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Mount Vesuvius: Not Just Another Volcano

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Mount Vesuvius Gallary
Quick Facts

Mt. Vesuvious, Italy
vesuvius_italy.jpg
Fig. 1 (http://volcano.und.nodak.edu/vwdocs/volc_images/img_vesuvius.html)

        Volcanoes have always fascinated and terrified mankind.  It is our feeling of fear that fascinates us to continue to study and be intrigued with volcanoes and their activities.  Volcanoes play a role in many ancient legends.  In some, volcanoes are gateways to the underworld and in others they are chimneys of the underground world of Volcan, the blacksmith god.  More scientifically, a volcano is an opening where gas and rock come from inside the earth onto the surface.  Any kind of outburst of hot melted rock is a volcanic eruption.  The opening where this takes place is called a volcanic vent (Gordon A. MacDonald).

        Mount Vesuvius is one of the most well known and studied active volcanoes.  It is most famous for the eruption on August 24th, 79 A.D., destroying the city of Pompeii, Italy.  During the eruption, the lava that covered people who were not able to escape perfectly preserved their bodies.  The remains of human and animals, buried beneath meter of pumice, helped archeologists determine what happened during the eruption.  This finding drew the most attention of scientists, and was what they call “decisive proof of a massive exodus” from the area (University of Buffalo).  Pliny the Younger, seventeen years old, was the only surviving eye witness to record his observations of the eruption and sent them in two letters.  Pliny stated, “I cannot give you a more exact description of its appearance than by comparing to a pine tree; for it shot up to a great height in the form of a tall trunk, which spread out at the top as though into branches” (Mount Vesuvius).  He described earthquakes before the eruption, the eruption column, air fall, the effects of eruption on the people, pyroclastic flows and even tsunami.  Due to his recordings, volcanologists now use the term “plinian” to refer to constant explosive eruptions which produce high altitude eruption columns and cover large areas with ash.  The eruption of 79 A.D. strongly affected the economy of what we call Naples today.  The eruption not only killed thousands of people, but it also destroyed the environment and land, covering thousands of kilometers, making the area uninhabitable for decades.

 

        The formation of Mount Vesuvius was caused by two occurrences.  The mountain started forming about 17,000 years ago, although the area of Naples has been an area of volcanic activity for 400,000 years.  Mount Vesuvius was then built up by a series of lava flows.  Before Mount Vesuvius was formed the area was home to another volcano known as Mount Somma.  Mount Somma collapsed 17,000 years ago and Mount Vesuvius was then formed partly from its remains.  The other event which assisted in the formation of the volcano is the collision of two tectonic plates, the African and the Eurasian.  The African plate is being pushed beneath the Eurasian plate, continuing deeper into the earth.  The crust material became heated, until it melted forming magma.  Because magma is less dense than the solid rock surrounding it, it was pushed up, cutting through a weak place in the Earth’s surface, forming the volcano.

         The Somma Rim, a caldera-like structure, was formed but the collapse of Mount Somma 17,000 years ago.  The Somma Rim now forms a half circle around Mount Vesuvius. 

         Mount Vesuvius is a stratovolcano (a.k.a composite volcano).  Stratovolcanoes are volcanoes composed of both lava flows and pyroclastic material.  Stratovolcanoes are the most scenic and most deadly of the volcano types.  Characteristics include lower slopes, but rise steeply near the peak, producing an overall morphology that is curved in, in an upward direction.  They typically form at convergent plate boundaries.  These types of volcanoes also form over long periods of time.  Stratovolcanoes can be compared to shield volcanoes, in the sense that they are both polygenetic; however, stratovolcanoes erupt rarely compared to shield volcanoes.  The most active stratovolcanoes are greater than 100,000 years old.

         Typically stratovolcanoes have a layered appearance with altering lava flows, air fall tephra, and/or pyroclastic flows (Department of Geological Sciences). (See Fig. 2).  The composition of these rock types vary from basalt to rhyolite in a single volcano.  The overall composition in all stratovolcanoes is AndesiticThe rocks formed at Mount Vesuvius are called tephrite.            

        Mount Vesuvius is one of several volcanoes which form the Campanian volcanic arc.  The arc forms the southern end of a larger chain of volcanoes produced by the subduction process of plates, similar to the formation of Mount Vesuvius (Vesuvius, Italy).  This arc extends north west along the length of Italy.

        Mount Vesuvius is one of fifteen “Decade Volcanoes”, volcanoes which are studied intensely since 1990.  This is because of Mount Vesuvius’ location, in a highly populated area of Naples, home to 3 million people (Department of Geological Sciences).

        More recently, French and Italian researchers have found a reservoir of magma, 8 kilometers below Mount Vesuvius.  They are continuing to monitor this pool for seismic clues that may signal earthquakes and; therefore, resulting in an eruption.  The concern is that because Vesuvius has access to this 400 kilometer lake of magma, the aftermath of an eruption could be disastrous.  However scientists are hopeful that only about 20 – 25% of the magma available to the volcano will be drained from the reservoir if an eruption (Science Daily).

Mount Vesuvius Today

        On June 5th, 1995 the area around Mount Vesuvius was publicly acknowledged as a national park.  The summit of Mount Vesuvius is open to visitors where they can follow a small system of trails around the volcano.  There is access by vehicle within 20 meters of the summit, but then admission is only by foot.  There is also a winding path around the volcano from the road to the crater. (See Fig. 7 in the gallary) 

 

The structure of a stratovolcano
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Fig. 2 (http://www.geology.sdsu.edu/how_volcanoes_work/Thumblinks/Vesuvius_page.html)

Glossary

Andesitic: the intermediate composition magma will crystallize to produce Andesite (fine grained, igneous rock).

Polygenetic:  having more than one source of origin
 
Pumice:  a frothy volcanic glass
 
Pyroclastic Flows:  high density mixtures of hot dry rock and hot gas
 
Pyroclastic Material: rock material formed by a volcanic explosion or ejection from a volcanic vent
 
Rhyolite: a silic rock, mostly made of felspar and some quartz
 
Tephrite: is basaltic in character and contains minerals of calcic, plagioclase, augite, and nepheline
 
 

Map of Mt. Vesuvius
vesuvius_campaniamap.gif
Fig. 3 (http://www.historywalker.com/public2/02/campania.html)

For a closer look on the concerns the people of Italy have about Mt. Vesuvius follow this video link
 
 
By: Christina Sabatino