The Impact of the Eruption of Thera on Ancient Minoan Decline
The cataclysmic eruption of Thera split the island of Santorini into three smaller ones.
By Jenna Frawley
During the Middle Bronze Age (ca. 1750-1450 BCE), the island of Crete emerged as a long-distance trading center. Modern scholarship characterizes this center as the Minoan civilization, which organized local production and trade in large regional structures usually referred to as “palaces” at Knossos, Malia, Phaistos, and Zakro.1 Most scholars agree that these “palaces” served as administrative centers, marketplaces, and places for religious ceremonies. Despite the name, no monarch seems to have seated these “palaces”. By 1750 BCE, the influence of this palace-directed trading culture grew in its archaeological visibility throughout the Aegean region, suggesting that Crete’s commercial and cultural dominance.i But by 1450 BCE, the palaces collapsed with no clear historical nor archeological explanation. Two explanations for this collapse express traditional views: 1) the eruption of the nearby volcanic island of Thera destroyed the palaces; or 2) the Mycenaeans—a contemporaneous culture from southern Greece—invaded and occupied Crete. Archaeological evidence indeed shows Mycenaean occupation of Knossos from ca. 1450-1250 BCE,2 but this overly simplistic argument cites only a single component of the Minoans’ loss of economic power.3
Recent scholarly debate has become more nuanced, seeking to understand the extent to which the volcanic eruption or other natural forces impacted the Minoan decline. For example, Jan Driessen and Colin MacDonald argued in 1997 that the Theran eruption led to a gradual breakdown of the Minoan economy and ultimately their social and political system.ii This paper independently arrives at a similar conclusion by comparing evidence for the eruption and its impacts with evidence from other, later volcanic events.
Minoan Influence Before the Eruption
The strongest evidence for the influence of Minoan palace culture on surrounding cultures is from the Aegean region. The Cycladic islanders adopted Minoan palace styles in ritual art and practices, including perhaps a distinctively Minoan type of “conical cup” made on the potter’s wheel and used for pouring libations.iii The use of these distinctive cups spread throughout the islands along with Minoan-style masonry, lustral basins, and figural frescoes. The widespread adoption of Minoan material culture implies an ongoing relationship between the Minoans and their Cycladic partners throughout the middle bronze age. The Minoans had economic ties outside the Cyclades as well. Frescoes depicting Minoan traders or “tribute-bearers” appear in the tombs of contemporary officials at Egyptian Thebes. The Minoans carry vessels, jewelry, ingots, and, in the tomb of Menkheperreseneb, a goat horn. Angela Hussein argues that the Cretan goat horn was imported into Egypt for the fabrication of composite bows.iv The value of the frescos as evidence for Minoan trade is often questioned, but Egyptian figurines, bowls, and alabastra have been found on Crete along with broken amphorae (or wine storage jars) from the Levant, and other pottery fragments from as far away as Italy.4 This evidence suggests that the Minoans were engaged in a wide commercial network in and outside the Aegean.
Thera, one of the Cycladic islands closest to Crete, held some of the strongest cultural ties to the Minoans. Excavations of the town of Akrotiri on Thera uncovered a significant amount of Minoan pottery, along with local pottery in a Minoan style.v Akrotiri became a major economic link between Crete and the northern Cycladic islands. The Minoans specialized in the production of olive oil, honey, wine, lumber and other agricultural products, but Crete lacked the metals necessary to produce weapons or tools. Because of this, the Minoans traded these products for ore. While most of their copper came from Cyprus, it had to be alloyed with zinc or tin to produce the harder bronze. The Minoans obtained tin via Akrotiri from the northern Aegean; Thera may have been an important mediator in that trade.vi Using island size and resources to simulate the routes followed by ancient traders, Carl Knappett, Ray Rivers, and Tim Evans have constructed a computer model that attempts to reconstruct the economic position of Thera in Aegean maritime networks.vii The model shows a particularly strong tie between Crete and Thera and suggests that, before the eruption, Akrotiri was a key trading post between the Minoans and the Cyclades.
The Impact of The Eruption on Minoan Agriculture and Trade
The cataclysmic eruption of Thera split the island into three smaller ones, the largest of which (Santorini) forms a crescent surrounding a large caldera. Just as in the eruption of Pompeii, volcanic ash buried and preserved Akrotiri. Its two-story houses and shrines lie along an irregular system of streets and squares. No human remains are yet discovered, since the presence of full storage containers for food (pithoi) and other functional items suggest that the inhabitants evacuated before the eruption.viii The date of the Thera eruption is controversial and—since the discovery of Akrotiri—the debate became inseparable from the controversy surrounding the fall of the Minoan palaces.
Carbon dating is the most common approach to dating the eruption. Sturt Manning compiled a list of organic materials preserved on Akrotiri and concluded that the eruption occurred in the late 17th century BCE (1650-1600); these carbon dates have been supported by others.5 Evidence from tree ring dating (dendrochronology) corroborates Manning’s date as well. This data came from M. Baillie and M. Munro, who observed oak trees from Northern Ireland’s bogs to determine patterns of global climate change. The Irish oak trees showed stunted growth, attributable to sudden climate changes, like a volcanic event posited to have happened around the year 1628 BCE.ix Volcanic eruptions often project massive amounts of ash and gas into the atmosphere, altering weather patterns worldwide. The overlap in the carbon and dendrochronological dates proposed by these studies appears to confirm a date for the eruption of Thera between 1650-1600 BCE and to uncouple that event decisively from the collapse of the Minoan palaces ca. 1450 BCE.6
Although observers have been aware of the effects of volcanic eruptions on human activity for centuries, systematic accounts of volcanic activity were not available prior to the 20th century. In 1982, the Volcanic Explosivity Index (VEI) was developed to rank the size and violence of an eruption by its intensity, destructiveness, energy release, and amount of ejecta. The VEI does not differentiate between ejecta—gas, ash, rock, lava—but rather gives a general impression of a volcanic event, allowing scholars to compare and categorize volcanic activity across time.x The VEI ranking of a prehistoric eruption is determined through geologic evidence, such as the size of the eruption’s caldera or the spread of volcanic tephra. In rare cases, eyewitness accounts survive, like that of Pliny the Younger, who described the eruption of Mount Vesuvius in 79 CE. This early account spurred the word “Plinian,” which describes a volcanic eruption like the one he witnessed: incredibly violent and explosive, ejecting lava, pumice, and ash hundreds of meters into the air. Geologists assign the eruption of Vesuvius a VEI of 5. Though there are no eyewitness accounts of the eruption of Thera, the geologic record suggests its similarity in size and character to the eruption of Mount Tambora in 1815.xi Mount Tambora is located on Sumbawa, an island of the Indonesian Archipelago, and British and Dutch colonizers recorded the eruption. The initial explosion was heard 1400 km away in Java, and some British officers reported volcanic ash falling on their ships.xii The VEI of this eruption is calculated at 7, one hundred times larger than that of Mt. Vesuvius.
Scientific models and archaeological data suggest that most of the ash cloud produced by the Theran eruption moved southeast over the lower Aegean and the Dodecanese. Rhodes received up to 1 m. of precipitation and Kos received up to 30 cm. Traces of ash and sediment have been found in the Nile River Delta and on the shores of modern-day Turkey.xiii The Minoans received less: though the western half of the Crete bears no evidence of volcanic precipitation, approximately 15 cm. of ash and pumice have been recovered at Palaikastro, a Minoan port on the northeastern end of the island.xiv The absence of significant ash, falling rock, or even fire in the period 1650-1600 BCE confirms the theory that the Minoan palaces did not suffer destruction because of Thera’s initial blast.
Historically documented eruptions often cause other natural disasters such as tsunamis, earth displacement, or ash veils that linger in the atmosphere for months or years. These can have longer term effects than the eruption itself. A tsunami, for example, is a massive displacement of water that results in waves that travel underneath the surface of the ocean. When a tsunami reaches shallow shores, it emerges as a huge wall of water followed by the withdrawal of the tide for up to hundreds of meters. Difficulties arise in estimating a tsunami’s size for many reasons, such as the differing heights and inundations of waves, which impact the shore differently; and isolating the tsunami’s geological evidence, when factoring in erosion.
A 2011 study by Novikova, Papadopoulos and McCoy used transfer of energy to theorize the size of the tsunami waves that resulted from two events in the Theran eruption: the fall of pyroclastic flows into the Aegean Sea, and the inward collapse of the caldera.7 The authors of the study hypothesize that the northern coast of Crete experienced waves that varied in height from a minimal rise (slightly higher than the daily tide) to 28 m., with inundations of 250-450 m., perhaps in relation to where the Theran pyroclastic flows entered the sea. The study observed that Palaikastro was struck by waves up to 9 m. tall with inundations of up to 300 m. inland.xv Other evidence suggests that Gouves—some 15 km. east of Knossos in the center of the northern coast—received waves which reached a height of at least 2-3 m. above the present sea level, and that travelled 30-90 m. inland from the Minoan harbor; a potter’s workshop uncovered there contained a layer of marine carbonate sand and pumice with tephra like that of the Theran eruption.xvi The comparative evidence from Palaikastro and Gouves clarifies that the impact of the waves was felt along the entire northern coast of the island with varied severity. Though Crete experienced some of the most intense waves, Novikova, Papadopoulos and McCoy calculated the waves which hit other islands, such as: a 10 m. wave for Naxos, 11 m. for Amorgos, and 24 m. for Ios.xvii
Though these studies measure tsunami height and physical devastation, they do not attempt to measure the human costs of the tsunami. Harbors and seaside settlements would have been likely decimated by the waves, as would any ships docked at Knossos, Palaikastro, Gournia and Malia. The costs to infrastructure and the loss of expert artisans (given that mariners and shipbuilders tended to live on the coast) cannot be estimated. Other Cycladic islands like Naxos, Amorgos, and Ios likely suffered similar losses in infrastructure, ships, and population. Many smaller islands likely lacked the resources resources and manpower to rebuild. These drastic losses among trading partners would have affected the Minoans economically as well.
Agriculturalists are also affected by eruptions and their associated disasters. For example, in 1956, an earthquake in the eastern Cyclades (including Santorini) precipitated an underwater landslide whose resulting tsunami inundated the vineyards and orchards surrounding Palaikastro with salt water, “rendering them useless” for almost 20 years.8 Since olive trees and grape vines take years to grow before producing fruit, operating without their fecundity can devastate a region’s economy. Earthquakes can also impact water sources, causing them to dry up or become brackish. In 1998, wells in Pennsylvania went dry after a 5.6 magnitude earthquake, and in 2001, the Gujarat earthquake in India caused groundwater levels to vary and increase in salinity. Changes like these may occur immediately as groundwater leaves the well, or in the months following the event when the changes in the porosity of the surrounding rock prevent fresh water replenishment.xviii Events like these easily destroy farms or entire communities, since wells are difficult and dangerous to dig, and it can be difficult to locate new sources of groundwater.9 Such a steady loss of water for agriculture often means famine and economic disaster.
Additionally, it has long been recognized that the ash veils from volcanic eruptions affect local and global climates for months to years. For example, Mount Tambora’s eruption in 1815 disrupted seasonal patterns across the globe and caused widespread crop failures. Due to its unusually cold temperatures caused by Tambora’s ash veil, 1816 was dubbed “The Year without a Summer” in New England. Crop failures resulting from the ash veil caused famine in Ireland, Germany, and the Yunnan province of China. Abnormally heavy rains flooded Geneva, and for years, the sunsets across Europe were an unusually vibrant red.xix Baillie and Munro’sxx dendrochronological work in Northern Ireland suggests that the Theran eruption had similarly long-term consequences. While ash veils from a volcano normally clear up within 2-3 years, the oak trees they studied showed limited growth for up to a decade. Although disruptions in temperature and light levels seem inconsequential to a modern audience, they would have had important implications for light-sensitive trees like the olive, which, debilitated, would not have the capacity to produce crop surpluses necessary to trade. Thus, while the levels of precipitated ash and tephra on Crete do not seem extreme, the culmination of environmental changes likely presented many long-term difficulties.10
The greatest impact of the eruptions on Minoan trade may have been the loss of Akrotiri as a trading center. Knappett, Rivers, and Evans argue that Akrotiri served as a vital trading post, and without it, Minoan ships had to take longer routes to get to other ports, which increased shipping costs. These researchers’ model of the Aegean trade network suggests that, after the eruption, once-prominent trade centers around the Aegean were forced to trade more regionally to cope with increased expenses, or as the authors explained, “invest their resources in just a handful of key exchange links, putting their eggs in a few baskets.”xxi This led to a new, more fragmented trade network, which the authors posit would be more susceptible to collapse because of the unexpected strains on the economic systems.xxii The findings from their model hold implications for the metal trade on Crete, since the island had limited sources of metal. The lack of the Minoan’s agricultural surpluses, combined with higher shipping costs and new difficulty in acquiring in critical resources, likely compromised the entire Minoan economy.
Though the Minoans seeded their influence throughout the Aegean region, by 1450 BCE the palace culture everywhere but Knossos had collapsed. Based on the presented evidence, a variety of factors clearly led to the decline of the Minoan civilization. The eruption of Thera somewhere between 1650 and 1600 BCE began a series of severe environmental changes that abased Minoan stability on Crete and throughout the Aegean. The Minoans maintained their regional power for some time, but faced a steady, gradual decline as the Mycenaeans established their own trade network across the Aegean. By the time the Mycenaeans’ influence grew, the Minoans were a shell of their former selves, no longer an economic powerhouse.
The argument presented here cannot cover every facet of Minoan culture and their economic decline. For example, some argue that the Minoans traded continuously into the 15th century BCE with Egypt, since Minoans are depicted as traders in frescos of that time.11 Studies on this tomb imagery cast doubt on their value as historical documents, but the issue illustrates the complexity of studying the Minoan palatial collapse. The traditional binary arguments are far simpler and more straightforward, which may explain the appeal they present to the popular imagination, with popular books and documentaries citing either the eruption or an invasion as the sole cause of Minoan collapse. In the face of this widespread oversimplification of the subject, it is important to remember that, as new archaeological evidence comes to light, theories on the course of history must be reevaluated to reflect such changes. In the end, it is rare for one, sole thing to cause the decline of an entire civilization.
- The palace culture of Crete is divided into two phases or periods—the protopalatial period and the neopalatial. The protopalatial extended from 1900 to 1700 BCE, when the palaces were destroyed by a major earthquake (Demand 2011, 137). They were rebuilt during the neopalatial period and served as both cultural and economic centers until ca. 1450, when all except Knossos were destroyed and never rebuilt.
- Mycenaean presence at Knossos after ca. 1450 is suggested by the discovery of Linear B tablets (Demand 2011, 180) and Mycenaean-style warrior graves in the surrounding area (Cavannagh 2008, 335).
- Similarly, Driessen and MacDonald 1997, 106-113, provide a useful summary of the arguments.
- Problem of the frescos as evidence: Anthony 2017, 79. Egyptian imports on Crete: Cline 1994, 259. Amphora sherds: idem. 173. Cline (1994, 183) lists a group of pottery fragments from Kommos, on southern Crete, as coming from Italy.
- Manning 1988, 63. Panagiotakopulu et al.’s study (2013, 683) of the preserved remains of bean weevils in storage jars from Akrotiri corroborates Manning’s work and deserves special consideration for determining that the eruption likely took place in the summer, a fact that could have interesting implications for the extent of the impact of the eruption from both a food production and a trade perspective. That question, however, is out of the scope of this paper.
- Driessen and Macdonald (1997, 23) prefer a “lower” date in the 16th century determined through comparisons with Egyptian records as opposed to carbon dating. In the end, however, they reach the conclusion similar to this paper, that the exact date does not matter, only that it certainly occurred well before the Minoan collapse.
- Novikova, Papdopoulos and McCoy 2011, 671-675. Pyroclastic flows consist of fast-moving currents of lava, tephra, and other volcanic matter downslope.
- Bruins et al. 2008, It is not clear what the authors mean by “useless” although the land would have to have been desalinated and it would have taken years for new olive trees and grape vines to become established
- Driessen (2013, 10) place less emphasis on groundwater than I do, in part perhaps because it has not been confirmed by archaeological evidence.
- This is in contradiction to Driessen (2002, 254-255), who argues that the ash-fall could have been incredibly detrimental to farms on the eastern half of the island. This paper does not explore that idea due to conflicting evidence that volcanic ash is frequently beneficial to farmland.
- On the other hand, recent studies of the Minoans (Keftiu) in Theban tombs (summarized by Anthony 2017, 79) suggest that these are not documentary representations of Minoans or other foreigners. The broader problem posed by Minoan trade goods in Egypt is beyond the scope of this paper.
i Girella and Pavuk 2016, 17.
ii Driessen and MacDonald 1997, 117-18.
iii Minoan influence in the Aegean: Girella and Pavuk, 2016, 18-23. Conical cups: Knappett and Hilditch, 2015, 109.
iv Hussein 2011, 559-561.
v Knappett and Nikolakopoulou 2008, 7-9.
vi Cypriote copper: Wiener 1990, 23. Sources of tin: Betancourt 2008, 213.
vii Computer Model: Knappett, Rivers and Evans 2011, 1019-1020.
viii Panagiotakopulu et al. 2013, 684.
ix Baillie and Munro 1988, 344-346.
x Newhall and Self 1982, 1234-1235.
xi Sigurdson and Carey 2006, 337.
xii Wood 2014, 24.
xiii Wood 2014, 58.
xiv Friedrich 2009, 95.
xv Novikova, Papdopoulos and McCoy 2011, 671-675.
xvi Workshop: Minoura et al. 2000, 60.
xvii Novikova, Papdopoulos and McCoy 2011, 671-675.
xviii Gorokhovich 2005, 219-220.
xix Wood 2014, 8-10.
xx Baillie and Munro 1988, 344-346.
xxi Knappett, Rivers, and Evans 2011, 1019-1020.
xxii Knappett, Rivers, and Evans 2011, 1019-1020.
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Originally published by Forbes & Fifth (Volume 10, Spring 2017), University of Pittsburgh, republished with permission for educational, non-commercial purposes.