EARLY QUARRIES IN TEPHRA DEPOSITS OF THE LATE BRONZE AGE ERUPTION OF THERA/SANTORINI, GREECE

The Aegean island of Thera (Santorini) (36° 22' N, 25° 25' E) was greatly modified and covered by ash from its cataclysmic Late Bronze Age (c. 3600 BP) eruption. Tephra sequences show a range of depositional and erosional histories, and thicknesses vary from 0 to >50 meters. Incised gullies provide access to ash from multiple eruption stages. Prehistoric to recent inhabitants excavated tephra for materials and buildings. Quarries range from ~2 to 5 meters wide and have well-defined, rounded sides and ceilings. They have limited depths, though some may be tunnels. Quarries are commonly exposed in gullies or in large, recent, inactive quarries. They were probably excavated over a range of periods from early post-eruption to medieval or recent periods. Some have stone walls at the entrance or interior and some are plaster-lined. Uses ranged from mining ash for building material (known since at least Roman times to have made a good ingredient in cement), and for dwellings, cellars, or cisterns. Caves may have been initiated by natural wind erosion processes that can be observed today. However, those considered here are unlikely to have been excavated naturally. We hypothesize that caves were dug from the natural gully walls that gave easy access to the ash. Digging down from the surface is difficult because the upper layer is densely-packed cobble to boulder lag. Some caves have been filled subsequently by natural processes. Cave fill contains repeating sequences of water-laid ash from flash floods in the gullies. Extensive quarrying began in the 19th century when the tephra was used to build the Suez Canal. 20th century quarries are now major topographic depressions in the landscape. Filled caves exposed in the modern quarry walls may have been initiated in gullies that were also the starting point of the modern quarries. Caves are absent in the inaccessible, near-vertical ash faces along the caldera walls.