Turkey has 14 active volcanoes known to have had eruptions of Holocene age and four historic eruptions have been recorded. The last eruption was at Ağri (Ararat) in 1840, when an estimated 1900 people died. The low rate of eruptions in Turkey might be construed as indicating low risk, but this is misleading for two reasons. Firstly, the Holocene record indicates that many of the volcanoes have had significant explosive eruptions, some including long run-outs of pyroclastic flows and blasts. Secondly, there has been huge population growth in cities on the flanks of active volcanoes, which greatly increases exposure. More than 3.1 million people live within 30 km of active volcanoes in Turkey.  Urban development on the surface of Holocene pyroclastic flows and blast deposits lead to high risk should volcanic activity resume. The vulnerability is further exacerbated through current populations having no experience of past eruptions. In the TurcVolc project, profiles of all Turkey’s active volcanoes were developed with an emphasis on hazards and risk assessment. Modelling of these hazards provides a baseline for identifying potential hazard zones for future eruptions. The above points are illustrated by presenting volcanic hazard and risk profiles for Erciyes Daği and Hasan Daği volcanoes. The Volcanic Hazard and Population Exposure Indices for each volcano were used to develop a risk matrix for Turkish volcanoes. Four volcanoes were identified at risk level III (high risk). These were Erciyes Dağı, Gölcük, Hasandağ and Nemrut. Three volcanoes exhibited dominantly effusive behaviour and small-scale explosive activity at risk level I (low risk). These were Karapınar Volcanic Field, Karacadağ and Kars Plateau. The remaining volcanoes (Ağri, Tendurek, Acıgol, Kula, Golludag, Süphan, Girekol) were classified at risk level II (intermediate risk).

How to cite: Sparks, S., Atici, G., Brown, S., Karaman-Little, B., and Woodhouse, M.: Hazards and risk assessment for Volcanoes of Turkey , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1687, https://doi.org/10.5194/egusphere-egu24-1687, 2024.

Turkey hosts various types of volcanic rocks in different areas due to evolving volcanic activity from the Miocene to the present. The Cappadocia region is one of the most prominent areas in these regions. In this study, geological and volcanological data, along with samples obtained through the anisotropy of magnetic susceptibility method (AMS), were used to determine the potential source area of Gördeles ignimbrite (ca. 6.3 My), a Miocene-aged ignimbrite found in the Cappadocia region of Central Anatolia. As a result of field observations, the Gördeles ignimbrite was divided into Lower and Upper Gördeles separated by a paleosoil layer. To the west of Güzelyurt, the largest pumice diameter was found to be 72 cm, while the lithic diameter was 33 cm in the ignimbrite. Near the village of Kayırlı, a lag breccia measuring 30 m in thickness was identified just below an 8m pyroclastic flow unit. The lag breccia contains pumices and andesites with a diameter of 70 cm. To determine paleoflow directions, 130 core samples were taken from 25 locations of the ignimbrite, and 2448 magnetic measurements were conducted using the anisotropy of magnetic susceptibility method. According to our AMS analyses, the paleoflow directions around the Güzelyurt area are distributed radially. Our magnetic fabric data, combined with field and stratigraphic information, suggests that the source area is located near Güzelyurt. The source area (the Güzelyurt resurgent caldera) spans roughly 9x9 km, and its highest point is about 2000 m. The pre-caldera lavas, situated on the eastern side of the caldera, have an elevation of about 1800 m. The caldera's lowest point is at an elevation of 1330 meters. Based on these measurements, the total subsidence amount is estimated to be 500 meters, which indicates the discharge of around 31 km³ of magma. The eruptions occurred in multiple stages and were explosive in nature. After the caldera collapse, the caldera floor rose up, forming a resurgent dome. A graben system was formed on this structural dome consist of marble and granite, reaching a height of 1900 m. Different types of alterations occurred on the edges of grabens and where the dome resurges. Intensive alteration zones have been identified within the ignimbrites in the caldera, particularly around the resurgent dome. The Güzelyurt resurgent caldera in Central Anatolia has significant geothermal potential due to geological events. The Narlıgöl maar, located just north of the resurgent dome towards the caldera boundary is a source of known geothermal potential. There are hot water and gas outlets in the maar, and geothermal facilities are operated on the northern flank of the maar. . Multiple gas emissions have been identified both inside and outside the Güzelyurt caldera, and an important geothermal field is also located just outside of the southern caldera wall (Bozköy Village). Detailed research about volcanism, especially in different regions of Anatolia, particularly in Central and Eastern Anatolia, is of great importance for increasing and revealing Turkey's geothermal energy potential.

How to cite: Atici, G., Aydar, E., Ulusoy, İ., and Ersoy, O.: Güzelyurt Resurgent Caldera - Cappadocia, Türkiye: The Origin of Gördeles Ignimbrite and Its Geothermal Potential , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-632, https://doi.org/10.5194/egusphere-egu24-632, 2024.

The Cappadocian plateau is a tectonic horst within the Central Anatolian Volcanic Province (CAVP), characterised by multiple thick and widespread ignimbrites accumulated since the late Miocene (e.g. Aydar et al., 2012). These Cappadocian ignimbrites blanketed an extensive area of at least 40,000 km²  with an estimate volume of pyroclastic material exceeding 1000 km³ (Temel et al., 1998). The source of the oldest Neogene ignimbrites still remains a subject of intense debate, as the area is primarily covered by younger volcanic products. However, it is well-known that the two youngest ignimbrites were produced by the Acigöl caldera (Druitt et al., 1995). These are the Lower Acigöl Tuff  (LAT) and the Upper Acigöl Tuff (UAT), erupted at 190 ± 11 ka and 164 ± 4 ka respectively (Schmitt et al., 2011). Post-caldera explosive volcanism continued in Acigöl until more recent times, especially in the last 25ka with the eruption of several rhyolitic tephra cones, maars and related tephra rings (Uslular et al., 2022).

Here, we propose that these monogenetic eruptions within the caldera basin may serve as precursory signals for larger caldera-forming events. Findings from a recent tephrostratigraphic investigation suggest that this series of volcanic eruptions has already occurred in Acigöl caldera as cascading events. This series includes the simultaneous emplacement of the Taskesik tephra ring and the UAT caldera-forming ignimbrite. Therefore, considering: 1) the high monogenetic volcanic activity in the last thousands of years within and outside the caldera, 2) the potential presence of eruptible magma beneath the caldera (Abgarmi et al., 2017), and 3) the increase in seismicity within the Central Anatolian Volcanic Province, the hypothetical scenario of a future caldera collapse eruption in Acigöl should not be dismissed.

This study was founded by the PÜSKÜRÜM project, a Marie Curie Action (Grant No. 101024337) funded by the European Union’s Horizon 2020.

Reference list:

Abgarmi, B., et al. (2017). Structure of the crust and African slab beneath the central Anatolian plateau from receiver functions: New insights on isostatic compensation and slab dynamics: Geosphere, v. 13, no. 6, p. 1774–1787, doi:10.1130/GES01509.1.

Aydar, E., et al (2012). Correlation of ignimbrites in the central Anatolian volcanic province using zircon and plagioclase ages and zircon compositions. J. Volcanol. Geoth. Res. 213, 83–97. doi:10.1016/j.jvolgeores.2011.11.005

Druitt, T.H., et al. (1995). Late-Quaternary rhyolitic eruptions from the Acıgöl Complex, central Turkey. Journal of the Geological Society (London, United Kingdom) 152, 655–667. DOI: 10.1144/gsjgs.152.4.0655

Schmitt, A. K., et al. (2011). Acigöl rhyolite field, Central Anatolia (part 1): High-resolution dating of eruption episodes and zircon growth rates. Contrib. Mineral. Pet. 162 (6), 1215–1231. doi:10.1007/s00410-011-0648-x

Uslular, G., et al. (2022). New findings on compositionally distinct maar volcanoes: A case study from Acıgöl (Nevşehir) caldera (Central Anatolia, Turkey)   . Front. Earth Sci.  DOI 10.3389/feart.2022.909951

Temel, A., et al (1998). Ignimbrites of Cappadocia (Central Anatolia, Turkey): petrology and geochemistry. J. Volcanol. Geotherm. Res. 85, 447–471. doi:https://doi.org/10.1016/S0377-0273(98)00066-3

How to cite: Sunye Puchol, I., Bolos, X., Ozsoy, R., Akkas, E., Aydar, E., Tavazzani, L., Nazarri, M., and Mollo, S.: Assessing the potential of a new widespread ignimbrite-forming eruption in Cappadocia, Central Anatolia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-550, https://doi.org/10.5194/egusphere-egu24-550, 2024.

The Greater and Lesser Hasandağ summits have both active and extinct fumarole vents, with evident hydrothermal alteration in their vicinity. Active fumaroles were documented on the western summit flanks of the Greater Hasandağ crater, at altitudes between 3000 and 3150 meters. Several hydrothermally altered zones are located inside the double craters of Greater Hasandağ and on the Lesser Hasandağ summit. In order to characterize the both completed and ongoing hydrothermal alteration process, a total of 27 rock samples were gathered from the hydrothermally altered rocks. The mineralogical compositions were examined by X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FT-IR) from the selected parts of altered rocks. Presence of common low–grade temperature (0 – 100 °C) secondary mineralization such as alunite, natro-alunite, halloysite, and opal-AN with scarce jarosite indicate existence of a continuous alteration process in a systematic order of crystallization. Recurrent temperature measurements from the fumarole vents also confirm the mineralogical findings. FT-IR analysis is also used synchronously to identify the spectral characteristics of hydrothermally altered rocks together with other analytical methods. Spatial distributions of the alteration minerals of Hasandağ were monitored comprehensively by using ASTER and Sentinel-2 imagery, relying on the reflectance and absorbance characteristics observed in the FT-IR data obtained from the altered samples. The combined results allowed us to produce precise hydrothermal alteration maps. Significantly, the zones where the alteration is prevalent are located along the Karacaören and Hasandağ Faults, which extend in the northeast-southwest and northwest-southeast directions, respectively.

How to cite: Diker, C., Akkaş, E., Ulusoy, İ., and Şen, E.: Pairing mineralogical and multispectral satellite imagery analysis to map the hydrothermal alteration on Hasandağ Volcano (Aksaray, Türkiye), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-748, https://doi.org/10.5194/egusphere-egu24-748, 2024.

Accurate knowledge of fault displacement rates is essential for seismic hazard assessments, with long-term slip rates being critical as constraints for the tectonic drivers of seismicity. The Tuz Gölü Fault Zone (TGFZ) is a NW-SE trending ~200 km long structure within the central Anatolian continental plateau. It consists of eleven parallel or sub-parallel fault segments, each ranging in length from 9 to 30 km, but seismic activity is scarce, making it difficult to pinpoint deformation mechanisms and magnitudes. Previous studies suggested that the TGFZ can produce earthquakes between M = 6.1 and 6.8, with generally higher displacement rates in the southern part of the TGFZ compared to the northern segments. Here, we studied the Akhisar-Kilic segment, which is located in the southern part of TGFZ. It dissects the southeastern flank of Mount Hasan, a prominent active stratovolcano, where several upper Pleistocene lava flows exhibit morphological evidence for faulting and hydrothermal activity. We conducted zircon double-dating, which merges U-Th and U-Pb geochronology and (U-Th)/He thermochronology, to date these variably offset lavas in order to establish fault geometries and offset rates.
Zircon crystallization ages of four lava flows, sampled in duplicate or triplicate on both sides of the TGFZ, permit correlation between proximal parts of the flows, and the more distal lobes across the TGFZ. The youngest zircon crystallization age population in each of the two northernmost flows overlaps within error, and they are closer to equilibrium than for the middle and southern flows. (U-Th)/He dates record eruptive cooling and indicate a systematic increase from north to south, with eruption ages between 39.0 ± 1.0 and 151 ± 3 ka.
Detailed morphological study of faulted lava flows utilizing a 5-meter digital elevation model (DEM) demonstrates that reasonable lava flow geometry can be restored within a range of oblique slip scenarios, ranging from primarily dip slip offset, to moderate right lateral oblique offsets. Combining the age dating and the geomorphic analysis yields vertical slip rates that can range up to between 0.5 and 0.6 mm/yr over the duration of lava emplacement in the southeastern sector of Mount Hasan. Because these rates are faster than previous estimates, we also expect that some TGFZ segments have the potential to produce earthquakes with considerably higher magnitudes than previously claimed. New slip rates covering a significant portion of the Late Pleistocene extend the fault history beyond the timescales of geodetic monitoring and historical records, thereby offering a significant vantage point for the derivation of seismic hazard estimates based on fault analysis. This is crucial to advance assessment of the multiple volcano-tectonic hazards that result from the coexistence of an active volcano and an active fault zone.
Keywords: multiple volcano-tectonic hazards, offset lavas, slip rates, zircon double dating

How to cite: Gencoglu Korkmaz, G., Schmitt, A. K., Harvey, J. C., Danišík, M., and Schoenbohm, L. M.: Spatial and Temporal Variability of Slip Rates on the Tuz Gölü Fault Zone: Insights from Zircon Double Dating of Offset Lavas of Mount Hasan, Central Anatolia , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1114, https://doi.org/10.5194/egusphere-egu24-1114, 2024.

Hasandağ has been one of the most active volcanoes in the Central Anatolian Volcanic Province (CAVP) during the late Pleistocene and Holocene. The past volcanic activity of Hasandağ is characterised by the eruption of multiple lavas, domes, block-and-ash flows (e.g., Aydar and Gourgaud, 1998; Kuzucuoğlu et al., 2020; Friedrichs et al., 2020). Additionally, this volcano has also experienced significant Plinian eruptions such as the Belbaşhanı Pumice, which is the focus of this work. Here, we present a complete volcanological investigation to better characterise this pumice fallout deposit and reconstruct the large explosive eruption that formed the Belbaşhanı Pumice approximately 400 ka ago.

By combining different methodological approaches (i.e., tephrostratigraphy, geological mapping, granulometric distribution, glass chemistry, geochronology, and shard morphology), we have derived isopach and isopleth maps, volume estimation, column height, and location of the eruption vent. The Belbaşhanı Pumice was formed by a Plinian column of about 23 km in height, which erupted ~2 km³ of bulk pyroclastic material. This column was erupted from a Hasandağ vent located at the intersection of the Tuz Gölü fault and a circular shape depression resembling a volcanic caldera. Major and trace element abundances show that the rhyolitic Belbaşhanı Pumice follows a compositional trend similar to those of documented for other Hasandağ pyroclastic deposits. The dispersal axis of the Belbaşhanı Pumice plume extended towards the NNE, leading to the accumulation of a pumice layer of at least 17-m-thick in proximal deposits and up to 2-m-thick in medial-distal areas (20 km from the vent). The highly vesiculated nature of the pumices and glass morphology indicate that Belbaşhanı Pumice was purely a magmatic eruption without any wet phases. Based on the abovementioned observations, we infer that the eruptive history of Hasandağ was related to VEI > 5 Plinian eruptions.

This contribution is relevant for a better understanding of hazard assessment within the CAVP, especially considering the current increase in fumarolic vents around the summit area, and in the seismic events  below and near the Hasandağ. In addition, the geochemical and geochronological data set is an important step to 1) foster future tephrochronological correlations, 2) constrain the distribution of the Belbaşhanı Pumices distal ashes and its eruptive magnitude, and 3) synchronize paleoenvironmental, paleoclimatic and archaeological records.

This research is part of Rengin Özsoy's Ph.D. thesis, funded through a PhD scholarship from La Sapienza – University of Rome and by the PÜSKÜRÜM project, a Marie Curie Action (Grant No. 101024337) funded by the European Union’s Horizon 2020.

References:

• Aydar, E. and Gourgaud, A. (1998). The geology of Mount Hasan stratovolcano, central Anatolia, Turkey. J Volcanol Geotherm Res 85:129–152. https://doi.org/10.1016/S0377-0273(98)00053-5
• Friedrichs, B., et al. (2020). Late Pleistocene eruptive recurrence in the post-collisional Mt. Hasan stratovolcanic complex (Central Anatolia) revealed by zircon double-dating. J Volcanol Geotherm Res 404:107007. https://doi.org/10.1016/j.jvolgeores.2020.107007
• Kuzucuoğlu, C., et al. (2020). Geomorphology and tephrochronology review of the Hasandağ volcano (southern Cappadocia, Turkey). Mediterranean Geosciences Reviews, https://doi.org/10.1007/s42990-019-00017-1

How to cite: Özsoy, R., Sunye-Puchol, I., Pedrazzi, D., Akkas, E., Costa, A., Aydar, E., Tavazzani, L., Massaro, S., Nazzari, M., Miggins, D. P., Kaya, S., and Mollo, S.: New insights into the Belbaşhanı Pumice Plinian eruption: tephrostratigraphy, eruptive history and implications for volcanic hazards posed by Hasandağ (Central Anatolia), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-659, https://doi.org/10.5194/egusphere-egu24-659, 2024.

Mt. Erciyes and Mt. Hasan are the two largest stratovolcanic complexes of the Central Anatolian Volcanic Province (Turkey). Despite geochronological evidence for early Holocene eruptions classifying both volcanic systems as active (Sarıkaya et al., 2019; Schmitt et al., 2014), their Late Pleistocene–Holocene chronostratigraphies remained poorly constrained. Combining zircon U–Th–Pb crystallization ages with trace element concentrations (zircon petrochronology) and (U–Th)/He cooling ages (zircon double-dating; ZDD), we identified contrasting magma recharge and eruptive recurrence patterns.

Mt. Hasan, magmatically and volcanically active since ca. 550 ka, predominantly erupted andesitic lava domes and flows as well as block-and-ash-flows. Zircon double-dating indicates a Late Pleistocene recurrence of at least one eruptive episode every ca. 5–15 ka. Combined with volume estimates, zircon geochronology suggests Middle–Late Pleistocene eruptive magma fluxes of ~0.3–0.1 km³/ka, similar to continental arc volcanoes (Friedrichs et al., 2020a).

Mt. Erciyes formed after the deposition of the Valibaba Tepe Ignimbrite with a U–Pb zircon age of 2.73 ± 0.02 Ma (all uncertainties 1σ). Its magmatic system is characterized by protracted zircon crystallization since at least ca. 800 ka. Episodes of scoria cone and lava dome as well as pyroclastic fall-out emplacement at ca. 105 and ca. 88–85 ka were followed by an extended eruptive lull. In an early Holocene resurgence, four peripheral rhyolitic–dacitic lava domes erupted, three of them with significant initial explosive phases. Yılanlı Dağ was emplaced at 9.4 ± 1.3 ka, Dikkartın at 8.9 ± 0.5 ka, and Karagüllü as well as Perikartın with their stratigraphically directly overlying pyroclastic deposits at 8.8 ± 0.8 ka (Friedrichs et al., 2021a).

Tephra glass major and trace element geochemistry identifies Karagüllü as the source of a cryptotephra found in a Black Sea gravity core, calling for a re-evaluation of its age model. The chemically indistinguishable Dikkartın and/or Perikartın eruptions are potential sources of the Eastern Mediterranean S1 tephra, an important marker horizon for archaeological and paleoclimatological research. Proximal fall-out from the Dikkartın eruption indicates eastward dispersal from a 20 ± 5 km high eruption plume, in agreement with probabilistic tephra dispersal modeling results. Distal S1 tephra, however, is distributed up to ~1300 km south of Mt. Erciyes, suggesting tephra transport by low altitude rather than stratospheric winds. This may either be due to eolian reworking of proximal deposits or due to co-ignimbrite ash cloud dispersal (Friedrichs et al., 2020b).

Contrasting thermochemical evolutions of the magma plumbing systems control the distinct eruptive styles and recurrence patterns. For Mt. Hasan, zircon crystallization temperatures and melt differentiation indices span comparably narrow, time-invariant ranges, whereas for Mt. Erciyes, these parameters fluctuate over broader ranges. Thermochemical modeling indicates moderate near-steady recharge into an upper crustal magma chamber beneath Mt. Hasan (“warm” storage, eruptible), but low and modulated magma recharge for Mt. Erciyes (“cold” storage, rheologically locked). Nonetheless, both systems may be reactivated by magmatic rejuvenation. Violent explosive eruptions would pose major threats for the local population, particularly for Kayseri metropolis at the base of Mt. Erciyes (Friedrichs et al., 2021b).

How to cite: Friedrichs, B., Schmitt, A. K., Danišík, M., Lovera, O. M., and Atıcı, G.: Eruptive recurrence and magma accumulation for Quaternary stratovolcanoes in Central Anatolia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1078, https://doi.org/10.5194/egusphere-egu24-1078, 2024.

How to cite: Madak, Z., Varol, E., and Dogan Kulahci, G. D.: Preliminary Investigation of Volcanic Succession and Mineralogy of the Southern part of Mount Ağrı, Eastern Anatolia, Turkey , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-746, https://doi.org/10.5194/egusphere-egu24-746, 2024.

The volcanoes of Nemrut and Süphan in the Eastern Anatolian Volcanic Province (EAVP) have been active throughout the late Quaternary, dispersing ash over wide areas. Numerous eruptions spanning the last interglacial to glacial period (130-30kya) are recorded in outcrops around the volcanoes and in the cores from Lake Van. A comprehensive tephrostratigraphy framework for the EAVP is an essential requirement for synchronising palaeoclimatic and archaeological records across the Mediterranean region. More information is required from the eruption deposits, including glass geochemistry on individual shards, and the stratigraphic order and precise ages for the eruptions.

Here we present the findings of our detailed tephra investigation for the palaeoclimatic record of Lake Van (Turkey), as part of the TephroMed project. The lake is located close to both Nemrut and Süphan. Fourteen visible tephra layers (called V-layers) from Lake Van PALEOVAN ICDP record underwent geochemical characterisation by using major, minor (EPMA) and trace element analysis (LA-ICP-MS). New chemical analyses and ⁴⁰Ar/³⁹Ar ages of eruption deposits from proximal outcrops, provide detailed insight into the complex volcanic history of the EAVP, particularly of Nemrut. These results have revealed new volcanic origins for certain V-layers to Nemrut and Süphan, with tentative correlations between Lake Van’s fourteen V-layers to previously published dated proximal outcrops. Additionally, new glass geochemistry from dated proximal outcrops confirm the ages of the key eruption events associated with V-51 and V-18a of Lake Van. This improves the chronology of the Lake Van record and provides an understanding for the timing of complex eruptions from Nemrut and Süphan. The results are a major step forward to building a detailed tephrostratigraphic framework for the EAVP.

How to cite: Kearney, R., Goff, J., J. Schwab, M., Neugebauer, I., Smith, V., Appelt, O., Günter, C., Özdemir, Y., Karaoǧlu, Ö., Thirwall, M., Burfod, D., Pickarski, N., Tjallingii, R., and Brauer, A.: Providing a detailed glass geochemistry for key tephra layers of Lake Van, Eastern Anatolian Volcanic Province, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12038, https://doi.org/10.5194/egusphere-egu24-12038, 2024.