Vesuvius Volcano

Vesuvius is one of the world’s best known and most dangerous volcanoes.

This famous volcano began its activity about 25,000 years ago. As a result of countless eruptions of lavas, pumice and ash, the volcanic activity has built up a conical mountain that is 1281 m in height.

Tectonic Setting

The volcanic activity of Vesuvius volcano is the result of the movement of large crustal plates in the Mediterranean region.

The volcano is located in southern Italy where the convergence of the Eurasian plate to the north and the African plate to the south produces a subduction zone.

Mediterranean seafloor is currently sinking beneath Sicily and Calabria, resulting in the formation of the Calabrian volcanic arc. The numbers on the curved lines on the figure below indicate the depth to the top of the subducting plate.

Subduction Zones

Subduction is the process by which an oceanic plate sinks below either another oceanic plate or a more buoyant continental plate. This process produces an oceanic trench at Earth's surface where the two plates meet (shown as the purple line on the map shown here, with "teeth" pointing in the direction of the sinking plate).

Subduction zones are some of the most geologically active areas of the planet, commonly producing both large earthquakes and explosive volcanic eruptions.

Magmas are generated in the mantle between the descending and overiding plates as a result of the release of water from the sinking plate.

These magmas are more buoyant than the mantle, and so they rise to the surface to feed volcanic eruptions along a narrow arc-shaped chain of volcanoes. They also tend to be very water-rich because of how they form, which makes them erupt explosively when that water forms bubbles as the magma nears the surface.

Explosive Eruptions at Vesuvius

Explosive eruptions of Vesuvius are mainly of three types:

1. Small to medium-size strombolian to vulcanian eruptions, with production of lava flows, and fallout of ash and pumice on and near the volcano.

2. Sub-plinian eruptions, which are medium to large explosive volcanic events, and result in extensive fallout of pumice and ash around the volcano, accompanied by some pyroclastic flows and surges.

3. Plinian eruptions, which are very violent and large explosive events, that produce widespread fallout of pumice and ash and extensive pyroclastic flows and surges. The 79 A.D. eruption is the type example of a Plinian eruption.

The diagram shows a chronological list of the main eruptions of Vesuvius, and gives an indication of their sizes. Just like the Richter earthquake scale, the eruption sizes are shown on a log scale. Every whole number increment of eruption size is actually an increase of a factor of ten!

Next, let's visit the the top of Mt. Vesuvius and take a look into the crater.