Icebergs are massive blocks of ice, irregular in shape; they float with only about 12 percent of their mass above the sea surface. They are formed by glaciers—large rivers of ice that begin inland in the snows of Greenland, Antarctica, and Alaska—and move slowly toward the sea. The forward movement, the melting at the base of the glacier where it meets the ocean, and waves and tidal action cause blocks of ice to break off and float out to sea.
Icebergs are ordinarily blue to white, although they sometimes appear dark or opaque because they carry gravel and bits of rock. They may change color with changing light conditions and cloud cover, glowing pink or gold in the morning or evening light, but this color change is generally related to the low angle of the Sun above the horizon. However, travelers to Antarctica have repeatedly reported seeing green icebergs in the Weddell Sea and, more commonly, close to the Amery Ice Shelf in East Antarctica.
One explanation for green icebergs attributes their color to an optical illusion when blue ice is illuminated by a near-horizon red Sun, but green icebergs stand out among white and blue icebergs under a great variety of light conditions. Another suggestion is that the color might be related to ice with high levels of metallic compounds, including copper and iron. Recent expeditions have taken ice samples from green icebergs and ice cores—vertical, cylindrical ice samples reaching down to great depths—from the glacial ice shelves along the Antarctic continent. Analyses of these cores and samples provide a different solution to the problem.
The ice shelf cores, with a total length of 215 meters (705 feet), were long enough to penetrate through glacial ice—which is formed from the compaction of snow and contains air bubbles—and to continue into the clear, bubble-free ice formed from seawater that freezes onto the bottom of the glacial ice. The properties of this clear sea ice were very similar to the ice from the green iceberg. The scientists concluded that green icebergs form when a two-layer block of shelf ice breaks away and capsizes (turns upside down), exposing the bubble-free shelf ice that was formed from seawater.
A green iceberg that stranded just west of the Amery Ice Shelf showed two distinct layers: bubbly blue-white ice and bubble-free green ice separated by a one-meter- long ice layer containing sediments. The green ice portion was textured by seawater erosion. Where cracks were present, the color was light green because of light scattering; where no cracks were present, the color was dark green. No air bubbles were present in the green ice, suggesting that the ice was not formed from the compression of snow but instead from the freezing of seawater. Large concentrations of single-celled organisms with green pigments (coloring substances) occur along the edges of the ice shelves in this region, and the seawater is rich in their decomposing organic material. The green iceberg did not contain large amounts of particles from these organisms, but the ice had accumulated dissolved organic matter from the seawater. It appears that unlike salt, dissolved organic substances are not excluded from the ice in the freezing process. Analysis shows that the dissolved organic material absorbs enough blue wavelengths from solar light to make the ice appear green.
Chemical evidence shows that platelets (minute flat portions) of ice form in the water and then accrete and stick to the bottom of the ice shelf to form a slush (partially melted snow). The slush is compacted by an unknown mechanism, and solid, bubble-free ice is formed from water high in soluble organic substances. When an iceberg separates from the ice shelf and capsizes, the green ice is exposed.
The Amery Ice Shelf appears to be uniquely suited to the production of green icebergs. Once detached from the ice shelf, these bergs drift in the currents and wind systems surrounding Antarctica and can be found scattered among Antarctica’s less colorful icebergs.
Paragraph 1: Icebergs are massive blocks of ice, irregular in shape; they float with only about 12 percent of their mass above the sea surface. They are formed by glaciers—large rivers of ice that begin inland in the snows of Greenland, Antarctica, and Alaska—and move slowly toward the sea. The forward movement, the melting at the base of the glacier where it meets the ocean, and waves and tidal action cause blocks of ice to break off and float out to sea.
1. According to paragraph 1, all of the following are true of icebergs EXCEPT:
○They do not have a regular shape.
○They are formed where glaciers meet the ocean.
○Most of their mass is above the sea surface.
○Waves and tides cause them to break off glaciers.
Paragraph 2: Icebergs are ordinarily blue to white, although they sometimes appear dark or opaque because they carry gravel and bits of rock. They may change color with changing light conditions and cloud cover, glowing pink or gold in the morning or evening light, but this color change is generally related to the low angle of the Sun above the horizon. However, travelers to Antarctica have repeatedly reported seeing green icebergs in the Weddell Sea and, more commonly, close to the Amery Ice Shelf in East Antarctica.
2. According to paragraph 2, what causes icebergs to sometimes appear dark or opaque?
○A heavy cloud cover
○The presence of gravel or bits of rock
○The low angle of the Sun above the horizon
○The presence of large cracks in their surface
Paragraph 3: One explanation for green icebergs attributes their color to an optical illusion when blue ice is illuminated by a near-horizon red Sun, but green icebergs stand out among white and blue icebergs under a great variety of light conditions. Another suggestion is that the color might be related to ice with high levels of metallic compounds, including copper and iron. Recent expeditions have taken ice samples from green icebergs and ice cores—vertical, cylindrical ice samples reaching down to great depths—from the glacial ice shelves along the Antarctic continent. Analyses of these cores and samples provide a different solution to the problem.
3. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
○One explanation notes that green icebergs stand out among other icebergs under a great variety of light conditions, but this is attributed to an optical illusion.
○One explanation for the color of green icebergs attributes their color to an optical illusion that occurs when the light from a near-horizon red Sun shines on a blue iceberg.
○One explanation for green icebergs attributes their color to a great variety of light conditions, but green icebergs stand out best among other icebergs when illuminated by a near-horizon red Sun.
○One explanation attributes the color of green icebergs to an optical illusion under special light conditions, but green icebergs appear distinct from other icebergs under a great variety of light conditions.
Paragraph 4: The ice shelf cores, with a total length of 215 meters (705 feet), were long enough to penetrate through glacial ice—which is formed from the compaction of snow and contains air bubbles—and to continue into the clear, bubble-free ice formed from seawater that freezes onto the bottom of the glacial ice. The properties of this clear sea ice were very similar to the ice from the green iceberg. The scientists concluded that green icebergs form when a two-layer block of shelf ice breaks away and capsizes (turns upside down), exposing the bubble-free shelf ice that was formed from seawater.
4. The word “penetrate” in the passage is closest in meaning to
○ collect
○ pierce
○ melt
○ endure
5. According to paragraph 4, how is glacial ice formed?
○By the compaction of snow
○By the freezing of seawater on the bottom of ice shelves
○By breaking away from the ice shelf
○By the capsizing of a two-layer block of shelf ice
6. According to paragraph 4, ice shelf cores helped scientists explain the formation of green icebergs by showing that
○ the ice at the bottom of green icebergs is bubble-free ice formed from frozen seawater
○ bubble-free ice is found at the top of the ice shelf
○ glacial ice is lighter and floats better than sea ice
○ the clear sea ice at the bottom of the ice shelf is similar to ice from a green iceberg
Paragraph 5: A green iceberg that stranded just west of the Amery Ice Shelf showed two distinct layers: bubbly blue-white ice and bubble-free green ice separated by a one-meter-long ice layer containing sediments. The green ice portion was textured by seawater erosion. Where cracks were present, the color was light green because of light scattering; where no cracks were present, the color was dark green. No air bubbles were present in the green ice, suggesting that the ice was not formed from the compression of snow but instead from the freezing of seawater. Large concentrations of single-celled organisms with green pigments (coloring substances) occur along the edges of the ice shelves in this region, and the seawater is rich in their decomposing organic material. The green iceberg did not contain large amounts of particles from these organisms, but the ice had accumulated dissolved organic matter from the seawater. It appears that unlike salt, dissolved organic substances are not excluded from the ice in the freezing process. Analysis shows that the dissolved organic material absorbs enough blue wavelengths from solar light to make the ice appear green.
7. Why does the author mention that “The green ice portion was textured by seawater erosion”?
○To explain why cracks in the iceberg appeared light green instead of dark green
○To suggest that green ice is more easily eroded by seawater than white ice is
○To support the idea that the green ice had been the bottom layer before capsizing
○To explain how the air bubbles had been removed from the green ice
8. The word “accumulated” in the passage is closest in meaning to
○collected
○frozen
○released
○ covered
9. The word “excluded” in the passage is closest in meaning to
○ kept out
○ compressed
○ damaged
○ gathered together
Paragraph 6: Chemical evidence shows that platelets (minute flat portions) of ice form in the water and then accrete and stick to the bottom of the ice shelf to form a slush (partially melted snow). The slush is compacted by an unknown mechanism, and solid, bubble-free ice is formed from water high in soluble organic substances. When an iceberg separates from the ice shelf and capsizes, the green ice is exposed.
10. The word “accrete” in the passage is closest in meaning to
○advance
○transfer
○flatten out
○come together
11. Which of the following is NOT explained in the passage?
○Why blocks of ice break off where glaciers meet the ocean
○Why blocks of shelf ice sometimes capsize after breaking off
○Why green icebergs are commonly produced in some parts of Antarctica
○Why green icebergs contain large amounts of dissolved organic pigments
12. The passage supports which of the following statements about the Amery Ice Shelf?
○The Amery Ice Shelf produces only green icebergs.
○The Amery Ice Shelf produces green icebergs because its ice contains high levels of metallic compounds such as copper and iron.
○The Amery Ice Shelf produces green icebergs because the seawater is rich in a particular kind of soluble organic material.
No green icebergs are found far from the Amery Ice Shelf.
Paragraph 2: Icebergs are ordinarily blue to white, although they sometimes appear dark or opaque because they carry gravel and bits of rock. They may change color with changing light conditions and cloud cover, glowing pink or gold in the morning or evening light, but this color change is generally related to the low angle of the Sun above the horizon. ■However, travelers to Antarctica have repeatedly reported seeing green icebergs in the Weddell Sea and, more commonly, close to the Amery Ice Shelf in East Antarctica. ■One explanation for green icebergs attributes their color to an optical illusion when blue ice is illuminated by a near-horizon red Sun, but green icebergs stand out among white and blue icebergs under a great variety of light conditions. ■Another suggestion is that the color might be related to ice with high levels of metallic compounds, including copper and iron. ■Recent expeditions have taken ice samples from green icebergs and ice cores—vertical, cylindrical ice samples reaching down to great depths—from the glacial ice shelves along the Antarctic continent. Analyses of these cores and samples provide a different solution to the problem.
13. Look at the four squares [■] that indicate where the following sentence could be added to the passage.
Scientists have differed as to whether icebergs appear green as a result of light conditions or because of something in the ice itself.
Where would the sentence best fit?
14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
Several suggestions, ranging from light conditions to the presence of metallic compounds, have been offered to explain why some icebergs appear green.
●
●
●
Answer Choices
○Ice cores were used to determine that green icebergs were formed from the compaction of metallic compounds, including copper and iron.
○All ice shelves can produce green icebergs, but the Amery Ice Shelf is especially well suited to do so.
○Green icebergs form when a two layer block of ice breaks away from a glacier and capsizes, exposing the bottom sea ice to view.
○Ice cores and samples revealed that both ice shelves and green icebergs contain a layer of bubbly glacial ice and a layer of bubble-free sea ice.
○Green icebergs are white until they come into contact with seawater containing platelets and soluble organic green pigments.
○In a green iceberg, the sea ice contains large concentrations of organic matter from the seawater.
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参考答案：
1. ○3
2. ○2
3. ○4
4. ○2
5. ○1
6. ○4
7. ○3
8. ○1
9. ○1
10. ○4
11. ○2
12. ○3
13. ○2
14. Green icebergs form…
Ice cores and samples…
Inagreeniceberg…
冰山就是形状不规则的大冰块；它们露出海面的部分大概只占总体积的12%。冰山是由冰川构成----始于格陵兰岛, 南极洲, 和阿拉斯加的内陆积雪汇聚形成冰河----然后缓慢流入海洋。向前移动进入海洋的过程中，冰川底部融化，波浪和潮汐变化造成冰块断裂，从而漂浮在海上。
冰山的颜色一般是介于蓝色和白色之间，尽管被有时会因为携带有着砂砾和石块而显得颜色很深或不透明。伴随光的变换以及云量的不同，它们呈现的颜色可能会随之不同。比如在早晨和傍晚的阳光下它会呈现
耀眼的粉色或金色，但这种颜色变化大致与太阳海平面上的太阳的仰角相关。不管怎样，有到过南极洲的旅游者们声称在威德尔海（Weddell Sea）看到过绿色冰山，而南极洲东部埃默里冰架（Amery Ice Shelf）的附近则更为常见。
对绿色冰山现象，有一种解释冰山呈现绿色由于蓝冰被接近海平面的红色阳光所照射而造成的错觉，但是绿色冰山在各种光的变换中都能与白色和蓝色冰山中区别开来。还有另一种解释是，它的颜色可能与冰内所含高密度的金属化合物有关，比如铜和铁。最近，探险队从南极洲冰架上带回了绿色冰山和冰核的样本----垂直圆柱型的深层的冰样本。对这些冰核和样本的分析给问题提供了一个不一样的解决方法。
215米（705英尺）长的冰架核已经足够穿透由压实的雪组成并含有气泡的冰川冰，并随后穿透在冻结在冰川冰底部的海水形成的透明气泡的冰。这种透明的海水冰的性质与绿色冰山的冰非常相近。科学家总结，当两层的陆架冰分开并翻转时，露出海水形成的无气泡的陆架冰，这时候会形成绿色冰山。
Amery Ice Shelf（艾默里冰架）西部的一块绿色冰山呈现出非常明显的两层：含有气泡的白蓝色冰和没有气泡的绿色冰，它们中间是由1米长的带有沉积物的冰分隔开的。海水的侵蚀决定了绿色冰的质地。由于光的散散，裂痕处的颜色是浅绿的；而没有裂痕的地方是深绿色。绿色冰中是没有气泡的，因为它是由冻结的海水所构成，而不是压缩的雪。沿着这个地区冰架的边缘，可以发现，带有绿色色素的单细胞生物非常多，而且海水里面含有它们丰富的分解有机物质。绿冰山虽没有包含很多这些生物体的微粒，但从海水中所积累的分解有机物质非常丰富。不同于盐，分解有机物质并没有在结冰过程中被排除掉。分析表明，分解的有机物质会从太阳光中吸收足够的蓝波段，从而使冰呈现出绿色。
化学证据表明冰的小盘（微小的平面部分）是在水中构成，然后依附在冰架底部形成一个雪泥（部分融化的雪）。雪泥通过一种未知原理压缩成冰，而这种泡的固态冰是由可溶解的有机物质多的水形成的。当冰山从冰架上分离并翻转过来时，绿色冰便呈现出来了。
艾默里冰架似乎很适合形成绿色冰山。一旦脱离冰架，这些冰山就会随着风系统和洋流围绕在南极洲，人们便能发现散落在南极洲的少量彩色冰山。
冰川冰，一种具有塑造的、透明的浅蓝色多晶的冰体。由粒雪经成冰作用而成。成冰作用分为冷型和暖型两种。冷型成冰作用是在低温干燥环境下，粒雪在粒雪静压下进行重结晶作用而逐渐变成冰。这种重结晶冰密度较小，晶粒较细，气泡多而压力大，成冰过程很慢。
