tsubame

Caves Around Mt. Fuji

In 864, Mt. Fuji erupted with lava flows running down the north slope of the mountain. The lava flowed into Lake Motosu and what was then known as Senoumi Lake. The lava flows divided Senoumi into three separate lakes, one of them becoming known as Saiko. The lava flows were very large and had many lava tubes. These tubes have since been discovered in the forests around Mt. Fuji. There are about 80 known caves created by the lava tubes. Cold even in summer, some of these caves were used as ice storage in the Edo Period. Water trickling down in late autumn and early spring supplied the ice makers with more ice.

The lava flow across the water at Lake Saiko

Last Sunday (September 17), my co-worker Basti and a German university student named Matthias and I went to Mt. Fuji with the idea of hiking up to the summit. Unfortunately, our timing was off. A typhoon passing over the Sea of Japan spread its soggy limbs over our way and made the weather difficult. We also weren’t aware of the off season bus schedule and were a couple of hours too late to catch the bus up to the starting point of the hike. Instead we went to a campsite at Saiko (West Lake) and stayed the night there.

We were rather fortunate with the courteous treatment we received. We got the tent for free since it was left behind by a previous camping party. We only had to pay the campsite fee. We also got the sleeping bags at half price – “Special price for foreigners,” we were told in English. We bought some firewood and after eating our bento dinners we got a fire going. The rain had reduced itself to a ultra-fine mist that was barely wet enough to dampen a tissue.

Basti wanted to keep the fire going so he got the idea to take branches cut from trees around the campground. The branches were stacked up near the entrance and we took turns going two together to bring back branches. We had quite a fire going for a while. When Basti ran out of cigarettes we went to ask to buy some from a nearby campsite. They gave him a pack for free. We insisted he would pay but they wouldn’t accept any money.

It was 1:30 by the time we put out the smouldering embers and went to bed. At six o’clock we were up again, though I could have stayed in the sleeping bag longer. The rain came down harder in the morning and sometimes was accompanied by a strong wind. We packed up but asked if we could leave the tent standing since it was soaked on the outside. Then we set out for the two-hour walk to the first of the caves.

Basti and Matthias (the one who looks like a professor in a poncho)

Koumori Ana, known as the Bat Cave in English, was our first stop. Don’t think the humour of the English name was lost on the Japanese. In the visitor centre were several posters advertising 1960s Batman movies – some in Japanese, some in English, and some in Italian and French!

A Japanese Batman poster in the Bat Cave Visitor Center

The cave itself was exciting. There were low tunnels with ribbed floors of ropey lava and open caverns. We had hardhats to wear, and tall Matthias was especially appreciative of his as it was his hat the made all the scraping sounds on the low ceilings. I saw two bats flying around inside but none hanging and sleeping. The forest outside was deep and thick with green and there were many mushrooms growing, but in many places big chunks of lava rock jutted up while in other places holes opened up in the forest floor.

A photo of the cave floor by Basti. You can see how the ropey lava flowed.

Our next stop was Ryuuguu Cave which was actually just a large gap in the rocks of the lava. One thing that was interesting was the cool air in the caves. You could see a mist hanging over each cave entrance where the humid forest air met with the cool air of the cave. Coming out from a hole and climbing up the stairs to the world above, we always felt the humidity and heat barrier that hung over the subterranean gateways.

A view from Ryuuguu Cave

The last two caves were Hyoketsu and Fuuketsu, the Ice Cave and the Wind Cave. Both were rather similar, caverns in the lava rock with areas where water dripped down and froze into ice pillars. The ice pillars were not much to see this time of year. Winter would be a better time to return. There were lots of interesting forms and shapes in the lava underground but after four caves I felt I had a pretty good idea of how it looked down there.

One surprise was when we reached the Ice Cave and I took of my plastic rain poncho and pack. I saw a large cricket-like insect sitting on my pack. I have seen these insects before in a cave in Saitama, sitting eerily up on the ceiling in groups. Since we left our packs in an office above ground I wondered how this cave-dwelling specimen managed to get on my pack. Either it was already in or near the office and hopped on or it was on my clothes from inside the cave and ended up on my pack and under my poncho.

The insect I found riding on my pack

The weather was clearing up by the end of the day but clouds still hung over the western sky and Mt. Fuji refused to reveal its peak. We were all tired by the time we got a bus back to the station. We didn’t get to climb the mountain but we saw some interesting things and I learned a little more about the volcanoes of Japan.

Note: Mt. Fuji erupted ten times between 781 and 1707 with additional non-eruptive activity during that period. Since 1707 the mountain has remained quiet. When will the next eruption be?

A sign for Hotel She Who along the road around Lake Saiko

Posted by tsubame at September 26, 2006 04:41 AM | TrackBack