Scanning Electron Microscopy (SEM)
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SANTORINI Floyd W. McCoy Department of Natural Sciences, University of Hawaii – Windward, Kane’ohe, HI, USA Santorini is the modern name for a collection of small islands in the southern Aegean Sea, the southernmost group in the Cyclades Islands. The ancient name is Thera, which is also the geographic name for the largest of the five islands in this archipelago (the other four are Therasia, Aspronisi, Nea Kameni, and Palaeo Kameni) (Figure 1). Theras, from Sparta, established a colony here in the fifth century BCE. Another ancient name is Kalliste, mentioned by Apollonius in the myth of Jason and the Argonauts in apparent reference to a spectacular geographic setting created by a ring of islands surrounding a waterfilled depression within which were additional islets that today have either subsided below sea level or been merged into Nea Kameni island. “Santorini” refers to the entire island cluster, and this name was applied during Venetian occupation of the islands from the early thirteenth century AD in reference to Santa Irini, the patron saint of sailors (who is reputedly buried on Therasia). The official government designation for the archipelago is “Thera” or “Thira,” depending upon the transliteration of the Greek “yZra.” Santorini is best known for an enormous explosive eruption that occurred approximately 3600 years ago. The eruption of Thera is considered the largest volcanic event in the past 10,000 years and one of the largest in human antiquity (McCoy and Dunn, 2002; Druitt, 2014; Johnston et al., 2014; and references therein); it devastated local and regional cultures, and it fueled later legends. The eruption occurred in the Late Bronze Age (LBA) of the
archaeological ceramic chronology developed for the Aegean. In the geologic chronology, the eruption was simply the latest explosive affair in a long sequence of such events, some of which may have been more than twice the size of the LBA event (Keller et al., 2014) (Figure 2). The consequence of this last eruption is the current Santorini archipelago, which forms one of the grandest landscapes on earth, a stunning geomorphological feature created by spectacular episodes of volcanism (Figure 3). The islands are the summit of a largely underwater volcanic feature, and the surface expression is more appropriately referred to as a volcanic field rather than a “volcano.” An assortment of eruptive vents and their products (tephra and lava flows) are exposed here and represent repeated episodes of volcanic activity over the past 645,000 years. The result is a dramatic and astounding scenic feature defined by a central water-filled caldera encompassing two small central islands where current volcanic activity is concentrated. This caldera has emerged from repeated, highly explosive, Plinian-type eruptions, each having excavated portions of this depression to form the modern feature. Repeat times for major explosive eruptions are on the order of about 20,000 years, although this has been hugely variable. Effusive volcanism during the intervals between Plini
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