Moisture = Mold
Moisture and organic material, e.g. wood, usually results in wood. Just like the wood under this house.
Wet Nasty Crawl Space
Signs of excess moisture were easy to identify.
Problems Get Worse
The pier just behind this pile sunk into the moisture ground. Rather than address the moisture problem in the crawl space, some added a homemade pier (that will also sink into the same moist soil).
CleanSpace Liner
The earth and foundation walls were covered in CleanSpace liner to prevent moisture vapor from the earth from reaching the subfloor of the home.