lava tubes

[terracore]

Here's a strange question: Who "owns" a lava tube? If the entrance is on my property, do i own the tube until the property line? If this tube is 40 miles long, it probably goes under hundreds of different owners. Could somebody erect a barrier to keep others out of "their" portion of the tube? What if somebody's cesspool is uphill and is draining into "your" portion of the tube?