<p>We examine 150 volcanoes and geothermal areas in the central, southern and austral Andes for thermal anomalies between the
years 2000 and 2010 from two different spaceborne sensors: (1) those automatically detected by the MODVOLC algorithm from
MODIS; and (2) manually identified hotspots in night-time images from ASTER (Advanced Spaceborne Thermal Emission and Reflection
Radiometer). Based on previous work, we expected to find eight volcanoes displaying thermal anomalies (Ubinas, Villarrica,
Copahue, Láscar, Llaima, Chaitén, Lonquimay and Chiliques). We document 35 volcanic areas with pixel-integrated temperatures
of 4 up to more than 100 K above background in at least two images, and another 16 areas that have questionable hotspots with
either smaller anomalies or a hotspot identified in only one image. Most of the thermal anomalies are related to known activity
(i.e. lava and pyroclastic flows, growing lava domes, fumaroles, and lakes) while others are of unknown origin or reflect
activity at volcanoes that were not thought to have surface activity. A handful of volcanoes exhibit temporal variations in
the magnitude and location of their temperature anomalies that can be related to both documented and undocumented pulses of
activity. Our survey reveals that low-amplitude volcanic hotspots detectable from space are more common than expected, based
on lower spatial resolution data, and that these features could be more widely used to monitor changes in the activity of
remote volcanoes. We find no evidence from ASTER or MODVOLC that the thermal anomalies were affected by six earthquakes with
<em>M</em><sub>w</sub> above 7 in our study area from 2000 to 2010, although the observations may not have been optimal to detect such anomalies.
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