Wave Patterns in a Mountain Pass Cutting
The Namiuchi Pass Cross-Bedding (浪打峠の交叉層, Namiuchi Toge no Kosaso) is an exposure of cross-bedded strata laid down in a shallow sea, at Namiuchi Pass in Ichinohe Town, Ninohe District, Iwate Prefecture, which in 1941 was designated a Natural Monument.
The Agency for Cultural Affairs lists it under the criterion for conformity and unconformity of strata. Ichinohe Town gives its location as straddling Okoshida and Odozawa in Ichinohe.
The Ichinohe tourism corporation places Namiuchi Pass on the old Oshu Kaido highway between the post towns of Ichinohe and Fukuoka, on today's boundary between Ninohe City and Ichinohe Town.
What Cross-Bedding Is
The designation text describes weathered faces of Tertiary sandstone showing clear cross-bedding like ripple marks, with many shell fragments in the layers, the typical features of shallow-sea deposits.
The tourism corporation explains cross-bedding as layering formed when sand settles in moving water in the shallows. Each time the current changes direction or strength, thin inclined layers shift their angle, producing criss-crossing stripes in section.
It adds that the Namiuchi Pass Cross-Bedding is thought to have been laid down about 15 million years ago, when the area was shallow sea.
What to Look For
According to the tourism corporation, strata with beautiful stripes and embedded shells are exposed on both sides of the cutting through the pass, and their wave-like look is thought to have given Namiuchi, wave-beating, its name.
At the exposure, look for places where the inclined stripes change direction, and for the white flecks of shell in the layers: the two features the designation text named as typical of shallow-sea deposits.
The tourism corporation notes a theory that Namiuchi Pass is one candidate for Sue no Matsuyama, a place celebrated in classical poetry, and that it was chosen as a rest stop during the Meiji Emperor's tour. The leading candidate is in Tagajo, Miyagi Prefecture.
Visiting the Namiuchi Pass Cross-Bedding
The tourism corporation says admission is free and there is parking for two cars. The road is very narrow, so it asks visitors not to come in large vehicles.
As a Natural Monument, the exposure must not be struck or chipped, and shell fossils must not be removed. Enquiries go to the Ichinohe Town World Heritage section, 0195-32-2652.
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Q&A
- When was the Namiuchi Pass Cross-Bedding designated?
- It was designated a Natural Monument on 1 August 1941.
- What is cross-bedding?
- Layering formed as sand settles in moving shallow water, with inclined layers crossing one another.
- How old is the Namiuchi Pass Cross-Bedding?
- According to the Ichinohe tourism corporation, it formed about 15 million years ago in a shallow sea.
- Where does the name Namiuchi come from?
- From the wave-like stripes of the strata on both sides of the pass.
- Can I visit the Namiuchi Pass Cross-Bedding?
- Yes, free of charge; there is parking for two cars, and large vehicles should be avoided.
Basic Information
| Name | Namiuchi Pass Cross-Bedding (浪打峠の交叉層) |
|---|---|
| Location | Okoshida and Odozawa, Ichinohe, Ichinohe Town, Ninohe District, Iwate Prefecture |
| Designation | Natural Monument |
| Year Designated | Designated 1941/8/1 (Showa 16) |
| Quantity | Not recorded in the Agency for Cultural Affairs database |
| Dimensions | Not recorded in the Agency for Cultural Affairs database |
| Owner | Not recorded in the Agency for Cultural Affairs database |
| Public Access | Free; parking for two cars |
References
- Agency for Cultural Affairs Database: Namiuchi Pass Cross-Bedding (Japanese)
- https://kunishitei.bunka.go.jp/bsys/maindetails/401/152
- Cultural Heritage Online: Namiuchi Pass Cross-Bedding (Japanese)
- https://online.bunka.go.jp/heritages/detail/204653
- Ichinohe Town: Cultural Properties (Japanese)
- https://www.town.ichinohe.iwate.jp/soshikikarasagasu/sekaiisanka/bunkazaikakari/1/935.html
- Ichinohe Tourism Corporation: Namiuchi Pass Cross-Bedding (Japanese)
- https://www.ichinohekankou.jp/sightseeing/history-2/kousasou/
Last verified: 2026.09.27