A.D. 1064? A Pilot Study of Archaeological Tree-Ring Samples to Search for Visible Evidence of the Eruption of Sunset Crater Volcano, Northern Arizona (TR2009-3) (PDF)
In 1958, Terah Smiley proposed that Sunset Crater Volcano erupted in A.D. 1064 based on morphological changes in a small set of tree-ring samples recovered from the prehistoric site of Wupatki in northern Arizona. This date has since become highly entrenched in the geological, archaeological, and dendrochronological literatures, as well as in popular accounts of the eruption.
The present study analyzed 39 dendro-archaeological tree-ring samples from the general Wupatki and Sunset Crater National Monument areas to ascertain whether other samples contained the same signature observed by Smiley, or whether an alternative date could be posited. Significantly, our findings strongly suggest an eruption date for Sunset Crater Volcano sometime between A.D. 1080-1090, and most likely in the five year period between A.D. 1085-1090. As Smiley observed, some sort of impact to trees in this area did occur in the A.D. 1060-1070 period, but the data suggest that this was the result of a relatively minor and localized event, possibly confined to the Medicine Crater/Medicine Valley area, which would have been one of the closest pine and fir tree source areas to the site of Wupatki.