After Hurricane Katrina, the fanlike pile of sand, mud, and silt that formed near a breached levee was unique in the urban environment of New Orleans. Over the 7,500-year history of the modern Mississippi River delta, however, it was just another splay deposit. Author Darwin Spearing explains the geologic forces behind the formation of the delta, shedding light on the human struggle to control the powerful river that breaches its own levees and switches...