IDENTIFYING INFLATION CHARACTERISTICS OF LAVA FLOWS ON EARTH AND MARS

Inflation is recognized as an important process active during the emplacement of relatively slow-moving pahoehoe basaltic lava flows. In February 2009 we conducted a field study of the distal portion of the 1859 Mauna Loa lava flow on the Big Island of Hawaii, supported by funds from the Smithsonian Institution, in order to document both the topographic and textural attributes of the pahoehoe portion of the flow present nearly 50 km from the source vents high on the NNW flank of the Mauna Loa volcano. The distal pahoehoe portion of the flow displays multiple levels, which we documented with Differential GPS surveys, where discreet portions of the flow inflated to remarkably uniform levels during emplacement. The flow also has numerous inflation rise pits, as described by GPL Walker, where the flow inflated around an older portion of the flow that remained as the floor of a pit well below the inflation surface level; the margins of these pits typically display overhanging relationships that are not consistent with collapse but which are consistent with inflation of the flow around the pit. Distinctive surface textures are present on portions of the flow, which we believe are related to the emplacement of separate portions of the inflated flow. HiRISE images of certain lava flows on Mars display many of the topographic relationships that we observed on the 1859 flow, but identifying textural differences on Martian flows will likely require close-up investigation by a rover in order for there to be unambiguous identification.