Mechanisms of debris supply onto rock glaciers

岩石冰川碎片供应机制

• 批准号: 12680086
• 负责人: MATSUOKA Norikazu
• 金额: $ 1.86万
• 依托单位: University of Tsukuba
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12680086/
• 关键词: Periglacial; Permafrost; Debris production; Rock glaciers; Frost weathering; Rockfall

Recent global warming has caused melting of rock glaciers in mid-latitude high mountains, possibly triggering rock avalanches and debris flows. This research aims at modeling rock glacier dynamics in terms of debris production processes. Field observations in the Swiss Alps involve : (1) automated monitoring of rock joint propagation and rock temperature on rockwalls ; (2) measurements of the size and volume of rockfall debris ; (3) longitudinal variation in the composition of rock debris ; and (4) DC resistivity tomography on rock glacier structure.The research provided the following outcomes. (1) Seasonal freezing enlarges rock joints and subsequent thawing triggers boulder falls, which means that the volume of rockfall debris depends mainly on the maximum freeze-thaw depth. (2) Fallen large boulders can deposit beyond the talus slope, which eventually develop the upper open-work blocky layer overlying the lower frozen debris layer with permafrost creep. Such fall sorting results in the two-layer structure. (3) Recent warming has accelerated the movement of many rock glaciers located near the lower limit of the mountain permafrost belt. However, this in turn decreases the thickness of the debris layer and surface gradient, eventually inactivating the rock glaciers. The rock glacier movement also shows significant inter-year variability in response to snow conditions.Finally, a model of the contemporary debris budget in rock glaciers was proposed on the basis of the field data on the rate of debris production from rockwalls and the tree-dimensional movement of rock glaciers.

最近的全球变暖导致中纬度高山的岩石冰川融化，可能引发岩石雪崩和泥石流。本研究旨在从碎屑产生过程的角度模拟岩石冰川动力学。瑞士阿尔卑斯山的野外观测包括：(1)岩壁上岩石节理扩展和岩石温度的自动监测；（二）测定岩屑的大小和体积；(3)岩屑组成的纵向变化；岩石冰川结构直流电阻率层析成像。研究提供了以下结果。(1)季节性冻结使岩石节理扩大，随后的解冻引发了落石，这意味着落石碎片的体积主要取决于最大冻融深度。(2)落下的大块巨石可在距骨坡外沉积，最终形成上部露天块状层覆于下部冻结碎屑层，并伴有多年冻土蠕变。这种落分选导致了两层结构。(3)近年来的气候变暖加速了位于山地多年冻土带下限附近的许多岩石冰川的运动。然而，这反过来又减少了碎屑层的厚度和表面坡度，最终使岩石冰川失去活性。岩石冰川运动也表现出显著的年际变化，以响应雪条件。最后，基于岩壁碎屑产生速率和岩石冰川三维运动的野外数据，提出了当代岩石冰川碎屑收支模型。

项目成果

Norikazu Matsuoka: "Geological control on the distribution and characteristics of talus-derired rock glaciers"Anuual Report of the Institute of Geoscieuce, University of Tsukuba. 27. 11-16 (2001)

松冈纪一：“距石冰川分布和特征的地质控制”筑波大学地球科学研究所年度报告。

Matsuoka, N., Hirakawa, K., Watanabe, T., Ikeda, A.: "Slope dynamics in the Alpine mountain permafrost belt"Journal of Geography. 109. 746-752 (2000)

Matsuoka, N.、Hirakawa, K.、Watanabe, T.、Ikeda, A.：“高山永久冻土带的坡度动力学”地理杂志。

松岡憲知: "欧州アルプス山岳永久凍土帯の斜面変動"地学雑誌. 109・5. 746-752 (2000)

Kentomo Matsuoka：“欧洲阿尔卑斯山永久冻土带的斜坡变形”地质杂志 109・5（2000）。

Matsuoka, N.: "Direct observation of frost wedging in alpine bedrock"Earth Surface Processes and Landforms. 26. 601-614 (2001)

Matsuoka, N.：“直接观察高山基岩中的霜楔”地球表面过程和地貌。

Norikazu Matsuoka: "Direct observation of frost wedging in alpine bedrock"Earth Surface Processes and Land Forms. 26・6. 601-614 (2001)

Norikazu Matsuoka：“高山基岩中霜楔的直接观察”地球表面过程和土地形态 601-614（2001）。