Plate 27. An eirght-foot cavity or “washout” in black shale immediately underlying the Culebra dolomite at 727 feet below land surface in the WIPP ventilation shaft. The photo shows the top of a corroded steel liner plate installed to prevent futher caving of the unstable shaft wall. Water can be seen dripping from the dolomite at right. (Photo by Lokesh Chaturvedi)