Tumulus:
What looks like smaller hills are also found on the caldera floor. These seem to have been formed by the crust being pushed upward as still fluid lava flowed beneath it.
Raised terraces flanking the trail probably formed when huge blocks of Pu‘u Pua‘i slid into the lava lake. Slowly rafted away from the base of the cone by gushing lava, these “floating islands” came to rest here. Each time the lake level rose, they were covered by molten lava. When lava drained back into the vent, the blocks were again exposed as terraces standing above the surrounding lake surface.