tubes are created when lava hardens over the top of a main pahoehoe
lava flow or channel on the surface. The crust forms a ceiling over
the lava flow closing it in. There is usually a main lava channel
and some smaller lava channels form a lava-flow field. The lava tube
is made when the flow of lava stops at the vent of the volcano and
the lava tube drains. Long strings of lava drip from the top of the
lava tube and form lava stalagtites.