Spectral analysis of Artemisia tridentata (big sagebrush), growing over the Cove Fort-Sulphurdale, Utah, thermal anomaly, has revealed vegetation health-related spectral variations that may be related to hydrothermal convection and permeable faults. This area is known for geothermally induced gas seeps. Reservoir pressure decreases in the past, resulting from production, may have increased boiling and the possibility of additional gases reaching the surface through permeable structures. Toxic gases and resulting soil acidification can have spectrally detectable effects on vegetation. Several vegetal-spectral anomalies were detected that are spatially related to geologic structures, suggesting that vegetal-spectral analysis can be a useful tool in geothermal exploration. (C) 2003 CNR. Published by Elsevier Science Ltd. All rights reserved.