TEMPERATURES AND BEHAVIORS OF LAVA LAKES FROM FIELD OBSERVATIONS AND COMPARISONS WITH IO

Field remote sensing observations of lava lakes with portable, handheld, low-cost, near-infrared imagers are revealing new aspects of their temperatures and behaviors and are providing comparisons with lava lakes on Io. Observations of the Marum/Mbwelesu lava lake in the Vanuatu archipelago in 2014 reveal a highly active, vigorously erupting lava lake. Active degassing and fountaining observed at the ~50 m lava lake led to large areas of fully exposed lavas and rapid (~5 m/s) movement of lava from the centers of upwellings outwards to the lake margins. These rapid lava speeds precluded the formation of thick crust; there was never more than 30% non-translucent crust. Temperatures were measured with a calibrated handheld camcorder as high as 1022°C, consistent with basaltic temperatures. At Kilauea, skylights, which have some similar thermal behaviors to lava lakes, had brightness temperatures of 1210°C and 1270°C and showed brightness temperature distributions consistent with most rapid flow at the center. Observations of the Erta Ale lava lake, Ethiopia in February 2011 revealed a fountaining lake with a peak in maximum brightness temperatures at 1164°C, consistent with previous studies. Steep temperature gradients were observed across centimeter-scale distances between the highly exposed fountain and cracks and the much cooler lava lake surface and crater walls. Temperature distributions in the lava lakes were different from each other – that for Vanuatu was much broader than at the more quiescent Erta Ale lava lake, which is attributed to the highly exposed nature of the rapidly circulating lake. All lava lakes, including those on Io, are confined, persistent and high-temperature; however there are subtle differences, such as their overall levels of activity, that are evident in the thermal remote sensing and that could be observed at much lower resolutions by telescopes and spacecraft at Io. Many of Io’s lava lakes exhibit similar behavior of gas emission, rapid overturn and fountaining, and reveal an active world that merits ongoing, closeup study.