Volcanology and Archaeology for Better Understanding the History of Campi Flegrei : Post-NYT Bradyseisms and More Rapid Deformation

The Campi Flegrei volcanic district includes insular (Ischia and Procida Islands) and peninsular volcanic activity (Campi Flegrei volcanic field) with the link to older activity till Ponza Island. The history of this area has been studied in detail since the eruption of the Campanian Ignimbrite (CI, age: 39 ky BP, volume: 200 300 km), which makes this one of the most powerful eruptions in Europe. In the Neapolitan Yellow Tuff (NYT: age: 15.0 ky BP, volume: 50 km), another powerful eruption occurred. Activity younger than the NYT can be subdivided in three epochs which include 70 recognized ephemeral eruptions. The volume of these individual eruptions is between 0.4 and 1 km (DRE). Probably, the long-lasting magma reservoirs (i.e., CI and NYT) represent eruptions that are fed by deep magma reservoirs. In deep reservoirs (>10 km), magmas stagnate, differentiate and are probably modified by crustal components (Hercynian basement). The long-lasting reservoirs are also the ones that feed the ephemeral shallow magmatic system (2 5 km) that gave rise to the post-caldera magmatic epochs. However, the magmas of the post-caldera epochs are isotopically heterogeneous and made by several components (i.e., least evolved (as an example the Minopoli eruption, 9500 y BP), CI, and NYT components). Mixing between ephemeral shallow reservoirs occurs. Mixing of long lasting reservoirs also occurs; and also during explosive eruptions. The concentration of earthquakes and the deformation history suggest that Campi Flegrei could erupt again with an ephemeral eruption, especially if the uplift will reach 5 6 m like Monte Nuovo eruption, given existing uplift of 1970-72 and 1983-84.


Introduction
Campi Flegrei (Figure 1) was named after the Greek settlement around Naples and in particular on the Islands of Procida and Ischia as "Campi Ardenti".Probably, their settlement began 4 -5 ka in the 3˚ epoch of activity of Campi Flegrei [1] [2].In the world, Campi Flegrei can be compared to Rabaul volcanic field and Yellowstone volcanic field.One characteristic is the deformation of the land, rising and sinking through time.This characteristic feature is called Bradyseism; it is well measured in Campi Flegrei through benchmarks which are remeasured regularly.Campi Flegrei is just a little piece in an area larger that goes from Campi Flegrei to Roccamonfina volcano including larger volcanic area (Ponza, Ventotene), volcanic field from Gaeta to Ischia, submerged below sea level (Figure 2), with ages from 1 -5 Ma up to now [3] [4].
Uncertainness about the cause(s) of deformation remain, specifically on the relative roles of magma at 3 -4 km deep and aqueous fluid tapped by silt and clay that cap the exit to the magma but influence the deformation in Campi Flegrei [5].I will try to trace the volcanic history versus the deformation history to address this question.The deformation history can be very important to: (a) understand the cause of deformation (fluid versus magma), (b) forecast the volcanic scenario of the next eruption.

Chronology of the Campi Flegrei
The chronology that will be analyzed goes from 60 Ka to up to now (Figure 3).
Since the beginning of the century, the scientists have studied the chronostratigraphy of Campi Flegrei [6] [7] [8] [9] [10].The new improved post-NYT stratigraphy of Campi Flegrei has been made by [11] (Figure 3).In this list are   A. Paone Two largest events are Campanian Ignimbrite (39 ka, from [12]) and the NYT eruption (15 ka from [13]), with volume 200 -300 Km 3 for CI and 50 km 3 for NYT.From Figure 3 we can understand the ratio between the eruptions and inter-eruption activity within the Campi Flegrei during 15 ka [2].The last eruption occurred in the 1538 forming a cinder cone called Monte Nuovo.It is the youngest cone of Campi Flegrei.On the other hand, there is a large dome called Mt. Olibano (Accademia Aeronautica).The only large effusive structure in the Campi Flegrei.

Some Information on Campanian Ignimbrites (CI) and Neapolitan Yellow Tuff (NYT)
Figure 4(a) shows an impressive outcrop of Breccia, named Breccia Museo.This type of deposit is a lag-breccia in Ignimbrite, deposited near its source caldera.
This kind of deposit contradicts the idea of the Ignimbrite pipe caldera and which has been inferred east of Campi Flegrei within the center of Naples, where people do not see any type of Breccia Museo.

Deformation Types: Bradyseism and Short-Lived
After the collapse of NYT, Campi Flegrei has started a long history of deformation.It is useful to differentiate two types of deformation-short, within the

Reference Points Most Meaningful for Explaining the Bradyseism
During the debate between Gradualism and catastrophism from Charles Lyell and James Hutton; Lyell had the brilliant idea to come in the Campi Flegrei to look the deformation where were shaped: The Serapeo, Macellum, Marketplace (Figure 7).He recognized that the three column were full of Lithophaga lithophaga living in intertidal level within the column, demonstrating that the land  second 3 mt are full of evidence of Lithophaga lithophaga (Figure 9) this imply that early in the last 2000 years, there was subsidence and a large ingression of the sea in Campi Flegrei, followed by uplift (Figure 10 and Figure 11).

Innovative Features on the Parascandola Modified Curve
One feature that can be highlighted from the Serapeo (marble column) is that the land rose much faster before the eruption of Monte Nuovo.The point lowest of the new curve is 1430 as suggest some historical data and this is clear in the picture called "La sorgente di Cantariello" (from Scottish codex) (Figure 10,

Figure 2 .
Figure 2. Simplified geological map of Campania plain.

Figure 4 (
b), Figure4(c), show the Ignimbrite (CI) and the Neapolitan Yellow Tuff (NYT).These outcrops are sitting in a position far from Campi Flegrei.While CI has climbed the Apennine the NYT has covered all the Napoli City in fact after the excavation by Romans now this part of Napoli can be visited in the commercial caves from tourists looking all the beauty of NYT.Costa et al.[14] use a novel method to quantify and reproduce the CI tephra deposit, applying a computational ash dispersion model combined with the analysis of a set of wind fields, and more than 100 thickness measurements of the CI tephra deposit declare that the CI is a super-eruption and the origin is from the Campi Flegrei.The distal tephra show again that the volcanic product of CI must originate in the Campi Flegrei. Figure 5 show how the thickness of the CI increase getting close to Campi Flegrei.This pose two controversy (a) CI is originate in Campi Flegrei, and CI is not a super-eruption.[15] state the magnitude of CI is 7.7 suggestive of a Collosal eruption.CI and NYT have difference in Sr-Nd-Pb isotopic variation together with Minopoli (ephemeral single eruption).This heterogeneity suggest that mostly of the activity after the largest eruptions (CI, NYT) derive by mixing from their magmas from the Deep and Hot Intrusion Zone [16] [17] [18]; Paone (unpublished data).

Figure 5 .
Figure 5. Thickness of the CI from boreholes and outcrops.

Figure 7 .
Figure 7. Serapeo as is seen nowadays by helicopter.

Figure 8 .
Figure 8.(a) Campi Flegrei DEM with the location of eruption and the deformation.(b) Structural map of the Campanian Plain.(c) Geological Section with a simplified of the resurgent block.(d) Parascandola curve.D 1 Deformation curve covering the last century(from [1]).

Figure 9 .
Figure 9. Serapeo during an uplift period probably before the eruption of Monte Nuovo volcano.Simplified figure how the Marble column were used by Lithophaga lithophaga.

Figure 10 .
Figure 10.New view of the Parascadola curve.The curve has many points to support such a diagram (modified from [21] [23] [24].

Figure 11 .
Figure 11."La sorgente del Cantariello" 1430 show the column under the see at least of 10 mt (from Scottish codex).

Figure 11 )
Figure 11).While the author was painting the marble column within the sea, he also showed that Serapeo had many hot springs.The range of time 1490-1538 is very short compared to the data of Parascandola.If this behavior is typical, a new Bradyseism could really lead to a new eruption.Of course, the magma volume will be under 1 Km 3 like the other ephemeral or short-lived eruptions in the last 15 ka.The most likely type of eruption will be monogenetic, phreatomagmatic, with only a low probability of a super-eruption.Actually, if we sum the land that rose in 1970-72 and 1983-84, with a new episode similar to

Figure 13 .
Figure 13.Four pictures that show how the ponte di Caligola varied its position subsideding after the eruption of Monte Nuovo.

Figure 14 .
Figure 14.New diagram with the reference point showing the subsidence of Campi Flegrei after the eruption of Monte Nuovo [22].

Figure 16 .
Figure 16.Monte Nuovo Cinder cone, with Averno lake maar behind it, nested in the older Archiaverno tuff ring.Averno lake was named as "the entrance of hell" during the Roman times, plus this locality is also famous for the legend of "Sibilla".

Figure 17 .
Figure 17.Gauro Volcano with the Marine Starza Terrace at its foot.

Figure 20 .
Figure 20.Between the Cigliano volcano (cinder Cone) and Gauro volcano (tuff cone).The flat floor tells us of the ingression of sea 5 Ka.

Figure 21 .
Figure 21.Cigliano volcano with Astroni and Agnano Monte Spina on the back.
Changes in structure, volume, deformation in the last 15 ka show the history of eruptions and unrest at Campi Flegrei.Campi Flegrei is monitored by INGV-OV and already under attention with yellow color.If more magma or/and fluid can rise, which can open a window and force its way out, it will be very dangerous, especially if the magma will come out in the sea that could produce more violence with the diluted currents.One particularly risky area is Via Napoli-Rione Terra.Some scientists have already noted that this was the focus of maximum uplift during 1983-84 and had a high concentration of epicentre quakes.This can be the next point of eruption, although not of great intensity like the CI and NYT.The paper reasoning suggests that such scenario can be real: the Monte Nuovo eruption can have started a new Epoch.