Tom’s guide to the volcanoes of Japan #4: Kaimon

Kaimon-dake (開聞岳)

Kaimon-dake (開聞岳) is a near-perfect stratovolcano that is located right at the bottom of Satsuma in the south of Kagoshima prefecture. Its beautiful conical shape inevitably draws comparison to Mt. Fuji and indeed the term Satsuma-Fuji (”the Mt. Fuji of Satsuma”) is quoted by many when making reference to Mt. Kaimon. Rising 922m out of the sea, it takes a particularly fine atmosphere to view the mountain about 50km north in Kagoshima city, but as a measure of clean air I would argue no finer landmark exists!

As a volcano, Kaimon-dake has sat quietly for over a thousand years. The Chinese characters representing its name, 開聞, mean ’sea gate’, and one cannot help but feel that its location next the opening of Kagoshima Bay really does serve as the entrance to Japan. Fukada Kyuya, of Nihon Hyakumeizan fame, touches on this in his Kaimon chapter, describing the mountain standing “sentry” as the first land he saw when returning from Shanghai after the war. Incidentally, Ernest Satow (the influential British diplomat at the time of Japan’s modernisation) made the same trip some 80 years earlier, instead describing his first sight of Japanese land as “Iwô Shima (Iojima), a volcanic island to the south of Kiû-shiû (Kyushu)”. It goes to show you: however you approach these islands, you’re bound to see a volcano of some sorts sooner or later…

Geology and History:

When discussing Kaimon-dake, it’s impossible not to consider the area as a whole, geologically known as the Ibusuki volcanic field. Volcanism in this area began about 110 thousand years ago after, yes you guessed it, another huge caldera eruption. Based on these series of ‘volcano guides’ you can be forgiven for thinking Kagoshima has suffered from one catastrophic eruption after another because that is exactly the case! For reference I’ve pasted in the image below so as to get an idea of each location (again). The caldera in question here is the Ata (阿多) caldera located at the mouth of Kagoshima Bay. However, its position has also been interpreted further to the north in the middle of the bay, as ignimbrite deposits from the eruption appear to radiate outward from here. I don’t think the issue has been officially settled, but most descriptions seem to go with the first theory.

Major volcanoes and calderas of southern Kyushu (from GSJ)

The supposed southern extent of the caldera (marked 阿多カルデラ) can also be seen on the aerial photo looking south-east below. Various volcanic formations are marked on the area in Japanese, but Kaimon-dake to right is clearly visible. A second obvious feature is the large lake in the centre, which is named Ikeda Lake (池田湖). This is also a caldera, albeit smaller with a diameter of approximately 4km, and was formed after a big fissure eruption almost 6,000 years ago. Essentially the area zipped open towards the west and continued to so forming several maar volcanos – the largest being Yamagawa, now a small bay with its namesake village on the shore.

Arial photo of the Ibusuki volcanoes (taken from Wikimedia Commons)

The first eruption of Kaimon-dake itself is believed to have happened approximately 4,000 years ago. Up until the latest eruption in A.D. 885, 12 major eruptions have been identified from nearby deposits. As the volcano is near the sea, eruptions were frequently associated with phreatomagmatic events, where magma interacts with groundwater causing violent explosions. The last eruption (A.D. 885) was extremely large and the resulting disaster is often referred to as Japan’s Pompeii. Over 3 cubic kilometres of material was ejected from the volcano (not including the 2.3 cubic kilometres calculated for lava flows) and the village of Hashimure was buried under volcanic ash. Many of the dwellings were preserved as they were back in the Heian period and naturally the remains are considered an important archeological site. I can find little information in English on the web, but if you’re interested you can have a go or visit the archeological museum in Ibusuki city. ‘Tis a shame…

The A.D. 885 eruption is also interesting because, in fact, a new volcano was actually formed in the existing summit crater. It’s difficult to describe without a diagram (annoyingly I don’t have one electronically), but if you look at the top photo you will see a notch on the right-hand side of the mountain, just over 2/3 of the way up. The old stratovolcano basically exists up until that point, but onto this the huge and presumably lengthy eruption of A.D. 885 deposited a a mound of scoria and lava flows. Finally, to finish with, viscous (thick) lava was squeezed out like toothpaste onto the summit forming a dome and thus representing the cherry on the beautiful cake that is Kaimon-dake as we see it today.

Recent Activity:

Fumaroles on the beach near Yamagawa Onsen and Kaimon behind

Hmmm, well as I said Kaimon-dake hasn’t erupted for over 1,100 years, which might be a little disconcerting. It is of course classified as an ‘active volcano’, a classification that encompasses volcanoes that have erupted in the past 10,000 years, so I suppose we just have to play the waiting game. The authorities have a few seismometers and other monitoring equipment keeping an eye on Kaimon so I don’t think there’s anything to worry about. Present activity in the Ibusuki area is that of vigorous fumaroles at several places including Yamagawa, mentioned earlier. The underground hydrothermal systems are still very functional and this has been utilised by a power plant close to Ibusuki city – I’m not quite sure why they don’t make use if this power source more in Japan, but I’m told there is a lack of people willing to invest.

Of course, the other consequence of hydrothermal activity is onsens…

What to do at Kaimon (Ibusuki):

Shamefully, I have never climbed Kaimon-dake. It’s not particularly difficult, but all my trips to the area have been for other purposes or weather scuppered my plans on the days I wanted to go. Over on the One Hundred Mountains blog, Captain Fantastic describes a memorable trip to the summit – incidentally one of only two of Fukada’s Hyakumeizan that are less than 1,000m high (the other being Mt. Tsukuba I’m told) – so you can get an idea of the scenery from the top and also the lack of access from Kagoshima. The trains are really infrequent and currently the earliest you can get down to the hike is midday – outrageous! The other choice is a long bus ride, or you can wait for a few mates (like I’m doing) and rent a cheap car. Locally the mountain is renowned for being climbed on New Year’s Eve and catching the sunrise so perhaps I shall do that. (UPDATE: Conquered! See photos here! It really was spectacular.)

Kaimon-dake viewed from Lake Ikeda

Down at sea-level there’s plenty more to do and whenever friends visit, we always do a bit of a tour of the area. You can get a fine view of Kaimon from almost anywhere – even from Cape Sata on the otherside of Kagoshima Bay – but Lake Ikeda (池田湖) provides a nice foreground. Surprisingly it’s actually the largest lake in Kyushu, but I would say it’s more famous for being home to a monster named Isshii. Many large eels do inhabit the lake, but the parallels with Loch Ness are far too convenient! In the same area, Tosenkyo Gorge in Kaimon Town you can eat a special type of somen nagashi (flowing noddles). Along with onigiri, fish and the normal Japanese set, you get a bowl of somen noodles and empty them into a rotating stream of fresh, natural spring water. It’s probably a bit wierd for most foreign tourists, but in the summer heat, washed down with a cold beer, it’s perfect!

Isshii-san

Somen nagashi (with a little lunchtime sake)

Finally, Ibusuki is obviously renowned all over Japan as a hotspring resort. It attracts a lot of honeymoon couples and inevitably the bus tours as well. However, don’t let that put you off as visiting an onsen in Ibusuki is extremely unique and should not be missed! Unlike anywhere else in the world (except perhaps Iceland?) the abundance of onsen in the Ibusuki area means they pop up all over the place including the shoreline. As a result steam is literally bubbling out of the beaches, which in turn offers people a natural sand steam bath! Unless you randomly find your own, I believe you have two choices: the first is located on the shore of Ibusuki city next to a huge hotel, but if you have a car I would definitely recommend the Yamagawa Onsen a bit further out in the sticks. Not only is it smaller and a bit more rustic, after your bath you can also walk along the beach to look at the steam spitting out of the wet sand and cliff. There’s a sign saying keep out, but ignore that.

As for the sand bath itself, it’s very hot, but I’ve been four or five times now and love it. You’re told to lie down in what worrying looks like a coffin-shaped hole, after which the kind old ladies bury you until only your head is protruding. You can then fall asleep, or if it’s all too much, challenge your mates to see who can last the longest. Do your best: a local English guide also says they “are medically proven to be effective for your health” so consider yourself informed!

End note: Thanks once again to Capt. Fantastic of 100 Mountains for providing an English version of Fukada’s Kaimon chapter from Nihon Hyakumeizan.

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