Summary of the eruptive history of Mt. Vesuvius

Mt. Vesuvius, or more correctly the Somma-Vesuvius complex, is a medium sized volcano reaching a height of 1,281 m above sea level at its highest point. It comprises the older volcano, the Somma, whose summit collapsed, creating a caldera, and the younger volcano, Vesuvius, which rises out inside of this caldera.

Volcanic activity in the Somma-Vesuvius area goes back at least 400,000 years, as shown by the age of lavas sampled at a depth of 1,345 m.

The history of Somma-Vesuvius volcanic edifice began almost 25,000 years ago, with the growth of Mt. Somma due to predominantly effusive eruptions, and subordinately low energy explosive eruptions. This activity lasted up until about 19,000 years ago and resulted in the formation of the volcanic edifice of Mt. Somma; its estimated profile is shown in red in the image below (based on Cioni et al., 1999). The northern part is partially preserved and forms Mt. Somma.

Qualitative reconstruction of the original profile of the older volcano, Somma, (in red - based on the work of Cioni et al., 1999). Mt. Somma consists of the remains of the northern side of the old edifice.

The first plinian eruption of Pomici di Base (18,300 years ago) marked the begin of severe change in the shape of the Somma volcanic edifice, with the formation of a caldera due to the collapse of its summit. After this event, volcanic activity and later phases of collapse contributed to the formation of the younger volcano, Vesuvius. The activity of this volcano, which had grown inside the caldera of Somma, has been characterised by great variability both in styles of eruptions and in chemical composition of the magmas emitted.

Temporal diagram of Vesuvian activity. The vertical axis shows the number of years from the present, the horizontal axis, the V.E.I. (Volcanic Explosivity Index). For a description of V.E.I. click on the graph. For details regarding Vesuvius' major eruptions click on their name on the graph.

The eruptive history of Somma-Vesuvius can be subdivided as follows:

Volcanism older than 19,000 years
The huge Flegrean eruption of Campanian Ignimbrite had buried a large part of Campania area under a thick blanket of tuffs, approximately 39,000 years ago. The volcanic edifice of Somma began to grow on top of these deposits; its activity was predominantly effusive, and secondarily low energy explosive.

Volcanism between 18.000 and 16.000 years
This period is dominated by two great plinian eruptions: the eruption of Pomici di Base (18,300 years ago) and the eruption of Pomici Verdoline (16,000 years ago). Lavas produced by small effusive eruptions has been found between the deposits from these two eruptions. With the first Plinian eruption of Pomici di Base, the collapse of the volcanic edifice of Somma began, with the formation of a caldera inside which the new volcano Vesuvius then grew.

Volcanism between 79 and 1631 A.D.
Activity in this period includes at least two subplinian eruptions: the Pollena eruption (472 A.D.) and the 1631 eruption, and a series of small, low-energy effusive and explosive eruptions of medioeval age, causing lava flows on the southern and western flanks of the volcano, and strombolian scoria deposits.

The Vesuvius' wide variety of eruptive behaviours can generally be attributed to the alternating of periods of open-conduit activity and longer periods of quiescence with closed-conduit, followed by major Plinian or Subplinian eruptions. The open conduit-periods are characterised by persistent strombolian activity, frequent lava effusions and sporadic, but even more dangerous, both effusive and explosive eruptions.