Abstract A mural excavated at the Neolithic Çatalhöyük site (Central Anatolia, Turkey) has been interpreted as the oldest known map. Dating to ∼6600 BCE, it putatively depicts an explosive summit eruption of the Hasan Dağı twin-peaks volcano located ∼130 km northeast of Çatalhöyük, and a birds-eye view of a town plan in the foreground. This interpretation, however, has remained controversial not least because independent evidence for a contemporaneous explosive volcanic eruption of Hasan Dağı has been lacking. Here, we document the presence of andesitic pumice veneer on the summit of Hasan Dağı, which we dated using (U-Th)/He zircon geochronology. The (U-Th)/He zircon eruption age of 8.97±0.64 ka (or 6960±640 BCE; uncertainties 2σ) overlaps closely with 14C ages for cultural strata at Çatalhöyük, including level VII containing the “map” mural. A second pumice sample from a surficial deposit near the base of Hasan Dağı records an older explosive eruption at 28.9±1.5 ka. U-Th zircon crystallization ages in both samples range from near-eruption to secular equilibrium (>380 ka). Collectively, our results reveal protracted intrusive activity at Hasan Dağı punctuated by explosive venting, and provide the first radiometric ages for a Holocene explosive eruption which was most likely witnessed by humans in the area. Geologic and geochronologic lines of evidence thus support previous interpretations that residents of Çatalhöyük artistically represented an explosive eruption of Hasan Dağı volcano. The magmatic longevity recorded by quasi-continuous zircon crystallization coupled with new evidence for late-Pleistocene and Holocene explosive eruptions implicates Hasan Dağı as a potential volcanic hazard.

Citation: Schmitt AK, Danišík M, Aydar E, Şen E, Ulusoy İ, Lovera OM (2014) Identifying the Volcanic Eruption Depicted in a Neolithic Painting at Çatalhöyük, Central Anatolia, Turkey. PLoS ONE 9(1): e84711. https://doi.org/10.1371/journal.pone.0084711 Editor: Victoria C. Smith, University of Oxford, United Kingdom Received: August 18, 2013; Accepted: November 18, 2013; Published: January 8, 2014 Copyright: © 2014 Schmitt et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Partial support for this study comes from NSF EAR 1029193 “Facility Support: The UCLA National Ion Microprobe”. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. No additional external funding was received for this study. Competing interests: Erkan Aydar is employed by ATERRA R&D. There are no patents, products in development or marketed products to declare. This does not alter the atuhors’ adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Introduction Starting from the discovery of the Neolithic settlement of Çatalhöyük in the early 1960s by British archaeologist James Mellaart, the excavations at this location have provided unique insights into the living conditions of humans at the transition from hunter-gatherer to settled agriculture societies. One outstanding find is a mural from level VII of Çatalhöyük (Fig. 1) famously described by its discoverer as depicting a volcanic eruption [1]–[3]. Similar interpretations, differing in detail, have been put forward since then, implicating this painting not only as the oldest depiction of a volcanic eruption, but as a contender for being the first graphical representation of a landscape or a map [4]–[6]. Detailed volcanological interpretations of the painting include reconstructions of the eruptive style with the summit region showing “falling volcanic ‘bombs’ or large semiliquid lava” [6]. According to these interpreters, the most likely candidate for the erupting volcano depicted in the upper register of the painting (Fig. 1) is the twin-peak volcano of Hasan Dağı, located ∼130 km NE of Çatalhöyük. This view, however, has been contested, largely because of the extraordinary age of the mural, and the absence of any other landscape art or map until much later in history [7] cf. [8]. The depiction of a leopard skin underlain by geometric patterns has been proposed instead [7]. PPT PowerPoint slide

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larger image TIFF original image Download: Figure 1. Location of the Çatalhöyük Neolithic site, Hasan Dağı, and other Holocene volcanoes in Anatolia. Overview map with inset showing map of sampling locations (A). Hasan Dağı volcano and sampling location of pumice dated in this study (B). Black-and-white rendering of Çatalhöyük wall painting (“shrine” 14; level VII) interpreted to show the twin-peaks of erupting Hasan Dağı and closely spaced buildings in the lower level [1]–[3] (C). An alternative interpretation is that of a leopard skin underlain by a geometric pattern [7]. Image reproduced from Fig. 2 in [7]. 3D rendering of Hasan Dağı twin peaks volcano as seen from N (D). https://doi.org/10.1371/journal.pone.0084711.g001 A testable prediction of the volcanic eruption hypothesis for the Çatalhöyük mural is a geologic record of an eruption which would fall into, or briefly predate, the time when the Çatalhöyük mural was painted. Protracted periods of oral tradition over ∼250 generations have been proposed for prehistoric native North American myths following the ∼5700 BCE Mount Mazama eruption [5]. For the Çatalhöyük map (and volcano) hypothesis to be plausible, however, we surmise that a brief line of oral tradition, or even an eye witness portrayal, is perhaps more likely than tradition of a myth that detached itself from its inspiration in the physical world. This is not to say that realism must prevail in Neolithic art, but many of the apparent details can be reasonably expected to become lost or obscured during a long period of oral tradition. A tradition that predated the settlement of Çatalhöyük thus appears very unlikely, and hence we would predict a time period for the eruption between ∼7400 and 6600 BCE based on the 14C chronology of the Çatalhöyük cultural strata [9]. Neither proponents nor opponents of the “volcano” hypothesis for the Çatalhöyük painting have thus far scrutinized if and when such a volcanic eruption might have occurred.

The Discovery and Semiotic History of the Çatalhöyük Mural The Çatalhöyük “map” mural was first described by [2] as an approximately 3 m wide painting on the N and E wall of “shrine” 14 of excavation level VII (6430–6790 BCE; [9]). Originally identified as cultic spaces, “shrines” are now viewed to represent domestic areas with more-or-less cultic or ritual significance [10]. Upon excavation, the wall-painting was photographed in-situ [2], and subsequently publicized as a graphical reconstruction [3]. The original has since then been removed from the excavation site and it is presently curated in the Museum of Anatolian Civilizations in Ankara (Turkey). A reproduction is on display in lieu of the original at the excavation location. The lower register of the mural (Fig. 1) contains ∼80 square-shaped patterns tightly arranged like cells in a honeycomb, and its upper register depicts an object that its discoverers initially identified either as a rendering of a mountain with two peaks with the cell-like patterns representing a plan view of a village with a general layout of the houses similar to that of Çatalhöyük and other nearby Neolithic settlements, or a leopard skin with its extremities cut off [1]–[3]. In the “map” interpretation, the volcano and its violent eruption are posited to have been significant for the inhabitants of Çatalhöyük because they procured obsidian in the vicinity of (albeit not directly from) Hasan Dağı [2]; cf. [11]. Alternatively, the natural spectacle of a cataclysmic eruption may have imprinted itself in the collective memory of the Çatalhöyük residents, charging the mountain with special cultic or religious significance [8]. In the “map” school of interpretation, different “villages” and “mountains” have been proposed by various authors, based on preferred topographic configurations that would provide the best match in shape and height of the twin-peak summits (with potential matches often assessed using landscape photography) with the corresponding fiduciary features in the painting. These scenarios include Hasan Dağı (a youthful volcanic edifice; [2], [12]), Melendiz Dag (a highly eroded volcanic complex; [13]), or Karapinar (a field of scoria cones; [5]) as the “mountain”, and Çatalhöyük [2] or Aşıklı Höyük [4] as the “village”. Whereas 14C ages for Asikli Höyük predate Çatalhöyük, the Aşıklı Höyük satellite site of Musular was coeval with the early to middle phase of Çatalhöyük [14]. Other archaeologists have dismissed the interpretation of a paired village-mountain altogether, and have reverted to Mellaart’s original “leopard skin” interpretation with a geometric pattern in the lower register [7]. This view is founded on the common and often central artistic representations of leopards in wall-paintings and sculptures recovered from Çatalhöyük, and the lack of any other archaeological records for maps in illiterate, non-urban societies [7]; cf. [4], [8].

The Hasan Dağı Study Location The Hasan Dağı (or Mount Hasan) stratovolcano has two characteristic peaks of similar elevation (3253 and 3069 m), forming Big and Small Mount Hasan. The composite edifice looms over the surrounding basins with their base elevation of nearly 1000 m. Its edifice was constructed over multiple stages identified as Paleo-, Meso-, and Neo-Hasan Dağı by extrusive dome emplacement and intermittent collapse events associated with ignimbrite volcanism [15]–[17]. Limited geochronological data [17] indicate emplacement of the oldest lavas at 7.21±0.01 Ma (K-Ar), and ignimbrites emplacement during an early caldera collapse at 6.31±0.20 Ma (40Ar/39Ar) which are contemporaneous with wide-spread Neogene ignimbrite volcanism in Cappadocia [18]. Only one K-Ar age for Meso-Hasan Dağı is published (∼0.58 Ma; [19]), and it is consistent with subsequent (<270 ka; [17], [19]–[20]) ignimbrite activity, dome extrusion with associated block and ash flow deposition, and peripheral scoria cones and maar eruptions that are collectively attributed to the Neo-Hasan Dağı stage. The Neo-Hasan Dağı edifice with its two summits is composed of collapsed andesitic to rhyodacitic lava domes creating a wide-spread apron of hot-emplacement pyroclastic deposits. The resulting nuée ardente deposits and interlayered lapilli-tephra beds are stacked in ∼10–20 m thick sequences which are exposed by channel erosion of the volcano’s flanks. Compositionally distinct rhyolitic lavas (including obsidian) and unwelded ignimbrites are restricted to the lower reaches of the Neo-volcanic edifice in the N, S, and W. Available radiometric ages for Neo-Hasan Dağı dome lavas are from whole-rock or groundmass dating using K-Ar techniques [17], [19]–[23]. These ages indicate late Pleistocene activity, with an andesitic lava dome from the N flank of the volcano yielding a maximum age of 6 ka [16], and another andesitic lava flow erupted at the W base of the volcano (near Aşağı Dikmen village) with zero-age 40Ar [22]. Two summit domes yielded K-Ar ages of 29 and 33 ka [22]. These ages, while suggestive of very recent activity, lack independent confirmation, and in case of late Pleistocene K-Ar ages excess radiogenic 40Ar remains an untested possibility. No radiometric age determinations for pyroclastic deposits from Neo-Hasan Dağı were available prior to this study.

Sampling Sampling complied with all relevant regulations, did not impact endangered or protected species, and did not require permits for the described study. Sample HD was collected from the summit region of Big Hasan Dağı peak (location 36S 602261E/4220954N; coordinates in UTM/WGS84 format). The outcrop is at 3160 m elevation, ∼22 m below the northern crater rim (Fig. 2 a). The deposit is located on a ridge with strewn pumice on the surface (Fig. 2 b-d). It is an unconsolidated single fall-out unit, lacking any major internal stratification except for potential reworking of the top 10–30 cm. Pumice clasts (9 cm maximum pumice diameter as average of the five largest clasts observed in outcrop) are angular, grey-white in color, with occasional pinkish discoloration. Lithic clasts comprise vitric lava and have an average maximum clast size of 7 cm. The second sample HDA is from the SW flank of the volcano (location 36S 599557E/4215676N) where pumice veneer was found as unconsolidated slope debris. A single pumice block ∼50 cm in diameter was collected. HD and HDA pumice as well as lithic clasts contain plagioclase and hornblende phenocrysts. Inductively coupled plasma (ICP) optical emission analysis revealed an andesitic composition of the sampled pumice clasts. Samples were retrieved from the subsurface by removing the top ∼20 cm of cover to exclude material possibly affected by reheating (e.g., lighting or wild fires). PPT PowerPoint slide

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larger image TIFF original image Download: Figure 2. 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 (A). Image ISS022-E-5307 courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center (http://eol.jsc.nasa.gov). Field scene of HD sampling location looking N (B). Light colored fall-out deposit abutting altered lava with geologist for scale (C). Close-up of pumice veneer at HD sampling location with camera pouch (center left) for scale (D). https://doi.org/10.1371/journal.pone.0084711.g002

Analytical Methods Zircon crystals were extracted from crushed and sieved rock powder. Matrix glass was dissolved through reaction with cold HF. The acid-insoluble mineral fraction was density-separated using heavy liquids (>3.3 g/cm3) to extract zircon. Large (>100 µm in width) euhedral crystals were then hand-picked and pressed into indium metal so that crystals’ prism faces were level with the mount surface. U-Th Secondary Ionization Mass Spectrometry (SIMS) analysis of crystal faces was conducted using established protocols for a CAMECA ims1270 in dynamic multi-collection mode [24]. Crater depths were ∼5 µm. A subset of crystals (preferentially those with old U-Th rim ages) was extracted for (U-Th)/He analysis using noble gas mass spectrometry (for 4He analysis) and ICP mass spectrometry (MS) for U and Th abundances following protocols in [25]. The remainder of crystals was subsequently grinded and polished to a depth of ∼20 µm to expose the interiors. The crystal interiors were then analyzed by SIMS in the same fashion as the rim analyses, permitting a direct comparison of rim and interior ages (between ∼20 and 25 µm depth) for the same crystals (Table 1). U-Th two-point isochron ages were calculated using SIMS zircon compositions and whole-rock U and Th abundances determined by ICP-MS (ACME Labs-Canada) as representative for the melt composition. Secular equilibrium was reasonably assumed for the melt given the overall longevity of the Hasan Dağı magma system, and an average value of (238U)/(232Th) = (230Th)/(232Th) = 0.882±0.015 was used as the model melt composition. The accuracy of U-Th and (U-Th)/He zircon ages was verified by analysis of secular equilibrium zircon standard AS3 (Duluth Gabbro) and FCT (Fish Canyon Tuff), respectively, interspersed with the unknowns. The resulting average values are: AS3 (230Th)/(238U) = 1.014±0.011 (2σ; mean square of weighted deviates MSWD = 0.63; n = 23) and FCT (U-Th)/He age = 28.0±0.87 Ma (MSWD = 0.06; n = 12). PPT PowerPoint slide

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larger image TIFF original image Download: Table 1. Summary of U-Th zircon ages. https://doi.org/10.1371/journal.pone.0084711.t001 For young (<380 ka) accessory minerals, U-series disequilibrium corrections are significant for accurate (U-Th)/He dating [26]. This is because a deficit in 230Th at the time of zircon crystallization translates into a deficit of 4He produced by radioactive decay relative to secular equilibrium. Other disequilibria in U-decay series (e.g., 231Pa, 226Ra) are of secondary importance. To enable a correction for 230Th deficits, U-Th ages were determined for all zircons used for (U-Th)/He dating. In order to preserve enough crystal volume for subsequent He analysis, only U-Th zircon rim ages (of unsectioned crystals) could be determined. The interior ages of the zircons thus remain unknown, but they must fall between the rim crystallization age and secular equilibrium. This uncertainty was propagated into our (U-Th)/He age correction using the MCHeCalc software developed at UCLA. Because crystals which have old (near secular equilibrium) rim ages also have the least uncertainty regarding the disequilibrium correction, these crystal were preferentially selected for (U-Th)/He analysis, and their ages bear more strongly for the error-weighted average age.

Conclusions Combined U-Th and (U-Th)/He zircon geochronology provides the first radiometric age evidence for an explosive volcanic eruption of Hasan Dağı during the Holocene. The eruption age for pumice veneer from the summit of Hasan Dağı closely overlaps with the occupation of Çatalhöyük, and it therefore plausible that humans in the region witnessed this eruption. The geometric characteristics of the “volcano” in the upper register of the Çatalhöyük mural appear consistent with the location and fall-out deposition of the pumice. An older explosive eruption at ∼29 ka is evident from (U-Th)/He zircon dating of a pumice deposits at the base of Hasan Dağı. This age agrees with a K-Ar age for a lava flow from Hasan Dağı. The youngest zircon crystallization ages are within uncertainty of the eruption age, but some rim and interior ages predate the eruption by at least 380 ka. The volcanic edifice of Neo-Hasan Dağı is underlain by a long-lived magmatic system in which zircon quasi-continuously crystallized over several 100,000 years in an evolved silicic magma. Zircon-bearing magma from this reservoir was episodically remobilized and tapped in eruptions that involved thermal and compositional rejuvenation of the shallow silicic magma by more mafic injections from depth. In the light of the overall longevity of the Hasan Dağı magma system and radiometric evidence for Holocene eruptions, there is no indication that its activity is waning.

Acknowledgments We thank Lütfiye Akın for carrying out mineral separation. MD thanks István Dunkl for sharing PepiFLEX software for ICP-MS data reduction and Peter Kamp for access to the (U-Th)/He laboratory. Journal reviewers Stuart Thomson and Phil Shane, and editor Victoria Smith are acknowledged for helpful comments. The UCLA ion microprobe facility is in part supported through NSF.

Author Contributions Conceived and designed the experiments: EA AKS MD. Performed the experiments: AKS MD. Analyzed the data: AKS MD EA EŞ IU OML. Contributed reagents/materials/analysis tools: AKS MD. Wrote the paper: AKS MD EA EŞ IU OML. Collected the samples and provided field descriptions: EŞ IU.