Panarea volcanic island, Aeolian Islands, Italy

volcano number: not catalogued in Volcanoes of the World

summit elevation: 421 m

location: XX.XX�N, XX.XX�E

Panarea is the smallest of the seven major islands in the Aeolian archipelago, and it can be considered some kind of the "St-Tropez of Southern Italy" for having attracted since a few decades the VIPs not only of Italy but of all the world. Many of Italy's richest persons possess holiday homes on the island, which lives a relatively brief but intense (compared to its neighbor islands) tourist season, mainly concentrated during the month of August. Starting in September, the island becomes unusually quiet and remains so until the late spring. However, there is not only jet-set tourism on Panarea. The island has one of the most important archaeological sites in the Aeolian archipelago (Capo Milazzese) and hikers will be surprised to find a well-maintained network of trails leading to all points of naturalistic interest, which also offer stunning panoramic views. Panarea is of charming beauty and deserves a visit by anyone interested in nature, history, and geology.
Besides the main island of Panarea, there are several other larger and smaller islands, rocks and reefs constituting a genuine miniature archipelago, including the islands of Basiluzzo, Dattilo and Lisca Bianca that lie in front of the main settlement of the island and form a scenic backdrop, with the symmetrical outline of Stromboli at the horizon. All of these smaller islands lie off the main island to the east and northeast. Panarea itself has a total surface area of about 3.3 km² and rises to a maximum elevation of 421 m at Punta del Corvo; the smaller islands add 0.4 km² of surface and rise to a maximum of 165 m (Basiluzzo). The entire Panarea archipelago represents the emergent portion of a much larger volcanic edifice that rises from a depth of more than 1200 m below the sea level, with a total surface area of about 460 km².
The morphology of Panarea is highly asymmetrical. While the eastern and southern parts of the island have relatively flat coastal areas marked by three important morphological steps (terraces formed by marine erosion when the sea level relative to the island was higher than today), the western and northwestern sides are extremely steep, in places vertical. These steep flanks are due to a combination of erosion and volcano-tectonic activity along faults plus collapse. In the southern portion of the island, in the Castello area, two prominent, steep-sided peaks rise nearly 300 m above the nearby coast. There is one settlement on the low eastern side of the island, extending from Ditella in the northeast over S. Pietro to Drauto in the southeast. Some 300 people live permanently on the island, but at the height of the tourist season the number of people increases tenfold, and furthermore thousands of tourists pay brief visits to the island every day in this period.
Geologically, Panarea has for a long time been considered quite old compared to the other Aeolian islands, but research starting in the early 1980s has shown that the youngest episodes of volcanism occurred as recently as 10,000 years ago, and thus at the beginning of the Holocene. The youngest portion of this complex volcano actually lies largely below the sea level, the smaller islands of the archipelago representing the emergent portions of this fairly recent volcanic edifice. Further evidence for continued active magmatism below the Panarea complex lies in the presence of active fumaroles on the northeastern tip of the main island, and below the sea level in the area of the islets Dattilo, Bottaro, Lisca Bianca and Lisca Nera. The submarine fumaroles are known since the Classical Age, and seem to have undergone periodic fluctuations in their output and intensity in the past. In early November 2002, strong upwelling and sulfurous odors were observed in several distinct areas close to the islets of Bottaro and Lisca Bianca, probably caused by a minor phreatic (vapor-driven) explosion. The intensity of the fumarolic emissions gradually declined through the following months and had returned to relatively low levels in the summer of 2003. On 28 January 2004, there was a new apparent intensification in the gas output, which caused some concern to the residents of the nearby main island of Panarea, but seems to have been due to the sliding of material from the submarine slope of the Lisca Bianca.
The recent and ongoing fumarolic area in the most recent portion of the Panarea volcanic complex is difficult to interpret. Many of the dormant and potentially active volcanoes on Earth show similar fluctuations in their fumarolic activity that are not followed by eruptions. It is rather probable that Panarea will not erupt in the foreseeable future. Like many other predominantly felsic volcanoes, Panarea has undergone long periods of repose between eruptive events, and the current repose period is lasting nearly 10,000 years. It is not known whether it will ever return to produce eruptive activity, but if it will do so, this activity will likely be similar to eruptions in the past. The latest eruptive cycle was characterized by the extrusion of viscous lava forming domes followed by collapse. A future eruption is most likely to occur in the area of the furmarolic activity - that is, away from the main island - and mainly produce extrusions of viscous lava to form lava domes which may rise out of the sea. The lack of voluminous pyroclastic deposits associated with the most recent dome-building eruption less than 10,000 years ago may be taken as an indicator that future eruptions will not be highly explosive. However, collapse of the flanks of growing lava domes into the sea might cause tsunamis that could endanger low-lying areas on the surrounding islands.

Geomorphological sketch map of Panarea (from Lucchi et al., 1999). Translation of keys: (A) Former shorelines; (A1) Morphological indicators; (1) cliff line; (2) internal margin of terrace; (3) external rim of terrace; (4) margin of terraced surface; (5) section through marine platform; (6) lateral incision; (A2) Sedimentary indicators; (7) littoral conglomerate deposit; (8) beach deposit; (9) fossiliferous sediments; (B) Geology and geomorphology; (10) pre-erosive volcanics; (11) Post-erosive volcanis (Brown Tuffs); (12) crater rim; (13) lava dome; (14) lava flow; (15) fault; (16) erosion scarp; (17) erosive incision; (18) talus cone; (19) colluvium; (20) eolian (wind-transported) deposit; (21) actual beach deposit; (22) inhabited area. A fine simplified geological map of Panarea has appeared in Calanchi et al. (2002)

Schematic reconstruction of the succession of the evolutionary stages during the formation of Panarea (from Calanchi et al., 1996). (A) Palaeo-Panarea; (B) intermediate stage; (C) final stage. Key: C=Calcara; CC=Costa del Capario; CD=Cardosi; CS=Castello di Salvamento; D=Ditella; LF=La Fossa; PF=Punta Falcone; PM=Punta Muzza; PP=Punta Palisi; PS=Punta Scritta; PTC=Punta del Tribunale and Castello; SLN=Scoglio La Nave

Geological evolution

The small size of Panarea belies a fairly complex volcanic history, which started about 200,000 years ago, and which is characterized mainly by the extrusion of viscous, (partially high-potassium) calc-alkaline magmas (basaltic andesites to dacites) to form domes and minor "coulée"-like flows. The volcanic products constituting the island are subdivided into three stages: Palaeo-Panarea Stage, Intermediate Stage, and Final Stage; these are followed by the most recent volcanics emitted from the eruptive centers lying 2-4 km to the east and northeast (Dattilo, Lisca Bianca, Lisca Nera, Bottaro, Panraelli, and Basiluzzo). The Palaeo-Panarea products occur in the northern part of the island, forming mainly domes and minor flows of andesitic-dacitic composition (Calcara, Punta Palisi, Scoglio la Nave, Punta Scritta). The dome-coulée of Ditella, lying in the northeast part of Panarea, and some lavas covered by pyroclastic breccias outcropping in the steep western face of the island might also belong to this stage. In the south part of the present island, explosive activity and emission of andesitic lavas was followed by the extrusion of two steep-sided dacitic lava domes or spines, the Punta del Tribunale and Castello, which are among the most peculiar morphological features of Panarea.
Extrusion of lava domes also characterized the eruptive activity of the Intermediate Stage, many of them forming a NW-SE oriented ridge that extends from Castello di Salvamento (northwest part of the island) to Punta Falcone, a steep-sided dome overlooking the village of Panarea; another row of domes extends SSW to Punta Muzza. The latest products of this stage, of andesitic composition, were emplaced in the northwestern and SSE parts of the island, the latter forming the spectacular peninsula of Capo Milazzese, which hosts the remains of a Bronze Age village.
The final stage of volcanism began after a period of repose and led to the formation of a large lava dome at Cardosi in the northwest part of the island, which constitutes much of the high central area including the present summit at Punta del Corvo; several thick lava flows extended from the base of the dome mainly to the southeast and south. Dome growth was accompanied by explosive activity that deposited andesitic scoriae in the Punta Falcone-Punta del Corvo area and dacitic pumice in the Castello di Salvamento area (all lying in the central-northern portion of Panarea). This period ended sometime before 130 ka; no volcanism has occurred since then on the island of Panarea.
This so-called final stage, however, did not mark the end of all things for Panarea's volcanism. Instead, the focus of volcanic activity shifted away from the main island out into the sea to the east, where about 130 ka ago, the dacites forming the Panarelli were erupted. Less than 10,000 years ago, a large lava dome rose out of the sea further to the north, to form what is now Basiluzzo island. This latest eruptive episode was followed by collapse and subsidence that has continued to very recent times, as is testified by the remains of Roman buildings that now lie beneath the sea level. This area of the latest volcanism in the Panarea complex still shows the presence of active fumaroles that lie at a depth of several tens of meters below the sea level. As noted above, these fumaroles increased their output notably in early November 2002; a new apparent increase in late January 2004 may be due to landsliding on the submarine slope of the Lisca Bianca and not to increased gas output.

Products of the Palaeo-Panarea Stage of volcanism on Panarea island. Left: view down the northwestern cliff of the island toward Scoglio la Nave, a rocky islet lying immediately off the island. The volcanics outcropping in the steep cliff and on the islet were produced by a single large lava dome complex. Center: the conspicuous, steep-sided dacitic lava domes or spines of Castello (right) and Punta del Tribunale (left) were extruded in the southern part of the island from an eruptive center that had previously produced explosive activity and andesitic lava flows. Right: the flat lava dome-coulée of Ditella rises above the harbor of Panarea, on the western side of the island. In the background the spectacular dome remnant of Dattilo is seen rising out of the sea. Photos were taken between July and September 2002

Products of Panarea's Intermediate Stage. Left: view over the harbor and village of Panarea, lying on the western side of the island. The hills in the left background are the La Fossa lavas, and the steep rock face looming over the village is the dome of Punta Falcone. Center: Capo Milazzese in the south part of the island, forming a spectacular peninsula that is occupied by the remains of a bronze-age village. The peninsula consists of andesitic lava flows emitted toward the end of the Intermediate Stage. Right: the low green hill lying downslope from the viewing point is one of several lava domes that formed during the Intermediate Stage. View is from the summit area of the island; in the background are the islands of Basiluzzo and, in the distance, Stromboli. Photos were taken between July and September 2002

Products of Panarea's Final Stage. Left: summit area of Panarea, culminating in the rounded hill in the background, Punta del Corvo (421 m). During the Final Stage, a large eruptive center formed in this area, from which dacitic lavas flowed in all directions, and a summit dome was emplaced. View is from south. Center: looking south toward the lower south slope of Panarea. The flat area in the center is Piano Milazzese, constituted by Palaeo-Panarea lavas. The dark ridge at right (cut by a high vertical cliff to the west) is a large lava flow erupted from the summit area during the Final Stage, now named Costa del Capraio. Capo Milazzese is seen in the distance at left; before it rises a lava dome belonging to the Castello-Punta del Tribunale complex. Right: the steep western face of Panarea seen from south, with Punta del Corvo forming the highest point in the background. The scarp at right (partially lying in the shadow) cuts through a thick lava flow erupted from the summit area, and constituting the Costa del Capraio. Photos were taken between July and September 2002

The small islands lying off the east coast of Panarea. Left: spectacular "satellite" of Panarea, Dattilo rises 103 m above the sea level and consists of strongly fumarolized breccias and dome lavas. View is from the southeast. Center: Lisca Bianca (white fishbone) is a flat (max. height 30 m above sea level), green island surrounded by steep cliffs. It is constituted by strongly altered dome lavas. Right: impressive flow-banding in dome lavas exposed in the vertical sides of the Scoglio Spinazzola, a 78 m high rock lying immediately to the west of Basiluzzo island. Erosion has enhanced the effect produced by the flow-banding in the rhyolitic lavas constituting Basiluzzo and the Scoglio Spinazzola. Width of the view is about 10 m. Photos were taken between July and October 2002

Following the dramatic increase in the output of the submarine fumaroles lying in the area between Lisca Bianca, Bottaro and Lisca Nera (about 3 km east of Panarea) in November 2002, the intensity of the emissions gradually declined and had reached nearly background levels by the spring of 2003. The left photograph is an aerial view (taken from a helicopter) showing two persons swimming in an area where several "plumes" of gas bubbles reach the sea surface. A portion of the small islet of Bottaro is seen at left. A closer view is seen in the right photograph, showing a circular area where gas bubbles rise to the sea surface, and Bottaro in the background. "Bubbling" area is about 2 m wide. A sulfurous smell was present in the area. A second "bubbling" area is seen in the background. Both photographs were taken on 18 August 2003

References

Calanchi N, Rossi PL. Sanmarchi F, Tranne CA (1996) Guida escursionistico vulcanologica delle Isole Eolie. Centro Studi e Ricerche di Storia e Problemi Eoliani (Panarea: 168-187).

Calanchi N, Tranne CA, Lucchini F, Rossi PL, Villa IM (1999) Explanatory notes to the geological map (1:10,000) of Panarea and Basiluzzo islands (Aeolian arc, Italy). Acta Vulcanologica 11: 223-243.

Calanchi N, Peccerillo A, Tranne CA, Lucchini F, Rossi PL, Kempton P, Barbieri M, Wu TW (2002) Petrology and geochemistry of volcanic rocks from the island of Panarea: implications for mantle evolution beneath the Aeolian island arc (Southern Tyrrhenian sea). Journal of Volcanology and Geothermal Research 115: 367-395.

Gabbianelli G, Gillot PY, Lanzafame G, Romagnoli C, Rossi PL (1990) Tectonic and volcanic evolution of Panarea (Aeolian Islands, Italy). Marine Geology 92: 313-326.

Lanzafame, G., Rossi, P.L. (1984) Evidenze di attività tettonica recente a Panarea (Eolie): implicazioni vulcanologiche. Geologica Romana 23: 131-139.

Lucchi F, Calanchi N, Carobene L, Tranne CA (1999) I terrazzi marini dell'Isola di Panarea (Isole Eolie): loro utilizzo nella definizione dell'eustatismo e del sollevamento tardo-Pleistocenico. Bollettino della Società Geologica Italiana 118: 545-562.

Romano R (1973) Le isole di Panarea e Basiluzzo. Contributo alla conoscenza geo-vulcanologica e magmatologica delle Isole Eolie. Rivista Mineraria Siciliana 139-141: 3-40.

Tallarico A, Dragoni M, Anzidei M, Esposito A (2003) Modeling long-term ground deformation due to the cooling of a magma chamber: Case of Basiluzzo island, Aeolian Islands, Italy. Journal of Geophysical Research 108, 2568, DOI: 10.1029/2002JB002376.

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Copyright © Boris Behncke, "Italy's Volcanoes: The Cradle of Volcanology"