Narusawa’s Lava Tree Molds

Lava tree molds are hollow lava formations formed around large tree trunks. They are created when lava flows through an area of trees. The lava engulfing a moist, cool tree has its temperature sufficiently lowered to leave a solid crust, but the tree within burns to ashes or bakes into charcoal, leaving a cavity. For a mold to form, the lava must be slow-moving, and there must be enough time for the mold to cool down.

The village of Narusawa is home to many lava tree molds, which were formed in the great eruption of Mt. Fuji in the year 864. In this area, visitors can walk around 12 lava tree molds––each one numbered and fenced off, to prevent accidental falls––and compare them. The sheer size and depth of these cavities speak to the impressive girth of the trees that once stood where the molds now are.

To have this many lava tree molds in such close proximity is comparatively rare even on a global scale. The molds have been designated special natural monuments by the Japanese government.