Application of the Landsat Thematic Mapper to the identification of potentially active volcanoes in the central Andes

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Landsat Thematic Mapper (TM) images have been used to make the first comprehensive study of the Central Andean volcanic province (∼ 14°S–28°S), one of the world's largest zones of active volcanism. More than 60 major volcanoes have been identified as potentially active, whereas only 16 had been previously cataloged. Most of these are large, composite cones, up to 6000 m in height, some of which threaten nearby settlements. Apart from its consistent coverage, the chief merit of the Landsat TM in making this study has been spatial resolution provided by the 30 m pixel size. This has been particularly important for the recognition of subtle glacial morphological features such as valley and terminal moraines which can be used to determine relative ages of the volcanoes. On the TM images we have classified a volcano as potentially active if it has: i) a well-preserved summit crater; ii) pristine lava flow texture and morphology; iii) flank lava flows with low albedo; and iv) evidence of post-glacial (< 10,000 years) activity. Where possible, these data are supported by field observations and published reports. The spectral observations and published report. The spectral capability of the TM has been valuable in addressing specific problems, such as the distribution of different lithologies in volcanic debris avalanches. The short wavelength infrared sensors (TM Bands 5 and 7) have been used to provide well-constrained temperature and size estimates of volcanic thermal phenomena such as lava lakes, fumaroles, and domes. The thermal band (TM Band 6) has been useful only in measuring temperatures in crater lakes.