Doors and windows that fail to open and close properly may be early warnings. Cracks, however small, along mortar joints in walls and in pavements may indicate subsidence. The ponding of rainfall may be the first indication of actual land subsidence. One of the earliest effects at an incipient sinkhole is lowering of the water table. Turbidity in well water.
Water sometimes becomes turbid during the early stages of development of a nearby sinkhole.
However, if any of these observations are made in an area of known sinkholes and if roads or buildings are potentially at risk, the property owner should consider acquiring the services of an engineering geologist or a foundations engineer. If you find a newly formed or forming collapse sinkhole, please report it at once. Direct general inquiries to the Maryland Geological Survey. Always exercise caution when walking around sinkholes. D.C. Prepared by James P. Reger Permission is granted to reproduce this FactSheet so long as the name of the Maryland Geological Survey appears on the copy.