This loop of GOES-8 6.7 micrometer IR ("water vapor") imagery shows the volcanic ash plume following the eruption of the Guagua Pichincha Volcano at 12:07 UTC on 07 October 1999. Although the IR difference product is normally used to track the motion of volcanic ash plumes, in this case the eastern portion of the ash plume was able to be tracked for a longer period of time on the GOES water vapor channel (past 19:00 UTC, versus about 16:00 UTC using the IR difference product). Due to the generally dry troposphere over northern South America on this day, the water vapor content within the ash plume was enough to create a discernible signature that could be followed as it drifted eastward across Ecuador toward Colombia and Peru.