Mount Zao

A mountain in the central-southern part of the Ou Mountain Range, spanning Yamagata City and Kaminoyama City in Yamagata Prefecture, and Shibata County and Karita County in Miyagi Prefecture. It is a general term for a group of stratovolcanoes, mainly made of andesite. It is also called the Zao mountain range. The main ridgeline extends from north to south for about 30 kilometers, with the highest peak being Kumanodake (1,841 meters). It is roughly divided into North Zao and the older South Zao, separated by the border between Sumikawa and Nambazawa, and North Zao is generally called Mount Zao. North Zao is a composite volcano with a series of outer rim mountains including Kumanodake, Karitadake (1,758 meters), and Umanose, which contain the crater lake Okama (also known as Goshikinuma, 360 meters in diameter, 40 meters deep) and the central crater cone Goshikidake (1,674 meters, cinder cone). Others include Jizoyama (1,735 meters), Myogoho (1,491 meters; the entire mountain is granodiorite and not a volcano), Torikabutoyama (1,401 meters), which surrounds the Takayu explosion crater from which Zao Onsen gushes forth, and Ryuzan (1,362 meters). In northern Zao, more than 40 eruptions (steam explosions), active fumarolic gases and hot springs, earthquakes, and rumbling have been recorded, beginning in 1183 (Juei 2) and ending in 1972 (Showa 47), and there are many fumaroles and hot springs. However, eruptions causing damage, such as the one in 1867 (Keio 3, 3 deaths), occurred inside and outside Okama. It is prone to producing volcanic mudflows. The vegetation around the summit is poorly developed except for alpine plants such as Dicentra, and the subalpine forests of Aomoritodomatsu and other trees that form frost spread from 1,300 to 1,600 meters above sea level. Southern Zao is a chain of conical volcanoes such as Byobudake (1,825 meters), Fubosan (1,705 meters), and Ushiroeboshidake (1,681 meters), and is well covered with vegetation, with subalpine forests especially spreading on the western slope. Mount Zao has also been called Fubosan and Kattamine since ancient times, but it is said that it has been called by this name since the monk Gyogan enshrined Zao Gongen from Mount Kinpu in Yoshino (Nara Prefecture) in the 7th century. Until the end of the Edo period, it was a mountain of faith and Shugendo (asceticism) where women were forbidden to enter. In 1950, it was ranked number one in Japan's Top 100 Mountains for Tourism, and tourism development progressed with the opening of the Echo Line in 1962. In addition to the magnificent volcanic scenery, it is known as a mecca for skiing and for its frost-covered trees and hot springs. It is the center of Zao National Park.

[Shige Nakagawa and Akira Suwa]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

奥羽山脈中南部にある山で、山形県の山形市、上山(かみのやま)市、宮城県の柴田(しばた)郡、刈田(かった)郡にまたがり、おもに安山岩の成層火山群の総称。蔵王連峰ともいう。主稜線(りょうせん)の南北延長は約30キロメートル、最高峰は熊野岳（1841メートル）。澄川(すみかわ)―難場(なんば)沢を境に、北蔵王と、生成のより古い南蔵王に大別され、一般には北蔵王を蔵王山とよぶ。北蔵王は、熊野岳、刈田岳（1758メートル）、馬ノ背などの連なる外輪山が火口湖御釜(おかま)（別名五色沼、直径約360メートル、水深約40メートル）と中央火口丘の五色岳（1674メートル、噴石丘）を抱く複式火山である。ほかに、地蔵山（1735メートル）、名号峰(みょうごほう)（1491メートル。全山が花崗閃緑(かこうせんりょく)岩で火山ではない）や、蔵王温泉を湧出(ゆうしゅつ)する高湯爆裂火口を取り囲む鳥兜山(とりかぶとやま)（1401メートル）、滝山(りゅうざん)（1362メートル）なども含む。北蔵王では、1183年（寿永2）を皮切りに、1972年（昭和47）まで、噴火（水蒸気爆発）、噴気・温泉活発化、地震、鳴動などが四十数回も記録され、現に噴気孔や温泉が多い。ただし、1867年（慶応3、死者3人）などの被害を伴った諸噴火は御釜の内外で発生した。火山泥流を出しやすい。山頂一帯はコマクサなどの高山植物以外は植生の発達が悪く、樹氷が形成されるアオモリトドマツなどの亜高山帯林は標高1300～1600メートルにかけて広がる。南蔵王は屏風岳(びょうぶだけ)（1825メートル）、不忘山(ふぼうさん)（1705メートル）、後烏帽子岳(うしろえぼしだけ)（1681メートル）などの円錐火山(えんすいかざん)が連なり、植生の被覆がよく、とくに西側斜面に亜高山帯林が広がる。蔵王山は、古来、不忘山(わすれずのやま)、刈田嶺(みね)とも称されたが、7世紀に僧行願(ぎょうがん)が吉野（奈良県）の金峰山(きんぶせん)から蔵王権現(ごんげん)を勧請(かんじょう)して以来、この名でよばれるようになったと伝える。江戸末期までは女人禁制の修験(しゅげん)、信仰の山であった。1950年（昭和25）に日本観光百選山岳部の第1位となり、1962年にエコーラインが開通するなど、観光開発が進み、壮大な火山景観に加え、温泉のある樹氷とスキーのメッカとして知られる。蔵王国定公園の中心。

［中川　重・諏訪　彰］

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