Lava tubes often collapse during the final stages of an eruption as the lava begins to drain from the tube. If the lava drains from the tube while the roof is still soft and plastic, the roof may simply sink as it loses its support from the lava beneath. Another cause of collapse in lava tubes is the shrinking and cracking that occurs as lava cools. This cooling process can shatter the roof of a tube. Over long periods of time, the forces of erosion can also cause lava tubes to collapse.
Water is a major force of erosion.
As water seeps into cracks in the winter it repeatedly freezes and thaws. This freezing and thawing gradually widens the cracks. Bit by bit, the cracks grow wider, weakening the ceiling. Even the roots of trees and shrubs have been known to cause lava tubes to collapse. As plants begin growing in the protected cracks and crevices on the surface where soil and water collect, their roots can extend down through the roof of a tube.