A Major Change in the Stratigraphy of the Santorini Volcano in Greece
One could argue that the LPS was locally eroded away prior to the LBA eruption, but it has not been found in drillings or at excava- tion sites. Furthermore, the so-called LPS deposits in deep-sea drillings are not from Santorini. Archaeological evidence of Cycladic objects at several localities under the socalled LPS proves that these objects were buried by the LBA eruption and not by an older layer of pumice some 200,000 years ago. Its products were partly deposited on the inner side of the commonly steeply sloping caldera wall. The topography, slumping and later erosion led to difficulties in interpreting the local stratigraphy.
A water-filled caldera existed at Santorini before the LBA eruption. The LBA pumice draped the entire landscape and was thickest on terraces on the caldera wall (Figure 2(d)). After erosion, pumice remained on terraces at distinct levels ( Figure 7). Pumice on two major terraces was interpreted as being formed by separate explosive volcanic eruptions 200,000 years apart, but in fact were both part of the same LBA eruptive event. Study of the caldera wall and localities on Thera suggests that the LPS does not exist and the magmatic cycle theory is consequently invalid. The pumice below Fira was deposited on the inner side of an existing caldera during the LBA eruption. The caldera wall, consisting of lavas and pyroclastic layers, was intersected by radial and concentric faults. We deduce this from small eruption points arranged in curved tectonic lines which predate the LBA eruption. Tectonic events gave rise to curved terraces and niches on the caldera wall upon which the products of the LBA eruption were deposited.
These deposits have been partly reworked by down-sliding since they contain xenoliths of older pyroclastic material, such as dark lapilli from the older Upper Scoria Series. This can possibly also explain the old radiometric data obtained for the LPS and its slightly darker colour. The locality below Oia where Druitt  sampled is an isolated occurrence of welded pumice which could be a relic of an old intra-caldera volcano.
One could argue that the LPS was locally eroded away prior to deposition of the LBA eruption, but it has not been found in drillings or at excavation sites. Furthermore, the so-called LPS deposits in deep sea drillings are not from Santorini. Archaeological evidence of Cycladic objects at several localities under the so-called LPS proves that these objects were buried by the LBA eruption and not by an older layer of pumice. Rediscovery of an old excavation site at Balos helped us to solve a 150 years old enigma: both the so-called LPS and the UPS were deposited by the same LBA eruption around 1613 BC. Its products were partly deposited on the inner side of the commonly steeply sloping caldera wall. The topography, slumping and later erosion led to difficulties in interpreting the local stratigraphy.
FIGURE 2 Satellite image, ESA (( d), right) of Thera, the main island of the Santorini volcanic group. ( a) Fira Quarry; ( b) North of Cape Alonaki; ( c) North of Karageorghis quarry where the UPS has been radiocarbon dated by an olive tree found in...
FIGURE 7 The pumice and ash of the LBA eruption had mantled the entire volcanic edifice including the inner side of the caldera. Erosion has removed most of it but remnants are still visible where concentric terraces existed on the wall. The caves of...