Lava pillars

Water that is trapped beneath the flow is heated and channeled upward through these gaps.

This cold water promotes rapid growth of the lava crust around the gaps.

After lava inflation ends and the eruption wanes, the molten interior of the sheet flow typically subsides leaving a series of "bathtub rings" along the sides of the pillars.

These rings are formed as the crust on the subsiding lava repeatedly adheres to and then breaks off from the pillar's sides.

Lava pillars may continue to act as fluid conduits for years after an eruption.