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Shimane: Japan’s ‘buried forests’ slept underground for 4,000 years

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A spiral staircase leads down to where a stump from a huge Jomon period cedar is on display. The trunks are shown at the Shimane Nature Museum of Mt Sanbe. The Yomiuri Shimbun

Shimane: Japan’s ‘buried forests’ slept underground for 4,000 years

About 40 “buried forests” have so far been discovered in Japan, forests that were buried in the ground due to such factors as volcanic eruptions.

The Sanbe-Azukihara Buried Forest Park in Oda, Shimane Prefecture, is a unique exhibition facility that contains large cedar trees from the Jomon period (circa 10,000BC to circa 300BC) standing upright in a dome 30m in diameter.

Located on the north side of the 1,126m Mount Sanbe, this exhibition space conveys the quiet but ever-present threat posed by volcanic eruptions and landslides.

Cool air caresses the skin as visitors descend the stairs into the cavern 13.5m underground. At the bottom, cedar trunks 12m high and 2m in diameter stand straight. Visitors exclaim, saying things like: “This is amazing” and “They’re so big.”

The giant trees were buried here for 4,000 years. “People who hear about this underground exhibit seem to imagine much smaller trees,” park guide Yo Mitomi, 73, said with a laugh.

Other nearby tourist spots include the Iwami Ginzan Silver Mine and Sanbe hot springs. The park isn’t conspicuous, but 70 per cent of its visitors come from outside the prefecture and many visit more than once.

First-time visitors have often heard about the park from friends who described it as a must-see when travelling in Shimane Prefecture.

Fumie Sakai from Osaka Prefecture was a second-time visitor to the park. She dropped by the facility with her husband on their way to her hometown of Misato in the prefecture.

“I came here a long time ago and wanted to see it again. It’s amazing that the trees here are as impressive as the famous cedars on Yakushima island, buried here with no one the wiser for 4,000 years. It’s something my home area can be proud of,” she said.

“A number of coincidences left a buried forest here,” said Tadashi Nakamura, 51, a staff member of the prefectural Shimane Nature Museum of Mt Sanbe.

When Mt Sanbe erupted in the Jomon period, a large amount of volcanic ash piled up, causing a major avalanche of debris. This flowed down a nearby valley, burying an entire area. It buried the Azukiharagawa river for about 500m upstream, mowing down trees the whole way, before coming to a stop close to these huge trees.

The earth and volcanic ash was more than 10m deep in the vicinity. Normally this would have been eroded by the river over time, but there was so much, it actually changed the course of the river, protecting it from erosion.

“Underground areas that contain a lot of water have little oxygen. This means microorganisms can’t break things down, which protected the buried forest,” Nakamura said.

The site was discovered in 1983 during construction work on agricultural land. The contractor that discovered the trunks reburied them and they were photographed by a local resident.

These photographs were seen by late Seiji Matsui, a Mt Sanbe researcher and high school teacher, who realized they were gigantic standing trees.

Nakamura took part in a survey the prefecture launched in 1998. “The colour of the cross sections when we cut them was as fresh as living trees. This colour darkened in about 10 minutes,” he said, describing how the flow of time resumed when this “treasure box” from the Jomon period was opened.

Some of the trees were slated to be moved to the nature museum, but the governor at the time decided that the impressive sight of fallen trunks piled up around the giant trees was worth displaying.

It was decided to preserve the entire site in an underground space, a rare feat.

“It was a time when municipal governments had more fiscal leeway. That was part of it,” Nakamura recalled.

Silver deposits were first discovered here in 1526 and mined for about 400 years, producing large quantities of high-quality silver in the 16th and 17th centuries.

The silver deposits are thought to have been formed about 1 million years ago by activity in the volcano group around the 808-meter Mt. Oetakayama located west of Mt Sanbe.

Iwami Ginzan Silver Mine and its Cultural Landscape was registered as Japan’s 14th Unesco World Heritage site in 2007.

The Sanbe-Azukihara Buried Forest Park is best visited by car or taxi. It’s about 20 minutes from JR Oda Station and 70 minutes from the Yoshidakakeya Interchange on the Matsue Expressway.

The Yomiuri Shimbun (Japan)


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