Sunday, 1 June 2014

Does the Çatalhöyük Mural depict a volcanic eruption?

Çatalhöyük is a Neolithic settlement in central Anatolia discovered in the 1960s and dated to about 6600 BC. It is considered to be one of the oldest known urban communities, pre-dating the earliest settlements in Egypt and Sumeria by over a thousand years, and providing key insights into civilization in the Middle East during the transition from semi-nomadic hunter-gatherer to settled agricultural communities. One of the more remarkable finds from Çatalhöyük is a wall painting known as the Çatalhöyük Mural, which either (depending on interpretation) depicts a volcanic eruption with a map of a village in the foreground or the skin of a Leopard with the limbs removed. If the mural is a map then it predates any other known map or depiction of a landscape by several thousand years, making the claim particularly remarkable.

The Çatalhöyük Mural  as preserved in the Museum of Anatolian CivilizationsAlamy.

Proponents of the map theory have argued that the village depicted in the map could be Çatalhöyük itself, Aşıklı Höyük, a slightly older settlement about 200 km to the northeast or Musular, which is close to Aşıklı Höyük and roughly contemporaneous with the earliest phases of settlement at Çatalhöyük. The volcano has variously been interpreted as Hasan Dağı, Melendiz Dag or Karapinar. None of these volcanoes would have been likely to produce an eruption visible from Çatalhöyük, but an eruption on Hasan Dağı would be visible from Aşıklı Höyük or Musular, and the civilization at Çatalhöyük is known to have used tools made from volcanic obsidian, which implies they were trading with communities closer to the volcanoes.

In a paper published in the journal PLoS One on 8 January 2014, Axel Schmitt of the Department of Earth and Space Sciences at the University of California Los Angeles, Martin Danišík of Earth and Ocean Sciences at the University of Waikato, Erkan Aydar of ATERRA R&D, Erdal Şen and İnan Ulusoy of the Department of Geological Engineering at Hacettepe University and Oscar Lovera, also of the Department of Earth and Space Sciences at the University of California Los Angeles, describe the results of an attempt to determine the plausibility of the map interpretation of the Çatalhöyük Mural by dating volcanic deposits at Hasan Dağı, the most likely site of a volcanic eruption.

(A) Location of the Çatalhöyük Neolithic site, Hasan Dağı, and other Holocene volcanoes in Anatolia. Overview map with inset showing map of sampling locations. Hasan Dağı volcano and sampling location of pumice dated in this study.  (C) Black-and-white rendering of Çatalhöyük wall painting interpreted to show the twin-peaks of erupting Hasan Dağı and closely spaced buildings in the lower level. An alternative interpretation is that of a leopard skin underlain by a geometric pattern. (D) Three dimensional rendering of Hasan Dağı twin peaks volcano as seen from the north. Schmitt et al. (2014).

Hasan Dağı is a composite stratovolcano (a stratovolcano is a cone-shaped volcano, a composite stratovolcano two or more cones fused together) with two peaks at 3253 and 3069 m connected by a central saddle, and known as Big and Small Mount Hasan. It is a distinctive landmark, rising over 1000 m above the surrounding plains. Schmitt et al. reasoned that if the Çatalhöyük Mural does in fact depict an eruption on Hasan Dağı, then the mountain must have erupted either during, or slightly before, the time Çatalhöyük was occupied, reasoning that a significant eruption might have been remembered for a generation or so, but ruling out oral histories lasting thousands of years.

In order to do this Schmitt et al. collected pumice samples from unconsolidated deposits at two locations, on the summit and southwest flank of Big Hasan Dağı peak. These samples were crushed and sieved in order to get zircon mineral samples that were then analysed for uranium-thorium/helium ratios using Secondary Ionization Mass Spectrometry. Zircon is a mineral formed by the crystallization of cooling lavas. When it forms it contains uranium which decays into thorium and helium at a known rate. Since helium will not have been present in the original lava, it is possible to calculate the age of a zircon crystal from the ratio between the three elements.

(A) Location and field pictures for andesitic pumice deposit (sample HD) collected near the summit of Hasan Dağı. Astronaut photography of Hasan Dağı summit showing the location of sample HD (red dot) outside the crater rim. Image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center. (B) Field scene of HD sampling location looking North. (C) Light coloured fall-out deposit abutting altered lava with geologist for scale. (D) Close-up of pumice veneer at HD sampling location with camera pouch (center left) for scale. Schmitt et al. (2014).

Schmitt et al. obtained ages of 8970 for the summit sample and 28 900 for the flank sample (i.e. ~6960 BC and ~27 000 BC).  This places the eruption that produced the flank samples firmly in the Pleistocene, clearly too old to have been observed by the makers of the Çatalhöyük Mural. However the age for the summit sample (~6960 BC) is close enough to the estimated time for the first occupation of Çatalhöyük (~6600 BC) that the two events are effectively indistinguishable (i.e. the margins of error on the two dates overlap), making it quite possible that the Çatalhöyük Mural does indeed depict an eruption on Hasan Dağı. 

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