Volcano Profile: Mt. Vesuvius

The latest in my Volcano Profiles Series, we turn to Europe and Vesuvius. You could fill many, many volumes with the works produced on Vesuvius since Roman times. This profile will barely scratch the surface when it comes to the vast geologic and human history surrounding the volcano, but it is a start. If you want to learn more about the archaeology surrounding Vesuvius, try visiting Blogging Pompeii.

VOLCANO PROFILE: MT. VESUVIUS

Mt. Vesuvius in Italy. Image courtesy of Dario Leone.

• Location: Italy
• Height: 1,281 m / 4,203 ft
• Geophysical location: The tectonics in the Mediterranean are very complex, with a multitude of microplates and collisionsal zones, but overall the existence of volcanism in Italy is due to the African plate suducting underneath the European plate. The subducting African plate is a small sliver that is the floor of the Adriatic Sea to the east of Italy and the volcanism in Italy likely stems from this subduction, producing an arc of volcanoes that includes Etna, Stromboli, Vulcano, Campei Phlegrei amongst other smaller features. Vesuvius is part of Calabrian arc that is divided into 5 zones: Tuscany, Latium, Campania, the Aeolian Islands and Sicily. Volcanism along these zones date back to at least 5 million years ago and Vesuvius is part of the Campania zone, which has produced significant eruptions from Vesuvius and the Campei Phlegrei in the last 25,000 years.
• Type: Composite volcano
• Hazards: Dominantly pyroclastic flows (nuee ardentes) and ash fall, combined with lahars and lava flows.
• Monitoring: Vesuvius Observatory run by the'Istituto Nazionale di Geofisica e Vulcanologia (INGV), the first volcano observatory in the world (founded in 1841). There is both a basic english site and a more indepth italian site. A healthy seismic network exists on the volcano as part of the Observatory. There is also this fellow.
• Summary: Mt. Vesuvius, overlooking modern Naples in Italy, might be the most famous volcano in the world. It is also considered the one of the most dangerous as well. More than three million people live near the active volcano that last erupted in 1944. The volcano could also be considered the birthplace of volcanology, with the famous letters (pdf link) of Pliny the Younger (the source of the term "plinian" for eruptive columns) that described many of the volcanic events during the famous 79 A.D. eruption of the volcano. That eruption was highly explosive - believed to be VEI ~5 - and buried the towns of Pompeii and Herculaneum, entombing the citizens of the city for thousands of years. This disaster killed many, but has also opened a unparalleled window into Roman culture and life.
• Current status: According to the Vesuvious Observatory, the volcano is at Green/Base level of alert, indicating no signs of activity.

Paintng of Vesuvius (1774) by Joseph Wright of Derby.

• Notable Recent Eruptions and History: The modern Vesuvius edifice has grown within the caldera of ancestral Monte Somma. This caldera has acted to channelize flows from Vesuvius towards the south and west from the modern volcano. In the last 17,000 years, Vesuvius has produced a multitude of eruptions, eight of which were large explosive eruptions. This includes the famous 79 A.D. eruption, along with large eruptions in 472, 685, 968, 1631, 1779, 1794, 1906 and 1944 amongst many others. The most recent activity at Vesuvius was in 1944, during a period of volcanism that latest almost 40 years from 1906. The largest eruption during this period was VEI ~3 and produced lava flows, pyroclastic flows, ash falls and deaths. It is most famously remembered as it was erupting as U.S. Forces arrived in Italy towards the end of World War II. The volcano likely destroyed more of the aircraft from the 340^th Bombardment Group than any German air raid. There have been no eruptions at Vesuvius since 1944, one of the longer periods of quiet at the volcano in the last two thousand years - with some suggestion that the system may be entering a new phase of its life.

  
  Mt. Vesuvius erupting in 1944. It has now been 65 years since the last eruption of the volcano.

  Since 1944, there have been a number of seismic events at Vesuvius, suggesting the magma system is still active under the volcano, which is definitely not surprising. The most recent of these was in 1999, when seismicity was the highest it had been in 50 years. These earthquakes were at 6-km depth under the volcano and likely reflect magma moving into the lower reaches of the system. An interesting study in 1998 suggested a connection between large earthquakes in the Appennines, ~55 km to the north of the volcano. They found that earthquakes in these mountains tended to accompany eruptions of Vesuvius, with an eruption occuring within ten years after seismicity. They conclude that there is "two-way coupling zone, within which normal-faulting events promote eruptions and eruptions promote earthquakes", which is a fascinating localized interconnectedness of tectonics and volcanism.

• Mitigation:
  
  Projected areas effected by ash fall and pyroclastic flows from a future eruption of Vesuvius.
  The Italian government plans to evacuate 600,000 people from the area around Vesuvius if the volcano were to show signs of major activity again. An explosive eruption at Vesuvius could claim 16,000-20,000 lives without proper monitoring and mitigation. This, in itself, is an amazing number and shows the real danger posed by the volcano. The volcano was named one of the "Decade Volcanoes" as well. A commission appointed by Ministry of Defense in 1991 defined two hazard zones - a red zone where most everything would be destroyed by pyroclastic flows and a yellow zone that would be dominantly affected by ash fall (see above), lapilli and lahars. Since then, there have been many studies (pdf link) that have examined the challenge of volcanic hazard mitigation in such a densely populated area. The mitigation plan includes banning new construction in hazards, monetary bonuses for people to live outside the hazard zone, moving public offices outside the hazard zone, changes to the the transportation system to improve evacuation and an information campaign.

Selected resources of Vesuvius:

• Scarth, A. and Tanguy, J.,-C., 2001, Volcanoes of Europe, Oxford University Press, 243 pp.
• Jashemski, W. and Meyer, F., 2002, The Natural History of Pompeii, Cambridge University Press, 502 pp.
• Nostro, C., R. S. Stein, M. Cocco, M. E. Belardinelli, and W. Marzocchi (1998), Two-way coupling between Vesuvius eruptions and southern Apennine earthquakes, Italy, by elastic stress transfer, J. Geophys. Res., 103(B10), 24,487-24,504.

Vesuvius as the sun rises. Image courtesy of Dario Leone, taken by Dionigi Caputo.