Geological gain or loss of ground?

Question

Can someone tell me how to use geological maps to determine wether there has been a gain or loss of ground.

Answer 1

When you see a thrust fault you have "lost" ground (crustal thickening/shortening).

When you see a normal fault you have "gained" ground (crustal thinning/lengthening).

Answer 2

That's an odd question. Geologists, to my knowledge, don't measure gained or lost "ground" (are you talking about land above sea level?). The Earth's crust continually changes configuration, as Geomatic pointed out, but without you asking specifically what you're looking for, it's difficult to give a correct answer.

Geomatic's answer is certainly one way to measure what you're asking, but it's not the only way. Furthermore, there are varying scales at which you can measure.

For instance, if you owned land on one side of a meandering river, you may gain or lose "ground." If your land is on an accreting point bar, and the property boundary is the middle of the river, you could easily gain acres of land over the span of a human lifetime. Not many surficial geologic maps show individual accretions of riverbank deposits, so you may not be able to see that example on a map.

However, a larger scale approach would be to look at a bedrock geologic map of the seafloor--say off the coast of the Pacific northwest. The Juan De Fuca tectonic plate is being created at the Juan De Fuca spreading ridge, but is being destroyed relatively close by at the subduction zone on the western portion of the North American Plate. I suppose that could be called 'gaining' or 'losing' "ground."