Figure1: With over 400 vents, the Springerville Volcanic Field in Arizona is  typical large volcanic field located on the margins of the Colorado Plateau in the western United States.  Most of the mapped vents formed between 2.1 and 0.3 Ma during volumetrically steady-state volcanism. Studies of vent distribution and timing have shown that rates of activity varied from cluster to cluster, suggesting that individual source regions for magma were localized and short-lived compared to the entire volcanic field. This idea is supported by geochemical trends. Vent symbols correspond to clusters, thick shading shows vent alignments, thin lines show faults.