Columnar jointing in baked soil, Flagstaff, Arizona


These structures are exposed in a roadcut (along highway 17) as you approach Flagstaff from the south.  When I first saw them, I thought I was seeing a thin basalt flow (quite oxidized, red!) that had deformed in way to produce miniature columnar jointing architecture.  One day I parked for a moment along the roadside and grabbed a few of these.  When I looked at them up close I realized that they didn’t look like basalt, nor did they have the ‘heft’ of basalt.  Our colleagues in the geo department at Northern Arizona University set me straight, and tried to make me feel good by saying that lots of geologists make the same mistake.  Regardless, I have my very own column! 

Age & Formation
A few million years or less in age.