Academic journal article
By Baillie, M. G. L.
Antiquity , Vol. 72, No. 276
In recent years the construction of long tree-ring chronologies has made it possible to view tree response to environmental factors, over wide geographical regions, at very high temporal resolution. From even the most preliminary analysis of these tree-ring derived environmental records come hints of possible 'patterns' in the data. In recent centuries widespread response to explosive volcanic eruptions is evident (Jones et al. 1995). Further back in time, the close juxtaposition of widespread tree-ring events with trauma in human populations has allowed the formulation of a variety of hypotheses linking aerosol-producing, presumably volcanic, events with such issues as the dating of Santorini and dynastic changes (Kuniholm et al. 1996; Kuniholm 1996; Baillie 1995). Critical discussion on such hypotheses is both welcome and necessary due to the fact that our understanding of the vectors for environmental change, over millennial timescales, is currently extremely poor. However, attempting to 'rubbish' the provision of such hypotheses is not normally part of the scientific method.
Buckland et al. (1997) appear to be unhappy with the hypotheses that Santorini may have erupted in 1628 BC, and that environmental events at 1159-41 BC and AD 540 may have had dire consequences for human populations. Their treatment of the issues offers only partial guidance to the readers of ANTIQUITY on the nature of the debates. For example, recent dates from Kuniholm et al. (1996) for Anatolian growth anomalies, 470 years apart, proximate to 1628 Bc and 1159 BC, suggest that, in the earlier case, some environmental event caused massively increased growth in drought-stressed trees downwind of Santorini. Kuniholm et al. (1996) state explicitly that their tree-ring anomaly most likely relates to 1628 BC, and to Santorini (p. 782):
The exceptional growth of relative ring 654 . . . (thus) . . . relates to 1628 BC. . . . If sustained, a date of 1628 BC for the Thera eruption will require a major revision of the Aegean chronology . . .
Similarly, aspects of the Santorini eruption have been suggested as a possible source for the biblical Exodus story (Rampino et al. 1988; Wilson 1985). Bruins & van der Plicht (1996) have now shown that radiocarbon dates from Jericho, which was traditionally destroyed c. 40 years after the Exodus, are consistent, indeed almost identical, with the radiocarbon dates from Akrotiri on Santorini. This suggests the destruction of Akrotiri may lie further back along the fiat section of the radiocarbon calibration curve, i.e. around 1570 BC or earlier. Like it or not, the weight of evidence increasingly suggests that Santorini is more likely to have erupted in the 17th, rather than in the 16th, century BC. Buckland et al. failed to present either of these pieces of information.
Instead, Buckland et al. chose to contest fundamental aspects of the 1628 BC debate, such as the correlation between bristlecone-pine frost rings and volcanoes. They indicated that the correlation was 'poor'. That accusation is not new or correct, and must be answered. By comparing the frost-ring dates (LaMarche & Hirschboeck 1984) only with the acid layers in the GISP2 ice core (Zielinski 1995), their analysis was partial. It is known that the ice cores do not replicate well unless realistic errors are taken into account (Alley et al. 1997; Baillie 1996). It is also known that the various ice cores fail to record important known eruptions (Buckland et al. 1997). In addition, they used Zielinski's over-optimistic [+ or -]2-year error on all the ice core acid-layer dates despite the fact that Zielinski & Germani (1998) state '. . . errors for the 0718-m depth are estimated at [+ or -]1%'. On this basis, the error estimates should have been of the order of [+ or -]10 years by AD 950, not the [+ or -]2 years used. To test the LaMarche & Hirschboeck frost-ring hypothesis properly, the most complete ice and historical record of large volcanoes must be used, and realistic error limits must be given to the ice-acid dates. …