Lava tree molds are cavities or holes in the ground that mark where forests once stood in the path of an approaching lava flow.  

When lava flows through a forest, it swirls around tree trunks and quickly solidifies. Moisture in the wood and gas bubbles in the rocks form excellent insulation against instant incineration. As the level of the surrounding flows rises, the trees eventurally burn off while a thick crust forms on the surface of the lava flow. Though the trees disappear, their footprints in the lava remain.

As time has gone by, a younger generation of forest has developed on top of the new lava rock here. Perhaps one day in the future, during a new eruption, the process will be repeated in this same place again.