Betsy screqamed out on the emergency channel:
While pulling weeds today my foot fell into a hole. I jumped back and
poked
around it finding it "hollow" underneath. I got the shovel and started
digging, and found a void about 2 feet wide and 1 foot deep. There is no
evidence of animal life in it, nor is there any debris.
snip
EGADS! PANIC! HELP!

It is probably (but not necessarily) the location of an old tree stump that
has now rotted away. Fill it in. Don't worry about it unless it
re-appears.

Austin