Land area: 72,678 ha
Designated on 4 Dec, 1934
Aso has Japan's representative caldera. While Mt. Asosan is still fuming vigorously, there are people living at its base. Smoke from the volcanoes rising into the clear sky, comforting fields of grass, and the people's daily lives ? the beauty of nature and people is in harmony here.
Aso-Kuju National Park is located in the central part of Kyushu and is composed of Mt. Asosan with the famous Aso caldera, the Kuju Volcanic Group in the northeast of Mt. Asosan, and the Kujukogen Plateau and other plateaus. It is a park of majestic volcanoes and fields of grass.
Mt. Asosan is a huge caldera formed by an eruption that occurred some 90,000 years ago. It is a typical double caldera about 16 km from east to west, 23 km from north to south, and the outer rim of the crater is about 128 km. It is one of the largest calderas in the world. Mt. Asosan is a common designation for five peaks, of which Mt. Nakadake of Aso (1,506 m) is still active and fuming. It is one of the few craters at which visitors can go to the edge of the crater and look into it when the volcano is calm. In the large crater basin, there are towns which have rice and vegetable fields and a railway. Kusasenri in the west is a basin-shaped grassland which is the remains of an explosion crater. In the field, pastured cows and horses graze peacefully.
The Kuju Volcanic Group located in the northeast of the Aso caldera has Mt. Kujusan (1,787 m) as its main peak and Mt. Nakadake of Kuju (1,791 m), the highest peak on the Kyushu mainland. While there is a range of volcanoes here, many of them don't have a crater. At the foot of the mountains spread out grand plateaus including the Kujukogen Plateau. Gushing sulfurous steam and other signs of volcanic activities can be seen in many places.
Mt. Yufudake (1,583 m) and Mt. Tsurumidake (1,375 m) in the west of Beppu constitute another group of volcanoes. They have many small lateral cones and their peaks command excellent views. The Beppuonsen Spa is a group of hot spas which obtains hot water from the volcanic activity of Mt. Tsurumidake. They collectively form a large, nationally renowned hot-spring resort.
The plain at the foot of Mt. Asosan is mostly covered with fields of Japanese pampas grasses and lawn-grasses. These fields are artificially controlled by mowing, open burning and grazing. As the natural environment has been stable for more than a thousand years, there is a biota peculiar to this area. Recently, measures to conserve the environment of the fields are being implemented since it is getting more difficult to maintain the biota.
One of the noteworthy plant species in this area is Jacob's ladder (Polemonium kiushianum) which is endemic to Mt. Asosan. There are some other rare plants which grow in limited areas. Also, some rare species of butterflies can be found.
Regarding trees, there are natural forests of Japanese red pines (Pinus densiflora), Japanese black pines (Pinus thunbergii) and sawtooth oaks (Quercus acutissima), and planted forests of Japanese cedars (Cryptomeria japonica) and Japanese cypresses (Chamaecyparis obtusa) in some places. In mountainous areas, the major vegetation is woods of beeches (Fagus crenata) and Japanese oaks (Quercus crispula). There are communities of wild azaleas called miyamakirishima (Rhododendron kiusianum) on the plateaus and they offer beautiful scenery when they bloom. The natural forest of broad-leaved trees in Kikuchikeikoku Valley located in the northwest of the Aso caldera is well-known. Inosedo, a basin-shaped plain land at the foot of Mt. Yufudake, contains an intermediate moor where some valuable swamp plants grow.