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Towada-Hachimantai NP, Aomori
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Tashirotai’s peat preserves a volcanic double-timestamp: ash from Towada’s 915 eruption lies beneath ash from a later 10th-century eruption of distant Baekdu (Paektu). The layers can be found together here.
Beneath the marsh, continuous peat deposits reach back to the end of the last Ice Age, about 15,000 years ago. Aomori Prefecture’s natural-history account describes Tashirotai as having Hakkoda’s most developed peat layer.
The marsh’s scattered pools are called “kami no ta”—the gods’ rice paddies—in Aomori’s natural-history account. The National Diet Library notes that this wetland image may explain the “ta” in Hakkoda.
Tashirotai brings together intermediate marsh, sphagnum-rich raised bog around pools, and low marsh dominated by reeds and sedges. This mix of wetland habitats helps make its plant life unusually varied.
At about 560m, Tashirotai lies well below many Hakkoda marshes, which sit around 780–1,300m. Aomori Prefecture notes that yachiyanagi and himeshakunage are unusually abundant here for the Hakkoda range.
The gomashijimi butterfly is one of Tashirotai’s rare residents. Aomori City says its habitat is extremely restricted and that, in the Tohoku region, it has been confirmed only in Aomori and Iwate prefectures.
Tashirotai’s early-summer colors shift quickly: pink toki-sō orchids and sawaran bloom in June, then golden kin-kōka flowers appear in July. Aomori Prefecture highlights all three as characteristic marsh flowers.
In the 1960s, ditches up to 1m wide and 1.5m deep were dug to drain the marsh for rice fields; cultivation ended after just 2–3 years. A later study found drainage still lowered groundwater and dried parts of the bog.
