Introduction & objectivesThe Plinian eruption of Somma-Vesuvius volcanic complex AD 79,which completely buried the Roman settlements of Pompeii andHerculaneum belongs to the most well-known eruptions inhistory. During this eruption almost the entire Sarno River plainwas covered by volcanic deposits (Sigurdsson et al., 1985)showing a specific and therefore easily identifiable stratigraphy(Fig. 1). Thus, these deposits can be considered as an idealchronostratigraphic marker.

The eruption AD 79 covered the Sarno River plain with volcanicdeposits of some meters. This not only caused a caesura in theexistence of an entire landscape, but also contributed to theexcellent preservation of the paleo-surface and the ancientpaleo-environmental conditions before the eruption of AD 79(Foss et al., 2002). Consequently, almost 2,000 years later, thispaleo-surface is still accessible for stratigraphical investigations.

The objective of this research project is to reconstruct the paleo-topography and paleo-environmental features of the Sarno Riverplain before the eruption of Somma-Vesuvius in AD 79. Theobjective is based on the hypothesis that the eruption caused acoating of the ancient topography which left ancientphysiographic elements still recognizable in the present-daytopography. The utilized methodology combines stratigraphicalinformation from core drillings,present-day topographicaldata,and classification and regression methods.

Reconstructing the Roman topography and environmental features of the Sarno River Plain (Italy)

before the AD 79 eruption of Somma-Vesuvius

SEBASTIAN VOGEL1 & MICHAEL MÄRKER2

1Deutsches Archäologisches Institut, 2Heidelberg Academy of Sciences and Humanities

Contact: Sebastian Vogel email: sv@dainst.de

Michael Märker email: michael.maerker@geographie.uni-tuebingen.de

http://www.dainst.org/index_7902_it.html

Fig. 2 : Present-day digitalelevation model (DEM) andfluvial network of the SarnoRiver plain with the location ofmore than 1,800 stratigraphicalcore drillings. Letters indicatesites of interest.

Fig. 1: Stratigraphicalcross-section southof Pompeii.

OutlookIn future studies this pre-AD 79 DEM will be used to identify potential locations of Pompeii’s marine or fluvial harbor, whose exactlocation is still debated. Moreover, the combination of the pre-AD 79 DEM with archaeological findings enhances the paleo-environmental reconstruction of the Sarno River plain. In the next project phase the pre-AD 79 DEM will be used to determinethe paleo-topographic setting of the known ‘villae rusticae’ of the Sarno River plain. In addition to paleo-pedological analyses, wewill use the pre-AD 79 topography to reconstruct soil and land use characteristics and to simulate the ancient cultural landscapeof the Sarno River plain.

ReferencesFoss, J.E., Timpson, M.E., Ammons, J.T., Lee, S.Y., 2002. Paleosols of the Pompeii Area. In: Jashemski W.F. ed.. The Natural History of Pompeii. Cambridge University Press, 65-79.Sigurdson, H., Carey, S., Cornell, W., Pescatore, T., 1985. The eruption of Vesuvius in A.D. 79. Natl. Geogr. Res. 1, 332-387.Stefani, G., Di Maio, G., 2003. Considerazioni sulla linea di costa del 79 d.C. e sul porto dell’antica Pompei. Riv. Studi Pomp. XIV, 142-195.Vogel, S. & Märker, M., 2009. Reconstructing the Roman topography and environmental features of the Sarno River Plain (Italy) before the AD 79 eruption of Somma-Vesuvius. Geomorphology, doi: 10.1016/j.geomorph.2009.09.031.

MethodologyTo reconstruct the pre-AD 79 topography and paleo-environmental conditions morethan 1,800 drillings from construction works, as well as from past archaeological andgeological studies, were collected to gain a representative network of stratigraphicalinformation for the entire Sarno River plain (Fig. 1). By means of the drilling coresthe stratigraphy was determined, the volcanic deposits of AD 79 and the pre-AD 79surface underneath were identified, and the pre-AD 79 stratum was characterized.We reconstruct the pre-AD 79 topography with a sophisticated geostatisticalmethodology based on a present-day high-resolution digital elevation model (DEM)and a classification and regression tree approach.

Figs. 4A & B compare the present-day topography with the predicted pre-AD 79 topography.Even though main physiographic elements appear on both DEMs, several differences can beidentified. Most evident is that the pre-AD 79 surface is approximately 5.7 m deeper thanthe modern surface. Thus, the entire coastal area is lying below the recent sea level. Incomparison to the canalized present-day Sarno River, the modeled paleo-Sarno River followsthe natural depth contours of the pre-AD 79 DEM, resulting in more pronounced meandertype fluvial patterns.By comparing the character of the pre-AD 79 stratum from the drilling data with the pre-AD79 DEM we reconstructed some paleo-environmental features before AD 79 such as theancient coastline and the flood plain of the paleo-Sarno River (Fig. 4C, D). The littoraldeposits before AD 79 are distributed parallel to the present-day coastline at a horizontaldistance of 1,000 to 1,500 m. The fluvial/palustrine deposits cover the area where the paleo-Sarno River most likely had its ancient riverbed.

Greater thickness of the volcanic deposits along the coast on the other hand most likelyindicate re-deposited material that was mobilized by the Sarno River and its tributaries andtransported towards the Thyrrenian Sea. This corresponds with thinner deposits in thecentral part of the Sarno River plain. Furthermore, an accu-mulation of volcanic deposits atthe foot of the Lattari and Sarno Mountains may result from slope deposits being mobilizedby mountain torrents or lahars after intense rainfall events.

Fig. 3: Modeled depth to the pre-AD 79surface of the Sarno River plain.

Fig. 4: Present-day DEM and Sarno River (A); modeled pre-AD 79 DEM and deduced paleo-river network (B); character of the pre-AD 79 stratum from the drilling documentations (C) and inferred reconstruction of pre-AD 79 environmental features (D).

Results & discussionFig. 3 illustrates the modeled depth to the pre-AD 79 surface of the Sarno Riverplain. It ranges from >0 to 15 m whereas the average depth is 5.7 m. The distinctspatial distribution of volcanic deposits since AD 79 is most notably controlled bytwo sets of processes: (i) the intial deposition during the eruption and (ii) thesubsequent redistribution by processes of erosion and transport. Originating fromthe vent of Somma-Vesuvius, the pumice lapilli fallout was dispersed concentricallytowards the southeast resulting in thickest deposits on its southeastern flanks, nearthe source of the eruption.

Fig. 5: Pre-AD 79 geomorphological map and paleo-environmental reconstruction of the Tyrrhenian coast of theSarno River plain.

On closer examination of the coastalarea of the Sarno River plain a bigfan delta can be identified on boththe present-day DEM and the pre-AD79 DEM (Fig. 4 & 5). This indicatesthat this landform already existed inRoman times. Converging contourlines at the foot of the adjacent hillslopes reveal escarpments that mayhave derived from abrasion action ofthe sea related to previouscoastlines. Southwest of Pompeii anelevation discontinuity can be seenin the pre-AD 79 DEM which is basedon deeper littoral deposits in thenorthern coastal area.This discontinuity seems to be overprinted by recent deposition as it cannot be identified onthe present-day DEM. This implies that it was formed before AD 79 possibly associated withthe seismic activity preceding the AD 79 eruption, such as the big earthquakes of AD 62 andAD 64.