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1、第六章 冰川地貌,Chapter 6 Glacial Landforms,一.冰川作用,1.冰川,注意：冰体不运动则不叫冰川，称为死冰。,年平均气温在0以下的地区，降雪量大于融雪量，不断积累的积雪经一系列物理变化转化为冰川冰，并在自身的压力作用下向坡下运动，称为冰川。,现代冰川占陆地面积的10%，总面积约1.6107km2，总体积约2.6107km3，占全球淡水资源的85%，若冰川全部融化，可以使海面上升66m。,2.雪线年降雪量=年消融量的界限。3.影响雪线高度的因素: 1)温度（低纬度/高纬度） 2)降水量（补给与消融的关系） 3)地形 A.一般阴坡雪线低，阳坡雪线高 B.地形 气候 雪线
2、,消融带,Ablation消融Firn粒雪,雪线,地球上的雪线分布高度(据卡列斯尼克),雪线位置最高不在赤道,而在南北半球的副热带高压带。原因是赤道附近降水量多。这两个地区温度对雪线的影响不如降水量影响大。接近赤道附近的东非乞力马札罗山，雪线高度45705425m；南纬20o25o的安第斯山雪线高度达6400m。,昆仑山雪线,喜马拉雅山南坡雪线高度44004600m 北坡雪线高度58005900m,4.冰川的形成过程,5.冰川的运动 1)冰川运动的前提条件 冰层厚度临界厚度（每增加1个大气压，冰的融点降低0.0075oC） 2)导致冰川运动的因素 重力流 山岳冰川 压力流 大陆冰川,3)影响冰
3、川运动速度大小的因素 冰层厚度 地形坡度 冰面坡度 冰川温度,天山冰川,长江源头-唐古拉山格拉丹东冰川末端,天山最高峰托木尔峰（海拔7435米）,4)冰川的运动速度 A.缓慢（数十数百m/a） B.冰川各部分运动 速度不同 C.裂隙、褶皱,Figure 12.8 Movement of a glacier Cross-sectional view,格棱兰西北部冰盖前缘冰川沿剪切面向上滑动,Figure 12.9 Crevasses on a glacier, looking down from Mount Logan, Yukon Territory, CanadaPhoto by C. C.
4、 Plummer.,冰裂隙,Figure 12.10 Crevasses along the course of a glacier,5)冰进、冰退 A.冰进 B.冰退表示的是冰川末端位置的变化,格陵兰冰川消融卫片,托木尔峰冰川,6.冰川作用1)冰蚀作用冰冻风化作用(冰劈)挖掘作用（Plucking,先压碎，后拔起。若冰层厚100m，压力可达90t/m2）磨蚀作用(Abration action),Glacial striation in a rock outcrop in the Van Horn Range in Alaska.Mapping Striations on a regiona
5、l scale enables geologists to trace the direction of ice movement.,Figure 12.14 Striated and polished rock surface in South Australia. Unlike glacial striations commonly found in North America, this was caused by late Paleozoic glaciation.,2)冰川的搬运作用,表碛,冰川的搬运能力极强，比流水大20倍，而且可以从低处向高处搬运。运动冰碛,运动冰碛,侧碛,中碛,
6、内碛,底碛,中碛,3）冰川的堆积作用 底碛 中碛 侧碛 尾碛,二.冰川类型,根据冰川的形态、规模、大小和所处的地形条件，可将冰川分为四类：1.山岳冰川在山区范围内形成、流动和消亡的冰川。 1)冰斗冰川 2)悬冰川 3)山谷冰川,冰斗冰川,山谷冰川,托木尔峰地区的悬冰川,唐古拉山冰川,雪峰连绵的祁连山,祁连山“七一”冰川,祁连山冰川的陡崖,珠穆朗玛峰绒布冰川,祁连山中段冰川融水补给的哈拉湖,祁连山是我国现代冰川研究最早的地区之一；北坡的冰雪融水对于甘肃河西走廊的工农业用水有着重要的作用。现代冰川集中了全球淡水资源的85%。,2.山麓冰川山谷冰川流出山口，漫流于山前平原之上，形成山麓冰川。3.大陆
7、冰川面积巨大，冰层很厚，运动不受地形限制，覆盖了大片陆地的冰流。 1)冰盾冰川表面中心部位上凸 2)冰盖冰川表面随下伏地形起伏（范围更大）4.高原冰川发育在高原上的冰川。,Antarctica is located in the Southern Hemisphere and covers 13,824,000 square kilometers. It is the fifth largest landmass on the globe.,Ice covers 98% of Antarctica. The continent is home to 70% of Earths freshwat
8、er, and 91% of Earths ice. The ice averages 2.3 kilometers in thickness (1.5 miles). The thickest ice is about 4.8 kilometers thick (almost 3 miles).,Antarctica if no ice covered the continent (modified from Bentley, 1972).,Two continental ice sheets separated by the Transantarctic Mountains. The Ea
9、st Ice Sheet is land-based, meaning that most of its base lies above sea level. Without the weight of the ice, the land would rise even more (isostatic adjustment) and East Antarctica would form a single large landmass above sea level. The West Ice Sheet is a marine-based ice sheet. The differences
10、between these two ice sheets are very important for how they respond to the changing global environment. The East One is fairly stable and responds to environmental changes slowly, in contrast, the West One may be capable of changing very rapidly.,南极冰山,全球变暖导致南极冰川年均流失350亿吨,南极冰架垮塌,Figure 12.5 An icebe
11、rg off the coast of Antarctica.Photo by C. C. Plummer.,三、冰蚀地貌,1.冰斗(Cirque)2.角峰(Horn)、刃脊(Arete)3.冰川谷(Glacial Trough),Figure 12.16 (A) A stream-carved mountain landscape before glaciation. (B) The same area during glaciation Ridges and peaks become sharper due to frost wedging, (C) The same area after
12、 glaciation,Figure 12.18 Development of rock steps. (A) Valley floor before glaciation. (B) During glaciation. (C) Rock steps and rockbasin lakes, Sierra Nevada, California.,冰川谷纵剖面形成机制图解R.冰坎；B.岩盆；E.扩张流区；C.压缩流区,角峰,冰川U型谷,悬冰川,4.悬谷(Hanging valley),Tarn冰斗湖,Figure 12.17 A hanging valley in Yosemite Nation
13、al Park, California. Photo by C. C. Plummer.,5.冰川三角面、羊背石(Roche moutonnee)6.冰蚀平原,7.冰蚀阶地,主要由冰川侵蚀形成的一种阶梯状地形。,四.冰碛物及冰川堆积地貌,1.冰碛物的基本特征 （1）地形方面 常构成尾碛垅，侧碛垅和底碛平原。在地形组合上，上游为冰蚀地形，下游为冰碛地形。 （2）岩矿成分 不稳定矿物多，长石含量较高。,（3）岩相特点,粒度成分 大小混杂，砾石粘土混杂堆积冰碛物的分选性 差冰碛砾石的磨圆度 差，砾石基本为棱角状冰碛砾石的表面形态 发育特殊形状的砾石，有压 坑和压弯现象冰川漂砾(Glacial Err
14、atic)冰碛物中的砂粒特征 石英表面发育贝壳状断口 砾石的排列方向,冰川漂砾,Figure 12.24 Unsorted debris, including boulders, transported on top of and alongside a glacier in Peru. View is downglacier.,2.冰碛地貌1)冰碛丘陵（基碛丘陵）基碛表碛、内碛、中 碛、底碛2)侧碛堤（垄）(Lateral moraine)3)尾碛垄(End moraine)4)中碛垄(Middle moraine),Figure 12.27 Looking downvalley in th
15、e Peruvian Andes. Lateral moraine alongside a glacier. Another high moraine to the left marks the former edge of the glacier.,Figure 12.28 Medial moraines on valley glaciers, Yukon Territory, Canada. Ice is flowing toward viewer and to lower right.,5)鼓丘(Drumlin),Figure 12.30 A drumlin in New York state.,6)冰碛阶地,冰川谷中，冰碛物组成的阶地。,五、冰水堆积地貌,冰雪融化以后形成的水流称为冰水。在冰川区内，这种水流可以形成冰面河、冰下河、冰侧河及冰下湖、冰面湖等。大部分冰水最后经冰川前缘流出，形成冰前河流及冰前湖泊。上述各种水流形成的堆积物，统称冰水堆积物。,1.冰砾阜及冰砾阜阶地,1)冰砾阜(Kame)A.常分布在冰川边缘最近终碛的地方。B.结构C.成因2)冰砾阜阶地(Kame Terrace),
