托福阅读背景知识之冰川地质学.docx

智课网TOEFL备考资料托福阅读背景知识之冰川地质学 摘要： 地质类的文章在TPO听力中出现的概率相比生物、文学、艺术历史、人类学等学科要少的多，但是每隔几场考试，还是会发现这类学科文章的身影，一旦此类文章出现的话，非常致命，有些难缠的题目比如排序题、多选判断题都是极容易出现在这样的话题中的。 地质学的相关话题可能很多考生没有注意到，主要是因为这类题目并不多，在 托福 阅读中不长出现，但是这类题目的难度却非常高，如果不提前了解下背景是很容易出错的。 回到咱们关于冰川这类话题，还是先来分析分析此类话题在真题中的比重与频率吧，托福TPO真题中直接涉及到冰川的话题文章一共有7篇，它们分别是： 阅读 TPO-19-3：Discovering the Ice Ages 发现冰期 TPO-15-3：Glacier Formation冰川的形成 OG Test 2：Green Icebergs 绿色冰山 TPO-9-1：Colonizing the Americas via the Northwest Coast通过西北海岸在美洲定居 OG Test 1：Geology and Landscape地质学和地貌 听力 TPO 7 Lecture 4 TPO 15 Lecture 2 以下内容是我们在听力和阅读中只要关于将冰川的话题，就随处可见的，只要读明白了，记住了下面的这段内容，后期关于冰川的形成无论怎么讲，怎么出题都难不倒咱们了。 Gorner Glacier in Switzerland Glaciers form where the accumulation of snow and ice exceeds ablation. The area in which a glacier forms is called a cirque (corrie or cwm) - a typically armchair-shaped geological feature (such as a depression between mountains enclosed by artes) - which collects and compresses through gravity the snow which falls into it. This snow collects and is compacted by the weight of the snow falling above it forming nv. Further crushing of the individual snowflakes and squeezing the air from the snow turns it into glacial ice. This glacial ice will fill the cirque until it overflows through a geological weakness or vacancy, such as the gap between two mountains. When the mass of snow and ice is sufficiently thick, it begins to move due to a combination of surface slope, gravity and pressure. On steeper slopes, this can occur with as little as 15 m (50 ft) of snow-ice. In temperate glaciers, snow repeatedly freezes and thaws, changing into granular ice called firn. Under the pressure of the layers of ice and snow above it, this granular ice fuses into denser and denser firn. Over a period of years, layers of firn undergo further compaction and become glacial ice. Glacier ice is slightly less dense than ice formed from frozen water because it contains tiny trapped air bubbles. Glacial ice has a distinctive blue tint because it absorbs some red light due to an overtone of the infrared OH stretching mode of the water molecule. Liquid water is blue for the same reason. The blue of glacier ice is sometimes misattributed to Rayleigh scattering due to bubbles in the ice. 更多的关于冰川知识的补充： 冰川(glacier)是一巨大的流动固体，是在高寒地区由雪再结晶聚积成巨大的冰川冰，因重力这主要因素使冰川冰流动，成为冰川。冰川作用包括侵蚀、搬运、堆积等作用，这些作用造成许多地形，使得经过冰川作用的地区形成多样的地貌。此外，若将冰川的体积换成水量，则除海水之外，占地球上所有的水量的 97.8%。 在极地和高山地区，气候严寒，常年积雪，当雪积聚在地面上后，如果温度降低到零下，可以受到它本身的压力作用或经再度结晶而造成雪粒，称为粒雪(firn)。当雪层增加，将粒雪往更深处埋，冰的结晶越变越粗，而粒雪的密度则因存在於粒雪颗粒间的空气体积不断减少而增加，使粒雪变得更为密实而形成蓝色的冰川冰，冰川冰形成后，因受自身很大的重力作用形成塑性体，沿斜坡缓慢运动或在冰层压力下缓缓流动形成冰川。 考点补充： 在托福文章中还频繁提到冰川的研究技术：同位素年代测定radiometric dating，来测定冰川作用发生的年代。托