[sarasmom]

Thank you very much for that information.
I live here, and did not know that!
It was reported today that the house was specifically inspected for sinkhole insurance reasons last September.
It was reported that there were no issues found.

Wouldn't a competent inspecter be able to spot the possible problem?
Or would this “man made void” not be easily identified?

[21twelve]

Ground radar might work. The photo upthread shows an electrical resistivity survey which is better for deeper voids and some soil conditions.

But I'm guessing that for an inspection they are just looking at visual things like vegetation changes, low spots, etc. The lack of extensions on the downspouts is a big no-no in sinkhole country. (Well - anywhere really).

I wonder if the guy is like me and a little bit lazy on maintenance and stuff. Could be he saw a depression getting worse in the backyard and didn't know the danger, and was thinking “I'll get around to filling it in some day”.