There is always a possibility of othre tubes being in the area.
As in the great rift which in some areas is hundreds of feet
thick. Usually where I found one I would find more.
Although I had also thought that lava tubes were also formed
by air or if you will hot gasses being trapped in the flowing
lava and expanding. Then as the lava cooled eventually these
gasses escaped as lava tends to become porous as it dries and
at least with some I've seen, cracks like a huge dry lake bed.
Only with these crevasas dropping several feet. 10 to deepest
maybe 50 foot unless you count the area where either fissures
or water has eroded (or combination of both) thru hungreds
of feet of lava.
One must understand the great rift covers hundreds of miles
as it flowed acrossed southern Idaho traveling virtually all
directions at one time or another. Creaters of The Moon National
Monument is located with in this rift and has excellent volcanos
cinder cones and blow holes all through that area.
OOoOOps Sorry I guess I really was getting carried away.
Take Care
D2