A FEW DAYS after Hurricane Katrina hit the Gulf Coast, I met a geologist in Waveland, Mississippi, whose parents' home had been moved hundreds of feet to the dead center of a railroad track. He worked in what was left, pulling out family photos and mementos as he talked about the sea-floor muck that had churned up into the 20-foot surges as they beat on the house.

Covered in brown mud, he explained his M&M theory. "Civilization is just the candy coating," he said.

I believe he was talking about the homes and businesses and roads that humans build. But in the days after Katrina, as photographer Larry Towell and I traveled the Gulf Coast, that candy coating was scraped away from normal social behavior, too. As law enforcement, public works, and the availability of gas broke down, the coasts of Mississippi and Louisiana mirrored the Mad Max movies I'd watched as a teenager.

The heart of the impact zone, near Pass Christian, Mississippi. Katrina pushed the Gulf of Mexico's waters far inland, producing destructive storm surges 25 feet high. (Larry Towell)

People were stealing fuel. Looting to survive became acceptable. Survivors with demolished homes broke into nearby dwellings for shelter. There was paranoia and fear, and we were in it.

Riding a Jeep loaded down with tanks of gas, jugs of water, military-issue meals ready to eat (MREs), junk food, and beef jerky, we headed down to see it all, traveling from Mobile, Alabama, along the coast of Mississippi to New Orleans, and farther south to Grand Isle, Louisiana.