Erosion of lava tubes

First stages of erosion

• 
  Cracks form in the roof of lava tubes.
• 
  The roof caves slowly in.
• 
  Parts of the roof fall down onto the cave floor, sometimes as a whole plate like here.

Disintegration of the roof

• 
  They leave a hole in the roof.
• 
  The hole expands and deepens.
• 
  A lava tube collapse trench is formed.

Remnants of lava tubes and ponds

• 
  In the end, after thousands of years, only the most resistant rock formations survive.