Santorini and its eruption in the Late Bronze Age

Chapter 7 Conclusion

7.6 Summary of the tephra fallout modelling

For full description of how the map is derived and other issues regarding tephra fallout from the Minoan eruption of Santorini, download the chapter 7 pdf.

Figure 7.28 Combined isopach of the Plinian and co-ignimbrite phases using manipulated wind vectors. Points indicate depth, in cm, of tephra found in cores and samples.

The above models have demonstrated a number of points about the tephra fallout of the Minoan eruption of Santorini. The wind vectors in the area can be divided into two basic types, roughly equating to winter and summer. The winds in the winter are of much greater force and are directed more to the east with little variation in the north and south directions. During the summer months the winds are not as strong in an easterly direction and indeed at higher altitudes some of them actually veer to the west. There is also a greater variation in the north and south direction. Simulations of tephra fall for summer wind patterns give much better fits to the observed thicknesses. On this basis and on the results of the model runs undertaken, I propose that it is most likely that the eruption occurred in the summer, probably June, July, August or September.

The model runs using monthly averaged values were not able to recreate the spread of material to the north east and south east of Santorini. In the model I have used only a single point source for the main vent. It may be that some of this north east - south east variation was caused by the elutriation of material from pyroclastic flows at a distance from the main vent. However, I suggest that the observed pattern of distribution was achieved through variable winds over the time period of the eruption.

It is highly unlikely that the west of Crete was affected by any significant deposition of tephra. Tephra did not fall on the west of Crete in any of the model runs conducted. It is also unlikely that even as much as 1 cm of material fell over the Minoan settlements of the Messera on the south coast. Most of the model runs create quite tight isopach contours, and so it may be that there was quite rapid fall off in the amounts of tephra. For example, Palaikastro on the east coast may have received as much as 10 cm of tephra, but Gournia on the Bay of Mirabello very little. This cannot be modelled, but if future excavation shows such an occurrence this would not be unreasonable.

On the evidence of the modelling it is not surprising that the island of Rhodes has provided the greatest amount of tephra yet found, since it lies almost directly east of Santorini which was the main axis of tephra dispersal. This also means that there should be significant tephra deposits on other islands to the east of Santorini, the largest of which are Astypalaa, Tilos, Symi, Chalki, Karpathos and Kasos. If there is another large eruption of the island in the future then the islands of the Dodecanese will probably be more at risk than those of the Cyclades.