The Chimneys are eroded remnants of a volcanic dike. There are petroglyphs on them somewhere, though I didn't see them.

Looking north from the south end of the Chimneys, 3/23/06.

Leafless Jatropha dioica and the Chimneys in the background, 3/23/06.

Grusonia schottii in the low desert near the Chimneys, 3/23/06. The low mountains in the distance are Burro Mesa.