Posted By Mike Falk on 2/8/2009 at 1:28 PM

Subsidence is more common than many may realize. USGS Fact Sheet-165-00 cites several examples and causes across America.

Subsidence due to ground water pumping.

Subsidence due to sinkholes and evaporative rock.

Simpler types of vertical movement are evidenced by the age-old axiom to not place bench marks in highway side slopes.

Another thing to consider would be to ask yourself why NGS adopted the NGS 3-D Monument