Narusawa Ice Cave: A Lava Tube and Natural Ice Store in Japan
Site at a Glance
- Rating
- 3.9
- Popularity
- Medium
- Country
- Japan
- Primary era
- Unclassified
- External website
- Open
- Eras represented
- Unclassified
- Civilizations
- Unclassified
- Site type
- Economic
- Remains
- Warehouse
On this page6 sections
History
Narusawa Ice Cave is a lava tube in Japan, formed during the large eruption of Mount Fuji in 864. It lies in the Aokigahara forest at the northern foot of the mountain, within present-day Narusawa Village in Yamanashi Prefecture. As the erupted lava cooled and hardened, hot gases and still-molten lava escaped through it. The remaining cavities developed into lava tubes, including the cave also known as Narusawa Hyōketsu.
Formation in the Mount Fuji landscape
The cave belongs to the volcanic landscape of Aokigahara, a forest formed in part by lava flows at the northern foot of Mount Fuji. Its position at approximately 1,030 meters above sea level reflects the high volcanic terrain in which the tube developed. The cave is one of three major lava tubes in this area, together with Fugaku Wind Cave and Lake Sai Bat Cave.
Ice storage and protection
The cave’s low temperature made it useful as a natural refrigerator. Grain was stored there, and ice was produced or kept inside the lava tube. During the Edo period, when Japan was ruled by the Tokugawa shogunate from 1603 to 1868, ice cut from the cave was sent to the shogun and his entourage in Edo, the former name of present-day Tokyo and the seat of the shogunate.
Ice continued to be used in the cave’s storage facilities during the Taishō period, the era from 1912 to 1926, and in the early twentieth century. This practice continued before electric refrigerators became widespread. On December 17, 1929, the former Ministry of Education designated Narusawa Ice Cave a Natural Monument of Japan, a legal status for natural features recognized for scientific, scenic, or other heritage value. Fugaku Wind Cave and Lake Sai Bat Cave received the same designation in 1929. The cave is also within Fuji-Hakone-Izu National Park.
Remains
Form and layout
Narusawa Ice Cave is a lava tube within the Aokigahara forest, reached by road from National Route 139 into the woodland. Its measured length along the route through the cave is 156 meters. The route follows two lobes in a roughly figure-eight arrangement, while the cave itself has a vertical, ring-shaped form. Its width varies from 1.5 to 11 meters, and its height ranges from 1 to 3.6 meters.
A stairway at the entrance descends into the lava tube. The deepest point is approximately 21 meters below ground level, and some passages have ceilings low enough to require stooping. These changes in height and the cave’s looping form reflect the irregular cavities left as the volcanic lava cooled and drained.
Ice and volcanic formations
An underground feature at the deepest level contains icicles and formations of basaltic lava, the dark volcanic rock created by cooled lava. Frozen water cones and other accumulations of ice occur within the cave. An ice-storage facility remains inside the lava tube, linking the surviving physical structure with the cave’s long use for keeping grain and ice.
