In June of 2023, Becky (my wife) and I were trekking Southern Italy, when we found an opportunity to explore Mount Vesuvius and it’s surrounding area.  Located on Italy’s west coast, Mount Vesuvius overlooks the Bay and City of Naples and sits in the crater of the ancient Somma volcano.

Vesuvius is a violent volcano lying in a densely populated region, (3 million people). This combination makes it the most dangerous volcano in Europe. Becky and I were able to book a bus that took us to the summit and/or Vesuvius National Park.

By bus, Becky and I reached the Vesuvius Crater (from the west) up a good but windy road from Torre del Greco (between Pompeii and Herculaneum).

As we traveled up the Vesuvius road, we passed the remnants of the pre-A.D. 79 mountain (on our left, now called Monte Somma) and the lava flows from the most recent 1944 eruption (pictured below). The access road, with hairpin bends, gently climbs for about 800m overlooking the Valle del Gigante.

The Vesuvius is a typical example of a volcano in a volcano made by an outer broken cone, Mount Somma, with a crateric belt most of which is destroyed, where a smaller cone represented by the Vesuvius can be found. The two cones are separated by a hollow called Valle del Gigante, a part of the ancient caldera, where Vesuvius later formed, probably during the eruption of 79 AD.

Mount Somma is 1,132 m high at Punta Nasone and has a diameter at the base of nearly 15 km. It’s the most ancient volcano of the complex and was partly destroyed by the eruptive events in the last 25,000 years, during which Vesuvius formed. Mount Somma is currently arc-shaped, open in the south, and surrounds Vesuvius in the north, (imaged below).

Vesuvius is part of the Campanian volcanic arc, (a line of volcanoes that formed over a subduction zone created by the convergence of the African and Eurasian plates).

Imaged above, this subduction zone stretches the length of the Italian peninsula, that formed nearly 2 million years ago, during the tectonic phases connected with opening of the Tyrrhenian Basin (Eurasian Plate), the settlement of the Apennine range and the opening and subduction of the Adriatic ocean basin (African Plate). {It should be noted that the Apennines were formed due to a highly inclined subduction to the west and shows low average elevation}. Three main forces are acting in conflict in this area. Along the southern edge of the European plate, the plate carrying the floor of the Tyrrhenian Sea is moving to the southeast, the small Adriatic and Apulian plates are moving westwards, and the margin of the African plate is pushing north-westwards and plunging beneath Sicily and Calabria in a vast subduction zone. The Tyrrhenian Sea is opening and widening, while the Adriatic Sea is being compressed. Caught between these pincers, the rocks of Italy have been folded, twisted, crumbled and fractured, making it easier for molten rocks to find passageways for volcanos.

The current shape of the volcano is a result of the constant succession of explosive and effusive eruptions in the last 25,000 years. These events have partly destroyed Mount Somma, the most ancient volcano, inside which Vesuvius formed. [This is now called the Somma – Vesuvius volcanic complex].

Vesuvius has a typical frusto-conical shape, with its highest peak reaching 1,277 m. The crater currently has a diameter of 450 m and a depth of 300 m. At the base of the crater and inside the caldera of Mount Somma there are several eruptive vents, from which ancient lava flows came out from 1631to the last eruption of 1944.

Pictured below, from the parking lot, it was a moderately steep 1 kilometer, 20 minute hike (with a 200m elevation gain), up a dirt access trail to the top.

Pictured below, the trail runs along the lower edge of the Vesuvius crater offering unforgettable views along the route, the Apennine mountains, the crests of Mount Somma, the Bay of Naples and its islands.

A view that varies with the seasons: from winter, when the snowy crater and the internal fumaroles create a rare contrast, to spring whithin the Valle de Gigante (Giant’s Valley) and the slopes of Vesuvius are colored with flowing broom, (picture below).

Pictured above, the path, with hairpin bends gently climbs of about 200m overlooking the Valle de Gigante, with remnants of the lava of the 1944 eruption, colored by the silver-grey of the lichen Stereoculon vesuvianum and the red & yellow broom. Rustic species grow on the sides of the volcano: bladder campion, yellow hornpoppy, red valerian, helichrysum, bloody dock.

Pictured above, the eruptive events that followed one another in time erased repetitively the vegetation of the Vesuvius and Mont Somma, but every time life has overbearingly regained possession of the territories invaded by lava, than to some pioneer species, that can colonize also very hostile environment such as volcanic soil.

The new vegetal settlement starts mainly thanks to some species of lichens, mosses and microbes that trigger the colonization process by micro-fracturation of the superficial lava grounds. Then, these species gradually create a sub-layer on which more exigent beings can slowly install; this is how an “ecologic succession” take place, characterized by the formation of more and more complex vegetal associations. On lava streams of the most recent Vesuvian eruptions (1944, 1929, & 1906) it is still possible to a admire the diffuse colonies of the first pioneer species of Vesuvius, (the coral shaped lichen Stereocaulon vesuvianum, thready and with its typical silver grey color). Other common lichens are Parmelia cospersa, (with its dark olive green color), and Trapelia mooreana, (which is light yellow).

Pictured above, on the most ancient lava stream together with Sterocaulon vesuvianum we can see other poineer species that represent a most advanced stage of vegetal succession: red valerian (Centranthus ruber), helichrysum (Helichrysum litoreum), cistus (Cistus sp.), wormwood (Artemisia compestris), and a rich variety of graminaceous, asteraceae and leguminous grasses; these associations prepare the soil for the future settlement of typical broom groups, constituted by Spanish broom (Spartium junceum), common broom (Cytisus scoparium) and Mount Etna broom (Genista aetnensis).

Mount Vesuvius is a typical polygenic mixed volcano, i.e. it’s made of lava of different chemical composition (e.g. trachytes, tephrites, leucitites) and is formed either by lava flows or pyroclastic sediments. All the zones on the slopes of the mountain are made of land that has been transported by lava of mud and goes down from the steep slopes in the rainy seasons through deep and narrow grooves called channels or more commonly lagni.

The high embankments are formed by piles of lavic scoriae, which precipitated in incandescent state and spread towards the low slopes, proving to be important for vegetation thanks to their fertile material, rich in silicon and potassium.

Scientific research shows that Vesuvius behaves in two main ways. Violent eruptions usually occurs only after several centuries of repose; it is just as well that they happen so rarely, for they are lethal and highly destructive, as the eruption of 79 A.D. so amply demonstrated, (Pompeii Eruption). The type of activity has been in a much lower key. It characterized the behaviour of Vesuvius from about 787 until 1139 A.D., and from 1631 until 1944, when frequent eruptions f lava flows, ash and cinders in both periods were interrupted by dormant interludes lasting only a few decades at most. These eruptions varied in vigor, but they were all usually just powerful and beautiful enough to provide an awesome spectacle from Naples.

Above on the left, Effusive eruptions characterized by quite fluid magma with low gas content, generate lava that steadily flows onto the ground, (this is the case of the lavas generated during the last eruption of 1944), whose marks can still be found from Valle dell’Inferno up to Fosso della Vetrana, near San Sebastiano al Vesuvio. Above on the right, Explosive eruptions have a greater impact than effusive eruptions, (the magma that reaches the surface is very viscous and rich in gas and leads to the expulsion of a high temperature mixture of pumice, ash, fragments of pre-existing rocks and gas, which can also reach a long distance, causing massive destruction).

Pictured above and below, most of the rocks on the crater-rim of Vesuvius and erupted from Vesuvius are andesite, an intermediate volcanic rock (about 53-63% silica). Andesite lava creates explosive eruptions on a variety of scales, which makes Vesuvius an especially dangerous and unpredictable volcano.

Somma -Vesuvius has erupted many times. Numerous others preceded the eruption in AD 79 in prehistory, including at least three significantly larger; an example is the Avellino eruption around 1800 BC, which engulfed several Bronze Age settlements. Since AD 79, the volcano has also erupted repeatedly, in 172, 203, 222, possibly in 303, 379, 472, 512, 536, 635, 787, around 860, around 893, 968, 991, 999, 1006, 1041, 1049, around 1073, 1139, 1150, and there may have been eruptions in 1270, 1347, and 1500.

 The Vesuvius erupted again in 1631, six times in the 18th century (including 1779 and 1794), eight times in the 19th century (notably in 1872), and in 1906, 1929 and 1944. There have been no eruptions since 1944, and none of the eruptions after 79 A.D. were as large or destructive as the Pompeian one.

Since 1944, the Vesuvius volcano has undergone in its longest dormant period for over 300 years. The longer it remains dormant, the longer the molten rock beneath it can develop into an explosive cocktail, and the more destructive, dangerous and lethal the re-awakening will be.

No-one can tell exactly when Vesuvius will spring back to life, but the experts have drawn up contingency plans to deal with the crisis that will inevitably ensue. The peril will be so serious that the plan is to evacuate all the people living in the most vulnerable areas before the eruption actually begins. Otherwise it will probably be too late to save them. Vesuvius is still the most dangerous volcano in Europe.