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[SVC34-P02] Estimation of the lava flow temperature by lava tube structure of Reunion island
Keywords:lava temperature, lava tube cave, surface tension, yield strength
[Introduction]
The Piton de la Fournaise volcano in Réunion Island of a French overseas department in the Indian Ocean is famous for its frequent eruptions that flow lava. Several times a year, basaltic lava flows (SiO2 45wt% to 50wt%). We conducted field surveys [1] to investigate the morphology of lava tube caves created by eruptions from 1989 to 2007 and their lava flows. Table 1 shows the results of investigating the height difference, length, etc. of lava tube caves formed by lava flows in 1998, 2004, 2005, and 2007. Figures 1 and 2 show Kapor Cave, and Figures 3 to 6 show Blanche Nord cave. We determined the lava yield strength and surface tension [2] and here, attempted to estimate the lava temperature from the lava yield strength and surface tension.
[Lava temperature estimated from lava yield strength]
The slope of the lava tube cave can be determined from the height difference and length shown in Table 1, then, the yield strength of the lava can be estimated from height H(H=2R)of the cave cavity. The relational expression is fB=(ρg sinα)H/4[ 3]. Here, fB: Bingham yield strength, ρ: density (2.5 g/cm3), g: gravitational acceleration, α: slope angle. Cavity height plotted against slope angle is shown in Figure 7. The yield strength of lava is 5x103dyne/cm2 to 2.5x104dyne/cm2 [2]. To estimate the temperature from this, the temperature-dependent formula for the yield strength fB of the lava flow erupted in 1951 at Miharayama, Izu Oshima[3]: log10fB=13.67-0.089θ, here, θ is the temperature in degrees Celsius, and fB is dyne/cm2, so the temperature θ is 1120°C to 1042°C.
[Lava temperature estimated from lava surface tension]
Inside the lava tube cave, you can see lava stalactites in the ceiling (Fig. 5) and rib structure (Fig. 6) where lava stalactites run down through the walls, and lava stalagmites (Fig. 2) accumulated on the floor. We have estimated the surface tension from the pitch of lava stalactites and rib-like lavas P=2π(γ /g ρ)1/2[4] and the relational :γ=rℓρg/2[4] for the dimensions of falling droplets that form lava stalagmites. Then, we used the temperature change formula for the surface tension of lava in 1950-1951 Miharayama lava flow[5]:γ = 2100-1.1θ , here, γ is the surface tension, ρ is the lava density, g is the gravitational acceleration, r is the radius of the droplet, and ℓ is the length of the liquid lava droplet [4]. The observed pitch of lava stalactites (Fig. 6) and rib-like lava (Fig. 7) is 3 to 4 cm, and if the average pitch of 3.5 cm is used, the surface tension will be 800 dyne/cm, and the average temperature will be 1200°C. The size of the falling droplet (Fig. 2) that forms a stalagmite is about r = 0.25 cm, ℓ = 4 cm, γ = 980dyne/cm, then, the temperature is 1020℃.
[Conclusion]
The temperature of the lava flow of the Piton de la Fournaise Volcano on Réunion Island is said to be between 1100°C and 1160°C [6] and around 1200°C [7]. The lava temperature estimated from yield strength and surface tension obtained from the shape and structure of the lava tube cave formed in the lava flow(1120°C to 1042°C, 1200°C, 1020℃) seems consistent with these temperatures.
References:
[1] T. Staudacher, L. Ruzie and A. Peltier (2008): Historique des eruptions du Piton de la Fournaise de 1998 a 2007, OVPF/IPGP
[2] T. Honda et al. (2014): A2-26 Investigation on the lava of 1998-2007 and lava tube caves in the Reunion Island, the Volcanology Society of Japan ,2014 Programme and Abstract p38
[3] T.Honda (2001): B10 Formation mechanism of lava tube caves in Mt. Fuji, the Volcanology Society of Japan Programme and Abstract 2001(2), p66
[4] T.Honda (2015): SVC46-07 Estimation of surface tension of lava from lava stalactite and lava stalagmite appeared in lava tube cave and tree mold lava tube cave and lava tree mold, Japan Geoscience Union 2015 Meeting
[5] Izumi Yokoyama, Susumu Iizuka (1970): Measurement of surface tension of molten volcanic rock, Hokkaido University Geophysical Research Report No. 24, p57-61
[6]Villeneuve, N., D. R. Neuville, P. Boivin, P. Bachèlery, and P. Richet (2008), Magma crystallization and viscosity: A study of molten basalts from the Piton de la Fournaise volcano (La Réunion island), Chem. Geol., 256, 242–251, doi:10.1016/j.chemgeo.2008.06.039.
[7] Patrick Bachelery,Jean-Francois Lenat,Andrea Di Muro,Laurent Michon(2016):
Active Volcanoes of the Southwest Indian Ocean,Piton de la Fournaise and Karthala,Springer,p178-179.
The Piton de la Fournaise volcano in Réunion Island of a French overseas department in the Indian Ocean is famous for its frequent eruptions that flow lava. Several times a year, basaltic lava flows (SiO2 45wt% to 50wt%). We conducted field surveys [1] to investigate the morphology of lava tube caves created by eruptions from 1989 to 2007 and their lava flows. Table 1 shows the results of investigating the height difference, length, etc. of lava tube caves formed by lava flows in 1998, 2004, 2005, and 2007. Figures 1 and 2 show Kapor Cave, and Figures 3 to 6 show Blanche Nord cave. We determined the lava yield strength and surface tension [2] and here, attempted to estimate the lava temperature from the lava yield strength and surface tension.
[Lava temperature estimated from lava yield strength]
The slope of the lava tube cave can be determined from the height difference and length shown in Table 1, then, the yield strength of the lava can be estimated from height H(H=2R)of the cave cavity. The relational expression is fB=(ρg sinα)H/4[ 3]. Here, fB: Bingham yield strength, ρ: density (2.5 g/cm3), g: gravitational acceleration, α: slope angle. Cavity height plotted against slope angle is shown in Figure 7. The yield strength of lava is 5x103dyne/cm2 to 2.5x104dyne/cm2 [2]. To estimate the temperature from this, the temperature-dependent formula for the yield strength fB of the lava flow erupted in 1951 at Miharayama, Izu Oshima[3]: log10fB=13.67-0.089θ, here, θ is the temperature in degrees Celsius, and fB is dyne/cm2, so the temperature θ is 1120°C to 1042°C.
[Lava temperature estimated from lava surface tension]
Inside the lava tube cave, you can see lava stalactites in the ceiling (Fig. 5) and rib structure (Fig. 6) where lava stalactites run down through the walls, and lava stalagmites (Fig. 2) accumulated on the floor. We have estimated the surface tension from the pitch of lava stalactites and rib-like lavas P=2π(γ /g ρ)1/2[4] and the relational :γ=rℓρg/2[4] for the dimensions of falling droplets that form lava stalagmites. Then, we used the temperature change formula for the surface tension of lava in 1950-1951 Miharayama lava flow[5]:γ = 2100-1.1θ , here, γ is the surface tension, ρ is the lava density, g is the gravitational acceleration, r is the radius of the droplet, and ℓ is the length of the liquid lava droplet [4]. The observed pitch of lava stalactites (Fig. 6) and rib-like lava (Fig. 7) is 3 to 4 cm, and if the average pitch of 3.5 cm is used, the surface tension will be 800 dyne/cm, and the average temperature will be 1200°C. The size of the falling droplet (Fig. 2) that forms a stalagmite is about r = 0.25 cm, ℓ = 4 cm, γ = 980dyne/cm, then, the temperature is 1020℃.
[Conclusion]
The temperature of the lava flow of the Piton de la Fournaise Volcano on Réunion Island is said to be between 1100°C and 1160°C [6] and around 1200°C [7]. The lava temperature estimated from yield strength and surface tension obtained from the shape and structure of the lava tube cave formed in the lava flow(1120°C to 1042°C, 1200°C, 1020℃) seems consistent with these temperatures.
References:
[1] T. Staudacher, L. Ruzie and A. Peltier (2008): Historique des eruptions du Piton de la Fournaise de 1998 a 2007, OVPF/IPGP
[2] T. Honda et al. (2014): A2-26 Investigation on the lava of 1998-2007 and lava tube caves in the Reunion Island, the Volcanology Society of Japan ,2014 Programme and Abstract p38
[3] T.Honda (2001): B10 Formation mechanism of lava tube caves in Mt. Fuji, the Volcanology Society of Japan Programme and Abstract 2001(2), p66
[4] T.Honda (2015): SVC46-07 Estimation of surface tension of lava from lava stalactite and lava stalagmite appeared in lava tube cave and tree mold lava tube cave and lava tree mold, Japan Geoscience Union 2015 Meeting
[5] Izumi Yokoyama, Susumu Iizuka (1970): Measurement of surface tension of molten volcanic rock, Hokkaido University Geophysical Research Report No. 24, p57-61
[6]Villeneuve, N., D. R. Neuville, P. Boivin, P. Bachèlery, and P. Richet (2008), Magma crystallization and viscosity: A study of molten basalts from the Piton de la Fournaise volcano (La Réunion island), Chem. Geol., 256, 242–251, doi:10.1016/j.chemgeo.2008.06.039.
[7] Patrick Bachelery,Jean-Francois Lenat,Andrea Di Muro,Laurent Michon(2016):
Active Volcanoes of the Southwest Indian Ocean,Piton de la Fournaise and Karthala,Springer,p178-179.