Large cavities below yard

Q: As I was walking in my backyard I noticed a few low spots. I got a narrow
shovel and excavated. Two of the low spots revealed large cavities below the
surface, about 18″ deep and 6″ in diameter. What could cause this?

A: Put on gloves and reach into a hole to see how it is lined. My neighbor
observed the exact same thing and she came up with a handful of pine bark
lining her landscape hole. I think both situations were caused by small pine
trees being taken down during the home construction several years ago. Their
trunks rotted underground. Eventually, a small cavern was made and some of
the covering subsided to make a noticeable low spot in the ground. I have
pictures and descriptions of several kinds of landscape holes at bit.ly/GAholes.