Vesuvius – The Most Dangerous Volcano in the World

Mount Vesuvius is best known for this, or something very close to it, happening in AD 79:
 


Done by Zero Animation and the Melbourne Museum.
 
We don’t know exactly how the volcano’s edifice appeared before that eruption. We do know that Vesuvius now threatens a far greater city – Naples, Italy.

The big cone (Gran Cono) on the right formed during the VEI 5 Pompeii eruption.  (Image source)

The big cone (Gran Cono) on the right formed during the VEI 5 Pompeii eruption. (Image source)

Bella Napoli

It seems to an outsider that the Neopolitans should move. The short answer for why they don’t involves history and a location that has proven its human worth down through the ages.

No one knows for sure who christened this volcano “Vesuvius.” People of many different backgrounds have settled here since the Iron Age. The Greeks moved in around 3,000 years ago. If the Greeks named the volcano, “Vesuvius” might be derived from Greek words meaning “unquenchable” or “hurling violence.” However, equally good arguments have been made that the name comes from the Latin or Oscan for “one who lightens.”

The area was inhabited long before the Greeks got there, of course. The first people arrived during the Neolithic Age some 7,000 years ago. Greece colonized it as Parthenope around 900-800 BC and then, in the 6th century, renamed the colony Neapolis – “New City” – pretty ironic considering that Naples is now one of the oldest continually inhabited cities in the world.

Parts of historic Naples have down to the modern era.  (Source)

Parts of historic Naples have down to the modern era. (Source)

Naples became part of the Roman Empire. The Romans made it a posh resort and allowed its residents to keep their Greek customs and language. The apostles Peter and Paul allegedly preached there, and the last emperor of the Western Roman Empire was exiled there in the 5th century AD.

Down through the ages, Naples was fought over and captured several times and has seen duchies, kingdoms and one empire come and go. It has always been a great cultural center.

No wonder, then, that Naples attracted Sir William Hamilton, the British special envoy in the late 18th century to what was then the Kingdom of the Two Sicilies. Hamilton enjoyed music and collected art and antiquities, but the frequent eruptions of Vesuvius at that time fascinated him. As it was the Age of Enlightenment, Hamilton had the training in empiricism and reasoning to bring to his work of studying the great volcano. The samples and letters he sent back to London’s Royal Society from Vesuvius won acclaim and helped to lay the basis for modern volcanology.

Yes, human roots go back millennia here, but violent Vesuvius was there long before humans wandered in and decided that the rich soil, beautiful climate, and ideal trading location were worth the risk of fire and brimstone.
 

And perfect for this.  Yes, Naples gave the world pizza.  (Source)

And perfect for this. Yes, Naples gave the world pizza. (Source)

The geologic history of Vesuvius

It begins, as usual for most volcanoes, with plate tectonics. The big plate carrying the African continent is subducting underneath the leading edge of the Eurasian plate. Vesuvius and other volcanoes are a result of this subduction.

That’s all I’m going to say because the tectonic situation is rather complicated.
 

You're welcome.  (Image is from source 2, below)

You’re welcome. (Image is from source 2, below)

Volcanic activity has been going on for at least 400,000 years but Vesuvius is quite a young firecracker in geologic terms, according to researchers who have painstakingly traced its history through the lava layers piled up in and around the volcano. Here are a few of the high points as I have gathered them (they may not be spot on – I’m not a volcanologist).

At least 25,000 years ago, construction began with a large Plinian eruption. Then multiple lava flows built the mountain, called Somma, higher and higher. After some seven thousand years, the eruption style turned explosive (probably because of a change in the chemical makeup of the lava).
 

Source:  Osservatorio Vesuviano

Source: Osservatorio Vesuviano (Italian language)

That’s right – there used to be an even bigger volcano there! It collapsed in the Basal Pumice VEI 6 eruption some 18,300 years ago. This made the huge Somma caldera in which Mount Vesuvius began to form (some people call the volcano Somma-Vesuvius because of that structure).

A 2,000-year-long period of relatively quiet lava flows followed. Then, boom! The Green Pumice eruption happened (VEI 5, like the one that buried Pompeii). Vesuvius then switched over to the relatively quiet side of its split personality until 8,000 years ago. The Mercato eruption (it’s also known as the Gemelle or Ottaviano) was a VEI 6.

People started moving in, remember, about 7,000 years ago. Vesuvius was quieter at this time and remained so until the VEI 5 Avellino eruption 3,800 years ago. This Bronze Age cataclysm destroyed – but also preserved – several nearby human settlements. Of important note to us moderns, pyroclastic flows from this eruption buried the site of modern Naples to a depth of almost 10 feet.

After this, Vesuvius went into a cycle of of more frequent but less explosive eruptions, culminating in the most recent (and titular) Plinian Pompeii eruption, shown above, in 79 AD. Since then, the volcano has had well over 30 eruptions.

At the end of the 13th century, it went all Dr. Jekyll and quieted down. As centuries passed, humanity and Nature once again encroached on its slopes. Then Mr. Hyde came back in December 1631 – about 3,000 people died. Vesuvius erupted almost continually, sometimes very violently, from then until 1944’s VEI 4 (I think) eruption that destroyed the villages of San Sebastiano al Vesuvio, Massa di Somma, Ottaviano, and part of San Giorgio a Cremano:
 

What would happen to Naples if Vesuvius erupted today?

Managing volcanic risk

Today Naples is the third largest city in Italy. Between 3 and 4 million people live in the region.
 

Vegetation appears red on this ear-infrared imagery of Naples and Vesuvius.  (NASA)

Vegetation appears red on this near-infrared imagery of Naples and Vesuvius. The red color is not the scariest thing seen here. (NASA)

The Vesuvius Observatory monitors (Italian language) the volcano.

No one can know for sure exactly what to expect from this Jekyll-Hyde volcano, but emergency managers and scientists are planning for a future eruption of the same intensity as in December 1631 (which reportedly was bigger than the 1944 eruption).

Some researchers are arguing that the plan should be for a worst-case scenario, I think something along the lines of the eruption that buried that became modern Naples under 10 feet of pyroclastic flows.

At least there will be some notice. This volcano has earthquakes before and during eruptions. Right now Vesuvius is a Decade Volcano and is monitored very, very closely. Still, best estimates are that it could take at least a week to evacuate just 600,000 people – those at most risk – away from Vesuvius.

The long-term goal is to get the evacuation time down to two or three days. Hopefully Vesuvius will wait peaceably for the 20-30 years this is expected to take.

 
 


 
Sources:

  1. Vesuvius, AD 79 (PDF). Michigan Technological University
  2. Osservatorio Vesuviano
  3. Emergency Plans. Protezione Civile.
  4. Vesuvius. Smithsonian Global Volcanism Program
  5. Mount Vesuvius. Lynn Peyton, University of Arizona Department of Geosciences
  6. Naples. Wikipedia
  7. Mount Vesuvius. Wikipedia


Categories: Sunday morning volcano

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