La Caldera, an enormous pit/sink in the Sierra de El Abra of Tamaulipas. Peter Sprouse photo, 1989.

"Fin karst" in the Selva Ocote, west of Tuxtla Gutierrez, Chiapas. Peter Sprouse photo, 2001.

The "Black Hole", now known as Pozo Chuzo, southwestern Sierra Australia, Coahuila. Peter Sprouse photos, 1999.

Dramatic folding in western Coahuila. Peter Sprouse photo, 1999.

Laura and Bev staying cool on the tarmac in Cd. Victoria, Tamaulipas. Peter Sprouse photo, 1999.  

Sotano del Barro, Queretaro. Peter Sprouse photo, 1989.