Tuesday, March 4, 2008
JPL's Ashley Davies has published several papers over the last 11 years presenting his cooling model for terrestrial and ionian lava flows. I know this is a gross over-simplification (I'm sorry, Ashley) but basically the model inputs the near-infrared thermal spectrum of a hotspot and some appropriate physical parameters (initial eruption temperature, flow thickness, porosity, etc.), and outputs flow age, area, temperature, and flow rate (note to self: apparently I don't have his 1996 paper from Icarus on my laptop). The model has also been used to investigate eruption styles at different Ionian volcanoes.
This abstract by Davies and a cast of several covers a test on the model to see how well it reproduces the near-infrared spectrum of a lava lake on Mount Erebus on Ross Island, Antarctica. The test was needed in order to see how close to reality the model is when dealing with volcanoes on Io where we can't (at the moment) just go out and more directly measure the composition, temperature, and flow rate.
The authors imaged the Erebus lava lake (shown above) using an infrared camera and derived an integrated thermal spectrum from that data. The authors compare the model fits obtained from both one- and two-temperature fits to the Erebus data, similar to those performed by other groups on Galileo NIMS data, and from the Davies (1996) model. While the two-temperature fit modeled the lava lake well with respect to areal extent, the Davies (1996) model appears fairly robust when modeling the Erebus lava lake. One issue they do note is that in order to obtain this match, they used an eruption temperature that was 175 K warmer than what it actually is at Erebus. The authors promise further investigation on this issue and how it might affect the parameters they use for modeling Ionian lava lakes (since obviously eruption temperature is poorly constrained on Io).
Link: Validation of Volcanic Thermal Emission Models Using Ground-Truthed Data of the Erebus volcano (Antarctica) Lava Lake: Implications for Io [www.lpi.usra.edu]