『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 19 Passage 3阅读练习：In paragraph 5, why does the author include the information that the “oxygen isotope ratio of the ocean changes as a great deal of water is withdrawn from it by evaporation and is precipitated as snow to form glacial ice”?真题题目及答案解析，TPO/Official 19 Passage 3阅读原文范文音频翻译

托福TPO/Official 19 Passage 3阅读原文In paragraph 5, why does the author include the information that the “oxygen isotope ratio of the ocean changes as a great deal of water is withdrawn from it by evaporation and is precipitated as snow to form glacial ice”?题目答案及解析-新东方托福官方网校手机版

在19世纪中叶，路易斯·阿加西是最早研究冰川的科学家之一 ，他从瑞士移民到美国，并且成为哈佛大学的教授，在那里他继续研究地质学和其他科学。

In the middle of the nineteenth century, Louis Agassiz, one of the first scientists to study glaciers, immigrated to the United States from Switzerland and became a professor at Harvard University, where he continued his studies in geology and other sciences.

为了进行研究，阿加西走访了欧洲和北美北部的许多地方，从斯堪的纳维亚和新英格兰的山脉到美国中西部连绵起伏的丘陵。

For his research, Agassiz visited many places in the northern parts of Europe and North America, from the mountains of Scandinavia and New England to the rolling hills of the American Midwest.

在所有这些不同的地区里，阿加西都发现了冰川侵蚀和沉积的迹象。

In all these diverse regions, Agassiz saw signs of glacial erosion and sedimentation.

在平坦的平原乡村，他看到了冰碛（冰川边缘形成的泥土和松散岩石的堆积），这让他想起了在阿尔卑斯山山谷冰川尽头发现的终碛。

In flat plains country, he saw moraines (accumulations of earth and loose rock that form at the edges of glaciers) that reminded him of the terminal moraines found at the end of valley glaciers in the Alps.

漂流物中的各种各样的材料（沉积在那里的沙、粘土和岩石）使他相信它来自冰川。

The heterogeneous material of the drift (sand, clay, and rocks deposited there) convinced him of its glacial origin.

这种材料覆盖的区域如此之广，以至于沉积它的冰川一定是比格陵兰岛或南极洲更大的大陆冰川。

The areas covered by this material were so vast that the ice that deposited it must have been a continental glacier larger than Greenland or Antarctica.

最终，阿加西和其他人说服了地质学家和公众，一块巨大的大陆冰川曾经将极地冰盖延伸到了现在属于温带气候的地区。

Eventually, Agassiz and others convinced geologists and the general public that a great continental glaciation had extended the polar ice caps far into regions that now enjoy temperate climates.

人们第一次开始谈论冰河时代。

For the first time, people began to talk about ice ages.

很明显，冰川作用发生在相对较近的过去，因为漂流物是软的，就像新的沉积物一样。

It was also apparent that the glaciation occurred in the relatively recent past because the drift was soft, like freshly deposited sediment.

我们现在通过对埋藏在漂流物中的原木的碳—14进行辐射测年，准确地知道了冰川的年份。

We now know the age of the glaciation accurately from radiometric dating of the carbon-14 in logs buried in the drift.

最后一次冰川的漂流物沉积在地质时代最近的一个时代，即更新世，从260万年前持续到11700年前。

The drift of the last glaciation was deposited during one of the most recent epochs of geologic time, the Pleistocene, which lasted from 2.6 million to 11,700 years ago.

沿着美国东海岸，形成长岛和科德角终碛的巨大沙子和漂流物沉积记录了这块冰的最南端的情况。

Along the east coast of the United States, the southernmost advance of this ice is recorded by the enormous sand and drift deposits of the terminal moraines that form Long Island and Cape Cod.

很快人们就清楚了，在更新世期间有多个冰期，它们之间有较温暖的间冰期。

It soon became clear that there were multiple glacial ages during the Pleistocene, with warmer interglacial intervals between them.

当地质学家在19世纪末绘制冰川沉积物图时，他们意识到有几层漂流物，较低的一层对应于早期的冰河时代。

As geologists mapped glacial deposits in the late nineteenth century, they became aware that there were several layers of drift, the lower ones corresponding to earlier ice ages.

在较老的冰川物质层之间是发育良好的土壤，其中含有暖性气候植物的化石。

Between the older layers of glacial material were well-developed soils containing fossils of warm-climate plants.

这些土壤是冰川随着气候变暖而消退的证据。

These soils were evidence that the glaciers retreated as the climate warmed.

到了二十世纪初，科学家们认为，在更新世时期，北美和欧洲经受了四次截然不同的冰川作用的影响。

By the early part of the twentieth century, scientists believed that four distinct glaciations had affected North America and Europe during the Pleistocene epoch.

20世纪末，地质学家和海洋学家在研究海洋沉积物时发现了海洋变暖和变冷的化石证据，从而使这一观点得到了修正。

This idea was modified in the late twentieth century, when geologists and oceanographers examining oceanic sediment found fossil evidence of warming and cooling of the oceans.

海洋沉积物比大陆冰川沉积提供了更完整的更新世地质记录。

Ocean sediments presented a much more complete geologic record of the Pleistocene than continental glacial deposits did.

埋藏在更新世时期的化石和更早的海洋沉积物是有孔虫——一种分泌碳酸钙外壳或方解石的小型单细胞海洋生物。

The fossils buried in Pleistocene and earlier ocean sediments were of foraminifera—small, single-celled marine organisms that secrete shells of calcium carbonate, or calcite.

这些外壳的普通氧（氧—16）和重氧同位素（氧—18）的比例不同。

These shells differ in their proportion of ordinary oxygen (oxygen-16) and the heavy oxygen isotope (oxygen-18).

在有孔虫外壳的方解石中发现的氧—16和氧—18的比例取决于有机体生活的水的温度。

The ratio of oxygen-16 to oxygen-18 found in the calcite of a foraminifer’s shell depends on the temperature of the water in which the organism lived.

在不同的沉积物层中保存的外壳的不同比例揭示了更新世时期海洋温度的变化。

Different ratios in the shells preserved in various layers of sediment reveal the temperature changes in the oceans during the Pleistocene epoch.

对外壳的同位素分析使地质学家得以测量另一种冰川效应。

Isotopic analysis of shells allowed geologists to measure another glacial effect.

他们可以追踪大陆冰川的增长和缩小，甚至于海洋的一些地方，比如赤道周围，那里的温度可能没有太大的变化。

They could trace the growth and shrinkage of continental glaciers, even in parts of the ocean where there may have been no great change in temperature—around the equator, for example.

海洋的氧同位素比率会发生变化，因为大量的水通过蒸发从海洋中提取出来，并以雪的形式沉淀形成冰川。

The oxygen isotope ratio of the ocean changes as a great deal of water is withdrawn from it by evaporation and is precipitated as snow to form glacial ice.

在冰川期间，较轻的氧—16比较重的氧—18更容易从海洋表面蒸发。

During glaciations, the lighter oxygen-16 has a greater tendency to evaporate from the ocean surface than the heavier oxygen-18 does.

因此，有更多的重同位素留在了海洋中，并被海洋生物吸收。

Thus, more of the heavy isotope is left behind in the ocean and absorbed by marine organisms.

通过对海洋沉积物的分析，地质学家了解到，与他们仅从大陆的冰川漂流物中认识到的情况相比，有些冰川和冰川消融的周期要短得多，规律得多。

From this analysis of marine sediments, geologists have learned that there were many shorter, more regular cycles of glaciation and deglaciation than geologists had recognized from the glacial drift of the continents alone.

The word “accumulations” in the passage is closest in meaning to

The word “heterogeneous” in the passage is closest in meaning to

According to paragraph 1, what persuaded Louis Agassiz that glaciation in the past had been widespread?

The word “enjoy” in the passage is closest in meaning to

It can be inferred from paragraph 2 that Agassiz and other geologists of his time were not able to determine

According to paragraph 3, what did geologists conclude as a result of finding well-developed soils containing warm-climate plant fossils between layers of glacial drift?

According to paragraphs 3 and 4, scientists modified their theory about the exact number of glaciations because of evidence obtained from

The word “reveal” in the passage is closest in meaning to

According to paragraph 4, scientists use foraminifera shells to learn about Pleistocene ocean conditions by

It can be inferred from paragraph 5 that foraminifera fossil shells containing calcite with high percentages of oxygen-16 were deposited at times when

In paragraph 5, why does the author include the information that the “oxygen isotope ratio of the ocean changes as a great deal of water is withdrawn from it by evaporation and is precipitated as snow to form glacial ice”?

According to the passage, when did scientists begin to realize that more than one ice age had occurred?

Look at the four squares  that indicate where the following sentence could be added to the passage. In his view, there could be no other explanation for the composition of such drift.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

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.

Discovering the Ice Ages In the middle of the nineteenth century, Louis Agassiz, one of the first scientists to study glaciers, immigrated to the United States from Switzerland and became a professor at Harvard University, where he continued his studies in geology and other sciences. For his research, Agassiz visited many places in the northern parts of Europe and North America, from the mountains of Scandinavia and New England to the rolling hills of the American Midwest.  In all these diverse regions, Agassiz saw signs of glacial erosion and sedimentation.  In flat plains country, he saw moraines (accumulations of earth and loose rock that form at the edges of glaciers) that reminded him of the terminal moraines found at the end of valley glaciers in the Alps.  The heterogeneous material of the drift (sand, clay, and rocks deposited there) convinced him of its glacial origin.  The areas covered by this material were so vast that the ice that deposited it must have been a continental glacier larger than Greenland or Antarctica. Eventually, Agassiz and others convinced geologists and the general public that a great continental glaciation had extended the polar ice caps far into regions that now enjoy temperate climates. For the first time, people began to talk about ice ages. It was also apparent that the glaciation occurred in the relatively recent past because the drift was soft, like freshly deposited sediment. We now know the age of the glaciation accurately from radiometric dating of the carbon-14 in logs buried in the drift. The drift of the last glaciation was deposited during one of the most recent epochs of geologic time, the Pleistocene, which lasted from 2.6 million to 11,700 years ago. Along the east coast of the United States, the southernmost advance of this ice is recorded by the enormous sand and drift deposits of the terminal moraines that form Long Island and Cape Cod. It soon became clear that there were multiple glacial ages during the Pleistocene, with warmer interglacial intervals between them. As geologists mapped glacial deposits in the late nineteenth century, they became aware that there were several layers of drift, the lower ones corresponding to earlier ice ages. Between the older layers of glacial material were well-developed soils containing fossils of warm-climate plants. These soils were evidence that the glaciers retreated as the climate warmed. By the early part of the twentieth century, scientists believed that four distinct glaciations had affected North America and Europe during the Pleistocene epoch. This idea was modified in the late twentieth century, when geologists and oceanographers examining oceanic sediment found fossil evidence of warming and cooling of the oceans. Ocean sediments presented a much more complete geologic record of the Pleistocene than continental glacial deposits did. The fossils buried in Pleistocene and earlier ocean sediments were of foraminifera—small, single-celled marine organisms that secrete shells of calcium carbonate, or calcite. These shells differ in their proportion of ordinary oxygen (oxygen-16) and the heavy oxygen isotope (oxygen-18). The ratio of oxygen-16 to oxygen-18 found in the calcite of a foraminifer’s shell depends on the temperature of the water in which the organism lived. Different ratios in the shells preserved in various layers of sediment reveal the temperature changes in the oceans during the Pleistocene epoch. Isotopic analysis of shells allowed geologists to measure another glacial effect. They could trace the growth and shrinkage of continental glaciers, even in parts of the ocean where there may have been no great change in temperature—around the equator, for example. The oxygen isotope ratio of the ocean changes as a great deal of water is withdrawn from it by evaporation and is precipitated as snow to form glacial ice. During glaciations, the lighter oxygen-16 has a greater tendency to evaporate from the ocean surface than the heavier oxygen-18 does. Thus, more of the heavy isotope is left behind in the ocean and absorbed by marine organisms. From this analysis of marine sediments, geologists have learned that there were many shorter, more regular cycles of glaciation and deglaciation than geologists had recognized from the glacial drift of the continents alone.