Living and Cooking Potatoes in a Dormant Supervolcano: Big Pics

Mar. 3, 2010 -- The last thing we would have expected to learn about food in Japan is an unusual way of cooking sweet potatoes. But the inhabitants of the tiny village on the shore of lake Unagi are not only effectively living in a volcano, but also put the volcanic gases rising to the surface in their back gardens to good use: they use them to steam-cook vegetables.

Very few foreigners venture to the volcanically active Satsuma Peninsula at the southern tip of Japan (pictured above is Mt. Kaimon). Had the weather been more suitable for viewing the spectacular eruptions of nearby Sakurajima volcano, which was the main focus for our small group of volcano photographers this past January, we would never have discovered the strange treasures of the Unagi crater.

The bottom of Satsuma lies in the massive volcanic Ata Caldera which was formed by the eruption of one of a whole series of supervolcanoes in southern Japan about 100,000 years ago. Smaller eruptions have occurred in more recent times, one of which forming the Unagi explosion crater about 5000 years ago.

Whilst driving around looking for volcanological features, we ventured across a small country road which fortuitously took us right into Unagi crater over a low point in its rim. We continued to the tiny village of Unagi, which consists of about 50 houses tucked in the northeast corner of the crater by the edge of the lake. As we drove, we noticed plumes of steam rising from various points along the road and even out of the small gardens and yards behind houses.

The Japanese adore geothermally heated Spas; there's one even in this tiny hamlet. But the idea of building a whole village in a fumarole field seemed at best odd, and the simple concrete structures which had been built around many of the steaming vents were even more puzzling.

I poked my head over a wall to get a closer look at the source of one of the plumes, and was startled to find two Japanese women fussing over a package laid on top of the vent.

In the package – basically two sheets laid over the top of one of the concrete-encased fumaroles – were freshly-cooked sweet potatoes. Basically, the women were using volcanic outgassing as a kind of large steam-cooker. Picture a visitor in Yellowstone National Park hopping out of their RV and boiling hot dogs in Old Faithful. Only the people of Unagi make their permanent homes on top of this active volcano.

Armed with not a word of Japanese, but a big smile, I walked around the wall and signaled that I would like to take a photo. Soon all three of us were invited to try the potatoes. I had expected a possibly sulphurous, rotten-egg taste, yet they were perfect.

Whilst boiling food in hot geothermal waters has been documented in a number of places, I have never before heard of steam-cooking on a fumarole. Japan is a country full of surprises for the foreign visitor.

The geothermal activity in the area suggests that magma remains relatively close to the surface and that future eruptions may be possible. Indeed, we encountered scientists who were measuring fumarole temperatures in Unagi village. A significant increase could serve as a warning to the villagers that renewed activity could occur.

Many people indirectly use the geothermal energy for cooking in a more conventional way, since the Yamagawa Geothermal Power Station located about 5km south of Unagi provides many of the local homes with power.

Images and text by Richard Roscoe, guest blogger for Discovery News. Dr. Roscoe is a microbial geneticist. He devotes much of his spare time to the study and photographic documentation of active volcanoes and penguins, and is the creator of Photovolcanica.com.