What to know - Stromboli
Stromboli is a volcanic island part of the Aeolian Islands archipelago, a natural reserve and UNESCO World Heritage Site. It is a volcano in continuous eruptive activity, populated and visited for centuries. The island hosts the inhabited centers of Stromboli and Ginostra, which are located on opposite sides of the volcano and fall under the municipality of Lipari. The island has about 500 inhabitants but, especially in the summer season, can welcome thousands of tourists.
The summit of the volcano reaches an altitude of 925 meters, while the eruptive vents are located further down on the crater terrace at an altitude of 750 meters. Stromboli's volcanic structure continues below sea level for another 2,000 meters and is about 3,000 meters high. The main morphological feature of the island is the Sciara del Fuoco: a steep slope that descends from the craters to below sea level on the northwestern slope of the volcano. Along this slope pours most of the materials erupted by the volcano, from which the name Sciara, "road" of fire.
The ordinary eruptive persistent activity of Stromboli is characterized by explosions with shreds of incandescent magma being thrown up to a few hundred meters in height and with the heavier materials falling back inland and up to a few tens of meters from the crater terrace. Such explosions, called Strombolian, occur with an average frequency of 10-20 minutes and characterize the volcano's ordinary state of activity.
The volcano can suddenly increase the energy of its eruptions, resulting in more dangerous explosions: major and paroxysmal.
Major explosions occur on average a few times a year and cause large volcanic products to fall back onto the summit of the volcano, well beyond the crater terrace. Paroxysmal explosions, such as those in 2003, 2007, and the two in 2019, are less frequent but even higher energy events, characterized by the formation of a dark eruptive cloud, with lapilli and volcanic ash that rises several kilometers above the volcano's summit. These explosions can result in the fallout of large products down to low altitudes, even into population centers, and the formation of pyroclastic flows: avalanches of gas, ash and glowing fragments. Such flows can stream down the flanks of the volcano at speeds of more than 100 km/h, most likely pouring down the Sciara del Fuoco, the Vallonazzo channel and the Forgia Vecchia, until they reach the sea and flow over its surface for several hundred meters. Paroxysmal explosions can also trigger large landslides and tsunamis.
The volcano also periodically gives rise to effusive eruptions from vents that can open at different elevations along the Sciara del Fuoco, feeding lava flows that can reach the sea. More rarely there have been effusive eruptions outside the Sciara del Fuoco, the last of which occurred in Roman times.
When the lava reaches the sea, explosions can be triggered by the interaction of magma with water, forming columns of steam and harmful gases.
Ordinary eruptive activity regularly causes boulders to fall back into the sea along the Sciara del Fuoco, even reaching significant distances. During extraordinary volcanic activity, large landslides can be generated in the Sciara del Fuoco, even in the emerged or submerged portion of the volcano.
Tsunamis at Stromboli can be generated by large landslides or even as a result of paroxysmal explosions. The last tsunami that caused extensive damage occurred on December 30, 2002, when the island's coastline was inundated up to about 10 meters above sea level. Like any coastal area of our peninsula, Stromboli can also be reached by tsunamis generated by strong earthquakes located in the Mediterranean Sea.
The fallout of incandescent volcanic products on the flanks of the volcano, as a result of explosive activity, can cause extensive fires.
Earthquakes related or unrelated to volcanic activity may occur. The strongest event at Stromboli was recorded in 1941 with an intensity of grade VIII and magnitude 5.3.
An advanced monitoring system of geophysical and geochemical parameters related to the volcano's activity is active on Stromboli, which allows the detection of possible evolutions of its state (changes in the number and intensity of explosions, seismicity, ground deformation, changes in gas composition and temperature, etc.). In particular:
lava flows are generally predictable because they are preceded, days before, by significant changes in parameters;
paroxysmal explosions are predictable a few minutes in advance;
major explosions are not currently predictable.
The national warning system for Italian volcanoes provides specific "alert levels" (GREEN, YELLOW, ORANGE, RED) that describe the state of volcano activity based on monitoring parameters and ongoing phenomena. Each level corresponds to progressively more important parameter changes and, in general, the possibility of increasingly dangerous phenomena occurring.
In order to cope with these variations, different operational phases (WARNING, PREALERT, ALERT), or civil protection measures for risk mitigation and the protection of the population can be activated. Local operational phases related to phenomena that can be managed by the territorial civil protection system. In this case, they are established by the Sicilian Region; and the national operational phases, related to phenomena that require intervention by the national level, are decided by the Civil Protection Department in agreement with the Sicilian Region.
Some dangerous phenomena, such as paroxysmal explosions and tsunamis, can occur suddenly, regardless of the current alert level. For this reason, two experimental automatic Early Warning systems that alert the population via sirens are active on the island since October 2019:
- a system for paroxysmal explosions, issuing the alert a few minutes before the explosion, warning the population with an alternating two-tone siren sound;
- a tsunami system, capable of issuing the alert a few minutes before the waves arrive on the island's shores, warning the population with a single-tone siren sound.
Planning at the different territorial levels
In case of an emergency, the first response is necessarily provided by the territorial civil protection system. Civil protection measures may change depending on the number of people on the island, also in relation to the tourist season.
In particular, the Municipal Civil Protection Plan identifies removal routes from the coastal zone (all roads leading inland from the waterfront), emergency areas, and activation and response procedures of the local system.
The national civil protection supports territorial systems when the situation calls for support, such as in the case of a tsunami. For this reason, the National Plan for Stromboli Island, besides describing the alert levels and the reference scenario, defines the actions to carry out by the different bodies involved for each operational phase
If you live on or visit Stromboli Island, always remember that you are on an active volcano.
There is a trail network on the island that allows you to reach the different elevations of the volcano. The viability of the routes is regulated by Ordinances of the Mayor of Lipari depending on the state of activity of the volcano.
Bathing and boating in the waters around the island, particularly in front of the Sciara del Fuoco, are regulated by Harbour Master's Orders, also depending on the dangers associated with volcanic activity.
At Stromboli and Ginostra, there is an acoustic warning system (sirens) that is activated with two different sounds in case of an impending paroxysmal explosion (two tones) or tsunami (one tone).