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梶山のタービダイト 深海の記憶：梶山のタービダイト South Nakaizu Area : Hinata Geosite Memories of the Ocean Depth: Kajiyama Turbidite Kajiyama Turbidite

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梶山のタービダイト 深海の記憶：梶山のタービダイト South Nakaizu Area : Hinata Geosite Memories of the Ocean Depth: Kajiyama Turbidite Kajiyama Turbidite しんかい きおく かじやま ひなた 中伊豆南エリア ：日向ジオサイト 梶山のタービダイト 深海の記憶：梶山のタービダイト South Nakaizu Area : Hinata Geosite Memories of the Ocean Depth: Kajiyama Turbidite Kajiyama Turbidite かたむ ちそう 対岸に傾いたしましまの地層が見えます。地層にはさまざまな「しましま」がありますが、 らんでいりゅう 海の時代 しんかい 伊 豆200 半0～100 島0万年 の前 生 い 立 ち 乱泥流 20～10 million years ago この地層は、はるか昔、伊豆が深海にあったころの歴史を語るしましまです。 Turbidity current 本州 Honshu S u プレート 800 ～ b 沈み込み口 400km 伊豆が南の海の海底火山だった頃のお話です。あちこちの海底火山から噴出した火山灰は、 ma Trench ふ つも くず 海底火山 r Submarine Volcanoes i n いったん火山付近の海底に降り積もりましたが、その後の噴火や地震によって崩れ、海底の斜 e らんでいりゅう V 深い海での火山活動 o l Deep marine stage 深海 c 面上をさらなる深みへと流れ下っていきました。このような現象を「乱泥流」と呼びます。 a n Deep ocean o e s 1000～200万年前 乱泥流で運ばれて深海にたまった土砂の地層を「タービダイト」と呼びます。深海に流れて 10～2 million years ago ただよ 本州 Honshu きた土砂は、重くて大きい粒ほど先に沈み、軽くて小さい粒は最後まで海底を漂うため、1 枚 プレート 400 ～ 沈み込み口 80km Trench タービダイト G 海底火山 の地層をよく見ると、地層の下から上に向かって粒の大きさが細かくなっています。 Submarine Volcanoes 小火山島 Turbidite eologi Small Volcanic Island フィリピン海プレート上の深海にたまったこの地層は、プレートの動きとともに本州に押し 浅い海での火山活動 りゅうき Shallow marine stage 衝突の時代 付けられ、隆起したり地層が傾いたりしながら地表に姿を現しました。 ca l Hi 200～100万年前 You can probably see a striped pattern in the inclined bank on the opposite side. A variety of striped patterns are seen on 2～1 million years ago 本州 Honshu st land, but these stripes mark a period from the remote past, when this Izu Peninsula was a landmass submerged in ocean Collision to Main Island (Honsyu) o depths. r 80～40km y o 陸地 熱海層群最下部の Izu block This history takes us back to the period when Izu was a landmass at the bottom of the South Sea. At that stage, layers of 砂や泥が堆積 f 本州への衝突のはじまり Iz volcanic deposits accumulated on the seafloor and later these deposits were transferred as ʻturbidity currentʼ through various Start of collision u Penin types of movements (such as subsequent volcanism or earthquakes). 100～60万年前 Soil strata created through deposition by turbidity current is called Turbidite. It is mainly composed of the fine particles of 1～0.6 million years ago 丹沢山地の隆起と浸食 sand and debris. Under water, bigger and heavier soil particles sink to the bottom quickly and lighter particles float above Uplit and Erosion of Tanzawa mountains s before eventually accumulating at the top of the layer. If you take a close look at a submarine soil strata formed in this ul 衝突とその後の時代 伊豆と本州の衝突にともなって隆起したり地層 a process you can clearly see that the soil grains get reduced in size as you travel upwards through the strata. 伊豆半島の隆起 が傾いたりしながら、地表に姿を現しました。 Uplift of Izu Massif The soil strata on the seabed of the Philippine Sea Plate was gradually pushed onto Honshu and uplifted. As a result, you can 衝突の進行 Soil strata from the seabed appear above sea level due to Progress of the collision see the landmass at an inclined angle today. collision of landmasses and land upliftment processes. These strata typically appear as inclined landforms. 60万年前 対岸に見えるタービダイト （陸上火山の時代）0.6 million years ago Turbidite from here 多賀火山 プレートが沈み込む場所である日本ではあちこちで「タービダイト」の地層が見られます。 Taga Volcano 達磨火山 You can see such turbidite strata in various places in the Japanese archipelago. Daruma Volcano 宇佐美火山 蛇石火山 Usami Volcano 北アメリカプレート Terrestrial Volcanoes Jyaishi Volcano 南崎火山Nanzaki Volcano North American Plate 伊豆半島の原型の完成 伊豆半島 Birth of Izu Peninsula 室戸岬 Izu Peninsula Cape Murotomisaki 60～20万年前 0.6～0.2 million years ago 日本海溝 箱根火山 日 本 Japan Trench Hakone Volcano Izu-Ogasawara Trench ユーラシアプレート 伊豆－小笠原海溝 室戸岬のタービダイト 天城火山 Eurasian Plate Amagi Volcano 南海トラフ Turbidite at Cape Murotomisaki Nankai Trough ほぼ現在の伊豆半島に The peninsula gets its present shape 太平洋プレート Pacific Plate 琉球海溝 20万年前～現代 Ryukyu Trench 0.2 million years ago～Recent 富士山 Fuji Volcano 丹那断層 フィリピン海プレート Tanna Fault Philippine Sea Plate ay 湾 B ga 河 ru 駿 Su 伊豆東部火山群 プレートが沈み込んでいる場所 石廊崎断層 Izu Tobu Volcano Group フィリピン Subduction line Irozaki Fault 生きている伊豆半島 Philippines この地図は ETOPO2 を使用して作成した。 This map created using ETOPO2 An active monogenetic volcano field and crustal movements マリアナ海溝Mariana Trench 伊豆半島ジオパーク IZU PENINSULA GEOPARK IZU PENINSULA 富士箱根伊豆国立公園 設置・管理者：伊豆市 産業振興課 監修：伊豆半島ジオパーク推進協議会 Fuji-Hakone-Izu National Park http://www.city.izu.shizuoka.jp/ http://izugeopark.org/.
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