Minoan eruption

As Minoan eruption ( Santorini or Thera also eruption ) of the Late Bronze Age eruption of the Aegean volcanic island of Thera (now Santorini ) denotes, in the 17th or 16th century BC, closely connected with the Minoan settlement of Akrotiri Culture ( modern name ) buried in Santorini. Its direct effects are controversial; which until the 1960s often stated view that he had brought about the downfall of the Minoan civilization on Crete, is rejected today. The ejected during the eruption pyroclastics can be found in archeological sites throughout the eastern Mediterranean, thus providing a fixed point in the stratigraphy. The dating of the eruption is controversial; are about 100 years between the science and the data historiographically determined.

  • 4.1 Archaeological and historiographical method
  • 4.2 Scientific Methods

The volcano of Santorini

The volcano of Santorini is a result of plate tectonic processes. He belongs to a volcanic island arc in the southern Aegean Sea, about a subduction zone, caused by the collision of the African with the Eurasian plate.

The core of the island consists of metamorphic rocks at the age of about 200-40 million years ago. They are now visible on the surface only at the highest elevation, the Prophet Elias ( 567 m ), but are at four sites at the southern island under younger layers. The rest of the island is composed of volcanic rock, which is at least twelve medium and larger and other smaller eruptions since the Pleistocene, so in the last 1.8 million years, emerged. These are predominantly pyroclastic deposits, it can, however, through the whole territory five lava flows detected. Age determinations of rocks can be an interval of 20,000 years between major and 5000 years between small outbreaks suspect.

Modern studies have shown that the group of islands already in the Minoan period approximately its present form had (including an island in the middle of the caldera ), which they already received by the Cape Riva eruption about 21,000 years ago.

Extent of the eruption

The Greek archaeologist Spyridon Marinatos 1939 published a theory that the eruption of the Thera volcano has led to the downfall of the Minoan civilization on Crete. For Marinatos had the Thera eruption of the Indonesian volcano Krakatoa which have resembled that around 36,000 people lost their lives in 1883. In addition to ash, which had darkened the sky in a radius of several hundred kilometers, especially those resulting from the eruption tsunami was an important parallel for him. With up to 15 m height, the wave triggered by Krakatoa in 1883 had washed over the coast of the neighboring islands and destroyed many cities. Marinatos adopted a similarly devastating coastal flooding Crete by the Thera eruption and speculated this might be the cause of the downfall of the Minoan civilization.

Meanwhile traces of tidal waves were identified in some places on the northeast coast of Crete. So in Pseira, Palaikastro and Papadiokambos. Even on the coast of Israel tsunami traces were found and dated. The excavations of Palaikastro show that the whole place was flooded and destroyed, but was at least partially rebuilt later; the Minoan culture that is still continued to exist.

The extent adopted by the eruption Marinatos - he guessed four times the amount of tephra ( 80-120 km ³ ) compared to the Krakatau eruption (20-30 km ³ ), which would correspond to an eruption of magnitude 7 on the Vulkanexplosivitätsindex ( VEI ) - was established in corrected over the years down. Since the thickness of the ash layers are not confirmed on the neighboring islands Marinatos ' assumption that we took a smaller eruption (30 km ³ ) on the strength of VEI 6. Also a pollen analysis of sediment layers before and after the Thera eruption pointed to minimal changes in regional vegetation and thus a relatively small eruption.

In 2002, however ash layers were found that can be understood on the basis of their thickness as an indication of more than twice as strong eruption (up to 100 km ³ of tephra ). Further investigations of the sea floor determined around Santorini in 2006 deposits of pyroclastic flows in considerable thickness. Based on this, new estimate now resulted in a total volume of 60 km ³ of magma, which the intensity increased by VEI safely back to 7.

Phases of the eruption

The outbreak is now divided into four major phases. He was preceded by several earthquakes. The inhabitants left the island then. They had plenty of time to take their valuables. During the excavations of the city of Akrotiri neither corpses nor jewelry or expensive tools were found. Shortly after the earthquake Akrotiri was apparently not revisited. They tried undestroyed pithoi ( storage tank ) and pieces of furniture to hide, tear down walls in danger of collapsing and sort materials for reuse.

The salvage operation was aborted, however, the helpers fled again, leaving the already provided storage container and furniture back. The cause is considered the first case of pyroclastics. It was only small amounts of volcanic ash and lapilli from a vent almost exactly in the center of the island. After a pause occurred. As were detected on some wall stumps in Akrotiri tufts of grass, there is speculation about a rest period of several months.

The first ejection of pumice

The first phase of the actual eruption consisted of an explosive eruption of light pumice and ash. The deposition was done with about 3 cm / min, the maximum thickness of the layer is 7 m. Where is the ash collected at steep slopes, 11 m can be achieved. The discharge began with white material and switched to pink, in the increasingly rocks in bright yellow, orange and red tones are embedded. The colors come from the increasing temperatures of the rock upon impact on the ground or on previous layers.

The energy of this phase is considered to be rather low. The material was ejected from volcanic gases; initially there was no water yet penetrated into the vent. The duration of this phase is estimated to be between one and eight hours. Only in the uppermost layers of the first phase, pyroclastic flows mix in the loose deposits. The lava had been contact with the sea water.

Pyroclastic flows

As sea water could get into the volcanic vent through cracks in the rock fracturing and evaporated, there was a phreatomagmatic explosion with a multiplied energy of the outbreak. The volcano could now emit significantly heavier material whose deposits are also distributed much more irregular.

The second phase began with the eruption of round lapilli with about 10 mm diameter, mixed with ashes and a few larger chunks. Deposits of this eruption reach a thickness of 5.90 m on Thirasia in the west and only about 10 cm in the far east of the island. This is followed by a layer of only 1-18 cm white ashes and another thick layer between 6 m and 15 cm in the west to the east and southeast. This second layer is composed of lapilli with intercalated volcanic bombs, ranging in size from a few centimeters to blocks ranges with 5 m diameter. The blocks consist mainly of black, smooth lava, which was typical for earlier volcanic eruptions on Santorini, about the skaros Rock.

The second phase lasted about an hour. The volcanic neck ripped open in a southerly direction, as can be concluded from the orientation of some deposits.

Phreatomagmatic deposits

In the third phase of the outbreak the largest emissions of volcanic material took place. The pyroclastic flows as a continuous stream and tore huge boulders with size. The blocks arrived during this phase diameter of 20 m, typically 0.5 to 2 m. They consist of porphyritic dacite and to a small extent from comparable with obsidian material.

The blocks are embedded in ash streams, rivers of lapilli and also towards the end rivers of mud from pumice with high water content. In some places in the south east of the island, the deposits of the third phase reach a thickness of 55 m.

The vent has shifted in this phase north again. The penetrating seawater mixed with the volcanic material, making for an interpretation of an immense mass of lahar -called, hot mud. He is said to have flowed up to 400 m high walls of the caldera. Here, so much material was ejected, that the resulting cavity collapsed and the island collapsed on him. Thus, the northern half of the present-day caldera was formed. On the outer side of the island the volcanic streams flowed into the sea, then extended it to flat coastal plains.

Ignimbrite, lahar and debris flows

In the fourth phase ended the outbreak. It is diverse. The deposition of ignimbrite layers alternated with lahar rivers, ash flows and massive amounts of debris. Maybe it got in the way and for ejection of ash clouds. Most quantities of material flowed from the edges of the island: while on the caldera only about 1 m thick layers of the fourth phase are attributed, they form the outside depending on the terrain profile alluvial fans of up to 40 m thickness.

The rocks of the fourth phase are smaller than before, the maximum size does not exceed 2 m more. Also it can be shown that flowed back in two places in the south lahar flows back into the caldera. The energy of the eruption must therefore have decreased significantly. McCoy / Heiken assume that only now, at the very end of the outbreak, the ring of the island collapsed, the northwestern channel between the main island and Thirasia was collapsed and the rock in the south Thirasias. Only the rock island Aspronisi, a remnant of a previous eruption, stopped.

Significance and dating

The deposition theräischer tephra over almost the whole eastern Mediterranean - from Nichoria in Messinia over Anatolia and the Black Sea to the Nile Delta - offers a unique fixed point for the synchronization of different relative chronologies from these regions. Same time, the total absolute chronology of the Late Bronze Age is practically dependent on the dating of this eruption, so understandably include the question of the dating of the Minoan eruption of the most controversial in modern archaeological research. Especially since the 1980s, led numerous studies with various methods essentially to a division of opinion into two camps: on the one hand, the representatives of the " late date" ( 1530-1520 BC) and, accordingly, the "short chronology " on the other that of the " early date" (1628-1620 BCE) and the "long chronology ". It is also noteworthy that the run " fronts " not between natural and social sciences, but across all stock. The debate, which is guided in large part in high-profile scientific journals such as Nature and Science, learned so far, however, no definitive answer.

Archaeological and historiographical method

Marinatos Minoan eruption dated the originally roughly 1500 BC ± 50 years, since he assumed this period also for the downfall of the Minoans on Crete. Although excavations in the following decades showed that the Minoan civilization did not suddenly, but only BC went down in a period of probably several decades from 1450, the date of the Minoan eruption proved at the end of the 16th century BC. of archaeological point of view as the most likely. Because in the meantime been made on Crete findings (eg enhanced vase painting styles ) that no longer occur on the one hand on Santorini, but on the other hand, clearly dated before the collapse of the Minoan culture.

The relative chronology of the Minoan civilization, which has already been worked out by Arthur Evans and has since been refined, was last linked, inter alia, 1989 by Peter Warren and Hankey Vronwy with the right secured, the absolute chronology of Egypt. Accordingly, the phase " Mittelminoisch III " is (MM III ) with the Hyksos, the phase " Late Minoan IA " ( LM IA ) to the end of the Second Intermediate Period and " Late Minoan IB " ( LM IB ) with the time of Hatshepsut and Thutmose III. in conjunction. If, with this argument, the Minoan eruption of about 30 years before the end of LM IA phase, this results in a period of 1530-1500 BC

Other archaeologists bring arguments for an early dating of the Minoan eruption, about Wolf -Dietrich Niemeier, who excavated the palace of Tell Kabri in Palestine, who points out that a threshold in the 1600 BC destroyed the building completely equivalent to that in Akrotiri was exposed. Similarly, the wall paintings exhibited significant stylistic connections to the frescoes at Thera. Niemeier therefore advocates the " long chronology " and a displacement of the end of LM IA from 1500 to 1600's. Along the same lines indicate results of the excavations at Tell el- cAjjul in Gaza. Since an early date but would have the consequence that in addition to the Minoan and the seemingly secure Egyptian chronology should be revised - and thus all dependent Chronologies in the Near East and Europe - to leading Egyptologists and especially Manfred Bietak spoke strongly against.

A special role is played by the ceramic style known as White Slip: He was found equally on Santorini before the eruption, in Cyprus and the Hyksos capital Avaris in Egypt today in relatively datable layers. If it is possible to arrange the pieces in a chronological order of development, they would not only allow the synchronization of the cultural spaces, but also clarify the issue of early or late dating of the Minoan eruption.

Since BC were in the middle of the 2nd millennium, the political situation in Egypt and Mesopotamia in transition, there is no clear written evidence of the disaster, with a historiographical date determination would be possible. So an Egyptian inscription, the so-called " storm stele " of Ahmose remains controversial. This - formally - highly unusual portrayal of a natural disaster reports of enormous roar and several days of darkness in Egypt, which is very reminiscent of associated symptoms of a severe volcanic eruption, for example, the Krakatau eruption of 1883., the time of the disaster lies between the 11th and the 22nd year of the reign of Ahmose, ie from 1539 to 1528 BC ( according to Beckerath ) or 1519-1508 BC (after Schneider).

If the described " storm " by the Minoan eruption have been triggered, hereby provides a date from a historiographical point of view. However, since so far no Tephraschichten the Minoan eruption was detected during the reign of Ahmose in Avaris or other places of Lower Egypt, that " storm " can also be interpreted symbolically as a state of devastation in Egypt after the Hyksos period.

Scientific methods

The "conventional " Dating the Minoan eruption at about 1500 BC, was first made in 1987 in question, when the then evaluation of ice cores from Greenland, the only major volcanic eruption of the mid-2nd millennium BC to about 1645 v. AD ( ± 20 years ) dated.

The increased concentration of sulfuric acid, which was found in strata from this time, though could not be clearly associated with therapy, but was due to the assumption that there had been in the 2nd millennium BC, no further major eruption, as " most likely candidate for the Minoan eruption " taken. The assumption that the Minoan eruption was large enough to leave acidic residues even in Greenland, based on Marinatos ' original theory of a comparable Tambora eruption. An outbreak of this size, however, also had to short-term changes in climate lead to a so-called volcanic winter, as it also the largest known eruption in historical times - had given (see year without a summer ) - Tambora in 1815.

In the dendrochronological study of the long-lived pine trees in the California White Mountains early 1984 (see Bristlecone Pines chronology ) found an unusually narrow annual rings from 1627 BC, which pointed to an extremely cold summer. The conclusion that this could have been the result of the Minoan eruption, in 1984, not yet drawn. This happened only in 1988 - against the background of the Greenland Eisbohrkernanalyse, as in a study of Irish oaks also a sequence of unusually narrow annual rings could be found starting in 1628 BC. A further study in 1996 with wood samples from Anatolia confirmed the climate anomaly, it could two unusually broad annual rings indicate unusually mild and wet summer. Finally, a further indication was found on a climate change in 2000 with an investigation of several pine logs from a peat bog in Sweden.

A direct assignment of climate change in the 1620s BC the Minoan eruption was not possible with the findings. This astronomical changes or the outbreak of another volcano as a cause of growth ring anomalies and the acid peaks in Greenland are much more likely. So beat 1990 Canadian researchers before the Avellino eruption of Vesuvius, which they dated to 1660 BC by radiocarbon dating (14C ) ( ± 43 years ). An eruption of Mount St. Helens was also dated to the 17th century BC.

1998: Investigations that found in 1987 in the ice core particles of volcanic glass or not chemically match the eruption on Santorini. 2004, these particles were associated with the eruption of Mount Aniakchak in Alaska with the help of newer methods of analysis. This was contradicted since then, the distribution of elements and isotopes of the acid peak would fit well to the data from Santorini, the high calcium levels in pottery shards from Santorini would not necessarily even in the ashes in the Greenland ice can be found again, so that it in itself the particles but could act to remove traces of the Minoan eruption.

Some newer 14C datings speak again for the years 1620 to 1600 BC: The 2006 successful radiocarbon dating of the branch of a buried by volcanic ejection olive tree on Thera, which was found in November 2002 in Bimsschicht the island, gave an age of 1613 v. AD ± 13 years. The detection of leaves shows that the branch was alive buried by the eruption. For the first time, the individual annual rings of the branch were individually 14C - dated and significantly reduce their known time intervals, the confidence intervals. 2007 was yet another piece of the same branch and a second, longer and superficially charred tree branch with several side branches in only nine meters were discovered from the first location, they are not yet dated.

The temporal discrepancy between the findings in Greenland ice from 1645 BC to the 14C dates from the 1620s could be relativized if, in addition to classical 14C data is analyzed and a corresponding curve of the beryllium isotope 10Be. There was a time shift to exactly 20 years, bringing the acid peak in the ice in the analysis would be much more accurate fit to the presumed data from Santorini.

For 2006, archaeological finds of tsunami deposits at Palaikastro in Crete again with refined methods an age of about 1650 ± 30 BC The deposits of the tsunami contain bones of farm animals and ceramics along with volcanic ash of the eruption, thus allowing the application and comparison of three different dating methods.

Socio-cultural impacts

It is unclear how the Minoan eruption has impacted directly or indirectly to the civilization of the Minoans, as they left no written or pictorial representations of the disaster. The aforementioned archaeological evidence speak "only" against a sudden destruction of the Minoan civilization by the eruption, the more they can not testify. Since the island of Santorini was to reach the most southerly island of the Cyclades as the sole within a day's journey from Crete, she was the main stepping stone for the trade of the Minoans to the north. A network model of the Bronze Age in the Aegean sea trade suggests that the destruction of the base of Akrotiri in the short term has triggered increased trade efforts on alternative routes. In the long run would have increased the cost considerably limited the long-distance trade, so that the decline of the Minoans may have been indirectly supported by the volcanic eruption.

Similarly, the impact on the Greek mainland is unclear, since the eruption of the Mycenaean civilization in the States from the 15th century BC emerging Linear B is not mentioned boards. Apart from the aforementioned, controversial stele of Pharaoh Ahmose there is no contemporary evidence of the Minoan eruption, which allows a conclusion on its impact.

It is not clear also whether the Minoan eruption was reflected in developed later myths. So many local, reporting of flooding myths and the myth of the Minoan eruption on the Deukalionflut as were brought based this week. As a rule, the struggle of a god Poseidon is reported that floods the land. However, none of these myths speaks explicitly of a volcanic eruption. Therefore it can be brought about only partly convoluted interpretation, and the adoption of a catastrophic flood after the eruption of Thera in conjunction. Interestingly, dated the Parian Chronicle, the Deucalion flood in the year 1529/1528 BC and thus is within the time span of the archaeological and historiographical method.

It was occurring in the Argonautica Talos interpreted as a reflection of the Minoan eruption, a bronze giant who guarded Crete and pelts enemy ships with boulders. Hennig assumes that this myth immediately before the eruption emerged in the decades when the island volcano showed more or less strong activity.

Even the Biblical ten plagues of the second book of Moses are brought by different authors with the Minoan eruption in conjunction. The Greek seismologist Angelos Galanopoulos suspected already in the 1960s, the eruption as a model for the sinking of the island nation of Atlantis, described by Plato in Timaeus and Critias, his works.