Qualla: Okadaira Shell Mound

Okadaira Shell Mound: Introduction

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Σ64, CC BY 4.0. In 1879, two students from Tokyo Imperial University -- Tadajiro Sasaki and Isao Iijima -- traveled to a plateau overlooking Lake Kasumigaura and began digging. They had just finished training under Edward S. Morse, the American naturalist who had electrified Japanese academic circles with his excavation of the Omori Shell Mounds near Tokyo. At Okadaira, Sasaki and Iijima conducted the first archaeological excavation ever led by Japanese scholars on Japanese soil. What they uncovered was not merely a heap of discarded shells. It was a ring-shaped village, seven thousand years in the making, that would reshape the understanding of the Jomon people who inhabited these coasts when the sea levels stood five to six meters higher than today.

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Image: Σ64 | CC BY 4.0

Okadaira Shell Mound: When the Sea Came Inland

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Σ64, CC BY 4.0. Between roughly 4000 and 2500 BC, during the early to middle Jomon period, the climate was approximately two degrees Celsius warmer than the present. Sea levels rose, flooding low-lying portions of the Kanto plain and turning the area around Lake Kasumigaura into a network of bay...

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Image: Σ64 | CC BY 4.0

Okadaira Shell Mound: Reading the Refuse

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Σ64, CC BY 4.0. The midden at Okadaira is not a single mound but a constellation of eight large and small shell deposits scattered across a tongue-shaped plateau measuring roughly 250 meters east to west and 150 meters north to south. The shell layers are arranged in a ring pattern, tracing the ...

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Image: Σ64 | CC BY 4.0

Okadaira Shell Mound: Saved by a Bubble

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Miyuki Meinaka, CC BY-SA 4.0. For all its scientific importance, Okadaira nearly vanished under concrete. In the 1970s, a real estate developer acquired lakeshore land and announced plans for a resort and residential complex, promising that "development and preservation" could proceed in parallel. Bulldozers ...

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Image: Miyuki Meinaka | CC BY-SA 4.0

Okadaira Shell Mound: An Island in the Plain

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Σ64, CC BY 4.0. From above, Lake Kasumigaura spreads across the Ibaraki lowlands as the second-largest lake in Japan, its shallow waters catching light across a surface that stretches nearly 220 square kilometers. The Okadaira site sits on the south-central shore, a subtle rise in an otherwise f...

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Image: Σ64 | CC BY 4.0