TPO 15 Glacier Formation（自然科学--地理）

字数：659

建议做题时间20分钟

Glaciers are slowly moving masses of ice that have accumulated on land in areas where more snowfalls during a year than melts. Snow falls as hexagonal crystals, but once on the ground, snow is soon transformed into a compacted mass of smaller, rounded grains. As the air space around them is lessened by compaction and melting, the grains become denser. With further melting, refreezing, and increased weight from newer snowfall above, the snow reaches a granular recrystallized stage intermediate between flakes and ice known as firn. With additional time, pressure, and refrozen meltwater from above, the small firn granules become larger, interlocked crystals of blue glacial ice. When the ice is thick enough, usually over 30 meters, the weight of the snow and firn will cause the ice crystals toward the bottom to become plastic and to flow outward or downward from the area of snow accumulation.

Glaciers are open systems, with snow as the system’s input and meltwater as the system's main output. The glacial system is governed by two basic climatic variables: precipitation and temperature. For a glacier to grow or maintain its mass, there must be sufficient snowfall to match or exceed the annual loss through melting, evaporation, and calving, which occurs when the glacier loses solid chunks as icebergs to the sea or to large lakes. If summer temperatures are high for too long, then all the snowfall from the previous winter will melt. Surplus snowfall is essential for a glacier to develop. A surplus allows snow to accumulate and for the pressure of snow accumulated over the years to transform buried snow into glacial ice with a depth great enough for the ice to flow. Glaciers are sometimes classified by temperature as faster-flowing temperate glaciers or as slower-flowing polar glaciers.

Glaciers are part of Earth’s hydrologic cycle and are second only to the oceans in the total amount of water contained. About 2 percent of Earth’s water is currently frozen as ice. Two percent may be a deceiving figure, however, since over 80 percent of the world’s freshwater is locked up as ice in glaciers, with the majority of it in Antarctica. The total amount of ice is even more awesome if we estimate the water released upon the hypothetical melting of the world’s glaciers. Sea level would rise about 60 meters. This would change the geography of the planet considerably. In contrast, should another ice age occur, sea level would drop drastically. During the last ice age, sea level dropped about 120 meters.

When snowfalls on high mountains or in polar regions, it may become part of the glacial system. Unlike rain, which returns rapidly to the sea or atmosphere, the snow that becomes part of a glacier is involved in a much more slowly cycling system. Here water may be stored in ice form for hundreds or even hundreds of thousands of years before being released again into the liquid water system as meltwater. In the meantime, however, this ice is not static. Glaciers move slowly across the land with tremendous energy, carving into even the hardest rock formations and thereby reshaping the landscape as they engulf, push, drag, and finally deposit rock debris in places far from its original location. As a result, glaciers create a great variety of landforms that remain long after the surface is released from its icy covering.

Throughout most of Earth’s history, glaciers did not exist, but at the present time about 10 percent of Earth’s land surface is covered by glaciers. Present-day glaciers are found in Antarctica, in Greenland, and at high elevations on all the continents except Australia. In the recent past, from about 2.4 million to about 10,000 years ago, nearly a third of Earth’s land area was periodically covered by ice thousands of meters thick. In the much more distant past, other ice ages have occurred.

题目

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答案解析

1. 词汇题

解析：inter-在...之间、在一起，lock锁，interlock互锁、紧密连接，选B

2. 事实信息否定题

解析：A根据hexagonal crystal定位到第2句，原文没说形成thick layer，错。B根据compact, grain定位到第2句，正确。C根据granules定位到倒数第3句，正确。D根据air space定位到第3句，正确。

3. 词汇题

解析：match匹配，选D

4. 词汇题

解析：trans-横穿、到...另一边、变化，form形成，transform改变、转换，选C

5. 事实信息否定题

解析：A根据pressure定位到倒数第2句，正确。B根据melting, evaporation, calving定位到第3句，正确。C根据bury定位到倒数第2句，而glacial ice在前段提到被称为firn，正确。D根据temperate glaciers定位到最后一句，两种glaciers是并列关系，没有D中的比较，选D

6. 推断题

解析：根据fast moving glaciers定位到最后一句，说按温度分，冰川可分为快速移动的temperate glaciers和慢速移动的polar glaciers。所以，fast moving需要的条件是temperate，选B

7. 词汇题

解析：deceive欺骗，选D

8. 修辞目的题

解析：该句说如果预计全球冰川融化释放的水，总量更惊人。前两句都是数据说明，段首句说冰川是第二大水源，所以高亮部分也是在说明冰川水很多，选B

9. 事实信息否定题

解析：A根据fresh water定位到第3句，说80%的淡水都在冰川，说明冰川有最多的淡水，A对。B根据ice age, sea level定位到最后两句，正确。C根据total amount of water能够找到在第4句有total amount of ice，不对，选C。D根据ice, Earth’s water定位到第2句，正确。

10. 词汇题

解析：原句说冰不static，后句说冰川move，根据move可知冰不是不动的，static静止的，选A

11. 句子简化题

解析：原句结构为冰川穿过陆地，形成最硬的岩层，重塑地貌。A没说到reshape； B对；C说reshape rock formations，原文说reshape landscape；D改变结构。

12. 事实信息题

解析：根据present time定位到第1句，说在地球历史上冰川不存在，但现在有10%的地表都覆盖冰川，所以说明有冰川覆盖是unusual，选A

13. 句子插入题

解析：插入句提到firn，说明前句或后句应该有firn，C前第一次出现firn,且是被称作firn，所以插入句应该在C后。C后这句又提到firn become ice，与插入句ice对应，所以选C

14. 段落小结题

解析：A对应第一段，正确
B对应第4段，正确
C与原文第2段最后一句相反，不选
D对应原文第1最后一句和第4段的最后两句，正确
E是第3段的一个细节，不选
F与原文第4段最后一句相反，不选

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