ヒマラヤ山脈における侵食と降雨の分離

D W Burbank¹, A E Blythe, J Putkonen

¹Department of Geological Sciences, University of California, Santa Barbara, California 93106, USA. burbank@crustal.ucsb.edu

Nature

|December 12, 2003

まとめ

山岳における高浸食率は,降雨の傾きによってのみ引き起こされるものではない. 運河の幅や堆積物の負荷などの他の要因は,降水量の違いを均衡させ,ヒマラヤの均一な侵食を明らかにします.

科学分野:

ジオモルフォロジージオモルフォロジー
テクトニクス (地質学) とは
気候科学気候科学

背景:

数値モデルは,空間的侵食グラデーションが活性オロゲンで高いストレート率を誘発することを示唆しています.
これらのモデルはしばしば,浸食と放電とチャネルの傾きを結びつける"ストリーム-パワー"ルールを使用します.
降水量と斜面の変動は,侵食と地殻のストレスの梯度と相関すると予測されています.

研究の目的:

空間侵食の梯度が,大ヒマラヤの降水梯度と相関しているという仮説を検証するために.
主要なアクティブオロゲンにおける侵食率,降水量,および構造的上昇の間の関係を調査する.

主な方法:

ネパール・グレター・ヒマラヤのネットワークからの気象データを組み合わせた.
低温サーモクロノメトリー (時間スケール>10万年) を用いた地質侵食率の推定.
ヒマラヤ山頂を横断する約20kmのゾーンのデータを分析し,著しい降水差がある.

主要な成果:

地質的侵食速度の有意な空間的変動は,研究対象の地域全体で検出されなかった.
降雨量の減少は,より急な運河の斜面によって補償されませんでした.
運河の幅と沈殿物の濃度などの要因は,切断率に影響を与える降水変動を均衡させるように見える.

結論:

広大なヒマラヤの空間的に均一な侵食率は,有意な降雨グラデーションにもかかわらず観察されています.
川の切断は,運河の幅と沈殿物の負荷を含む,降水量と傾斜を超えた要因の影響を受けます.
均一な侵食は,地殻の斜面上の岩石の安定した,上向きの構造的移動と一致しています.

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