Sobo, Katamuki and Okue Biosphere Reserve
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| Sobo, Katamuki and Okue Biosphere Reserve | |
|---|---|
| 祖母傾大崩ユネスコエコパーク | |
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 Interactive map of Sobo, Katamuki and Okue Biosphere Reserve | |
| Location | Ōita Prefecture and Miyazaki Prefecture, Japan |
| Area | 1,580 ha (3,900 acres) core, 17,748 ha (43,860 acres) buffer, 224,344 ha (554,370 acres) transition[1] |
| Established | 2017 |
The Sobo, Katamuki and Okue Biosphere Reserve also known as Sobokatakue Unesco Eco Park (祖母傾大崩ユネスコエコパーク, Sobokatamuki Okuzure yunesukoekopāku) was created in 2017.[2][3] It incorporates the 1965 quasi national parks of Sobo Katamuki Prefectural Natural Park (Ōita)[4] (also previously known as the Sobo-Katamuki Quasi-National Park, Sobo Katamuki Prefectural Natural Park (祖母傾県立自然公園, Sobo Katamuki kenritsu shizen kōen)) and Sobo Katamuki Prefectural Natural Park (Miyazaki).
Geology
The reserve derives its name from Mount Sobo (1,756 m (5,761 ft)), Mount Katamuki (傾山) (1,602 m (5,256 ft)) and Mount Ōkueyama (大崩山), also known as Mount Ōkue (1,643 m (5,390 ft)).[5][6] The Quasi-National Park borders two homonymous Prefectural Parks, namely the Sobo Katamuki Prefectural Natural Park (Ōita) and Sobo Katamuki Prefectural Natural Park (Miyazaki).[7][8]
The landforms of the Biosphere Reserve are the heavily modified result of volcanic activity over the last 14 million years. A massive eruption about 13.7 million years ago involved the Okueyama Volcano-plutonic Complex,[9] and measured 8.0 on the Volcanic Explosivity Index.[10] This formed the almost rectangular Okueyama Caldera with the eruption of an estimated dense rock equivalent (DRE) volume of 1,029 km3 (247 cu mi) leaving a caldera orientated to NW to SE that was 33 km (21 mi) by 23 km (14 mi) in size. Further eruptions over only a few million years formed the smaller more elliptical Sobo Caldera which was 18 km (11 mi) by 13 km (8.1 mi) in size on a NNE to SSW axis with a DRE erupted volume of 177 km3 (42 cu mi) and the Katamukiyama Caldera again on a NW to SE axis which was 11 km (6.8 mi) by 6 km (3.7 mi) in size with a DRE erupted volume of 50 km3 (12 cu mi).[10] Later, most recently about 90,000 years ago, mainly the lower lying land was modified by pyroclastic deposits from the Aso Caldera to the west whose eruption was 384 km3 (92 cu mi).[11]