These huge mushrooms were formed when lava flowed out from a crack in the forest that opened nearby and surrounded the trees, setting fire to the forest. Then it drained away back where it came from to leave these tree-moulds of the biggest trees.
Frozen lava flows have a mesmerising quality. They are so like water, with rapids and pools, and then you come across a crack and start to think about what lies beneath your feet. You find lava flows winding through forest, lava lakes in craters, lava in little rivers frozen in time and then, suddenly, the forest ends in a 20km lava field and you get a sense of awe at the sheer quantity of rock.