From the BCRA Bulletin Number 13, August 1976

Authors note: This is an historical article, based on information available to me in 1976, much of which was translated from Japanese or taken down as handwritten notes at the time. It may contain errors of fact or transliteration of names. I am happy to publish corrections.


By Rob Kay


NHK TV interview, October 1975After graduating from SheffieldAkiyoshi cave entrance University, I was fortunate to live and work in Japan for a year from mid 1975 to 1976, taking up a post as an English teacher in a small private conversation school in Kure city, near Hiroshima. As an active member of SUSS - Sheffield University Speleological Society, I was also keen to get underground as soon as possible. An old copy of "British Caver" contained the key contact details, and on arrival I phoned Dr Tadashi Kuramoto at the Akiyoshi Dai karst museum, sixty miles or so to the south in Yamaguchi prefecture. He was very friendly, spoke some English, and invited me down for a weekend to tour the caves and meet his family and colleagues.


The study and exploration of caves in Japan was still relatively new in '75. Geographically and culturally isolated, speleologists in other parts of the world have to date shown little interest in the work carried out by Japanese cavers. Few western cavers have visited the country, and most of the information available has been published in Japanese.



There are no extensive karst regions in Japan. Instead, the limestones are separated by volcanic rocks into numerous small plateaus and lenticular blocks. These small areas are distributed fairly widely, except in Hokkaido, the northern island of Japan, often like beads on a string in obvious lines. Most of the limestones have been affected by major tectonic and volcanic events, and this has played a role in affecting cave formation. The best surface karst is to be found in the south-west of Japan around the Inland Sea; Akiyoshi Dai (plateau) in Yamaguchi Prefecture, Honshu Island; Hirao Dai on Kyushu Island, and Onogahara Dai on Shikoku Island.


In this part of Japan the limestones are Permian to Carboniferous, whereas in the north-east, Iwate and Fukushima Prefectures for example, they are Permian to Silurian, and generally forested. It is worth noting that there are few active sinks or potholes due to the lack of caprocks, thus most caves are either resurgences, dry, chambered fossil systems or shafts, the deepest of which is over 400 metres. Rainfall is heavy, between 100 and 400 cm p.a., and temperatures range between sub-zero in winter and 300-400C in summer, which, more than anything, is responsible for an erosion rate nearly as rapid as that in the tropics, and the creation of a distinctive 'karst of Japanese type'. Despite the smaller catchment, underground rivers' can be as big as those,say, in Yugoslavia, and there are a number of mature, canyon-type underground river systems.


Akiyoshi Dai

rice paddy gour pools in Akiyoshi caveThe plateau of Akiyoshi in the south of Honshu is regarded as the finest karst of Japanese type. About 130 km2 in extent, it contains over 200 caves, and is the home ground for both the Japan Speleological Society (JSS), and the Yamaguchi Caving Club, the largest in Japan, with over a hundred members. The plateau can be easily reached from Ogori by bus, and Ogori is about six hours from Tokyo by 200 km.p.h. bullet train.






On successive visits I descended about ten caves on the plateau. The three largest areriding across Akiyoshi Dai karst commercialised; Shuhu do, also called Akiyoshi do, Taisho do, and Kagekiyo do. Akiyoshi do is the most impressive, a big resurgence. The cave takes the form of a capital Y, with the main entrance at the bottom; the total length being over two kilometers. The trunk of the Y is a river passage up to 40 metres in height and 90 metres wide, the largest in Japan. The river flows between lakes and cascades. On the sides are some extremely fine rimstone pools. The left fork leads to a dry passage, decorated with various spectacular formations including "The Golden Pillar", some 8metre in diameter, 25 metres high and perfectly sculpted in form. The right fork is commercially undeveloped due to deep lakes and some rather steep climbing and can be followed between massive boulders to a sump. This has been dived and leads to a 200 metres extension. Beyond this is another siphon, and as the sink is some 10 kilometres away but with very little height difference it has been assumed that the river is more or less continuously sumped. see also: http://apike.ca/japan_akiyoshido.html


Abukuma do, Fukushima province JapanOther caves on the plateau vary considerably in character. The recently discovered Sugie do is a beautifully decorated stream cave over four kilometres in extent, reached by a ladder descent. Kagekiyo do is another resurgence, so big that a road has been made for some way up it, after which the water gradually becomes deeper. In a dry season the water can be followed upstream to the sink, about two kilometres away, but the vertical development is minimal. Other caves have a more vertical aspect; within a hundred metres of the Natural History Museum are two open shafts, one of which goes into a free 57 metre pitch, the other drops into the roof of Akiyoshi cave itself.


Nakao do and Taisho do are fossil systems with dry canyons like those in Ogof Agen Allwedd. The limestone is pure and Carboniferous.


Back up on the surface, you enters a strange new world. On the plateau surface dense pampas grass waves over your head; jagged grey pillars with a pattern of rills rise above to a height of three or four metres in some cases. There are shakeholes everywhere; the biggest ones being several hundred metres in circumference. Entrances, usually in the side of these, are numerous. There are numerous footpaths, as the area is a quasi ­national park and receives many visitors. To the north of the plateau the caves are reached by walking past flooded paddy fields, past peasants in their waders and colourful cotton smocks and straw hats, thatched wooden cottages, and steeply uphill through bamboo groves to the limestone.


The Natural History Museum was established in 1959 after a closely fought battle with the US airforce, who wanted the plateau as a bombing range. Amongst the small group of scientists working at the museum is Dr Ota, a geologist, whose research, including deep boring for rock core samples, has shown that the plateau was formed under reef conditions in a Paleozoic sea. By comparing fusilina fossils taken from the top of the limestone with those much deeper down, he has proved that much of the plateau has been totally inverted.


Dr Ota is also a keen caver, and was one of the two divers who first successfully passed the Akiyoshi do siphon.


Tadashi Kuramoto, a zoologist, is in charge of the underground laboratory, split between two chambers in a nearby, convenient cave with a small stream. Various experiments are carried out in large glass jars filled with various pieces of rotting wood, worms, lice etc. I was impressed by the large centipedes, six inches long, that infest the cave. Other common troglobites are the little cave shrimp, a species of semi-transparent fish with scales over the eyes, cave crickets, and bats, which exist in large numbers. Tadashi has carried out wide research into the Japanese bats, including successful ringing programs to study 0 migratory habits. Air temperatures in Akiyoshi caves are roughtly 150-17 C, so the wildlife proliferates rather more than Northern Europe; also there are more dry caves where guano can accumulate.


Other scientists from Universities throughout Japan have come to observe the karst geomorphology, flora, geology, paleontology and anthropology. Emperor Hirohito, a well-known marine biologist, has visited the Museum and Akiyoshi do, and his wife composed a short haku about the cave-creatures, demonstrating that cherry-blossom and maple leaves are not the only fit subject for poetry.


NHK TV appearanceThe Japan Speleological Society was founded at a general meeting at the museum in October 1975, thus reorganising the existing groups into a national speleological body similar, though on a more modest scale, to the BCRA. The meeting was covered by the press and the TV network, and an hour-long programme ensued later in November. As the only foreigner present, I was pleased to be able to make a few remarks, and to extend an invitation to the 1977 International Speleological Conference in Sheffield to cavers from Japan.


Other Karst Regions of Japan

The meeting was a good chance to make contacts with other regional and University caving clubs, particularly Masachi Kikuchi of the Japan Cavers Club, a Tokyo-based society. He invited me on the spot to join a weekend trip to Fukushima Prefecture in November. True to his word, I was met at Tokyo station one misty Friday afternoon a few weeks later. The next morning four of us, rather hungover from an extremely festive dinner-party in a Tokyo restaurant with the club the night before, proceeded to Fukushima by train past misty, forested mountains with the first winter snow gathering and falling as the afternoon grew darker.


Fukushima caves

After a night spent at a walkers' lodge, we rose early to visit two caves, Irimizu do and Abukuma do. ("do" means cave, and is pronounced as in money.)


Irimizu Do, JapanIrimizu do is a resurgence cave about 700 metres long. The stream is fairly small, but as the roof lowers steadily from the initial walking-sized passage, semi-immersion becomes reasonably inevitable. In some places the passage direction has clearly been influenced by dikes of a dark-brown, hard dolerite. It proved to be an easy and interesting trip.


After emerging we visited Abukuma do, discovered quite recently by my guides. The entrance is in a quarry, and the cave features some spectacular formations and a short stream which originates from a cave some 1.7 kilometres long not far away which, unfortunately, we did not have time to descend. I was pleased to make the acquaintance on this trip of Kazuaki Kishimoto, "Tarzan", (photo left) who spent three months caving in Brazil with three other members of the JCC last year, and Naofumi Itoda, who is planning a return trip in 1977. I was also interested to hear of the JCC's explorations in Korea.








Back in Hiroshima the next couple of months were cold and off-putting, and apart from a couple of trips to Akiyoshi, little caving was done. In February, however, a group of speleologists from Korea came to Japan for a two-week tour, and I joined the group on a trip to Hirao dai in Kyushu, the most southerly of the four islands of Japan.


Kyushu caves


Kishimoto Kazuaki and Rob Kay - a Ryokan in FukushimaThe limestone of Hirao dai is crystalline, and rather higher than Akiyoshi, being above 400 metres. The limestone pillars are thus rounded in shape, quite different from the angular pillars of Akiyoshi dai. Kyushu has many caves, the deepest being about 250 metres. We visited Senbutsu do and Ojika do. The former begins as a show-cave, but after three or four hundred metres of White Scar Cave type resurgence passage, the form changes into a tight rift above, with a body-sized rift containing the stream beneath. Three inlets enter from avens in the roof. Being the only possessor of a wet-suit, I pushed on to the apparent end of the system, where the streamway becomes too tight and sumps. Climbing upwards in the third inlet I located the higher-level phreatic tube utilised by the inlet stream. It sumped upstream under a flowstone barrier, which proved to be a straightforward 2 metre freedive. The passage, walking-sized, led invitingly on, but, inevitably, proved to sump around the first corner, in a rather awkward fissure. As support was rather unlikely from the boiler-suited crowd back in the larger passages I decided to call it a day.


Abukuma do in FukushimaOjika do proved to be an undemanding descent down a slimy wooden staircase into an open pit for about 30 metres, followed by a descending passage into a T-junction streamway. Upstream was sumped, downstream the passage descended over some cascades into a canal section which ended in a sump too. This part has been 'modified' by blasting for the occasional visitor, and is not particularly interesting, but the entrance pit is quite impressive and worth a trip. In both caves you can examine white pipeclay weathered out of the igneous rocks. Not so far away in Beppu, where an active volcano smokes like a slumbering dragon, and hot springs galore. On Fukue Island, N.Kyushu, are many lava-tube caves, some of which once formed a tube 1400 metres long, now opened to the sky in several places due to its proximity to the surface.


Iwate Caves


At the end of April I travelled north again, this time to Iwate Ken (prefecture) at the north-east tip of Honshu Island. The journey takes a full 20 hours, as the distance from Hiroshima is some 1600 kilometres. The group consisted of five or six men from the JCC and half a dozen from Akita Mining College CC, plus Sasaki, a local caver, and the seven days spent at Iwaizumi were fully occupied with caving and hydrological research. We stayed at a small caving hut used as a field centre by the JCC directly opposite to Ryusen do.


Eating sukiyaki in Tokyo with members of JCCIn the week that followed I managed to visit nine caves. Akka do (8 kilometres), the longest cave in Japan, was not visited due to access problems, but two trips were made down the Sigawatori/Tsubosawa system (2.7 kilometres) and one down Uchimagi do (3.2 kilometres) as well as several shorter but nevertheless impressive caverns and a rather unique pothole, Hadakagara no Ana (87 metres deep).


Tsubosawa no Ana, entered by a 55 metre free shaft high in a forested hillside, drops into a long, massive rift chamber. One way leads into a group of grottos containing elegant, snow white columns, helictites and speleothems of every description. The other leads into the rapids and deep lakes of the Sigawatori river, one of the finest sporting streamways in Japan, which we explored the next day. Parts were inaccessible due to high water conditions, but the parts we could reach were reminiscent of the Lancaster­Easgill master cave, with waist-deep lakes, fine formations, and numerous side-passages and ox-bows.


Hadakagara no Ana, a pothole, is hardly the sort of trip one takes for the health. The elevation is basically like a 'V'. The descent down a 1-2 metre diameter tube at between 450_900, in a shower of pebbles, is hair­raising enough, but is followed by an ascent, of over 85 metres, up a similar tube, made without aid. The cave involves chimneying all the way, and with very few ledges, so that a pebble or portion of chert, once dislodged, hits everyone in the party on its way down. At the top, two hours from the surface, there is a vocal connection to a small hole in the limestone barely 50 metres away from the entrance, which is situated at the head of a dry valley.


I explored Uchimagi do with Sasaki on our last day in Iwate. At the entrance we were surprised to encounter a large number of residual ice formations, curtains, mini-glaciers, and columns, which glittered brightly in our lamps. We moved over a tight high-level bypass and greasy traverse to drop into the stream, which we followed upstream until we reached a 20 metre waterfall which effectively barred further progress. Returning, we found Mr Sasaki's Konica camera, which had been lost the year before. Tearing off the rotten cover, we were amazed to find that the shutter still worked, and there was no sign of rust, though it was left a mere 30 centimetres from the stream.


map of limestone in JapanRyusen do, a show-cave, is famous for its deep lakes, in one of which a cave­diver died. (The only other caving fatality occurred this year on Hiroa Dai due to a fall.) These lakes are over 100 metres in depth, and their water somehow passes under a surface river to resurge in Ryusen Shin do, a couple of hundred metres away, on the opposite side of the steep valley. Ryusen Shin do (New Cave), is a small but beautifully decorated model show cave, carefully laid out by speleologists to ensure conservation of the delicate calcite floors, false-floors and speleothems, and includes a caving museum, with a waxworks Neolithic family, reproductions of cave paintings from France, USA and S.Africa, and a display of caving equipment. The cave is protected by clear plexiglass screens, so that the visitor can see but not touch, a feature that has succeeded admirably in its object and will probably be incorporated elsewhere. The cave was discovered in the course of a road-improvement project, and is own by the municipality of Iwaizumi.


Returning to Hiroshima past the tall, elegant cone of Mt Fuji, I was reminded that there, too, are a large number of lava-tube caves, up to 400 metres long.


Three major areas I have not visited are Okinawa, Niigata Ken, and Taishakudai. Briefly, Okinawa is sub-tropical, largely limestone, and contains thousands of caves in a thin, extremely friable, Quaternary limestone band. On Okinoerabu Island the Shoryu do ground water system has been studied by various expeditions, and despite its length, the cave is rarely more than ten metres from the surface, the stream flowing over an impermeable baserock. Niigata Ken boasts Japan's deepest pothole, Omi Senri Do, 405 metres deep, and it seems likely that deeper potholes may be found, as this region is remote and not well investigated. Taishaku dai has been well-investigated however, and the levels of five distinct terraces have been correlated with horizontal cave levels on the opposite side of the valley. As the ages of each terrace can be determined stratigraphically, it follows that the ages of these caves can also be determined with a fair degree of accuracy.


One of the single, most important discoveries has been in mammal paleontology, which has aided the determination of the relationship between Okinawa and the main archipelago of Japan. Extinct mammals found in main­land caves include Naumann's elephant, lion, moose, rhinocerous, giant deer, bear, antelope, wolf, pig and badger, in addition to animals still at large such as bear (a different type), monkey, whale and so on. These bones have been found in caves and fissures as far apart as Shiriya-zaki, the north­ eastern promontory of Honshu Island, Akiyoshi dai, Kyushu and Kuzuft (one of the most important as some finds are unique). As in Britain, many of these indicate the last glacial advance. Human remains are rather scarce, though Pleistocene man has been found as a result of quarrying in Shizuoka and the eastern part of Aichi Ken. The fossil mammals found in the Ryukyu Islands, including Okinawa, are different from those on the mainland, indicating to paleontologists that the Islands were already separate from the mainland in the middle or late Pleistocene age.



Caving in Japan has been a fascinating experience in several respects. Not the least of these is that it has enabled me to meet, talk and cave with many Japanese cavers, who have shown great patience, hospitality and friendliness in allowing me to join their trips and answering floods of questions in a foreign language. It would be impossible to name them all, but I owe particular thanks to Tadashi Kuramoto, who has taken greater pains to give me the best impression, to Yashinari Kawamura of Kyoto University, and to Kazumitsu Tokutomi for help with this article. Grateful thanks are also extended to Dr Ota and the Akiyoshi Museum for the photographs with this article.



Further Sources of Information


All the information about Japanese caves is published in Japanese. However, I would particularly recommend Kazumitsu Tokutomi's excellent hardback collection of colour photographs of Japanese caves. It can be obtained from Akane Shobo, Tokyo-To, Chiyo Daku, Nishikanda 3-2-1 Japan, under the title Shonyo Do Adventure, Kagaku no Album 30. Price ¥780 plus postage - roughly $4 US.  (nb historical prices true in 1976!) 


For further information, I would suggest writing to:

Speleological Society of Japan
2-4-1 Higashida, Yahatahigashi-ku, Kitakyushyu , Fukuoka 805-0071 JAPAN
Phone : +81-93-681-1011   FAX : +81-93-661-7503
E-mail info@speleology.jp