Column On Column Structures As Indicators Of Lava-Ice Interaction, Ruapehu Andesite Volcano, New Zealand

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Journal Article: Column On Column Structures As Indicators Of Lava-Ice Interaction, Ruapehu Andesite Volcano, New Zealand

Abstract
Lava flows of the Mangawhero Formation (ca. 15-60 ka) on Ruapehu volcano erupted during the last glaciation. In a distal flow lobe at Tukino, on the east side of the mountain, small secondary columns (10-20 cm thick) have formed on the sides of large, rectangular, primary (0.5-3 m thick) cooling columns. Thick (10 m+) zones of such small columns form a lateral and basal outer rind of the lobe. As they do not mark glassy zones of quenching, these secondary columns are interpreted as being formed by a second cooling event at temperatures below the boundary between the low creep and elastic regimes (~ 600°C) by rapid influx of copious amounts of water. Temperature drops deduced from extensional strains of the two sets of columns were used to gauge the viability of such a two-stage process. Absence of reliable data on andesite contraction coefficients was overcome by using a sliding scale to assess a large range of values. The estimates indicate that two-stage chilling is feasible. After flowing across relatively ice-poor terrain, the lava flow must have interacted with a valley glacier that provided water for further chilling the already formed primary columns and formation of the outer rind small columns. Given this evidence for lava/ice interaction, it is likely that prominent, thick flows elsewhere in the Mangawhero Formation may have been constrained to their ridge-top locations by ice conditions similar to those described by Lescinsky and Sisson (Lescinsky, D.T., Sisson, T.W., 1998. Ridge-forming, ice-bounded lava flows at Mount Rainier, Washington. Geology, 26, 351-354).

Authors 
K. B. Sporli and J. V. Rowland








Published Journal 
Journal of Volcanology and Geothermal Research, 2006





DOI 
Not Provided
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Citation

K. B. Sporli,J. V. Rowland. 2006. Column On Column Structures As Indicators Of Lava-Ice Interaction, Ruapehu Andesite Volcano, New Zealand. Journal of Volcanology and Geothermal Research. (!) .