Bradyseism in the Flegrea Area

Description

The site is located in the extended area of the Regional Park of Campi Flegrei, that approximately includes the area of the municipality of Pozzuoli, Bacoli, Monte di Procida and the Flegree islands (Ischia, Procida, Vivara) and the western areas of the municipality of Naples.

The site Baia is located in the southern area of Campi Flegrei, along the inner western area of the bay of Naples. The site is positioned at sea level, at a distance of approximately 15 km west of Naples. The small Gaiola islet is located within the urban area of Naples, along the south eastern coast of Posillipo hill, facing the bay with the Vesuvio mountain behind.

The area of Campi Flegrei, inlcudes the municipality of Pozzuoli (latitude 40° 29’ N; longitude 14° 7’ E), Bacoli, Monte di Procida and the Flegree Islands, the western areas of the municipality of Naples.

The ancient town of Baia and the Gaiola islet in Naples, are typical rapresentatives sites of the worldwide known phenomenon of bradyseism, as the coastline of Roman age is actually at a depth of 10 m below the present day sea level, and the rests of the harbour structures and ruins of the same age are actually at a variable depth along the coast. The term bradyseism (from the greek bradus = slow and sism = movement) has been coined by Issel in 1883 to mean slow subsidence or uplift of the ground. The word is in use in the volcanological literature concerning the Campi Flegrei volcanic area since the beginning of this century to mean the vertical ground movements in historical times. These kind of movements have been recently called short-term deformation to distinguish them from the long-term deformation of the same type occurred in Campi Flegrei in the past 15,000 years. Therefore bradyseism is the evidence in historical times of a long lasting phenomenon of generalized subsidence and localized uplift of the area of Campi Flegrei. This area is included in a large volcano, the Campi Flegrei caldera, which is a nested structure resulting from two major episodes of ancient caldera collapse, related to the Campanian Ignimbrite (39,000 years BP) and the Neapolitan Yellow Tuff (15,000 years BP) eruptions. The Campi Flegrei caldera includes the area of Campi Flegrei, the city of Naples, the western part of the bay of Naples and the bay of Pozzuoli until Capo Miseno. It has been demonstrated that in the past 15,000 years the areas outside the caldera have been stable, while a general subsidence has affected the area due west of the Sebeto valley, the area between the Posillipo coast and the Agnano plain, and the coast between Averno and Capo Miseno. The central part of the caldera is affected by an ongoing resurgence, which determined a net uplift of about 90 m in the past 15,000 years. This uplifting has been not continuous through time, but it occurred intermittently and determined by the summation of several short-term deformation (or bradyseismic) events. The occurrence of the roman coastline at about 10 m b.s.l. and of numerous roman and medieval remains below sea level is a further evidence that the caldera has generally subsided in the last 2,000 years. Parascandola reconstructed the ground vertical deformation at the s.c. Serapeo, from Roman times to 1905. Serapeo is a roman monument, located not far from Pozzuoli coast line, which was first supposed to be a temple devoted to the egiptian god Serapis, from which the name, and only at the beginning of this century was recognized as a marketplace by Dubois (1907). Excavation of the monument began in 1750 by order of the king of Naples Carlo III of the Borbone dinasty, in an area called “the vineyard of the three columns” because three marble columns were coming out of the ground. After excavation, the columns showed lythodome’s holes up to 7 m above the floor of the monument, testifying the maximum subsidence of the area. The monument, constructed between the end of the I and the beginning of the II century d.C., was restored at the beginning of the III century d.C. because sea water had invaded its floor. Since then the ground was subsiding until the X century d.C. when it began to uplift. This uplifting lasted until the Monte Nuovo eruption, occurred in 1538. Since the beginning of the XVI century there was an acceleration of the uplift as testified by royal edicts with which newly-formed land was ceded to the town of Pozzuoli. In the last few days before the Monte Nuovo eruption an uplift of 5 to 8 m took place in the area of the eruption event. In the modern times, the area was affected by several positive and negative mouvements, with an excursion of maximum 2,00 m, permanently studied by the Vulcanology Institute.

The area is also of great interest due to its archaeologic heritage that, in this case, represents a “measuring instrument” of the natural phenomenom analysed by this project. The seafloor of the Gaiola islet is rich in archeological ruins, submerged as a consequence of bradyseism. The islet was part of a larger human settlement built around the “villa” of Publio Vedio Pollione, then inherited by Augusto. The inlet of Baia was anciently a lake (Baianus lacus, connected by a canal to the open sea) and the banks were studded with luxurious “villas” with piers and fish-ponds. In particular between I and III b.C. emperors had their residence in this area. Among the many submerged buildings the Imperial “Ninfeo” of Punta Epitaffio, the villa of Pisoni, thermal baths, located on a stone road, and a semicircular fish-pond. Also the inner area shows the signs of urban structure of ancient Baia, in particular in the Archaeological Park, where there is evidence of residencial “villas”, private and public thermal baths. By the end of IV century a.C., the first signs of bradyseism started to appear, leading to the complete destruction of the coastal area. The Roman settlement of Baia is considered one of the most singnificant after the Imperial “Villa Adriana” at Tivoli.

Statements of authenticity and/or integrity

The geographic area of Campi Flegrei, created by volcanic activity that goes back to 50.000 years ago, is encompassed in the coastal area that is located on  the Northwestern side of the bay of  Naples. The entire area is protected by the Regional Park of Campi Flegrei. The protected area extends for 7.350 hectares, in the suburbs of Naples.

The Submarine Park of Baia is located in the bay of Pozzuoli (district of Napoli) and stretches out in the sea for 176,6 hectares. The area includes the shores of Bacoli and Pozzuoli, between the southern pier protecting the harbour of Baia and the pier of Lido di Augusto, immediately east.

The park established in 2002, also a as protected marine area, by the Ministry for the Environment in agreement with the Ministry for Cultural Heritage and Activities, the Ministry of Infastructure and Transport, the Ministry of Agriculture and Forestry and the Campania Region.

The protected area with complete limitation (zone A), facing Punta Epitaffio, extends in the sea for 20,7 hectares, while the remaining area is a protected area with general limitations (zone B) and protected area with partial limitations (zone C), on the eastern side of the Park.

The temporary managing authority is represented by the Administration in charge for the archaeological heritage of the province of Napoli and Caserta.

The Submarine Park of Gaiola lies at the foot of the hill of Posillipo in the sea surrounding two small islets, for an overall extension of 41,6 hectares. Also this area includes a protected area with overall limitations (zona A) of 6,4 hectares, around the islets and a protected area with general limitations (zone B).

As the Submarine Park, the islets of Gaiola enclose on dry land a great environmental and cultural value. Besides preserving the sea and the natural beauty and archeological heritage, the area is subject to initiatives aimed at protecting and emphasizing the entire insular heritage promoted and supported jointly by the environmental association "Marevivo" and the Region Campania.

The Park of Gaiola, such as the Park of Baia, was established in 2002 as submarine park.

In both parks the following activities are prohibited: to remove, violate and damage archeological ruins and geological formations, underwater fishing, to capture and disturb existing fauna, to damage flora, water pollution and solid or liquid waste dumping. Within zone A, swimming, scubadiving, navigation and fishing is prohibited (there are special permits only for scientific activities of study and research).

Each specific Harbour Office in the area is responsible of supervising together with the Carabinieri of the Department for the protection of historic treasures.

Comparison with other similar properties

The phenomenom of bradyseism in the flegrea area is unique: wide extension of the phenomenom, mecchanisms, gradualness and periodic positive and negative movements of different intensity according to the areas, emphasize the peculiarity of this phenomenom. Evidences of  subsidence are known to be found in the eastern Mediterranean area. We can recall the example of  the island of Thera, destroyed  around XIV century b.C. by the seaquake caused by volcanic eruption; such destruction can be related to the subsidence of many areas of the northern coast of Crete and the southern Peloponnesian coast. The destruction in 373 b.C. of the town of Helike in northern Peloponneso and in 356 b.C. of Cirene and part of the great harbour of Apollonia can be linked to similar phenomena such as earthquakes and seaquakes.