The volcano helpfully called ‘Vulcano’, one of the islands, north of Sicilyhas give its name to all volcanoes in the world. Vulcano last eruption was in 1888-1890. During the long repose period, a settlement has grown from a few houses to villas and hotels. Frazzetta et al. wrote in 1984 (quoted by Boris Behncke)
“A volcanic hazard exists where there is the potential for loss of life or property as the direct result of volcanic activity. The major effects of all activity at Fossa are confined to within 2 km of the vent. The village of Porto with a population of about 250 inhabitants lies within this zone to the north of the main cone. During the summer the population of this town swells to more than 10,000. It is quite dangerous for a village to be located so close to an active volcano.”
The settled community has grown from 250 to 450 since 1984, and in August there may now be 12,000 tourists each day (Behncke, private communication). The location of this community so close to the crater has made Vulcano into the second most dangerous volcano in Italy, after only Vesuvius. And now the alert level has been raised to yellow. Luckily this is after the summer and the height of the tourist season. But we are concerned.
The following post is one from the archives. It was written by Henrik in 2013, and is well worth resurrecting. At the end, we also reproduce a description of past eruptions from the current crater, Fossa, based on an article by Boris Behncke and reproduced by permission.
Over to Henrik:
Hephaistos, the lame son of Zeus and Hera, the King and Queen of the Hellenistic Pantheon, was the god of blacksmiths, artisans, craftsmen, metals, metallurgy, fire and volcanoes. He was also the weaponsmith of the Gods and crafted, amongst other things, the thunderbolts of Zeus.
Of course the Romans, the greatest copyright infringers ever produced by mankind incorporated the Greek Pantheon as their own religion and mythology. Here, Hephaistos was known as Vulcanus. The roman scholar Marcus Terentius Varro (116 – 27 BC) cites the Annales Maximus, which go back to at least 400 BC, as the source of the first mention of Vulcanus. He mentions that king Titus Tatius (d.748 BC) dedicated a series of altars to deities among which Vulcan is mentioned.
Perhaps more suggestive is the fact that a new eruptive centre formed in the strait between Vulcano and Lipari with the first recorded eruption occurring in 183 or 123 BC. The eruptions went on for more than a century, thus were contemporary with Varro, and formed a new island Vulcanello. This was volcanic creation of new land where only sea had been before and must have been considered by the ancient world as very significant proof of divine existence and omnipotence. In addition to its theological usefulness, Vulcano provided the Romans with wood, alum and sulphur, activities continued as the main produce of the island until the last, or rather, most recent series of eruptions of 1888-90 ruined the mining works. Today, Vulcano is home to some 500 year-round inhabitants while in the summer, the population grows to about 10,000. But not to worry, renewed activity will almost certainly be preceded by irrefutable signs of unrest well in advance of any potentially devastating event.
The visual appearance of Vulcano is very suggestive with the most ancient centre of activity, the collapsed stratovolcano “South Vulcano” (ca. 120-98 kA) and Piano Caldera (ca. 98-97 kA) to the south, the Lentia Complex (15.5 kA) with the Lentia or Fossa Caldera (16 -13 kA) in which the new La Fossa cone (~6 to 5 kA) grew. To the NE of the Fossa cone an extrusion is obvious but no date has been given for it (14 kA Punta Roja lava flow?). Finally, to the north is the already mentioned Vulcanello complex (2.1 kA).
Activity at Vulcano began a mere 150,000 years ago and is divided into four major stages. The first, South Vulcano center, began at about 120 kA by building a trachybasaltic to trachyandesitic stratovolcano where pyroclastic fall and flow deposits constitute only a minor portion. The activity at South Vulcano came to an end with the collapse of the stratovolcano around 97 kA into the 2.5 km diameter Caldera del Piano. Interestingly, it seems that the caldera was formed, not by an eruption that led to a collapse but the collapse of the stratovolcano “for reasons unknown or unspecified”. Post-caldera activity continued for some 45,000 years which resulted in most of the caldera being filled by lava flows. Then there seems to have been a period of inactivity covering the next 30,000 years.
About 15½ thousand years ago, activity renewed at Quadrara and Spiaggia Lunga as well as the formation of the large rhyolitic to trachytic lava dome and flow complex of Lentia, the “Lentia Lava Dome Complex”, in the northwest. From somewhere in the strait between Vulcano and Lipari (proto-Vulcanello?) violent ash-flow forming eruptions occurred and deposited brown tuffs over a large area of the old Caldera del Piano to the south.
About 15-14 ka ago, another caldera collapse affected the island, this time in its northern part, forming the Lentia caldera. Again, there seems to have been no explosive eruption associated with the caldera collapse, which may have been “tectonically triggered”. Activity continued within the new caldera with at least five cycles of pyroclastic and lava flows, the most significant being the Punta Roja lava flow that crops out at the E base of the La Fossa cone. Eruptions also occurred from N-S trending fissures in the NW part of the older Piano caldera where the Alighieri formation and the edifice of Monte Saraceno were formed.
About 11,000 years ago, activity began to concentrate in the centre of the Lentia Caldera and at least four eruptive cycles formed the massive-looking albeit only 391 m high La Fossa cone. Over the past 2½ thousand years, there have been at least 15 confirmed eruptions with a further ten possible from La Fossa with the last terminating on March 22nd 1890.
Although activity at La Fossa continues and cannot be said to be over, the last major eruptive period recognised is the already mentioned one that began in the second century BC and led to the formation of the Vulcanello Island and complex. Eruptive activity continued with at least two further eruptions after the initial, island forming series ended in ~10 AD. The final eruption, that of 1550, connected Vulcanello with Vulcano. The activity produced three overlapping tephra and scoria cones with craters shifting from E to W, and a gently sloping lava platform mainly on the N, W and S sides of the cone cluster. The Vulcanello products are generally more mafic than most other Vulcano eruptives, being of leucite-tephritic composition, only the most recent lava flow, Punta del Roveto of 1550 being trachytic.
Henrik ended his post with: For further reading, I highly recommend Dr Boris Behncke’s former site, thankfully saved for posterity by the Michigan Technological University
This site does not appear to exist any more. We reproduce here part of the content, describing the eruptive cycles of the Fossa cone over the past 6000 years. The text is slightly edited from the original. The images as shown here are available at https://slidetodoc.com/3-volcanoes-killers-and-creators-dr-daniel-barker/
The evolution of the Fossa cone, the most recently active volcanic center on Vulcano island, has been described in detail by Frazzetta et al. (1983) and briefly reviewed by Frazzetta et al. (1984) and Frazzetta & La Volpe (1991). The following is a summary from those sources.
The Fossa eruptive center developed only during the past 6000 years, after the presumably tectonically triggered formation of the Fossa caldera, about 14-16 ka ago. Its birth followed post-caldera effusive activity of which the 14 ka Punta Roja lava flow gives testimony. Activity of the Fossa cone has been divided into several cycles by Frazzetta et al. (1983, 1984) and Frazzetta & La Volpe (1991). The cycles have generally shown a characteristic succession of eruptive styles and each had an individual eruptive vent. Some cycles began with powerful vent-clearing explosions leading to deposition of “phreatic breccias” near the eruptive vents. The hydromagmatic initial stages of other cycles produced wet and/or dry surge deposits. Later products of each cycle show a decreasing influence of external water, the final products being fully magmatic (pumice-fall deposits or lava flows).
There is a complete lack of erosional surfaces and paleosoils between the products representing a cycle. It is assumed that activity during each cycle was more or less continuous. This contrasts with distinct erosional unconformities between the products of various cycles, evidence of longer repose periods separating different eruptive cycles.
Punte Nere cycle
The initial activity of this first recognized Fossa eruptive cycle was hydromagmatic and produced a more than 60 m thick sheet of dry surge deposits overlying the Punta Roia lava flows (14±6 ka). The basal strata of this sheet are composed of coarse and fine clasts and are overlain by sandwave and massive beds. Fragments of a trachytic lava flow that may have been ruptured by the eruptions and a thick block-fall deposit are present in the middle part of the sequence. A fall deposit composed of normally bedded and occasional reversely bedded layers with interbedded surge beds make up the uppermost pyroclastic unit of the cycle. It was followed by the emplacement of the trachytic Punte Nere lava flow that forms a delta-like feature on the N base of the Fossa cone. This flow was dated at 5400±1300 years.
Frazzetta & La Volpe (1991) estimate the volume of tephra produced during the Punta Nere cycle at 195 x 106 m3 and that of lava at about 3 x 106 m3. The activity left a cone about 250 m high. The NE crater rim is still well discernible in the eastern part of the Fossa cone.
At least three undefined eruptive cycles occurred after the Punta Nere cycle and left wet and dry surge deposits as well as the Campo Sportivo lava flow (see the map of lava flows), on the NW base of the Fossa cone. That flow has a radiometric age of 4600±1700 years and thus falls into the same time window as the Punta Nere flow; stratigraphically, though, it lies in a higher position. The volume of the Campo Sportivo lava flow is 2.6 x 106 m3 while that of the tephra presumably associated with it is 25 x 106 m3. The volume of tephra from the other undefined cycles is about 10 x 106 m3.
Following a repose period of unknown duration, hydromagmatic activity led to the emplacement of wet surge deposits followed by dry surge beds. Accretionary lapilli in these initial deposits give testimony of a high water component during the opening stage of the cycle. Later activity produced a stratified, normally graded pumice horizon which shows evidence of a brief erosional interval at its top. When activity resumed, it was again hydromagmatic and deposited another set of basal wet and overlying dry surge horizons.
Like during the preceding cycle, the late stage activity was effusive, producing about 0.6 x 10^6 m^3 of trachytic lava that forms a narrow tongue on the southern flank of the Fossa cone (Palizzi lava flow, see the map of lava flows). The volume of all tephra emitted during the Palizzi cycle is given as 5 x 106 m3. The age of the Palizzi lava flow is 1600±1000 years. This is well within the historic period but no correlation of the deposits with recorded historic eruptions of Vulcano is possible.
This cycle began with powerful explosive activity of which a basal breccia gives testimony. The breccia is composed of yellow hydrothermally altered clasts and is overlain by a pyroclastic flow unit with numerous fumarolic degassing pipes. The activity then shifted to hydromagmatic and produced wet and then dry surge deposits with abundant Pele’s hair (!) before it became again magmatic with the extrusion of the Comenda obsidian lava flow that is still partially visible on the SW flank of Fossa cone (see the map of lava flows). Its volume is 2.6 x 106 m3, slightly more than one tenth of the tephra volume (25 x 106 m3).
Frazzetta et al. (1983) assumed that the upper and larger of the two Forgia Vecchia (“Old Forge”) craters was formed during the Comenda eruptive cycle. These craters are well distinguishable on the two photos below of the 1888-1890 eruption but have been subjected to intense erosion since then and are densely vegetated.
The initial activity (breccia and pyroclastic flow) probably occurred before the mid 6th century AD since these deposits are overlain by the white ash from the most recent explosive eruption of Monte Pilato, Lipari that is thought to have occurred around AD 550. The Pilato ash is overlain by the wet and dry surge deposits. Historic documents indicate that the emplacement of the Comenda lava flow may correspond to an eruption recorded for the year AD 785.
Pietre Cotte cycle
Initial activity was hydromagmatic, producing wet surge and soon after, dry surge deposits. A pyroclastic fall sequence (described as “pumice” by Frazzetta and La Volpe 1991) rests on top of these early products. The exact timing of the eruption’s beginning is not known but it is probable that one of its more peculiar events, the formation of the lateral Forgia Vecchia II crater (on the NW rim of Forgia Vecchia I crater), occurred in 1727. Twelve years later, lava seems to have filled the main Fossa crater and spilled over its low N rim, forming the obsidian lava tongue of Pietre Cotte (“Cooked Stones”) that is still conspicuous on the steep northern slope of the Fossa cone (see the map of lava flows). Its volume is 2.4 x 106 m3.
Unlike other cycles, the Pietre Cotte cycle apparently did not end with the lava outflow. Following the effusive activity, eruptions resumed in 1771 and continued intermittently until 1890. All activity before the latest major eruptive episode, in 1888-1890, is not well documented whereas very detailed scientific descriptions of the most recent activity are available (see below).
Vulcano last erupted in 1888-1890. Although it had erupted frequently in historic times, this eruption was the only one that was observed by scientists and was described in detail (Mercalli & Silvestri 1891). The activity observed by them was used for the introduction of a new scientific term, the so-called “Vulcanian” style of volcanic activity, now applied for powerful magmatic activity somewhere transitional between Strombolian and sub-Plinian.
The eruption was particular for the ejection of countless large breadcrust bombs. Meter-sized bombs fell in the area now occupied by the village of Vulcano Porto, on the crater rim they are much larger.
The buildings of the sulfur mining company located at Porto Levante were heavily damaged by falling tephra already during the first days of the eruption (starting on 3 August 1888), their residents could escape without fatalities or injuries. Later eruptions caused occasional ash and rare lapilli falls at Lipari. No major damage was done there, but the area now occupied by the village of Vulcano Porto was subjected to heavy bomb and lapilli showers.
The eruption ended on 22 March 1890, after gradually declining for several days. There were repeated unconfirmed reports about eruptive unrest at or near Vulcano, but no significant eruptive activity took place after 22 March 1890.
With the 1888-1890 eruption, the Pietre Cotte cycle seems to have come to a close. The volume of tephra produced during the entire cycle is given by Frazzetta & La Volpe as 25 x 106 m3 of which the 1888-1890 products do not make up more than one fourth.