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122 8 433 444 2016 8 Jour. Geol. Soc. Japan, Vol. 122, No. 8, p. 433 444, August 2016 doi: 10.5575/geosoc.2016.0036 巡検案内書 Consider revising the volcanic disaster prevention: Field excursion guide to Fuji Volcano 1 1 2 3 3 4 Takahiro Yamamoto 1, Akira Takada 1, Mitsuhiro Yoshimoto 2, Tatsuro Chiba 3, Kenichi Arai 3 and Seiji Hosone 4 2016 5 27 2016 7 20 123 2016 H 1 Geological Survey of Japan, AIST, Tsukuba 305-8567, Japan 2 Mount Fuji Research Institute, Yamanashi Prefectural Government, Fujiyoshida, Yamanashi, 403-0005, Japan 3 Asia Air Survey Co., Ltd., Manpukuji 1-2-2, Kawasaki, 135-0016, Japan 4 Daiwa Exploration & Consulting Co., Ltd., Toyo 5-10-4, Koto, 135-0016, Japan Corresponding author: K. Arai, ken.arai@ajiko.co.jp PDF J-STAGE https://www.jstage.jst.go.jp/browse/geosoc/-char/ja Yamamoto and Nakada, 2015 864 1707, 2004 70 Keywords The 1707 eruption craterthe Hoei craters, Slush flow, Lava tube, Pillow lava, Debris avalanche, Basaltic pyroclastic flow 125,000 The Geological Society of Japan 2016 433

434 20168 1 5 2 3 2 Stop 1 35 20 30 N, 138 44 47 E Stop 2 35 20 06 N, 138 47 39 E Stop 3 35 26 47 N, 138 47 31 E Stop 4 35 23 07 N, 138 42 36 E Stop 5 35 28 33 N, 138 41 27 E Stop 6 35 29 35 N, 138 40 22 E Stop 7 35 29 08 N, 138 36 28 E Stop 8 35 20 04 N, 138 33 57 E Stop 9 35 18 08 N, 138 39 44 E Stop10 35 09 08 N, 138 37 34 E 5 10 km 4 1707 300 10 1 km 3, 2007 864 1.3 km 3, 2007 0.7 km 3 Miyaji et al., 2011, 2007, 2016 13.5 km Fig. 2 1968 19642003 1988, 2004 13.5 km 2001 2003 2, 2016,, 2005;, 2007 110 2 10, 2007; Yoshimoto et al., 2010 1940, 1968, 1971, 2007 1964

122 8 435 Fig.. Topographic map of Fuji Volcano and surrounding area. (source: Chiba, 2011), 2011, 2007 2005 3 10 2 2 8, 2007 1964 8, 2007 10 2 ;, 2016 2, 2005, 2007, 1977;, 1990, 1993, 1998, 2003, 2015 22 5600 2, 2016 1 km 3 1 30 km m

436 20168 Fig.. Schematically image of stress direction (Right) and eruptive fissure pattern of Fuji volcano on the DEM image (Left). Circle showing the restriction of region for fissure eruptions within 13.5 km in radius. (source: Takada et al., 2007, 2016) 13.5 km source, 2007, 2016 1m, 2007 3 5600 2300 5600 3500 5600, 2005, 2007 3500 2300 S-10, S-11, Yamamoto et al., 2005, 2016 S-22 Yu-2 2, 2016 3300 307040 y BP, 2005, 2007 3300 3010 40 y BP, 2005, 2007 2900, 2004 Fig. 3 42300 2300, 1992;, 1998a, b 2000 S-23, 2005 6, 2005

122 8 437 Fig.. Distribution of Gotemba debris avalanche deposit (Goda) and Gotemba mud flow deposit (Gomf) at eastern foot of Fuji volcano, and isopachmap of these deposits. Unit in m. (sourcemiyaji et al., 2004) GodaGomf m, 2004 700 900 1 2 864 1.3 km 3, 2007 Fig. 4 3 900 1000, 2005,, 2007 2 12 km8 km 1 2, 2011 9 2 2002, 2003 11 13 2σ Cal AD 1030 1230, 2005 5 1707 1707 4 12 16 cm, 2007 49 M8.4 12 15 12 16 1 3 Fig. 5 2 100, 2007 20 cm cm

438 20168 Fig.. Lake Seno-umi has been divided by the lava flow. As a result, the two lakes of Lake Motosuko and Lake Shojiko was born. You can read its history from the three-dimensional view and gray color conversion made from DEM (making LIDAR system by Fuji Sabo work office). Lava distribution range which the colored area has erupted in the Jogan eruption in AD864 to866. (source: Chiba et al., 2007) 2007. Fig.. Change in column height throughout the Hoei eruption. The periods of ash fall in Edo and rainfall, deduced from document analysis, are also shown. (source: Miyaji et al., 2011) Miyaji et al., 2011

122 8 439 Stop1 125,000 35 20 30 N, 138 44 47 E Fig. 6 2 3500 2300 Fig. 7 Fig.. Pyroclastic cone inside the Hoei-I crater (Photo by Takada) Stop 2 5 125,000 35 20 06 N, 138 47 39 E S-23 S-22Yu-2 9 20 2014a, 2007 Stop 3 10 km 125,000 35 26 47 N, 138 47 31 E 1968 2500 2000, 1988, 25001350 y BP, 2004 2004 2,200 2009 Fig. 8, 2010 Fig.. Stop 1: Dike on the wall in the Hoei-I crater (Photo by Takada) Stop 4 125,000 35 23 07 N, 138 42 36 E 4 5 km 2 1 2 1,300

440 山元 2016 8 孝広ほか Fig. 8. Stop 3: Red Relief Imaging Map (with gray color conversion) of Gan-no-Ana was made using Lidar data. 第 8 図 雁ノ穴火口付近の航空レー ザ計測データによる赤色立体地図 グレー色調表示 Stop 5 ジラゴンノ 溶岩樹形 地形図 1 25,000 鳴沢 位 置 35 28 33 N, 138 41 27 E 解 説 富士山緑の休暇村の裏手にあるグラウンドの周り一 体では 青木ヶ原溶岩流の断面と青木ヶ原溶岩流の底部に赤 色酸化した約 3300 年前の大室スコリアを観察できる 溶岩 溶岩 断面露頭には複数の溶岩樹形が分布しており Fig. 9 中の気泡のサイズや形が縦方向に変化する様子を観察できる ほか 厚さ 5 m 程の溶岩には溶岩膨張の発生を示唆する構 造が見られる Stop 6 精進湖 枕状溶岩等 地形図 1 25,000 精進 位 置 35 29 08 N, 138 36 28 E 解 説 貞観六 七年 西暦 864 年 866 年初頭 の貞観噴 火では 2 列の割れ目火口から流出した大量の玄武岩質溶岩 うみ 流が本栖湖とせの湖に流れ込み 現在の本栖湖 精進湖 西 湖を形作ったとされる 精進湖に流れ込んだ青木ヶ原溶岩流 には 急冷 固化する過程で生じる進行方向と直交方向にで Fig. 9. Outcrop of tree molds formed by the Aokigahara lava flow at the Narusawa-Michinoeki. (Photo by Chiba) 第 9 図 鳴沢道の駅裏のジラゴンノの溶岩樹型露頭 撮影 千葉 きる しわ や網目状の複雑な模様など 特徴的な表面構造を Fig. 10 観察できる 例えば, 海野, 2007

122 8 441 Fig.. Note the detail structures of Aokigahara Lava and the Syojiko Lake shown by Red Relief Image Map made on using LIDAR data.) A large axial crack on the subaqueous lava flow lobe in Syojiko Lake. (Photo by Chiba) Stop 7 125,000 35 29 35 N, 138 40 22 E 350 m Stop 8 125,000 35 20 04 N, 138 33 57 E 2 Cal BC 18,000, 2007 12 mm Fig. 11

442 山元 孝広ほか 2016 8 Fig. 11. Tanukiko Debris Avalanche Deposit. Shooting point s o u t h w e s t o f t h e Ta n u k i k o. (source Takada, A., 2015) 第 11 図 田貫湖岩屑なだれ堆積物 写真 下 は田貫湖の南西 撮影 高田 Fig. 13. Outcrop of Suijin Lava at Fujigawa river side. (Photo by Chiba) 第 13 図 富士川沿いで観察できる水神溶岩の露頭 溶岩断 面の樹形と節理が見える 人の左側 溶岩の下位は砂層 2,800 年 頃の玄武岩質火砕流堆積物が露出する 北垣ほか 2007 この時期の富士山は 約 5600 年前 Cal BC 3,600 Fig. 12. (source: Tajima et al., 2006 第 12 図 南西山麓に分布する火砕流堆積物の確認箇所 田島 ほか, 2006 年 頃から始まった現火山錐の形成途上で 今の山頂部は存 Cal BC 1,700 在していない 山頂部の完成は約 3700 年前 年 頃である ほぼ同じ年代値を示す火砕流堆積物は 南山 山元ほか, 2005 腹の標高 1,700 m 付近にも分布するほか 2006 が 西山腹の大沢沿い標高 1,500 m 付近にも田島ほか Stop 9 風祭川 玄武岩質火砕流 おそら 岩樋火砕流と呼ぶ玄武岩質火砕流がある Fig. 12 地形図 1 25,000 天母山 位 置 35 18 08 N, 138 39 44 E く 大規模な火砕丘の形成 崩壊イベントが現火山錐の成長 解 説 南西山腹の風祭川沿いには約 5800 年前 Cal BC と見られる また 南西山麓に広がる土石流 高密度洪水流 過程あり このような広範囲に分布する火砕流を生じたもの

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