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?
○B(yǎng)y the compaction of snow
○B(yǎng)y the freezing of seawater on the bottom of ice shelves
○B(yǎng)y breaking away from the ice shelf
○B(yǎng)y 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.
查看正確答案和解析
版權(quán)聲明：本原創(chuàng)文章版權(quán)歸“新通外語網(wǎng)（）”所有，未經(jīng)書面許可不得轉(zhuǎn)貼、轉(zhuǎn)載。否則，新通教育網(wǎng)將追究其相關(guān)法律責(zé)任。
參考答案：
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…
冰山就是形狀不規(guī)則的大冰塊；它們露出海面的部分大概只占總體積的12%。冰山是由冰川構(gòu)成----始于格陵蘭島, 南極洲, 和阿拉斯加的內(nèi)陸積雪匯聚形成冰河----然后緩慢流入海洋。向前移動進(jìn)入海洋的過程中，冰川底部融化，波浪和潮汐變化造成冰塊斷裂，從而漂浮在海上。
冰山的顏色一般是介于藍(lán)色和白色之間，盡管被有時會因?yàn)閿y帶有著砂礫和石塊而顯得顏色很深或不透明。伴隨光的變換以及云量的不同，它們呈現(xiàn)的顏色可能會隨之不同。比如在早晨和傍晚的陽光下它會呈現(xiàn)
耀眼的粉色或金色，但這種顏色變化大致與太陽海平面上的太陽的仰角相關(guān)。不管怎樣，有到過南極洲的旅游者們聲稱在威德爾海（Weddell Sea）看到過綠色冰山，而南極洲東部埃默里冰架（Amery Ice Shelf）的附近則更為常見。
對綠色冰山現(xiàn)象，有一種解釋冰山呈現(xiàn)綠色由于藍(lán)冰被接近海平面的紅色陽光所照射而造成的錯覺，但是綠色冰山在各種光的變換中都能與白色和藍(lán)色冰山中區(qū)別開來。還有另一種解釋是，它的顏色可能與冰內(nèi)所含高密度的金屬化合物有關(guān)，比如銅和鐵。最近，探險隊從南極洲冰架上帶回了綠色冰山和冰核的樣本----垂直圓柱型的深層的冰樣本。對這些冰核和樣本的分析給問題提供了一個不一樣的解決方法。
215米（705英尺）長的冰架核已經(jīng)足夠穿透由壓實(shí)的雪組成并含有氣泡的冰川冰，并隨后穿透在凍結(jié)在冰川冰底部的海水形成的透明氣泡的冰。這種透明的海水冰的性質(zhì)與綠色冰山的冰非常相近�？茖W(xué)家總結(jié)，當(dāng)兩層的陸架冰分開并翻轉(zhuǎn)時，露出海水形成的無氣泡的陸架冰，這時候會形成綠色冰山。
Amery Ice Shelf（艾默里冰架）西部的一塊綠色冰山呈現(xiàn)出非常明顯的兩層：含有氣泡的白藍(lán)色冰和沒有氣泡的綠色冰，它們中間是由1米長的帶有沉積物的冰分隔開的。海水的侵蝕決定了綠色冰的質(zhì)地。由于光的散散，裂痕處的顏色是淺綠的；而沒有裂痕的地方是深綠色。綠色冰中是沒有氣泡的，因?yàn)樗怯蓛鼋Y(jié)的海水所構(gòu)成，而不是壓縮的雪。沿著這個地區(qū)冰架的邊緣，可以發(fā)現(xiàn)，帶有綠色色素的單細(xì)胞生物非常多，而且海水里面含有它們豐富的分解有機(jī)物質(zhì)。綠冰山雖沒有包含很多這些生物體的微粒，但從海水中所積累的分解有機(jī)物質(zhì)非常豐富。不同于鹽，分解有機(jī)物質(zhì)并沒有在結(jié)冰過程中被排除掉。分析表明，分解的有機(jī)物質(zhì)會從太陽光中吸收足夠的藍(lán)波段，從而使冰呈現(xiàn)出綠色。
化學(xué)證據(jù)表明冰的小盤（微小的平面部分）是在水中構(gòu)成，然后依附在冰架底部形成一個雪泥（部分融化的雪）。雪泥通過一種未知原理壓縮成冰，而這種泡的固態(tài)冰是由可溶解的有機(jī)物質(zhì)多的水形成的。當(dāng)冰山從冰架上分離并翻轉(zhuǎn)過來時，綠色冰便呈現(xiàn)出來了。
艾默里冰架似乎很適合形成綠色冰山。一旦脫離冰架，這些冰山就會隨著風(fēng)系統(tǒng)和洋流圍繞在南極洲，人們便能發(fā)現(xiàn)散落在南極洲的少量彩色冰山。
冰川冰，一種具有塑造的、透明的淺藍(lán)色多晶的冰體。由粒雪經(jīng)成冰作用而成。成冰作用分為冷型和暖型兩種。冷型成冰作用是在低溫干燥環(huán)境下，粒雪在粒雪靜壓下進(jìn)行重結(jié)晶作用而逐漸變成冰。這種重結(jié)晶冰密度較小，晶粒較細(xì)，氣泡多而壓力大，成冰過程很慢。
