SINTER MORPHOLOGY AND THERMAL INFRARED IMAGERY: A DUAL APPROACH TO TRACKING HYDROTHERMAL CHANGES AROUND OLD FAITHFUL GEYSER, YELLOWSTONE, USA

Abstract

Geysers are among the world’s most dynamic geothermal features. Our research, combining Scanning Electron Microscopy (SEM) with Thermal Infrared (TIR) imagery, demonstrates that Old Faithful Geyser in Yellowstone National Park, USA, varies at time scales well beyond eruption intervals. In 2015, we collected 13 siliceous sinter samples from the sinter apron surrounding Old Faithful Geyser, Yellowstone National Park, USA. These were the first sinter samples to be collected in 22 years from this area. Samples were examined using a Scanning Electron Microscope (SEM) to observe the sinter morphology. SEM results indicated three samples experienced on-going deposition of opal-A silica, while three other samples revealed intermittent deposition of opal-A silica. Four samples displayed mild, moderate or aggressive dissolution features indicating post-depositional overprinting via acidic steam condensate. One sample indicated both intermittent deposition of opal-A silica and dissolution textures. A further two samples revealed the sinter was altering to clay. We then compared the SEM information with calibrated and georectified 2007-2012 airborne night-TIR images. This dual process identified that samples in a northeast-southwest alignment have significantly higher ground temperatures than those indicated in the airborne night-TIR images. The combination of these unique samples with the publically available 2007-2012 airborne night-TIR images has provided useful information on the changing hydrology of the area surrounding Old Faithful Geyser.