That picture shows what teenagers call a "donut." It's caused when you take your daddy's F-150 out and turn the wheels as far as you can and floor the gas pedal. The rear wheels spin out to form two large concentric outer rings and the front wheels form two smaller inner rings in the dirt, though sometimes one of the front tire rings overlapps one of the rear.
And you were there.
Took measurements.
Are 100% certain nothing heavy pressed 5" into the earth.
You could be right.
I wasn't there either.
However, having met Linda Moulton Howe and knowing her personality and tenacity for not publishing something she hasn't verified . . .
I'd say that the alternate explanation offered is full of teenage . . . farts.
I remember a morning spent raking out those exact type of rings in the High school parking lot after a heavy rain. I thought I was early enough not to get caught.