The Itoigawa-Shizuoka Tectonic Line, which separates Japan into eastern and western halves, runs along the western border of Fossa Magna. The fault line mostly follows the path of the Himekawa River, but between Negoya and Kitaotari it runs along the mountains just east of the river. The area along this fault produced many landslides and topographical basins, resulting in the area’s gentle slope seen today. It was by connecting these basins and gentle-sloping areas that the Salt Trail was created. Construction of the road was not without peril, though, as the Himekawa River often floods and landslides are fairly common.
Along this road, various goods from the sea were transported from Niigata to Nagano and exchanged for products like tobacco and cereal grains. One area along the road is known by the name of ‘Utou.’ The slope here is not natural; rather, it was excavated by the early roadworkers to permit easier travel. In addition to the ruins of old teahouses and guideposts, one can find the remains of an old trade road here.
At nearby Fossa Magna Park, one can observe the Itoigawa-Shizuoka Tectonic Line, outcrops, and pillow lava as well as learn about the formation of Fossa Magna.
Itoigawa Global Geopark – Itoigawa-Shizuoka Tectonic Line and Salt Trail(nouthern area) Geosite
AloJapan.com