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[MIS25-P01] Lava temperature estimated by lava yield strength obtained from the pit of the Moon
Keywords:moon pit, lava flow, yield strength, lava temperature
[Introduction]
The thickness of the lunar lava flow has been conventionally estimated from the outer appearance of the lunar lava flow, and the lava yield strength is obtained as 4000 dyne/cm2 (1),and 1000-2000 dyne/cm2 (2).On the other hand, the lunar vertical holes were discovered by Haruyama et al (3 - 5), after then, the cross section of the vertical hole was imaged by LRO, and the approximate lava layer thickness estimated from the layered cross section was reported by Robinson et al (6). Here, the yield strength obtained from the vertical hole is compared with the yield strength obtained from the outer appearance of the lunar lava flow. Then, the lava flow temperature when the lunar lava flow stopped is tried to estimate.
[Lava yield strength estimated from lava layer thickness and slope angle of the cross section of the moon vertical hole]
The layered lava (Fig. 1) in the vertical hole cross section of the Marius Hills Hole (MHH) consists of a lava layer with a thickness of 4 m to 12 m (6 m on average) (Robinson (6)). Here, the average thickness is H = 6 m and 0.31 degrees (Greeley (7)) is used as the inclination angle α in region Rille-A, The yield strength:fB = ρgHsinα = 1310 dyne / cm2 (Honda (9)) from the lava flow stop condition (8) of simple flow is obtained. Here, the density ρ = 2.5 g / cm3 and the surface gravity g = 162 cm / s2 are used. This value is close to the yield strength obtained from the outer appearance of the lava flow : 1000 dyne / cm2. The issue is whether the lava flow seen from the lava layer cross section can be judged by cross-section observation as simple flow, compound flow, or inflated flow.
[Lunar lava yield strength and lava flow stop temperature of the moon]
It may be possible to estimate the temperature of the lava if the temperature-dependent equation of the lava yield strength is obtained. As an example on the earth, Ishihara et al. (10) presents the yield strength temperature dependence equation on the 1951 lava flow of Mt.Mihara: logfB = 13.67-0.0089 θ. Where θ is the temperature in degrees Celsius and fB is dyne/cm2. Table 1 shows the relationship between the 1951 lava flow temperature and the yield strength of Mt. Mihara together with the viscosity coefficient (11,12). There is no temperature-dependent equation for the lunar lava yield strength, however, the viscosity coefficient (13) of the lunar lava collected by Apollo-11,12 is one tenth of the viscosity coefficient of the earth's basaltic lava. In some cases, it may be one-hundredth. The lunar viscosity coefficient (13) is about an order of magnitude smaller than the 1951 lava flow of Izu Oshima Mt.Mihara shown in Table 1, so it is assumed that the yield value is also an order of magnitude smaller. The yield strength temperature-dependent equation with the constant of 13.67 for the equation logfB = 13.67-0.0089θ is changed to 12.67. The yield strength temperature-dependent equation with the constant changed to 11.67 is also used, by assuming that it will be further reduced by two orders of magnitude. The results are shown in Table 2. The estimated lava flow stop temperature for the lunar lava yield range of 1000 to 4000 dyne / cm2 is around 1000 ° C as shown in Table2② and③.
[Conclusion]
According to virtual data based on lava flow of Izu Oshima Mt.Mihara 1951, the simple flow stop temperature of lunar lava is estimated to be around 1000 ° C. Temperature-dependent data of the yield strength of lunar lava can be obtained from synthetic lava or sampled lava in advance. In any case, it is desirable to obtain more accurate data on the stratified structure and thickness of the lava cross section, the chemical composition, and the inclination angle of each layer of the lava cross section by exploration.
References:
(1) G.Schaber(1973): Proc.4th Lunar Science Conference, 73-92
(2) H.J.Moore and G.G.Schaber: Proc.Lunar Sci.Conf.6th,pp101-118,1975
(3)J.Haruyama, et al(2009): Geophysical Research Letters, Vol.36,L21206,2009.
(4)J.Haruyama, et al(2010): 41st Lunar Planetary Science Conference,Abstract 1285,2010.
(5)J.Haruyama, et al(2012): Moon,Chap6,pp139-163,Springer,2012.
(6)M.S.Robinson, et al(2012): Planetary and Space Science 69,pp18-27,2012
(7) R.Greely(1971):The Moon, Volume 3, Issue 3, pp.289-314,1971
(8) G.Hulme(1974): Geophys.J.R.Astr.Soc.,Vol.39,pp361-383,1974.
(9)T.Honda(2017): JPGU(2017),SVC50-05
(10)K.Ishihara et al(1988):Kazan,SPCL 2,Vol.33,S64
(11)T.Minakami(1951):Bulltin.ERI,Univ.Tokyo 29,487
(12)T.Minakami,S.Sakuma(1953):Bull.Volc.14,79-132
(13)D.Williams,et al(2000):J.G.R,vol.105,No.E8,pp20189-20205
The thickness of the lunar lava flow has been conventionally estimated from the outer appearance of the lunar lava flow, and the lava yield strength is obtained as 4000 dyne/cm2 (1),and 1000-2000 dyne/cm2 (2).On the other hand, the lunar vertical holes were discovered by Haruyama et al (3 - 5), after then, the cross section of the vertical hole was imaged by LRO, and the approximate lava layer thickness estimated from the layered cross section was reported by Robinson et al (6). Here, the yield strength obtained from the vertical hole is compared with the yield strength obtained from the outer appearance of the lunar lava flow. Then, the lava flow temperature when the lunar lava flow stopped is tried to estimate.
[Lava yield strength estimated from lava layer thickness and slope angle of the cross section of the moon vertical hole]
The layered lava (Fig. 1) in the vertical hole cross section of the Marius Hills Hole (MHH) consists of a lava layer with a thickness of 4 m to 12 m (6 m on average) (Robinson (6)). Here, the average thickness is H = 6 m and 0.31 degrees (Greeley (7)) is used as the inclination angle α in region Rille-A, The yield strength:fB = ρgHsinα = 1310 dyne / cm2 (Honda (9)) from the lava flow stop condition (8) of simple flow is obtained. Here, the density ρ = 2.5 g / cm3 and the surface gravity g = 162 cm / s2 are used. This value is close to the yield strength obtained from the outer appearance of the lava flow : 1000 dyne / cm2. The issue is whether the lava flow seen from the lava layer cross section can be judged by cross-section observation as simple flow, compound flow, or inflated flow.
[Lunar lava yield strength and lava flow stop temperature of the moon]
It may be possible to estimate the temperature of the lava if the temperature-dependent equation of the lava yield strength is obtained. As an example on the earth, Ishihara et al. (10) presents the yield strength temperature dependence equation on the 1951 lava flow of Mt.Mihara: logfB = 13.67-0.0089 θ. Where θ is the temperature in degrees Celsius and fB is dyne/cm2. Table 1 shows the relationship between the 1951 lava flow temperature and the yield strength of Mt. Mihara together with the viscosity coefficient (11,12). There is no temperature-dependent equation for the lunar lava yield strength, however, the viscosity coefficient (13) of the lunar lava collected by Apollo-11,12 is one tenth of the viscosity coefficient of the earth's basaltic lava. In some cases, it may be one-hundredth. The lunar viscosity coefficient (13) is about an order of magnitude smaller than the 1951 lava flow of Izu Oshima Mt.Mihara shown in Table 1, so it is assumed that the yield value is also an order of magnitude smaller. The yield strength temperature-dependent equation with the constant of 13.67 for the equation logfB = 13.67-0.0089θ is changed to 12.67. The yield strength temperature-dependent equation with the constant changed to 11.67 is also used, by assuming that it will be further reduced by two orders of magnitude. The results are shown in Table 2. The estimated lava flow stop temperature for the lunar lava yield range of 1000 to 4000 dyne / cm2 is around 1000 ° C as shown in Table2② and③.
[Conclusion]
According to virtual data based on lava flow of Izu Oshima Mt.Mihara 1951, the simple flow stop temperature of lunar lava is estimated to be around 1000 ° C. Temperature-dependent data of the yield strength of lunar lava can be obtained from synthetic lava or sampled lava in advance. In any case, it is desirable to obtain more accurate data on the stratified structure and thickness of the lava cross section, the chemical composition, and the inclination angle of each layer of the lava cross section by exploration.
References:
(1) G.Schaber(1973): Proc.4th Lunar Science Conference, 73-92
(2) H.J.Moore and G.G.Schaber: Proc.Lunar Sci.Conf.6th,pp101-118,1975
(3)J.Haruyama, et al(2009): Geophysical Research Letters, Vol.36,L21206,2009.
(4)J.Haruyama, et al(2010): 41st Lunar Planetary Science Conference,Abstract 1285,2010.
(5)J.Haruyama, et al(2012): Moon,Chap6,pp139-163,Springer,2012.
(6)M.S.Robinson, et al(2012): Planetary and Space Science 69,pp18-27,2012
(7) R.Greely(1971):The Moon, Volume 3, Issue 3, pp.289-314,1971
(8) G.Hulme(1974): Geophys.J.R.Astr.Soc.,Vol.39,pp361-383,1974.
(9)T.Honda(2017): JPGU(2017),SVC50-05
(10)K.Ishihara et al(1988):Kazan,SPCL 2,Vol.33,S64
(11)T.Minakami(1951):Bulltin.ERI,Univ.Tokyo 29,487
(12)T.Minakami,S.Sakuma(1953):Bull.Volc.14,79-132
(13)D.Williams,et al(2000):J.G.R,vol.105,No.E8,pp20189-20205