高山冰川地貌区垂直分带性与地质灾害空间配置关系

Relationship between vertical zonality and spatial allocation of geological hazards in alpine glacial geomorphology

高山冰川地貌因垂向落差大,受垂直性气候条件和局地水热环境影响,造就了典型的垂直分带性特征。而地质灾害作为表生岩土圈动态平衡失稳外在动力形式,必然与其禀赋的构造地貌与气候环境密切相关。基于青藏高原冰川地貌区地貌特征及地质灾害统计分析,梳理各地貌单元垂直分带性界限标志及典型特征,进而构建高山冰川地貌区垂直分带性与地质灾害的空间配置关系。研究表明:(1)高山冰川地貌区可按雪线、冰线、雨线与高山苔原线等“四线”进行界限标志划分,且大陆性与海洋性冰川地貌区界限高度存在显著差异;(2)夷平面为高山冰川地貌区地质灾害重要物源场所,因冰川类型差异存在明显不同。具体而言,大陆性冰川区普遍存在山顶面、高原面2级夷平面物源区;而海洋性冰川区则普遍存在山顶面、山前侵蚀面及河谷侵蚀面3级夷平面物源区。(3)高山冰川地貌区地质灾害按照“四线”界限标志存在典型的垂直分带性特征,具体按照“四线”界限范围、动力地质作用方式、海拔高度可划分为:超高位冰蚀型(雪线以上/冰-岩作用带,对应划分依据,下同)、高位溃蚀型(雪线-冰线之间/冰-水-岩屑作用带)、中位冻融剥蚀型(冰线附近/冰-水-土作用带)及低位降水侵蚀型(高山苔原线以下/水-土-生物作用带)4类。(4)不同界带间地质灾害存在一定的链式放大效应,代表性链生组合关系有:①冰(雪)岩崩→冰湖及溃决→强补给型泥流;②冰(雪)岩崩→冰雪型碎屑流→堰塞湖及山洪;③冰碛物堆积滑坡→冰雪型碎屑流→强补给型泥流。研究可为我国“一带一路”、川藏铁路等重大工程地质灾害分区分带防控提供基础参考。

Due to the large vertical drop,the alpine glacier geomorphology is affected by vertical climatic conditions and local hydrothermal environment,resulting in typical vertical zoning characteristics.As an external dynamic form of dynamic equilibrium instability of epigenetic lithosphere,geological hazards must be closely related to its endowment of tectonic geomorphology and climatic environment.Based on the geomorphological features and statistical analysis of geological disasters in the glacial geomorphology of the Tibetan Plateau,this paper combed the typical characteristics of vertical zonation and endowment of each geomorphological unit,and then constructed the spatial allocation relationship between vertical zonation and geological disasters in alpine glacial geomorphology.The main results are as follows:(1)Alpine glacial geomorphology can be divided according to“four lines”,such as snow line,ice line,rain line and alpine tundra line,and there is a significant difference in boundary height between continental and marine glacial geomorphology.(2)The planation surface is important provenance of geological hazards in alpine glacial geomorphology area,which is obviously different due to the difference of glacier type.Specifically,there are two-grade planation plane provenance areas on mountain top and plateau surface in continental glacier area,while there are three-grade planation plane provenance areas on mountain top,Piedmont erosion surface and river valley erosion surface in marine glacier area.(3)There are typical vertical zoning characteristics of geological disasters in alpine glacial geomorphology according to the boundary mark of“four lines”.According to the boundary of“four lines”,the mode of dynamic geological action and altitude can be divided into:ultra-high ice erosion type(above snow line/ice-rock interaction zone).There are four types:high erosion type(between snow line and ice line/ice-water-cuttings interaction zone),middle freeze-thaw denudation type(near ice line/ice-water-soil interaction zone)and low precipitation erosion type(below the alpine tundra line/water-soil-biological interaction zone).(4)There is a certain chain amplification effect of geological disasters between different boundary zones.the representative chain assemblage relationships are as follows:①ice(snow)rock avalanche→glocial lake and outburst flood→strong replenishment type mud flow;②ice(snow)rock avalanche→ice and snow debris flow→barrier lake and mountain torrent;③moraine accumulation landslide→ice and snow debris flow→strong replenishment mud flow.The study can provide a basic reference for the regional and zonal prevention and control of major engineering geological disasters such as Belt and Road Initiative and Sichuan-Tibet Railway.