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Disaster recovery work destroys natural phenomenon at UNESCO gorge in Kumamoto Pref.

The natural vertical cracks at Tateno Gorge in Minamiaso, Kumamoto Prefecture, are seen in December 2015. (Photo courtesy of a citizens' group)
The largely demolished vertical cracks are seen following restoration work, in Aso, Kumamoto Prefecture, on Sept. 8, 2017. (Mainichi)

ASO, Kumamoto -- Parts of columnar joints, or natural vertical cracks, in a gorge here that were formed directly from Mount Aso lava have been demolished as part of restoration work overseen by the national government, it has been learned.

    The demolition work took place in Tateno Gorge, an area designated as a UNESCO Global Geopark. As a result, the demolished lava cracks may have a negative effect on the area's Global Geopark status in the future.

    The restoration work in the area includes the construction of a new bridge designed to replace the Great Aso Bridge that collapsed following the Kumamoto earthquake disaster in April 2016. The central government, however, did not inform the Kumamoto Prefectural Government that it would be tearing down the naturally formed columnar joints in the process.

    The vertical cracks, which were created after lava from nearby Mount Aso cooled down and solidified, are considered to be a geological phenomenon. The demolished cracks were discovered by a member of a citizens' group on Aug. 30.

    Work on the new bridge is being overseen by the Ministry of Land, Infrastructure, Transport and Tourism's Kumamoto disaster recovery office. In order to create a 250-meter-long road needed for bridge construction, the office raked off a 110-meter-wide, 70-meter-high section of the riverbank, in which the cracks were located. The work commenced in November 2016 after the government purchased the riverbank, which had, until that point, been mainly privately owned.

    According to the prefectural government's Aso development bureau, which belongs to the Aso Geopark Promotion Council, the disaster recovery office told the bureau that it was planning to build a bridge, but did not explain specific procedures such as the demolition of the joints.

    In an interview with the Mainichi Shimbun, a disaster recovery office representative said, "There were people requesting that the redevelopment work be carried out as soon as possible."

    Daiji Hirata, the head of the Kanagawa Prefectural Museum of National History and a member of the Japan Geopark Committee (JGC), said, in his personal opinion, "It is a great shame that the cracks were destroyed without the relevant parties being informed first. The JGC acknowledges projects for local vitalization and sustainable development works, and it should think about better ways of working together with the Aso Geopark Promotion Council while telling the council members about these things in advance."

    UNESCO Global Geoparks have their status reviewed every four years. If it is concluded that a geopark hasn't been preserved appropriately, then the status is downgraded. The next review for the Global Geopark at Aso is due to take place in 2018.

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