首页
登录
职称英语
For all their great diversity of shapes and sizes, glaciers can be divided
For all their great diversity of shapes and sizes, glaciers can be divided
游客
2023-09-03
43
管理
问题
For all their great diversity of shapes and sizes, glaciers can be divided into two essential types: valley glaciers, which flow downhill from mountains and are shaped by the constraints of topography (地貌), and ice sheets, which flow outward in all directions from dome--like centers of accumulated ice to cover vast expanse of terrain. Whatever their type, most glaciers are remnants of great shrouds of ice that covered the earth years ago. In a few of these glaciers the oldest ice is very ancient indeed; the age of parts of the Antarctic sheet may exceed 500,000 years.
Glaciers are born in rocky womb above the snow line, where there is sufficient winter snowfall and summer cold for snow to survive the annual melting. The long gestation period of a glacier begins with the accumulation and gradual transformation of snow flakes. Soon after they reach the ground, complex snowflakes are reduced to compact, roughly spherical ice crystals, and the basic components of a glacier. As new layers of snow and firm, snow that survives the melting of the previous summer, accumulate, they squeeze out most of the air bubbles trapped within and between the crystals below. This process of recrystallization continues throughout the life of the glacier.
The length of time required for the creation of glacier ice depends mainly upon the temperature and the rate of snowfall. In Iceland, where snowfall is heavy and summer temperatures are high enough to produce plenty of melt--water, glacier ice may come into being in a relatively short time--say, ten years. In parts of Antarctica, where snowfall is scant and the ice remains well below its melting temperature year round, the process may require hundreds of years.
The ice does not become a glacier until it moves under its own weight, and it cannot move significantly until it reaches a critical thickness--the point at which the weight of the piled-up layers overcomes the internal strength of the ice and the friction between the ice and the ground. This critica} thickness is about 60 feet. The fastest moving glaciers have been gauged at not much more than two and a half miles per year, and some cover less than 1/100 inch in that same amount of time. But no matter how infinitesimal the flow, movement is what distinguishes a glacier from a mere mass of ice. [br] Why does the author mention the formation of glaciers in Iceland and Antarctica in the third paragraph?
选项
A、To show the temperature in the two places.
B、To show the environment in the two places.
C、To show the importance of temperature and the rate of snowfall in the formation of glaciers.
D、To show these two places contain the oldest glaciers in the world.
答案
C
解析
根据题干关键词formation of glaciers in Iceland and Antarctica,the third paragraph定位到原文第三段。文章第三段以冰岛和南极地区的冰川形成为例来说明由于降雪量和夏季气温的不同而导致冰川形成时间的不同,由此可以推断出降雪量和夏季气温在冰川形成过程中起着很重要的作用。
转载请注明原文地址:https://tihaiku.com/zcyy/2982482.html
相关试题推荐
Plato,anancientGreekphilosopher,believedthatmenaredividedintothre
Plato,anancientGreekphilosopher,believedthatmenaredividedintothre
Plato,anancientGreekphilosopher,believedthatmenaredividedintothre
Humanity’sprimal(原始的)effortstosystematizetheconceptsofsize,shapes,
Humanity’sprimal(原始的)effortstosystematizetheconceptsofsize,shapes,
Humanity’sprimal(原始的)effortstosystematizetheconceptsofsize,shapes,
Humanity’sprimal(原始的)effortstosystematizetheconceptsofsize,shapes,
Humanity’sprimal(原始的)effortstosystematizetheconceptsofsize,shapes,
Humanity’sprimal(原始的)effortstosystematizetheconceptsofsize,shapes,
Humanity’sprimal(原始的)effortstosystematizetheconceptsofsize,shapes,
随机试题
[originaltext]M:Ijuststoppedbyyourofficeinthebank.Theytoldmethaty
操作风险评估的步骤中,属于准备阶段的有( )。A.识别评估对象 B.绘制流程
社区服务具有精神文明建设的功能,体现在()A.培养了居民的文明意识 B
患儿男,7岁。因发热、恶心、呕吐1周,近2天巩膜黄而就诊。出生时注射过乙型肝炎疫
60岁以上的老年人的用药剂量是成年人剂量的A:1/2 B:2/3 C:3/4
能够从上述材料中推出的是:A.2021年全国普通高校毕业生人数超过201
某广告牌上需安装特殊的艺术字模型,大字价格是小字价格的2倍,而大字字数是小字字数
A.骨损伤 B.高原病 C.急性胰腺炎 D.剧烈运动 E.肥胖症淀粉酶增
下列各项中,能够成为法律关系主体的有()。A.甲市财政局 B.大学生张某
按照流动负债产生的原因,下列负债中.由于利润分配而产生的流动负债是()。
最新回复
(
0
)