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[SVC36-P14] Estimation of the lava flow temperature at the C2 lava tube cave formation of Chu B’luk volcano in Vietnam
Keywords: lava tube cave, lava yield strength, lava temperature, viscosity
1. Introduction
The Chu B’luk volcano is located in the Krongno district, Dak Nong province, The Central Highlands of Vietnam. It is one of the continental volcanoes that blew a large amount of soft lava having a silicic acid weight fraction of 48.3 to 52.4%[1]. From 2012-2017, NPO Vulcano-Speleological Society officially cooperated with Vietnamese geologists from the Vietnam Geological Museum,Vietnam National Museum of Nature respectively conducted a series of surveys, measuring and mapping in detail 16 caves out of a total of 50 volcanic caves in the Krongno area. After that, 5 more caves were measured and mapped by Vietnamese geologists. Hence, the whole number of measured and mapped caves is 21[2].
2. C2 lava tube cave
The C2 lava tube cave(Fig.1,Fig.2) is one of the 21 measured, mapped lava tube caves mentioned above. The K/Ar isotopic age dating on the basaltic rock sample collected at the highest lava level mark of the cave wall shows a value of 0.671 ± 0.17 Ma[3]. In this paper, the C2 lava tube cave was chosen as a case study in the Krongno lava cave system to identify the yield strength of lava flow, using the hydrodynamic model of Bingham fluid flow for a lava tube. In detail, we will attempt to estimate the lava flow temperature during the C2 lava tube formation of Chu B’luk volcano by using the yield strength obtained from the lava tube cave slope angle and height[4](Table.1).
3.Estimation of the temperature and viscosity
As the temperature-dependent data of yield strength and viscosity for Chu B’luk volcano’s lava do not exist, those of Mt. Fuji 1707 basalt[4], Etna volcano basalt[4], and Izu-Oshima 1951 basalt[4,6] are used. The obtained yield strength of the lava of 2.3x104 dyne/cm2 which leads to the range of 1045° C to 1067° C as lava tube cave formation temperature. Further, the viscosity coefficient of the lava flow was also estimated from these temperatures as in the range of 2.2x104 to 2.5x105 poise(Table.2). These are reasonable values for basaltic lava flow.
4.Conclusions
If the temperature dependence data of yield strength and viscosity are obtained in advance, the formation temperature can be estimated from the yield strength obtained from the shape of lava tube caves formed in the past. Furthermore, it is possible to estimate the viscosity of lava from the temperature.
References:
[1] N. Hoang & M. Flower (1998):Petrogenesis of Cenozoic Basalts from Vietnam: Implication for Origins of a ‘Diffuse Igneous Province’,J. Petrology,vol39,No3, pp. 369-395.
[2] La The Phuc, H. Tachihara, T. Honda, Luong Thi Tuat et al. (2018). Geological values of lava caves in Krongno Volcano Geopark, Dak Nong, Vietnam. Vietnam Journal of Earth Sciences, 40(4), pp.299–319.
[3] La The Phuc et al. (2020). Report “Research on the value of cave heritage, propose building on-site conservation museums in The Central Highlands; take for example the volcanic cave in Krong No, Dak Nong province”, code TN17/T06. Archived at the Vietnam Museum of Nature.
[4] T.Honda, J.Haruyama (2020): 3E11 Identification of lava temperature by lava tube cave structure on the Earth and the Moon. 64th Space Science and Technology Union Conference, The Japan Society for Aeronautical and Space Sciences.
[5]T.Honda, H.Tachihara, La The Phuc, Luong Thi Tuat, Truong Quang Quy(2015):P87 Lava tube caves and tree molds of Chu B’luk volcano in the central highlands of Vietnam,Autumn Meeting of the Volcanological Society of Japan.
[6] K.Ishihara, M.Iguchi, K.Kamo (1988): Reproduction of the 1986 Izu Oshima lava flow by numerical calculation, Bulletin of the volcanological society of Japan, Vol.33, S64-S76
The Chu B’luk volcano is located in the Krongno district, Dak Nong province, The Central Highlands of Vietnam. It is one of the continental volcanoes that blew a large amount of soft lava having a silicic acid weight fraction of 48.3 to 52.4%[1]. From 2012-2017, NPO Vulcano-Speleological Society officially cooperated with Vietnamese geologists from the Vietnam Geological Museum,Vietnam National Museum of Nature respectively conducted a series of surveys, measuring and mapping in detail 16 caves out of a total of 50 volcanic caves in the Krongno area. After that, 5 more caves were measured and mapped by Vietnamese geologists. Hence, the whole number of measured and mapped caves is 21[2].
2. C2 lava tube cave
The C2 lava tube cave(Fig.1,Fig.2) is one of the 21 measured, mapped lava tube caves mentioned above. The K/Ar isotopic age dating on the basaltic rock sample collected at the highest lava level mark of the cave wall shows a value of 0.671 ± 0.17 Ma[3]. In this paper, the C2 lava tube cave was chosen as a case study in the Krongno lava cave system to identify the yield strength of lava flow, using the hydrodynamic model of Bingham fluid flow for a lava tube. In detail, we will attempt to estimate the lava flow temperature during the C2 lava tube formation of Chu B’luk volcano by using the yield strength obtained from the lava tube cave slope angle and height[4](Table.1).
3.Estimation of the temperature and viscosity
As the temperature-dependent data of yield strength and viscosity for Chu B’luk volcano’s lava do not exist, those of Mt. Fuji 1707 basalt[4], Etna volcano basalt[4], and Izu-Oshima 1951 basalt[4,6] are used. The obtained yield strength of the lava of 2.3x104 dyne/cm2 which leads to the range of 1045° C to 1067° C as lava tube cave formation temperature. Further, the viscosity coefficient of the lava flow was also estimated from these temperatures as in the range of 2.2x104 to 2.5x105 poise(Table.2). These are reasonable values for basaltic lava flow.
4.Conclusions
If the temperature dependence data of yield strength and viscosity are obtained in advance, the formation temperature can be estimated from the yield strength obtained from the shape of lava tube caves formed in the past. Furthermore, it is possible to estimate the viscosity of lava from the temperature.
References:
[1] N. Hoang & M. Flower (1998):Petrogenesis of Cenozoic Basalts from Vietnam: Implication for Origins of a ‘Diffuse Igneous Province’,J. Petrology,vol39,No3, pp. 369-395.
[2] La The Phuc, H. Tachihara, T. Honda, Luong Thi Tuat et al. (2018). Geological values of lava caves in Krongno Volcano Geopark, Dak Nong, Vietnam. Vietnam Journal of Earth Sciences, 40(4), pp.299–319.
[3] La The Phuc et al. (2020). Report “Research on the value of cave heritage, propose building on-site conservation museums in The Central Highlands; take for example the volcanic cave in Krong No, Dak Nong province”, code TN17/T06. Archived at the Vietnam Museum of Nature.
[4] T.Honda, J.Haruyama (2020): 3E11 Identification of lava temperature by lava tube cave structure on the Earth and the Moon. 64th Space Science and Technology Union Conference, The Japan Society for Aeronautical and Space Sciences.
[5]T.Honda, H.Tachihara, La The Phuc, Luong Thi Tuat, Truong Quang Quy(2015):P87 Lava tube caves and tree molds of Chu B’luk volcano in the central highlands of Vietnam,Autumn Meeting of the Volcanological Society of Japan.
[6] K.Ishihara, M.Iguchi, K.Kamo (1988): Reproduction of the 1986 Izu Oshima lava flow by numerical calculation, Bulletin of the volcanological society of Japan, Vol.33, S64-S76