if you super-size a resurgent dome, then you have an entire caldera floor rising upwards. Just imagine the pressure needed to push up a ten kilometer wide plug 900 meters in 28 000 years.

I know, we are only talking about 3.2 millimeters per year on average, but it still requires rather stunning amounts of power. The uplift is though larger than that, the reason for that being failures in the resurgent dome with rock-slides and sector failures of the dome as it started to stick up above the caldera rim. 5 600 years ago the dome passed the rim. During the push up phase the dome had also dragged the caldera rim with it above surface, and around the island an elevated area has been created by the pressure. So, a lot of pressure has gone also into moving parts that technically are not a part of the resurgent dome.

Eruptive and other behaviors

The most common type of eruption at Ischia is smaller eruptions taking place between the resurgent dome and the caldera rim. There are quite literally hundreds of fissures, cones, and other volcanic vent types encircling the dome. These eruptions normally follow episodes of rapid surging (uplift) of the dome.

There are two more dangers on top of the island caused by the resurgent dome. The first one is quite simply sector collapses, landslides and rock-falls as the brittle welded tuff suffers structural failure. Some of these slides and rock-falls have reached as far as the coast line.

General volcanic map of Ischia showing major features of the volcano. Click for larger image.

The more dangerous version of failure is the lateral flank eruption. That happens as magma pushes upwards and builds up tremendous pressure and swelling of the side of the dome and the side of the caldera rim. Think Mount Saint Helens here and you get the picture. This causes a large pyroclastic flow going laterally over the island until it reaches the coast, then it will continue over the water. If it happens in the wrong direction it will hit inhabited land.

Critical lateral collapse of the resurgent dome towards the Bay of Naples.

During the last 12 000 years there has also been 3 sub-surface collapses of the island causing massive debris flows running out into the Tyrrhenian Sea. And there are several spots along the coast line where parts of the Island have calved off into the ocean. When this happens large tsunamis will race into the Bay of Naples destroying any part not high up. The latest known widespread tsunami in the area is known to have happened 800BC according to written records.

Debris flow from a sub surface failure of the shelf around the island. The surge direction caused a large tsunami to go into the Bay of Naples.

In the end though it is probably the super part of Monte Epomeo that interests people more than anything else. Because however you look at it, there is between 70 and 210 cubic kilometers (conservative estimate) of magma in various grades of fractionalization down under that ever uplifting plug. The volcano also has an ample supply of fresh water to drive up the pressure for a larger eruption, and when that happens the same thing that happened to Krakatoa and Santorini will happen to Ischia. And as with the two more famous volcanoes, it has happened before.

Current status of Ischia

Even though Ischia is currently not showing any sign of erupting other than the steady uplift she is deemed by INGVs Director Guido Bertolaso to be the most likely volcano to erupt due to the rapid buildup of magma that they have recorded. Bertolaso even went so far as stating “if I had to say which is the volcano with the most loaded gun barrel, I’d say it’s not Vesuvius but the island of Ischia”. He though went on to state that no eruption is imminent. This becomes evident if one looks at the lack of heightened volcanic tremor, and minimal amount of magmatic earthquakes.

Risks of Ischia

The risks are roughly discussed below in the order of likelihood. Ischia is the volcano most likely to have a large eruption in the Naples area. One should though remember that it is most likely to have a normal VEI-1 to VEI-4 eruption when it erupts next. This would mainly affect the 60 000 residents on the island, and the same amount of tourists.

Rock falls, dome failures and landslides from Monte Epomeo is also fairly likely to happen in the foreseeable future due to the resurgent dome uplifting. This will also only affect the local residents and tourists.

Large landslides either at the coast, or out on the elevated shelf that surround the island is fairly likely to happen within the next few thousand years as the pressure building up raises the land up and weakens the structure of the flanks. When this happen large tsunami waves will hit the Bay of Naples causing widespread destruction. This is also the risk that is hardest to predict and mitigate.

In the same timeframe there could be another partial dome collapse causing a Mount Saint Helens style eruption. This would destroy all buildings on the island, cook the inhabitants, and depending on the direction of the pyroclastic surge hit areas far into the Bay of Naples. I do not think we need to contemplate the effects of a hydro-magmatic eruption at the VEI-7 scale. I would only like to point out that Ischia is the most likely candidate of having such an eruption in the neighbourhood of Naples. Right now there is nothing pointing towards it happening within the next millennia, but in the end it is likely to happen within the next ten millennia due to catastrophic failure in the resurgent dome.

Ischia early in the morning. The sleeping Dragon rests calmly.

Ischia is more likely to kill people than any other volcano. This is due to the absolute lack of places to run to quickly since it is a heavily populated island, and that half of the inhabitants at any given time are tourists not knowing where to go. So even the smallest event will get messy, best case scenario is probably a VEI-1 eruption with clear precursors for INGV to order a complete evacuation. Anyhow, anything interesting happening at Ischia is more likely to kill thousands up to millions than any of it’s siblings due to it having more modes of operation.

Not only do we live in interesting times, now we have an inflamed Ischia.

Short addendum on the Turkish quake

There has been an earthquake just south Antalya. It ranged between 5.8 and 6.2, figures are going to be revised. The distance from Antalya, and depth is very likely to cause damages to houses and fatalities.

The associated beach ball has a rather odd look to it. But this is also likely to change. The EMSC-CSEM site has gone down due to pressure from people trying to get info. USGS is open for business. Here is a link to their beach ball and other technical data.

http://earthquake.usgs.gov/earthquakes/eqarchives/fm/neic_b000ac4h_fmt.php

Oddball beach ball of Turkey.

CARL

The world’s most ill-begotten piece of real estate

Gulf of Naples (Campi Flegrei Caldera) with Vesuvius in the background.

Few cities on the planet can even start to compete with Naples in being ominously placed from a geological standpoint. The city has not only a tremendous historical background; it is also totally surrounded with active super volcanoes.

A few years ago I had the pleasure of having dinner in a villa on the slopes of Monte Vesuvius together with Italy’s car tycoon numero uno. After a tasty dinner together with nice wines we were sitting looking out at the ocean drinking a ridiculously old grappa (grappa tastes like a rotting hamster-cage smells) and I just had to ask if he never where worried about having a villa on one of the worlds more famous volcanoes. The answer was rather Italian; He turned around, raised all five fingers into the air in the general direction of Vesuvius and uttered the Italian immortal phrase “va’fan’culo”. I interpreted it as “who cares”. Actually it is a bit stronger than that in translation.

Vesuvius residing within the Monte Somma Caldera.

But in a way it summed up the Neapolitan view on their 3 troublesome super volcanoes. To hell with them. Basically this opinion explains why the citizens even do their best to impede scientific work on their volcanoes. In 2010 the mayor of Naples stopped drilling into Campi Flegrei to increase the monitoring of the volcano.

Naples has more than 4 million inhabitants in the greater Naples urban area; at least 1 million of them are directly threatened by the 3 giants under them. In theory there is a plan to evacuate the citizens, but 3 factors would most likely hamper any evacuation.

Image by NASA. Campi Flegrei seen from space.

The first one is of course the issue with the “va’fan’culo” attitude against their volcanoes. Most likely many would not heed an evacuation order in time. The second issue showed itself during the Campi Flegrei inflation periods of 1970 and 1984 to 1985. Back then inflation pushed Pozzuoli up more than 3.3 meters, and still only an area of 10 city blocks was evacuated. This points to it being likely that political pressure would impede any scientific call for evacuation before it was too late. The third reason is quite simply the poor state of the road network in and out of Naples. There is just no way to evacuate 1 million people in the stipulated 3 days. An amount of time that could well be quite less after the usual Italian political infighting.

Not even mighty ancient castle walls are protection for Naples.

This was the first part out of a 4 piece special. In the next 3 I will go through all 3 super-volcanoes in turn. Since all 3 of them are so different, and pose so different types of risks they deserve at least one post each.

Now you are most likely going, where did he find a third super volcano? Well, that will become clear in the next post.

CARL