Yatsugatake

A group of volcanoes on the border between Nagano and Yamanashi prefectures, separating the Saku Basin from the Suwa Basin. They erupt on the eastern edge of the Central Rift Valley, and from the north, mountains around 2,500 meters high, such as Yokodake, Shimagareyama, Tengudake, Ioudake, Yokodake, Akadake, Gongendake, and Amigasayama, stretch for about 20 kilometers from north to south. The highest peak is Akadake near the southern end, at 2,899 meters above sea level. They form vast foothills to the east, south, and west, and include plateaus such as Hirohara, Nobeyama, Fujimi, and Kiyosato. The mountain is divided into North and South Yatsugatake at Natsuzawa Pass, which passes through the saddle of Mt. Iodake. South Yatsugatake has been eroded to the point where a valley reaches the summit, but North Yatsugatake has a gentler shape, with lakes such as Shirakome, Ameike, and Futago on the east side of the summit. The foothills are dominated by larch and red pine up to about 1,600 meters, and up to about 2,500 meters there are species such as silver fir, hemlock, and Erman's birch, and above that there is a change to pumila. There are also many alpine plants such as willow herb and scabious lily. Between Mt. Iodake and Mt. Yokodake there is a habitat of yellow rhododendrons, which has been designated a national natural monument. From the summit one can see a magnificent view of the high mountains of central Japan, including the Japanese Alps, Mt. Fuji, and Mt. Asama. There are passes that cross the mountain range, including Mugisawa Pass, Ogawara Pass, and Natsuzawa Pass, but only Mugisawa Pass (2,151 meters) has a road, making it a comfortable driveway. On the mountainside, there are hot springs such as Honzawa, Inagoyu, and Kasuga on the east side, and Okutateshina on the west side. Of the hiking courses, the course that goes from Inagoyu Hot Springs via Natsuzawa Pass, traversing Minami-Yatsugatake, to Kobuchizawa Station on the JR Chuo Main Line takes about 18 hours, or three days and two nights.

[Hiroyoshi Kobayashi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

長野・山梨県境にある火山群で、佐久盆地と諏訪盆地(すわぼんち)を分ける。中央地溝帯の東縁に噴出し、北から横岳、縞枯(しまがれ)山、天狗(てんぐ)岳、硫黄(いおう)岳、横岳、赤岳、権現(ごんげん)岳、編笠(あみがさ)山など2500メートル前後の山々が南北約20キロメートルにわたって続く。最高峰は南端に近い赤岳で標高2899メートル。東、南、西に広大な裾野(すその)を形成し、広原、野辺山(のべやま)、富士見(ふじみ)、清里(きよさと)などの高原がある。硫黄岳の鞍(あん)部を通る夏沢峠(なつざわとうげ)を境に、北八ヶ岳と南八ヶ岳に分かれ、南八ヶ岳は侵食が進んで山頂付近まで渓谷が達しているが、北八ヶ岳は穏やかな山容で、山頂部東側に白駒、雨池、二子などの湖がある。裾野一帯は1600メートルあたりまでカラマツやアカマツが多く、2500メートル付近まではシラビソ、コメツガ、ダケカンバなど、それより上部はハイマツに変わる。またヤナギラン、マツムシソウなどの高山植物も多い。硫黄岳と横岳の間にはキバナシャクナゲ自生地があり、国の天然記念物に指定されている。山頂からは日本アルプスをはじめ、富士山、浅間山など中央日本の高山が大観できる。連峰を横断する峠は麦草峠、大河原峠、夏沢峠などがあるが、車道が通じるのは麦草峠（2151メートル）だけで、快適なドライブウェーになっている。山腹には東側に本沢(ほんざわ)、稲子湯(いなごゆ)、春日(かすが)、西側に奥蓼科(おくたてしな)などの温泉がある。登山コースのうち、稲子湯温泉から夏沢峠を経て南八ヶ岳を縦走し、JR中央本線小淵沢(こぶちざわ)駅へ至るコースは約18時間、2泊3日を要する。

［小林寛義］

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