A Dish That Serves No One

From publisher blurb:

Gamma World 1E for 4-6 Beginning Characters

A settlement built upon the ruins of a military installation has recently come under bombardment from space junk falling from the sky. Almost daily, giant chunks of twisted and broken metal and parts of large vessels fall from the sky near or onto the settlement! Many people have been injured or have died. The village elders do not want to leave as they have finally established a productive farm near a drinkable water supply.

What is even more strange, however, is that a large object on the roof of a plateau building nearby has
begun moving recently, often several times a day. Are these two things related? Is the impenetrable plateau structure the source of the falling debris?