Mysterious Yard Holes: Identifying Subsidence from Rotting Tree Roots

Q: We built a fire pit where previous owners had an above-ground pool. I tilled grass and covered with stone. A friend's chair leg fell into a 6-8 inch wide, 2-foot deep hole.

Since no earth is piled around the hole, my best guess: soil is subsiding where a tree root, branch, or trunk rotted under the original pool.

Frankly, I'd fill it with soil, pack it down, and be done.