バッドランド斜面における侵食プロセスに関する地化学的検討

• 中田 英二

  （財）電力中央研究所

• 千木良 雅弘

  京都大学防災研究所

書誌事項

タイトル別名

• Geochemistry of Erosion Processes on Badland Slopes
• バッドランド シャメン ニ オケル シンショク プロセス ニ カンスル チ カガクテキ ケントウ タイワン ナンブ デイカザン ガ ブンプ スル コテイコウソウ デ ノ チョウサ
• A Case Study of the Gutingkeng Formation Where Mud Volcanoes are Distributed in Southern Taiwan
• ―台湾南部，泥火山が分布する古亭坑層での調査―

抄録

 Understanding erosion processes is important to prevent natural disasters such as slope failure and bedrock erosion in immature sedimentary rocks. Pliocene–Pleistocene illite-rich, non-smectite mudstone of the Gutingkeng Formation is distributed over 250 km² in southern Taiwan, forming badlands (locally called moon-world) with mud volcanoes nearby. These volcanoes erupt saline water and natural gas, and producing a Na⁺, Ca²⁺, Cl^-, and SO₄^2- rich unsaturated Popcorn crust, which covers the mudstone slope surfaces in the moon-world area. In the crust porewater, ion strength reaches about 10 mol/L; zeta potential on particle surfaces shows a highly positive voltage. Repulsion occurs between particles under this high voltage in the crust, which is rapidly slaked to form mud by heavy precipitation. The zone that is rapidly slaked by precipitation reaches 10-20 cm beneath the crust surface. Ion strength of porewater of fresh mudstone is 0.5 mol/L approaches 0 mV (range 0.2-0.5 mol/L, pH 4-6). The surface charge of particles decreases with the infiltration of precipitation into the crust and fresh rock, with a minus surface charge occurring with increased rain infiltration. This leads to many cracks forming on the surface of mudstone, which is different from the mechanism of rapid slaking.<br> Evaporation from the 10-20 cm-thick zone between the crust and the underlying fresh mudstone would stop if water was not supplied from depth, which is supported by in-situ measurements of water evaporation in the field. These mudstones erode readily under high precipitation because of the repulsion caused by the high ion strength of porewater. High-salinity porewater including mudstone is distributed near the active mud volcanoes where saline water rises and there is a rapid uplift rate. Rapid slaking occurred with some elements in the concentrated crust and near the surface drying zone.

収録刊行物

• 地学雑誌

  地学雑誌 118 (3), 511-532, 2009

  公益社団法人 東京地学協会

キーワード

• 水質
• 急速スレーキング
• 侵食
• 泥火山
• バッドランド
• 月世界
• 台湾

詳細情報

• CRID: 1390001204230210560
• NII論文ID: 10030365781
• NII書誌ID: AN00322536
• DOI: 10.5026/jgeography.118.511
• ISSN: 18840884
• ISSN: 0022135X
• NDL書誌ID: 10386654
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I10386654
• データソース種別:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
  • KAKEN
• 抄録ライセンスフラグ: 使用不可