Dating the Thera eruption
Why is the dating of the Thera eruption so important in Eastern Mediterranean Archaeology?
Ruiha Smalley, December 2006
Introduction
During the Late Bronze Age (LBA) of the Aegean a volcano erupted on the island of Thera, now known as Santorini. The eruption split the island and created the caldera that now exists (figure 1). The eruption caused ash and pumice to spread across the eastern Mediterranean, created frosts around the globe and tsunamis which hit the shores of the island of Crete, some 100 kilometres to the south, and completely buried the Theran town of Akrotiri.
The dating of the Theran eruption has far reaching archaeological implications and has produced much debate since Professor Marinatos’s paper of 1939 titled "The volcanic destruction of Minoan Crete". Professor Marinato proposed a date of 1500BC based on the synchronisation of Egyptian material such as pottery fragments and scarabs. This date has since been ’canonised’ and has meant that others have had to adjust their dates to fit the established view. (Kuniholm, 1989)
Conventional chronology
Both sides of the argument agree that pottery found at Akrotiri has a distinctive style belonging to the LMIA phase, a phase considered to be the height of Minoan civilisation. The eruption took place in the later LMIA phase so that any sites that have pottery styles dating later than LMIA must therefore post-date the eruption. With this in mind relative chronologies have been able to be constructed despite the controversy over absolute dates. (Balter, p.508)
The conventional chronology derives from the cross study of ’material culture exchanges and stylistic associations’ between the historically dated Egyptian and Aegean cultures. Here the start of the cultural phases of Crete termed Late Minoan IA and IB (LMIA, LMIB) are put at c. 1600/1580 to 1480BC and c. 1480 to 1425BC respectively. The eruption of the volcano (late LMIA) is then dated c. 1520 to 1500BC (figure 2). (Manning et.al., 2002, p.733)
| Late Minoan IA | c. 1600/1580 - 1480BC |
| Late Minoan IB | c. 1480 – 1425BC |
| Thera eruption | c. 1520 – 1500BC |
Conflicting evidence
Evidence from C14 radiocarbon dating and other methodologies support a different argument. These procedures produce dates which place the eruption from between 100 and 150 years earlier. (Balter, p.508)
The first serious attempt to apply radiocarbon dating to dating the eruption took place in the 1970s. Using the ’bristlecone pine calibration technique’, samples of carbonised material from Thera produced calibrated results of approximately 1625BC. (Kuniholm, 1989)
In 1987 a Danish report published data based on the study of ice cores from Greenland. They noted a high acidity signal at 1644BC and suggested a 1645BC eruption with an estimated error limit of +20 years. Dendrochronology has also produced interesting results. In 1988 Dr. Baillie published results from a study of Northern Irish bog oak rings where samples were examined from a long established chronology. In Irish bogs volcanic activity results in extremely narrow bands of rings which can continue for some years after the event. Those from 1628-1626BC were the narrowest rings in the entire lifetime of the tree. Other evidence for a volcano-narrow ring relationship could be seen for the years 540AD and 207BC when significant volcanic activity is believed to have taken place. At Cornell University almost continuous dendrochronological sequences exist for the eastern Aegean and were examined for signs of volcanic activity around 1500BC. "There is no obvious anomaly in the Aegean tree-rings around 1500BC." (Kuniholm, 1989)
A team lead by S. Manning, of Cornell University, recently took radiocarbon data from sites in the southern Aegean to create a chronology for the LMIA and LMIB phases. This data showed that the Thera eruption took place in the late 17th Century BC. (Manning et.al., 2006, p.566).
Another recent study, led by W. Friedrich of Aarhus University, produced a similar date for the eruption. A large branch of an olive tree, alive at the time of the eruption (figure 3), was discovered on Santorini having been covered by the eruption’s ash. Friedrich’s team used radiocarbon analysis to examine a whole series of annular rings in the branch. This enabled them to pinpoint the date of the eruption to 1613BC, with a margin of error of up to 13 years. (Aarhus University)
Why does dating matter?
"Precise dating of this eruption is important because the tephra layer acts as a universal time marker of Late Bronze Age contexts in the Eastern Mediterranean region." (Friedrich et.al., p.548)
The conventional dates are inconsistent with findings from carbon dating techniques. This suggests either a defect in the conventional links to Egyptian chronologies in the mid-second millennium BC or a problem with the chronology itself. The Egyptian chronology is considered relatively strong for the 14th Century. It correlates well with the Mesopotamian historical chronology and also with other carbon dating evidence. This suggests that the problem lies more with the ’interculture linkages in the mid-second millennium BC’. (Manning, 2006, p.568)
The revised dates imply that the overall LMIA and LMIB phases began earlier and so were much longer than previously thought. The overall New Palace period of Crete, when the island dominated Aegean trade and culture, is therefore a much longer era. The LMIA Aegean world would not be contemporary with, or influenced by, the Egyptian 18th Dynasty which started c. 1550/1540BC (The New Kingdom). It would instead be contemporary with the very different Hyksos period of Egypt, when northern Egypt was controlled by a Canaanite dynasty with links to the Levant. (Manning, 2002, p.569, 742)
The revised dates for the eruption have major consequences for relations between Egypt and the Aegean civilisation of the Late Bronze Age. Archaeologist, J.Rutter of Dartmouth College said, "The issue of which direction artistic and other cultural influences was travelling may change significantly". (Balter, p.508)
A realignment of dates would mean that the famous Mycenaean shaft graves would also be contemporary with the Hyksos. "Some archaeologists had speculated that the Mycenaeans owed their rise to a strategic alliance with the New Kingdom; the new radiocarbon dates would instead raise the possibility that they were allied with the Hyksos, Rutter says. At the very least Manning says "it would make the Hyksos world much more important and interesting". Manning adds that the earlier chronology would create "a different context for the genesis of Western civilisation". (Balter, p.509)
Conclusion
The scientific evidence produced since the 1970s indicates an earlier date (late 17th Century BC) for the Theran eruption than conventional chronologies would agree to (1500BC).
Some scholars refuse to accept the new data. Egyptologist M. Bietak states "I am not impressed" and argues that radiocarbon dating is unreliable and that the earlier date for the eruption is contradicted by excavations which have found LMIA pottery in statigraphic layers that Egyptian records date to later periods. (Balter, p.509)
It will be some time before the relationships between cultures of the Aegean Late Bronze Age can be placed in context alongside an agreed chronology.
References
AARHUS UNIVERSITET, FACULTY OF SCIENCE (2006) New research in Science: date of the largest volcanic eruption in the Bronze Age finally pinpointed. [Online] Available: http://www.nat.au.dk/default.asp?id=11296&la=UK [20 December 2006]
ANSWERS.com (2006) Santorini. [Online] Available: http://www.answers.com/topic/santorini [20 December 2006]
BALTER, M. (2006) New carbon dates support revised history of ancient Mediterranean. Science, Vol.312, 28 April, pp.508-509.
FRIEDRICH,W.L. et.al. (2006) Santorini eruption radiocarbon dated to 1627-1600 BC. Science, Vol.312, 28 April, p.548.
KUNIHOLM, P.(?) (1989) Overview and Assessment of the Evidence for the Date of the Eruption of Thera. [Online] Available: http://www.arts.cornell.edu/dendro/thera.html [20 December 2006]
MANNING, S.W. et.al (2002) New evidence for an early date for the Aegean Late Bronze Age and Thera eruption. Antiquity, Vol.76, pp.733-744.
MANNING, S.W. et.al. (2006) Chronolgy for the Aegean Late Bronze Age 1700-1400BC. . Science, Vol.312, 28 April, pp.565-569.
