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Relating Thermal Inertia of Basaltic Lava Flows To Their Texture

Presentation #119.10 in the session Moon & Earth (Poster)

Published onOct 23, 2023
Relating Thermal Inertia of Basaltic Lava Flows To Their Texture

Remote sensing of planetary bodies provides invaluable data about their surfaces. Due to limitations in spatial resolutions, it is currently unable to distinguish the variety of surface textures of lava flows. The surface texture of a lava flow, including roughness and porosity, can inform on the emplacement and rheology of the flow. A property that could be used to distinguish between surface textures is thermal inertia, a measure of a material’s resistance to temperature change over time, specifically the diurnal (day-night) cycle. Thermal inertia cannot be measured remotely, but an estimate can be determined from apparent thermal inertia (ATI), calculated from the albedo and diurnal temperature difference. This project aims to relate the surface texture of several Holocene basaltic lava flows to their thermal inertia. The flows are Carrizozo, Paxton Springs, and Aden Crater, located in central, western, and southern New Mexico, respectively. Laboratory analysis of collected samples included petrography, geochemistry, density, heat capacity, thermal diffusivity, and monitored cooling experiments. The laboratory thermal inertia was compared with the field and satellite ATI, derived from thermal images collected in the field using a Forward Looking Infrared (FLIR) camera and Landsat imagery. Laboratory data suggests that thermal inertia could differentiate pahoehoe from a’a’ texture, but neither the field nor satellite data could distinguish between surface textures. While ATI is unable to distinguish between surface textures, it might be able to provide a rough estimate of sample porosity. The monitored cooling experiments involved heating cubes cut from each sample to 500°C and recording a time-lapse of their cooling with the FLIR thermal camera. The thermal budget of the samples was modeled by calculating the radiative and conduction fluxes. From the observed cooling history, we could calculate heat lost by convection and fit the model by adjusted the convection coefficient. For the New Mexico basalts the free convection coefficient ranged from 4.0 to 22 W/m2K. In addition to the New Mexico basalts, cooling experiments are currently being conducted for obsidian, rhyolite, pumice, and tuff for free and forced convection.

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