Numerical modeling and remote sensing to determine depths of lava tubes and buried cylindrical hot sources

Abstract

Estimating depths of buried lava tubes is important for determining the thermal budgets and effusion rates of certain volcanic systems. This research uses a laboratory experiment scaled to an observed lava tube system to measure the 3D temperature field surrounding a buried depth adjustable glass tube with hot honey flowing through it at varying conditions such as flow rate and temperature. Numerical techniques are used to model the laboratory experiment. The input parameters are then applied to non-laboratory situations. The surface thermal distributions from these models are analyzed to empirically derive a depth estimation function using regression techniques. This depth function is the first scaleable depth estimation technique which can be solved with remote sensing data alone. The minimum temperature, maximum temperature and width of a Lorentzian distribution, fit to a surface thermal transect, are used in the function to predict depth to the hot source. Sensitivity and error analysis of the function is carried out for depths ranging from 0.01 m to ±60 m with good results. The function gives accurate depth estimates of 0.2 m for extreme arctic environments, ±0.3 m for lava tubes and ± 55 m for subsurface coalfires.