The Pleistocene-Holocene Uinkaret volcanic field is one of three active, largely basaltic volcanic fields in Arizona. The others are the San Francisco volcanic field near Flagstaff and the Pinacate field on US-Mexico border. This image clearly shows the track of basaltic lava flows that spilled into the Canyon damming the Colorado River. The red line shows the trace of the Quaternary Hurricane Fault in Whitmore Canyon. Image courtesy of NASA Earth Observatory.