Cold weather can crack underground pipes, often creating sinkholes that can trap trucks, gulp down cars and, as happened last week in Arlington, even swallow a cherished pet.

Sampson, a pit bull, and owner Marisa Peacock were out for a walk Wednesday in a park near their home when the 80-pound dog “just fell through the earth,” Peacock said.

Indeed, the ground in a grassy area near North Edgewood Street known as Rockwell Park had washed away after a 12-inch sewage main broke near Edgewood and First Road North, said Harry Wong, head of the county’s Bureau of Water, Sewers and Streets.

And, yes, the cold was the culprit, said Jessica Baxter of the county’s Department of Environmental Services.

Sampson’s leash was fastened to him in two places, suspending him far down in the nether world. “It was scary,” Peacock said. “There was a lot of water.”

Shouting for help, she hauled and Sampson scrambled. Finally, she said, he got his paws on the rim and then was out.

Peacock said she was “so fortunate that we were unharmed,” in comments that were posted first on the ArlingtonNow Web site. She was later reached by The Washington Post.

Authorities said Friday that the area had been cleaned and repairs were underway.