Mount Vesuvius - Italy Mount Vesuvius: Plate Tectonic Setting

Mount Vesuvius - Italy Mount Vesuvius: Plate Tectonic Setting

Article by Jessica Ball Vesuvius is part of the Campanian volcanic arc, a line of volcanoes
that formed over a subduction zone created by the convergence of the
Mount Vesuvius Introduction African and Eurasian plates. This sub-duction zone stretches the
length of the Italian peninsula, and is also the source of other
Vesuvius is the only active volcano in mainland Europe, volcanoes like Mount Etna, the Phlegraean Fields (Campi Flegrei),
and has produced some of the continent's largest volcanic Vulcano, and Stromboli.
eruptions. Located on Italy's west coast, it overlooks the
Bay and City of Naples and sits in the crater of the Under Vesuvius, the lower part of the subducting slab has torn and
ancient Somma volcano. Vesuvius is most famous for the detached from the upper part to form what is called a "slab window".
79 AD eruption which destroyed the Roman cities of This makes Vesuvius' rocks slightly different chemically from the
Pompeii and Herculaneum. Though the volcano's last rocks erupted from the other Campanian volcanoes.
eruption was in 1944, it still represents a great danger to
the cities that surround it, especially the busy metropolis
of Naples.

Mt. Vesuvius and Naples Bay A panorama of the Gulf of Simplified plate tectonics cross section (A to B) Simplified plate
Naples, Italy, showing the high population density and tectonics cross-section showing how Mount Vesuvius is located
commerce. Mt. Vesuvius rests quietly in the background. above a subduction zone formed where the African plate descends
Image © iStockphoto / Danilo Ascione. beneath Italy. Magma produced from the melting African plate
creates the large, violently explosive volcanoes of the Italian
Peninsula.

Mount Vesuvius: Eruption History

Mount Vesuvius has experienced eight major eruptions in the last 17,000
years. The 79 AD eruption is one of the most well known ancient
eruptions in the world, and may have killed more than 16,000 people.
Ash, mud and rocks from this eruption buried the cities of Pompeii and
Herculaneum. Pompeii is famous for the casts the hot ash formed
around victims of the eruptions. The unfortunate people suffocated on
ash in the air, which then covered them and preserved amazing details
of their clothing and faces.

Plaster casts of people
who died in the city of
Pompeii during the 79
AD eruption of Mount
Vesuvius. They were
buried by the ashfall.
Image: Garden of the
Fugitives, This photo
was taken by
Lancevortex and is
distributed under a GNU
Free Documentation

Brick columns
stand among ruins
of the ancient city
of Pompeii. Image
© iStockphoto /
Evgeny Bortnikov.

Locating Mt. Vesuvius Map showing the location of Mount
Vesuvius on the west coast of Italy. Map by Geology.com and
MapResources. Nearby Volcanoes: Etna Stromboli

bMount Vesuvius: Eruption History (continued) POMPEII and HERCULANEUM

Starting in 1631, Vesuvius entered a period of steady volcanic Pompeii was a resort town inhabited by wealthy Romans who were
activity, including lava flows and eruptions of ash and mud. known for lavish spending on their homes. The fertile, volcanic slopes
Violent eruptions in the late 1700s, 1800s and early 1900s of Vesuvius provided an ideal climate for grapes and olive groves.
created more fissures, lava flows, and ash-and-gas explosions. Pompeii and Herculaneum are 2 hours' drive from Rome.
These damaged or destroyed many towns around the volcano,
and sometimes killed people; the eruption of 1906 had more Since the mountain had last erupted long before anyone alive at the
than 100 casualties. The most recent eruption was in 1944 time had been born, people thought that living near the most
during World War II. It caused major problems for the newly- recognizable landmark looming over the bay of Naples was completely
arrived Allied forces in Italy when ash and rocks from the safe. The town had imposing temples, a beautiful forum, a perfectly
eruption destroyed planes and forced evacuations at a nearby built theater and a stadium. (photo below)
airbase.
Below is a view of Naples at the height of the eruption of
Mount Vesuvius in 1944.

Theatre-Stadium

Did You Know? villa

The 79 AD eruption of Vesuvius is why volcanologists use It was lunch time in August 79 AD when Vesuvius began 19 hours of
"Plinian" to describe large volcanic eruption clouds. Pliny the spectacular eruptions. All the people in the 700-year-old town of
Younger, a Roman historian who witnessed the 79 AD 20,000 could have escaped. There was time to flee. But no one
eruption, wrote the oldest surviving description of the tall, recognized the inherent danger of the mountain's warnings.
tree-shaped cloud that rose above the volcano. Modern
volcanologists use the term to describe large-volume, violent By the time Vesuvius stopped belching poisonous gas, the bustling city
eruptions that produce quickly-expanding clouds of rock, ash of Pompeii was silent, completely buried by volcanic ash and debris. It
and gases which rise many miles into the atmosphere. Some remained silent for 1700 years. Herculanum underwent the same
more recent examples of Plinian eruptions include Mount St. destiny, although it was immediately destroyed by hot toxic gasses,
Helens in 1980 and Pinatubo in 1990. Here is Pliny's and only later covered with layers of lava.
description...
By the time Vesuvius stopped belching poisonous gas, the bustling city
"On 24 August, in the early afternoon, my mother drew [my of Pompeii was silent, completely buried by volcanic ash and debris. It
uncle's] attention to a cloud of unusual size and appearance. its remained silent for 1700 years. Herculanum underwent the same
general appearance can be best expressed as being like an destiny, although it was immediately destroyed by hot toxic gasses,
umbrella pine, for it rose to a great height on a sort of trunk and and only later covered with layers of lava.
then split off into branches, I imagine because it was thrust
upwards by the first blast and then left unsupported as the The eruption was the first ever to be described in detail. From 30 km
pressure subsided, or else it was borne down by its own weight so (18 miles) west of the volcano, Pliny the Younger witnessed the
that it spread out and gradually dispersed. Sometimes it looked eruption and later recorded his observations in two letters .
white, sometimes blotched and dirty, according to the amount of letters. Volcanologists now use the term "plinian" for the first stage of
soil and ashes it carried with it." devastating volcanic eruptions, as the one occurred in the Pompeii
eruption, in which dust, ashes, cinders, and rocks erupt high into the
About the Author… air, and in time settle back to earth. This stage may last for hours or
even days.
Jessica Ball is a graduate student in the Department of Geology
at the State University of New York at Buffalo. Her
concentration is in volcanology, and she is currently
researching lava dome collapses and pyroclastic flows. Jessica
earned her Bachelor of Science degree from the College of
William and Mary, and worked for a year at the American
Geological Institute in the Education/Outreach Program. She
also writes the Magma Cum Laude blog,

fin

POMPEII and HERCULANEUM (continued) Silent for thousands of years, Pompeii and Herculaneum are
now living museums of life in the Roman Empire during the
No lava flows occur during the plinian stage. In areas near the first century of the Common Era.
eruption, the amount of these materials can be enormous. The sacrifice and horrendous sufferings of its inhabitants resul-
ted in a generous gesture, as they donated us the means to
During the first eight hours of the eruption of Vesuvius in 79 AD they understand not only the architecture of their houses, buildings
fell on Pompeii to depths of 2 to 4 meters (8-10 ft.). The heaps of small and infrastructures, but also their paintings, the furniture, and
rocks that landed on the houses caused many roofs to collapse, even the ordinary objects for everyday use. We know their
although the process was relatively slow, allowing most people to habits, their customs, even their political graffiti, or their love
escape. messages.
We are thus able to understand their culture, having an insight
In the next stage of the eruption, a super-hot cloud of steam and mud of the ancient world otherwise impossible.
(called "pyroclastic") flowed down the side of Vesuvius. At the speed People in ancient times used mill wheels to grind flour, and
of 30 mt. per second (nearly 100 Km or 60 miles per hour, as the bird they stored food in large terra-cotta jars. To maintain the food
flies), it took less than four minutes for the boiling mud to flow from at constant temperatures, all but the top of a jar was buried in
Vesuvius to both Pompeii and Herculaneum, a sea port distant about 7 the ground.
kilometers (4 miles).
Mills and Baker's oven
As mentioned, up to 4 meters (13 ft.) of ash and rocks fell on Pompeii, Pompeii had outdoor food taverns where its citizens could
burying everything except the roofs of some buildings. The city was enjoy a snack and a cool drink. Shops were clearly marked with
abandoned and its location forgotten. carved signs: a goat for the dairy, grapes for the winery, bread
for the bakery. In the baker’s house one could find a fresco of a
In 1595, excavations discovered artifacts at Pompeii and centuries of man selling bread
pillaging followed. Archeological excavations began in the mid- In the taverns food was stored in jars built in the counter, to
nineteenth century. Now, much of Pompeii has been excavated and it keep them warm, and to be served. This is why in Italian up till
has revealed much about how people lived during that time (and how now a snack bar is called tavola calda (hot table).
they died during the eruption).

Herculaneum was buried under 23 mts. (75 ft.) of lava. Once a seaside
resort with 5,000 inhabitants, the former town became inland, and is
now surrounded, actually surmounted by the modern city of Ercolano

Surprisingly sophisticated, Pompeii had a grid lay-out (see photo). It

had a three-stream running water system. One stream went to public
fountains, another to public baths, and a third traveled to homes of
wealthy residents. People in Pompeii even had a version of indoor
plumbing, but they did not have a good sewer system.

Flowing through lead pipes from a central water tower (called the
Castellum Aquae), the water delivery system was ingenious for its day.
When water supplies were low, the town stopped the flow of water
streams in order of priority. First the wealthy homes were with-out
water, then the public baths. Public fountains were shut down last.

Pompeii Grid layout Tavern with tavola caldo

POMPEII and HERCULANEUM (continued) The mold of a dog is shown below. The poor animal was
chained to a post and struggled for hours before finally
The town was endowed with a huge amphitheatre and large training succumbing to the ash.
facilities. Gladiator's fights were the highlight of the shows.
Gladiators were very popular, and their fans would write graffiti on
walls to boast their exploits.

The Amphitheatre Cast of a poor chained dog

Typical upper class residences usually included fresco wall murals, The excavations of Herculaneum stretch over a smaller area,
a fountain, private baths, mosaic floors, an atrium with and inner yet they are no less interesting. The once sea town as
garden (called a peristyle), and a shrine. mentioned was destroyed immediately by a super hot cloud of
steam and mud, and only later covered with lava. Generally,
the archaeological relics are in better shape than in Pompeii,
and many objects of everyday like were found.

Pompeii: Villa of Venus: painting of Venus
In the 1860s, Italian archaeologist Giuseppe Fiorelli discovered that
mounds of ash often contained the moulds of those who perished in
the catastrophe.

Herculaneum wine shop

Casts of the victims of the eruption Herculaneum mosaic in a villa

This method of retrieving the shapes of Vesuvius' victims, now
known as the "Fiorelli method", was even extended to recreating the
forms of furniture, doors and shutters on Pompeiian buildings. The
casts show the shapes of the victims in their final moments, trying
to filter the noxious fumes of the eruption, and to breathe, as the
terror-filled faces reveal.