10:45 AM - 12:15 PM
[MIS21-P04] Estimation of lava flow behavior based on lava layer thickness of the pit of the Moon
Keywords:Moon pit, Yield strength, Lava flow layer, Lava temperature
[Introduction]
In the previous report (T.Honda(2022):MIS25-P01, Estimation of lava yield value and lava flow stop temperature based on thickness of lava layer at vertical hole outcrop, Japan Geoscience Union Meeting 2022) [1],by assuming a reasonable temperature dependence of the yield strength of the lunar lava, together with the lava yield strength(1310 dyne/cm2(=131Pa)obtained from the lava flow stop condition, an estimation was made to estimate the lunar lava flow temperature(950C to 1075C)when the lava flow stops(Fig.1 and Fig.2).
Here, we attempted a case study on the flow velocity, etc., by changing the lava flow depth that flowed through Rill A at the estimated temperature of the lava flow:950C to 1075C, and examined the behavior of the lava flow that flowed through Rill A. Furthermore,a case study was also attempted for the case of a higher lava flow temperature of 1200C.
[Summary of the results]
Tables 1 and 2 show the results when changing the flow depth of lava(flow thickness)from 600cm to 1000cm. The lava flow depth when the lava is actually flowing is unknown, but when the lava flow depth is 600cm, the flow velocity becomes 0 and the flow stops. When the flow depth is 1000cm, the plug flow thickness part is 600cm. At 950C, the Hedstrom number is on the order of 103 and the Reynolds number is low, so the flow is laminar. At 1075C,Reynolds number is high but Hedstrom number of the order of 104 indicates a laminar flow(Fig.3).
At 1200C, from the viscosity coefficient of Apollo-12, it is assumed to be 100 poise[2].
Yield strengths are set as one-tenth and one-hundredth of the value of the 1951 lava flow at Mt. Mihara[3], as 100dyne/cm2 and 10dyne/cm2. Tables 3 and 4 show the results. All flows are turbulent at the assumed flow depth (Fig.3). As a high temperature (>1200C)[4] has been proposed as the temperature at which magma rises and erupts from the lunar surface, long-distance lava flows with high temperature and high eruption rate are considered to be changed from turbulent to laminar flow by cooling, and then the lava flow stops.
References:
[1] T.Honda(2022):Geoscience Union Meeting JPGU(2022),MIS25-P01
[2] C.Meyer(2003):Mare Basalt Volcanism, NASA Lunar Petrographic Educational Thin Section Set,15
[3] K.Ishihara, M.Iguchi, K.Kamo(1988):Bulletin of the volcanological society of Japan,Vol.33, S64-S76
[4] M.A.Wieczorek et al(2001):Earth and Planetary Science Letters 185(2001)71-83
In the previous report (T.Honda(2022):MIS25-P01, Estimation of lava yield value and lava flow stop temperature based on thickness of lava layer at vertical hole outcrop, Japan Geoscience Union Meeting 2022) [1],by assuming a reasonable temperature dependence of the yield strength of the lunar lava, together with the lava yield strength(1310 dyne/cm2(=131Pa)obtained from the lava flow stop condition, an estimation was made to estimate the lunar lava flow temperature(950C to 1075C)when the lava flow stops(Fig.1 and Fig.2).
Here, we attempted a case study on the flow velocity, etc., by changing the lava flow depth that flowed through Rill A at the estimated temperature of the lava flow:950C to 1075C, and examined the behavior of the lava flow that flowed through Rill A. Furthermore,a case study was also attempted for the case of a higher lava flow temperature of 1200C.
[Summary of the results]
Tables 1 and 2 show the results when changing the flow depth of lava(flow thickness)from 600cm to 1000cm. The lava flow depth when the lava is actually flowing is unknown, but when the lava flow depth is 600cm, the flow velocity becomes 0 and the flow stops. When the flow depth is 1000cm, the plug flow thickness part is 600cm. At 950C, the Hedstrom number is on the order of 103 and the Reynolds number is low, so the flow is laminar. At 1075C,Reynolds number is high but Hedstrom number of the order of 104 indicates a laminar flow(Fig.3).
At 1200C, from the viscosity coefficient of Apollo-12, it is assumed to be 100 poise[2].
Yield strengths are set as one-tenth and one-hundredth of the value of the 1951 lava flow at Mt. Mihara[3], as 100dyne/cm2 and 10dyne/cm2. Tables 3 and 4 show the results. All flows are turbulent at the assumed flow depth (Fig.3). As a high temperature (>1200C)[4] has been proposed as the temperature at which magma rises and erupts from the lunar surface, long-distance lava flows with high temperature and high eruption rate are considered to be changed from turbulent to laminar flow by cooling, and then the lava flow stops.
References:
[1] T.Honda(2022):Geoscience Union Meeting JPGU(2022),MIS25-P01
[2] C.Meyer(2003):Mare Basalt Volcanism, NASA Lunar Petrographic Educational Thin Section Set,15
[3] K.Ishihara, M.Iguchi, K.Kamo(1988):Bulletin of the volcanological society of Japan,Vol.33, S64-S76
[4] M.A.Wieczorek et al(2001):Earth and Planetary Science Letters 185(2001)71-83