Mountains · Oita
Kujū Mountains
九重山くじゅうさんKujū-sanThe roof of Kyūshū: volcanic domes, azalea slopes and high moors.
The Kujū Mountains (九重山) are a group of volcanoes in Ōita Prefecture whose highest peak, Nakadake, reaches 1,791 m – the highest point on the main island of Kyūshū. Known for pink azalea slopes in early summer, the Bōgatsuru and Tadewara wetlands and the steaming Iōyama, they lie in Aso-Kujū National Park.
Overview
The Kujū Mountains rise in south-western Ōita, north-east of Aso, a compact cluster of more than twenty peaks – among them Nakadake, Kujū-san, Hiijidake, Mimatayama and Taisenzan – separated by upland basins. Most peaks exceed 1,700 m, and on clear days Aso and even the Sobo mountains are visible.
The area is one of Kyūshū's favourite hiking destinations. Trails from Makinoto pass and Chōjabaru reach the summits in a few hours, and the Hokkeiin Onsen hut in the Bōgatsuru basin, the highest hot spring in Kyūshū, is a place of pilgrimage for mountaineers. The song Bōgatsuru Sanka, written by students in the 1950s, is known among Japanese hikers nationwide.
Landscape and formation
Kujū is a group of lava domes and small stratovolcanoes that formed over the last 200,000 years; the dome of Kurodake and Nakadake's cone are among the youngest. Iōyama, on the northern side, emits continuous volcanic gas and was mined for sulphur until the mid-twentieth century.
Between the peaks lie flat basins filled with volcanic sediments and peat, such as Bōgatsuru and the Tadewara marsh near Chōjabaru, together recognised as a Ramsar wetland. Rain and snowmelt feed the Kusu and Ōno rivers and many hot springs at the foot.
Highlights
Nakadake
中岳NakadakeThe highest peak, 1,791 m, overlooking the Miike crater lake, the highest lake on Kyūshū.
Kujū-san
久住山Kujū-san1,787 m, the peak that gives its name to the group, with a classic pyramid shape seen from the south.
Bōgatsuru
坊ガツルBōgatsuruA high moor surrounded by peaks, with a campsite and the Hokkeiin Onsen hut.
Iōyama
硫黄山IōyamaA steaming fumarole field on the north side, visible from the trails; entry is prohibited.
Kokonoe Yume Ōtsuribashi
九重“夢”大吊橋Kokonoe Yume ŌtsuribashiA 390 m pedestrian suspension bridge over a gorge at the foot of the mountains.
Ecology
The upland basins and slopes support a mosaic of grassland, marsh, shrub and forest. Tadewara and Bōgatsuru are among the few extensive mountain wetlands of western Japan, maintained partly by traditional spring burning.
Flora
Miyama-kirishima
ミヤマキリシマmiyama-kirishimaThe pink azalea of Kyūshū's volcanoes, blanketing the Kujū slopes in June, most famously on Hiijidake.
Kokemomo
コケモモkokemomoCowberry at the southern edge of its range, on the summit rocks.
Marsh plants
サワギキョウsawagikyōPurple lobelia flowers in the Tadewara and Bōgatsuru marshes in late summer.
Fauna
Japanese serow
カモシカkamoshikaOccasionally seen in the forested valleys.
Japanese skylark
ヒバリhibariSings over the grasslands of the plateaus in spring and summer.
Culture
Hokkeiin, a Tendai temple founded in the Muromachi period in the Bōgatsuru basin, made the Kujū Mountains a training ground for ascetics; its lodgings later became the mountain hut and hot spring of Hokkeiin Onsen. The Bōgatsuru Sanka, a hikers' song about the basin, became a nationwide hit in the late 1970s. The grassland villages at the foot, such as Kuju and Kokonoe, are known for dairy farming.
Hokkeiin Onsen
法華院温泉Hokkeiin onsenA mountain hut with hot spring at about 1,300 m, reachable only on foot.
Chōjabaru Visitor Centre
長者原ビジターセンターChōjabaru bijitā sentāInformation on trails, wetlands and volcanic activity at the northern trailhead.
History
Muromachi period
Hokkeiin temple is founded in the Bōgatsuru basin.
1934
Aso National Park is designated, including the Kujū Mountains; renamed Aso-Kujū in 1986.
1995
A small phreatic eruption occurs at Iōyama.
2005
The Bōgatsuru and Tadewara wetlands are designated a Ramsar site.
Through the seasons
Spring
Burning of the grasslands in March and April; fresh green in May.
Summer
Azaleas from late May to mid-June; cool hiking weather in July and August compared with the lowlands.
Autumn
Colours on Taisenzan and Mimatayama in October; susuki grass on the plateaus.
Winter
Rime ice and snow on the summits; the Makinoto pass road can be icy.
Routes and trails
Makinoto-tōge – Nakadake
From the pass via Kutsukake-yama and Kujū-wakare, about 2.5 hours to Nakadake; the most popular route, moderate.
Chōjabaru – Bōgatsuru
Through the Amagaike area to the Bōgatsuru basin and Hokkeiin, about 2 hours; easy, often continued to Taisenzan or Nakadake.
Tadewara wetland walk
A boardwalk loop of about 1 hour at Chōjabaru; easy.
Practical notes
- Makinoto pass and Chōjabaru are on the Yamanami Highway, reached by car or seasonal bus from Beppu, Yufuin or Kumamoto.
- Fog is frequent on the plateaus; carry a map and follow markers.
- Keep away from the Iōyama fumaroles; volcanic gas can be dangerous.
- Kujū is monitored as an active volcano by the Japan Meteorological Agency.
Frequently asked questions
What is the difference between 九重 and 久住?
Both are read Kujū. 九重山 (Kujū-san) names the whole group, while 久住山 (Kujū-san), 1,787 m, is one individual peak. The highest summit of the group is Nakadake, 1,791 m.
How long does it take to climb Nakadake?
From Makinoto pass at about 1,330 m, about 2.5 hours to Nakadake via the Kujū-wakare junction; Kujū-san is a short detour. It is a moderate, well-marked hike.
When do the azaleas bloom?
Miyama-kirishima azaleas turn the slopes of Hiijidake, Mimatayama and Kujū-san pink from late May to mid-June.
Is Kujū still volcanically active?
Yes. The Iōyama fumaroles steam continuously, and a small phreatic eruption occurred there in 1995. The Japan Meteorological Agency monitors the group.
Related
Sources
- 1.日本の主な山岳標高 (opens in a new tab) — 国土地理院 (Geospatial Information Authority of Japan)
- 2.阿蘇くじゅう国立公園 (opens in a new tab) — 環境省 (Ministry of the Environment)
- 3.火山登山者向けの情報提供ページ（九重山） (opens in a new tab) — 気象庁 (Japan Meteorological Agency)
- 4.大分県ホームページ (opens in a new tab) — 大分県 (Ōita Prefecture)