The Metaxa mine (also known as Mavromatis Mine) is located at Megalochori village in Santorini, very close to the abrupt caldera cliffs. The owner of the Megalochori mine “HERMES” SA was Anastasios Mavromatis, who began mining operations (according to workers’ testimonies) in 1973-74, ending activity in August 1984. A total of 4,5 million m3 is estimated to have been extracted from the Metaxa mine, which contains the so-called LBA Famous Section (Antoniou et al., 1019), showing the layers of the Late Bronze Age (Minoan) eruption across a length of 150 m. The LBA eruption of Santorini has influenced the decline of the great Minoan civilization on Crete, making it an iconic event in both volcanology and archaeology disciplines (Marinatos 1939; Manning et al. 2006; Druitt, 2014).
The ‘Minoan’ eruption was the last plinian eruption of Santorini (Sparks and Wilson, 1990; Druitt, 2014; Cadoux et. al., 2015). It discharged between 30 and 80km3 (dense-rock equivalent; Johnston et. al., 2014) of rhyodacitic magma, mostly as pyroclastic flows which entered the sea and which are preserved as ignimbrite deposits in the surrounding submarine basins (Sigurdsson et. al., 2006). According to numerous volcanological studies, there is a consensus that the eruption occurred in four major phases with an initial precursory phase (P0) (Reck, 1936; Heiken and McCoy, 1990; Druitt, 2014):
i) Phase 0: The eruption began with precursory explosions that left down two lapilli fallout layers from a subplinian plume 7–10km high blowing to the SSE and a phreatomagmatic ash totaling 10cm in thickness (Heiken and McCoy, 1990).
ii) Phase 1: A sustained plume estimated at a height of 36 ± 5km generated and produced a reverse-graded pumice fall deposit that ranges from 6m to less than 10cm in thickness on the islands of Santorini, Therasia and Aspronisi (Sparks and Wilson, 1990; Sigurdsson et al., 1990; Druitt, 2014). The deposit has, from the base upwards, a reversely graded, crudely bedded unit (P1a) overlain by a coarser, unbedded unit that is normally graded in its upper part and contains up to a few percent of andesitic scoria (P1b) (Druitt et al., 2014).
iii) Phase 2: Access of seawater to the vent initiated violent phreatomagmatic explosions and triggered the generation of base surges that spread radially away from the vent and formed stratified deposits up to 12m thick (Sparks and Wilson, 1990; McCoy and Heiken, 2000). The phase 2 products are dominated by pyroclastic surge deposits with multiple bedsets, dune-like bedforms with wavelengths of several meters or more, bomb sag horizons, and TRM temperatures of 100–250°C (Heiken and McCoy, 1984; McClelland and Thomas, 1990). The lowest bedset, P2a, is fine-grained and contains accretionary lapilli. The overlying sequence of multiple bedsets (P2b) is much coarser grained than P2a and contains lenticular layers of surge-reworked plinian fallout pumice, showing that the P2b surges were synplinian.
iv) Phase 3: Increasing water–magma ratios produced denser, partly wet, low-temperature pumiceous pyroclastic flows transitional to mud flows. These deposits formed a fan of numerous amalgamated single flow deposits as opposed to one giant, massive flow (Sparks and Wilson, 1990; Pfeiffer, 2001).
v) Phase 4: Pyroclastic flows of high-temperature (300–500°C) were vented, producing fine-grained, nonwelded ignimbrites around the caldera rim and the coastal plains (Heiken and McCoy, 1984; Sparks and Wilson, 1990; Druitt et al., 1999). The dominant facies are a tan-to pink- colored compound ignimbrite (“tan ignimbrite”) (Druitt, 2014), which is mostly fine grained (ash and lapilli grade), with a high abundance of comminuted lithic debris in the ash fraction. Minoan ignimbrite, possibly up to 80 m thick, lies offshore of Santorini (Sigurdsson et. al., 2006) and is the most voluminous Minoan unit. In the section, volcanic products of the phases P0, P1, P2 and P4 are distinguished clearly.
Credits: UAV-based survey and 3D DOM by Fabio L. Bonali; funding is from MIUR project ACPR15T4_00098 (http://argo3d.unimib.it/). The model has an extent of 170×70 m and a height of 26 m. The analysis of the volcanic phases, as well as the model description, was provided by Paraskevi Nomikou.
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