Yajiyagama Cave: telling geologic time and human history

Okinawa, Japan’s 47th prefecture, is different and distinctive from the Japanese mainland in myriad ways relating to its location and geology as well as its people and their unique cultural history. A surprising place to explore some of those differences is Yajiyagama Cave on Kumejima island, about 100 kilometers west of Naha.

Yajiyagama, once the site of an underground river, is the largest limestone cave on Kumejima. It is about 800 meters long and about a third of it is open to visitors. It is also an ancient mortuary site where many people say they can still feel the spirits of those ancient ancestors who were laid to rest in the cave.

Although the cave is open to visitors, as it is a grave site and has no electrical lighting, it is advisable to book a guide from Hotaru-kan, a nature center first established to protect the habitat of Kumejima’s fireflies (plentiful in April and May) and now also providing information on various flora and fauna of the island and its coastal waters. The guide will provide gum boots (to prevent tracking bat guano away from the cave floor), a hard hat and a flashlight as well as fascinating explanations (limited English).

The guide explains both the geology of the cave and the death rituals that led to the cave being used as a mortuary site. Out of respect for the dead, our guide began with the latter.

Although the practice has now ceased, it was once common pratice on Kumejima for the bodies of the dead to be left out in the open so that the bones could be cleaned by scavengers and the elements. The bones were then collected, placed in a large ceramic pot, and put into the cave. Studies have shown that a single pot often contained the bones of two or even three individuals, although I’ve yet to find an explanation for that practice.

Usually a single spot in the cave, near its mouth, was used by a single family or community. Often a square stone dais was built and pots lined up on top of it, or an area was delineated by stones and the pots placed inside. In other cases, several pots would be placed together in natural niches in the cave walls. Unfortunately, most of the pots have been broken (vandals?) and the bones lie scattered on the ground. Presumably other pots have been removed to other locations for safekeeping.

The guide also explained that a prayer or moment of silence when entering and leaving the cave is appropriate because of the cave’s role as a cemetery.

The large mouth of the cave through which we entered is actually the site of a cave-in. The morning light made the cave walls glow and once we entered we could also see a small hole above us where a watercourse had once poured in.

The passage quickly narrowed and we walked into darkness, working our way along what felt like a narrow corridor before emerging into a larger chamber where our flashlights revealed all manner of Speleothem (stalactites, stalagmites, and columns) formed as water seeping through the earth above carries minerals into the cave. A pathway through the cave was marked off, making it easy to walk through. At one low spot that tends to fill with water in the wet season, there was even a catwalk.

To help us better grasp the age of this cave and its formations, the guide explained that it takes about fifty years for a stalactite “straw” to grow a single centimeter. He also explained that sometimes after stalactites and stalagmites have grown together to form a column, the column is split by an earthquake, leaving a seam or even a gap in the middle.

One particularly interesting formation, where water has dripped in along a fissure, creating a line of conjoined stalactites, is known as a curtain or drapery.

We also found tiny pools known as rimstone dams. These are shallow pools of water formed as calcite deposits left by evaporating water create pool walls. Large versions of these pools can be found in various locations around the world (eg, Yamaguchi, Szechuan, and Turkey), but here the rimstone dams were Barbie doll-sized, or even smaller.

Besides the spirits of long-dead ancestors, the cave is also home to a number of living creatures, including crickets, long-legged centipedes, sea roaches, snails and land crabs. Perhaps more intimidating are the bats and habu, Okinawa’s indigenous poisonous snake. Fortunately, we met no snakes and saw only a few small bats, weather conditions having driven the rest deeper into the cave to an area that is off limits. Snails, crickets, and centipedes were the only other fauna we could see.

Our cave exploration stretched from the mouth created by a cave-in to the site of another cave-in, open to the sky and feeling very other-worldly. Although the cave continued, entry beyond this point is prohibited.

To get out of the cave, we had to reverse course and go back the way we had come, giving us a chance to see more formations in the eerie light of our flashlights.

Yajiyagama cave was geologically fascinating with the added interest of its ancient human connection. Without a visit, I could not have understood this unusual mortuary practice.

© 2022 Jigsaw-japan.com and Vicki L. Beyer
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