Невзат Озгур1, Кошкун Сари2
1Университет Сулеймана Демиреля, инженерный факультет, кафедра геологической инженерии, Испарта, Турция
2Университет Докуз Эйлул, инженерный факультет, кафедра геофизической инженерии, Измир, Турция
nevzatozgur@sdu.edu.tr
Морфологическое строение района Гѐльчук показывает, что крупные долины между Гѐльчук и Испарта дренируются в район провинции Испарта с населением 250 000 человек. В случае извержения вулкана в районе Гѐльчука, пирокластические материалы будут двигаться по этим долинам, открытых в основном на северном фланге вулкана Гельчук. Недавние землетрясения (глубиной до 5 км) вокруг вулкана Гѐльчук, особенно в районе разлома Кайкѐй на СВ, имеют скорее вулканическое происхождение и связаны с предполагаемой магматической камерой. В связи с этим рассматривается связь между выходами газа в зоне между разломами Кайкѐй и Бурдур и возможной магматической камерой. Для защиты 250 000 жителей столицы провинции Испарта от вулканических опасностей вулкана Гѐльчук может быть установлена система мониторинга для прогнозирования вулканической активности путем измерения сейсмической активности, газосодержания и гидрогеохимических параметров.
Ключевые слова: Турция, Испарта, Гѐльчук, вулкан, вулканическая опасность 1. Introduction
The Gölcük volcano is located in the southern part of the Kırka-Afyon-Isparta volcanic province within the Isparta Angle which forms the North pointing cusp and belongs to the post- collisional alkali potassic-ultrapotassic magmatism in connection with tectonic structures resulting from the main alpine orogenic phases of the Helleno-Tauric belt. The entire activity of the Gölcük volcano took place during Pleistocene and is disconnected from the older volcanism in Pliocene age (6 Ma). As a first volcanic cycle, it might be considered as a new volcanic period starting with a major explosive regional event at 206,1 ± 9,8 ka and lasting about 50.000 years after with at least 6 explosive episodes relatively spaced in time. Tephriphonolitic lava flows, domes and dykes of second volcanic cycle occurred between 115 ± 3 ka and 62 ± 2 ka with probably some tephra deposits at the bottom of the tuff-ring. As last volcanic cycle, the tuff-ring formed from 72,7 ± 4,7 ka to 24 ± 2 ka with ending by trachytic dome intrusions. Moreover, average disequilibrium-corrected (U-Th)/He zircon ages are 14,1 ± 0,5 and 12,9 ± 0,4 ka. The both ages are indistinguishable within analytical uncertainties suggested these both lavas erupted quasi simultaneously. The periodicity of eruptive events indicate that the volcano is at rest and will activate in near future. This paper aims to describe a possible volcanic hazard of the Gölcük volcano in the province capital of Isparta, Turkey.
2. Gölcük volcanism
The Gölcük volcano is located in the southern part of the Kırka-Afyon-Isparta volcanic province within the Isparta Angle which forms the North pointing cusp and belongs to the post- collisional alkali potassicultrapotassic magmatism in connection with tectonic structures resulting from the main alpine orogenic phases of the Helleno-Tauric belt. The entire activity of the Gölcük volcano took place during Pleistocene and is disconnected from the older volcanism in Pliocene age (6 Ma). As a first volcanic cycle, it might be considered as a new volcanic period starting with a major explosive regional event at 206,1 ± 9,8 ka and lasting about 50.000 years after with at least 6 explosive episodes relatively spaced in time (Figure 1: Özgür et al., 2008:
Elitok et al., 2008; Platevoet et al., 2008). Tephriphonolitic lava flows, domes and dykes of second volcanic cycle occurred between 115 ± 3 ka and 62 ± 2 ka with probably some tephra deposits at the bottom of the tuff-ring. As last volcanic cycle, the tuff-ring formed from 72,7 ± 4,7 ka to 24 ± 2 ka with ending by trachytic dome intrusions. Moreover, average disequilibrium-
corrected (U-Th)/He zircon ages are 14,1 ± 0,5 and 12,9 ± 0,4 ka. The both ages are indistinguishable within analytical uncertainties suggested these both lavas erupted quasi simultaneously. The periodicity of eruptive events indicate that the volcano is at rest and will activate in near future.
3. Volcanic Hazard Risks
The morphological structure of the area shows that major valleys between Gölcük and Isparta drain and dip to the City of Isparta with 250.00 inhabitants (Figure 2; Özgür et al., 2008;
Platevoet, 2008). In case of a volcanic eruption in the Gölcük area, the pyroclastic materials flow through these major valleys opened on the northern flank of the Gölcük volcano mostly.
Moreover, the pyroclatics distributing in a large area between Gölcük and Isparta consist of poorly welded materials. At the same time, the study area has very poor flora and shows a steep topographic features. In case of a volcanic eruption in the Gölcük area, pyroclastic materials and/or tephriphonolitic towards trachyandesitic and/or trachytic lava flows flow through major valleys to the city of Isparta with 250,000 inhabitants and can lead to loss of people and properties in the area mainly. Moreover, the arrival of erosions and floodings in the city of Isparta form an another great danger in connection with strong rainfall in the area additionally.
Recent shallow earthquake activities (up to 5 km) around Gölcük volcano, especially at Kayıköy fault in the NE, point to a volcanic origin associated with a possible magma chamber rather than the tectonic origin. In relation, it is assumed that there might be a link between the gas outlets in the area between Kayıköy fault and Burdur fault zone and a possible magma chamber. To protect the 250.000 inhabitants of province capital Isparta from volcanic hazards by the Gölcük volcano, a monitoring system for the prediction of volcanic activity can be installed by measurements of seismic activities, gas contents and hydrogeochemical parameters.
Figure 1 – Gölcük volcanism and eruption cycles. A: First volcanic cycle and ignimbritic pyroclatics; B:
Second eruption cycle and tephriphonolitic domes, dykes and lava flows; C: Third eruption cycle and pyroclastic rocks; D: Caldera and trachytic lava dome (modified from Özgür et al., 2008; Elitok et al., 2008;
Platevoet et al., 2008)
Figure 2 – A possible volcanic hazard risk of the Gölcük volcano in the area of province capital of Isparta References
1. Elitok, Ö., Özgür, N., Yılmaz, K.: Geological evolution of Gölcük volcanism (Isparta), SW Turkey (in Turkish), Suleyman Demirel University, Research Project, 171 p., 2008.
2. Özgür, N., Yağmurlu, F., Ertunç, A., Karagüzel, R., Görmüş, M., Elitok, Ö., Yılmaz, K., Çoban, H.: Assesments of tectonics and volcanic hazards in the area of Isparta around the Gölcük volcano. Suleyman Demirel University, Research Project, 46 p., 2008.
3. Platevoet, B., Scaillet, S., Guillou, H., Blamart, D., Nomade, S., Massault, M., Poisson, A., Elitok, Ö., Özgür, N., Yagmurlu, F., Yilmaz, K.: Pleistocene eruptive chronology of the Gölcük volcano, Isparta Angle, Turkey. Quaternaire.19, p. 147-156, 2008.