More Mole: Where is the "Defense?"

On one of those discouraging days of disappearing garlic, I was punching holes in the sticky soil with my long screwdriver, and injecting a squirt of stinky repellant. In many places, as I was moving along the rows, the screwdriver would almost disappear, either penetrating a tunnel or some kind of underground cavity in the soil. Then, toward the outermost five rows, I began to notice I was hitting some pretty solid feeling rocks. I stopped to rest for a moment, and as I looked around, I suddenly realized the mole was mostly moving up and down rows three and four. One or two plants from row five were gone, but that was all. Those outer rows had no gaps or missing plants. Was something going on underground, something I could not see from my above-ground perspective? Was there a hidden defense?
"Defense", in any endeavor, can never win "the game". We still have to score some points or make some gains. The garlic had been planted and was prospering, but without some defense, it was possible all could be lost. A good defense is critical to not losing.
A couple of months earlier during the soil preparation and tilling of the ground, I now remembered I had hit some stoniness, and every so often some rocks that the tiller couldn't even budge. But I really didn't pay too much attention simply because the tiller would prepare the upper 8-10 inches of soil, more than sufficient for the garlic to prosper.
Enter the Mole, but obviously at tunneling depths deeper than the tilled soil, and I hadn't been concerned with those depths, that is until Miryam Mole started the beginnings of a Moleville. Now my attention was sharply focused on those underground things!
Miryam the Mole appeared to have tried to probe and enter those outer rows, but she had stopped. Why? Perhaps, at those deeper depths there are underground rock or stone formations that even the most expert and determined Miryam couldn't bore through (much less try to move!).
Now wouldn't that be "neat" if the Defense had a formidable front line---The Rock---which Miryam the Mole could not move or burrow through! (Note: rocks on the Golan are volcanic in origin, roundish, very dense and heavy. They literally "rained down" in a cataclysmic and violent volcanic event, Sodom-like in fury, onto the Golan landscape. Those hot-rock showers can still be seen on the surface.)
So long before I (or Miryam the Mole for that matter) ever appeared on Zavitan Street, those rocks had been set in place by the Rock-Man in anticipation of this day. Now that is really impressive! Also, reassuring for the garlic and Baruch.