Qualla: Horinouchi Shell Mound

Horinouchi Shell Mound: Introduction

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Fred Cherrygarden, CC BY-SA 4.0. Four thousand years ago, the ocean lapped at the foot of a low ridge in what is now the city of Ichikawa, Chiba Prefecture. The Jomon people who lived there ate clams and cockles from the brackish shallows of Tokyo Bay, tossing the spent shells into growing heaps around their settlement. Over centuries, those heaps fused into a horseshoe-shaped mound 225 meters wide -- a trash pile so vast and so perfectly preserved that it became one of Japan's most important archaeological sites. The Horinouchi Shell Mound is a National Historic Site, a type site for an entire pottery tradition, and a window into a world that vanished when the sea retreated.

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Image: Fred Cherrygarden | CC BY-SA 4.0

Horinouchi Shell Mound: When the Sea Came Inland

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Øyvind Holmstad, CC BY-SA 4.0. During the early to middle Jomon period, roughly 4000 to 2500 BC, sea levels stood five to six meters higher than today, and temperatures ran about two degrees Celsius warmer. Tokyo Bay extended much farther inland, and the Shimosa Plateau -- where Ichikawa now spreads its suburb...

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Image: Øyvind Holmstad | CC BY-SA 4.0

Horinouchi Shell Mound: Reading the Shells

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit User:Xser21 User:掬茶 User:Shadow Fox User:Kentagon User:くろふね ja:利用者:Skink User:Yamato-i, CC BY-SA 4.0. The mound stretches 120 meters from north to south and 225 meters from east to west, forming a partial shell ring -- a horseshoe of debris that archaeologists can read like a book. The shells themselves are mostly brackish-water species: hamaguri clams, cockles, whelks, ibo-kesag...

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Image: User:Xser21 User:掬茶 User:Shadow Fox User:Kentagon User:くろふね ja:利用者:Skink User:Yamato-i | CC BY-SA 4.0

Horinouchi Shell Mound: A Name That Traveled

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Fred Cherrygarden, CC BY-SA 4.0. Archaeologists have known about the Horinouchi mound since the early Meiji period, and the first formal excavation took place in 1901. Teams from Tokyo Imperial University, Rikkyo University, Waseda University, Keio University, and Meiji University have all dug here over the deca...

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Image: Fred Cherrygarden | CC BY-SA 4.0

Horinouchi Shell Mound: Ancient Ground, Modern City

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit katorisi, CC BY 3.0. The site was designated a National Historic Site of Japan in 1964, with the protected area expanded in 1967 and again in 1972. Today the mound sits in the Horinouchi neighborhood of Ichikawa, about eight minutes on foot from Kita-Kokubun Station on the Hokuso Railway Hokuso Line....

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Image: katorisi | CC BY 3.0