MODELS OF THE PRE-MINOAN ISLAND (prior to ca. 1645 BC)
The white Minoan pumice and ash
tuff covers most of the island
Until about 20 years ago, it was thought that the shape of the island before the Minoan eruption was circular with a central cone or a system of several overlapping volcanic shields. This model, however, has been considerably modified over the last years (see graphic to the left).
Evidence has been found that the present-day
caldera that consists of several basins existed already before
the eruption, at least in parts.
1. First of all, if the pre-Minoan island was a central cone the volume of the caldera collapse would be around ca. 60 km3 (Druitt and Francaviglia, 1992) which exceeds greatly all dense rock estimations of the total eruption volume, most probably 27-30 km3 DRE (Pyle, 1990). Such a huge discrepancy between the collapse and eruption volume is difficult to explain.
2. The Minoan deposits dip into the caldera at several points, especially in southern Thera and on Therasia, thus indicating that a depression existed before (Pichler and Friedrich, 1980; Heiken and McCoy, 1984; Friedrich, 1994).
3. Stromatolites occur in the deposits and are described by Eriksen and others (1990). Their analysis showed that probably in the northern basin a shallow sea-flooded lagoon existed before the eruption where these stromatolites grew.
4. Druitt and Francaviglia (1990) found deposits of the Minoan pumice plastered in situ at some places on the inner side of the present caldera wall thus proofing that the walls existed before. Further, they observe that other parts of the northern cliffs are relatively eroded and probably not from the Minoan collapse but from the previous Cape Riva collapse.
Friedrich (1994)'s and other recent
reconstructions of pre-Minoan Santorini are qualitatively equal
and based upon the one from Druitt and Francaviglia (1990).
Druitt and Francaviglia (1991) claim that their model is the
up-to-date most accurate one.
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© Tom Pfeiffer, page last modified on 3 February 2004.