İnan Ulusoy

Morphological analysis of active Mount Nemrut stratovolcano, eastern Turkey: evidences and possible impact areas of future eruption

Abstract Mount Nemrut, an active stratovolcano in eastern Turkey, is a great danger for its vicinity. The volcano possesses a summit caldera which cuts the volcano into two stages, i.e. pre- and post-caldera. Wisps of smoke and hot springs are to be found within the caldera. Although the last recorded volcanic activity is known to have been in 1441, we consider here that the last eruption of Nemrut occurred more recently, probably just before 1597. The present active tectonic regime, historical eruptions, occurrence of mantle-derived magmatic gases and the fumarole and hot spring activities on the caldera floor make Nemrut Volcano a real danger for its vicinity. According to the volcanological past of Nemrut, the styles of expected eruptions are well-focused on two types: (1) occurrence of water within the caldera leads to phreatomagmatic (highly energetic) eruptions, subsequently followed by lava extrusions, and (2) effusions–extrusions (non-explosive or weakly energetic eruptions) on the flanks from fissures. To predict the impact area of future eruptions, a series of morphological analyses based on field observations, Digital Elevation Model and satellite images were realized. Twenty-two valleys (main transport pathways) were classified according to their importance, and the physical parameters related to the valleys were determined. The slope values in each point of the flanks and the Heim parameters H/L were calculated. In the light of morphological analysis the possible impact areas around the volcano and danger zones were proposed. The possible transport pathways of the products of expected volcanic events are unified in three main directions: Bitlis, Guroymak, Tatvan and Ahlat cities, the about 135 000 inhabitants of which could be threatened by future eruptions of this poorly known and unsurveyed volcano.

Texture discrimination of volcanic ashes from different fragmentation mechanisms: A case study, Mount Nemrut stratovolcano, eastern Turkey

Abstract Multicondition-driven mechanisms may produce pyroclastic deposits varying in fundamental properties such as dispersal, grain size, vesicularity and morphology of juvenile clasts, and the abundance of lithic or “wall rock” ejecta (xenoliths). Volcanic ash particles from different fragmentation mechanisms have different surface textures and morphologies. The analysis of the volcanic clast shape remained largely qualitative. A new method for ash particle characterization based on quadtree decomposition and surface gradient analysis is introduced. The approach is applied for assessing fragmentation mechanisms operating during eruptions. The surface descriptor variables like the number of quadtree blocks (nQT), the mean block size (mQT), the standard deviation of block sizes (sQT) and the surface descriptors derived from gradient analysis seem to be suitable for quantifying the structural changes of the ash surface due to variable explosion conditions. These parameters are presented in volcanology as distinctive key parameters for different eruption types. This may enrich our capabilities for effective prediction for the basis of planning to overcome the impending danger of eruptions.

Identifying the volcanic eruption depicted in a neolithic painting at Catalhoyuk, Central Anatolia, Turkey.

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.

A Rhinocerotid Skull Cooked-to-Death in a 9.2 Ma-Old Ignimbrite Flow of Turkey

Background Preservation of fossil vertebrates in volcanic rocks is extremely rare. An articulated skull (cranium and mandible) of a rhinoceros was found in a 9.2±0.1 Ma-old ignimbrite of Cappadocia, Central Turkey. The unusual aspect of the preserved hard tissues of the skull (rough bone surface and brittle dentine) allows suspecting a peri-mortem exposure to a heating source. Methodology/Principal Findings Here we describe and identify the skull as belonging to the large two-horned rhinocerotine Ceratotherium neumayri, well-known in the late Miocene of the Eastern Mediterranean Province. Gross structural features and microscopic changes of hard tissues (bones and teeth) are then monitored and compared to the results of forensic and archaeological studies and experiments focusing on heating effects, in order to reconstruct the hypothetical peri-mortem conditions. Macroscopic and microscopic structural changes on compact bones (canaliculi and lamellae vanished), as well as partial dentine/cementum disintegration, drastic enamel-dentine disjunctions or microscopic cracks affecting all hard dental tissues (enamel, cementum, and dentine) point to continued exposures to temperatures around 400–450°C. Comparison to other cases of preservation of fossil vertebrates within volcanic rocks points unambiguously to some similarity with the 79 AD Plinian eruption of the Vesuvius, in Italy. Conclusions/Significance A 9.2±0.1 Ma-old pyroclastic density current, sourced from the Çardak caldera, likely provoked the instant death of the Karacaşar rhino, before the body of the latter experienced severe dehydration (leading to the wide and sustainable opening of the mouth), was then dismembered within the pyroclastic flow of subaerial origin, the skull being separated from the remnant body and baked under a temperature approximating 400°C, then transported northward, rolled, and trapped in disarray into that pyroclastic flow forming the pinkish Kavak-4 ignimbrite ∼30 km North from the upper Miocene vent.

Multi-directional derivation of self-potential/elevation gradient (Ce) maps – swirl procedure

The derivation of gradient maps in geophysics, particularly in the field of self-potential has the potential to improve our understanding on the source of a signal. Self-potential/elevation gradient maps are beneficial in significantly reducing the topographic effect. Manual calculation of the gradient for large data sets in two-dimensions is time consuming and highly dependent on the direction of the calculation. Automation of the calculation process has the potential to overcome the time and directional dependency problems. The derivation of gradient maps in the multi-direction improves the result and array based operators can perform the automatic calculations rapidly. Four different gradient calculation methods based on a new automatic array oriented procedure (swirl procedure) are discussed and tested with artificial and field data sets. These four methods can be simply defined by the number of data contributing to the calculation (full-swirl or limited-swirl procedures) and the mathematical operator (maximum value or mean value) used in the calculation. The mean value operator using the full-swirl procedure gave the most reliable result in terms of gradient range and accuracy. The swirl procedure can effectively perform the self-potential/elevation gradient calculations and it has a potential use in various applications.

Dağıtılmış Anahtarlamalı Özdirenç Görüntüleme Sistemi

Within last three decades, direct current resistivity imaging method has been subjected to a considerable development both due to the instrumental evolution and due to the increase in the speed and the capacity of the computation. The application is generally made using a central switching system or another switching system which is distributed over electrodes, called smart electrode system. In terms of field surveys, both systems have advantages and disadvantages. Smart electrode systems may be advantageous due to the possibility of producing lightweight cables. The smart electrode system developed in the Hacettepe University is 75% lighter than the equivalent systems that are operating with a central switching unit. Principally, system is composed of a small central control unit, smart electrode units that are connected to the electrodes and the main cable. Inside the main cable, there lie 6 inner cables; two of them are isolated due to interference. System runs automatically via a laptop computer which is serially connected to the control unit. The system was tested with short and long profiles and observed to be working properly. The lightweight of the system provides a considerable ease especially during the measurement İ. Ulusoy e-posta: inan@hacettepe.edu.tr