A Boundary Is A Line That Marks A Limit Of Space. So If You Live In A Neighborhood, Then There Would Be Fences, And That Would Be A Boundary line. It Marks Space And Divides Space. Hope That Helps.
Answer:
I think the answer us sulfuric acid
The rock layer on the bottom will decompose and either turn to sand, gravel, or blend in with the dirt (but most likely not the last one).
