Cm to 10s cm 7 pahoehoe toes entrail pahoehoe 8 ropy

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Unformatted text preview: ) 7 Pahoehoe Toes Entrail Pahoehoe 8 Ropy Pahoehoe Active A’a Flow 9 Pahoehoe & A’a P a h o e h o e i s o n ly o b s e r v e d in r e la tiv e ly lo w v is c o s ity la v a s Basalts and rarely andesites, never dacites or rhyolites. Suggests viscosity is a factor P a h o e h o e a n d a ’ a l a v a s o fte n o c c u r o n th e s a m e v o lc a n o ; in d e e d p a h o e h o e f lo w s c a n tr a n s itio n to a ’ a . (But a’a never transforms to pahoehoe). (But W h a t fa c to r s d ic ta te th e s u r fa c e m o r p h o lo g y ? Obviously, composition & viscosity can’t be the sole factors. Transition from Pahoehoe to A’a 10 Pahoehoe to A’a Transition Tr Σ surface emissivity S tensile strength κ thermal diffusivity ε extension before failure σ Stefan-Boltzman Constant T temperature ρ density cp heat capacity Energy supplied to break the crust vs rate at which crack Energy can be healed is critical f...
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