新TOEFL阅读真题详解:地中海的地质历史

　　In 1970 geologists Kenneth J. Hsu and William B.F. Ryan were collecting research data whileaboard the oceanographic research vessel Glomar Challenger. An objective of this particularcruise was to investigate the floor of the Mediterranean and to resolve questions about itsgeologic history. One question was related to evidence that the invertebrate fauna (animalswithout spines) of the Mediterranean had changed abruptly about 6 million years ago. Most ofthe older organisms were nearly wiped out, although a few hardy species survived. A fewmanaged to migrate into the Atlantic. Somewhat later, the migrants returned, bringing newspecies with them. Why did the near extinction and migrations occur?

　　Another task for the Glomar Challenger’s scientists was to try to determine the origin of thedomelike masses buried deep beneath the Mediterranean seafloor. These structures had beendetected years earlier by echo-sounding instruments, but they had never been penetrated inthe course of drilling. Were they salt domes such as are common along the United States GulfCoast, and if so, why should there have been so much solid crystalline salt beneath the floor ofthe Mediterranean?

　　With question such as these clearly before them, the scientists aboard the Glomar Challengerprocessed to the Mediterranean to search for the answers. On August 23, 1970, they recovereda sample. The sample consisted of pebbles of gypsum and fragments of volcanic rock. Not asingle pebble was found that might have indicated that the pebbles came from the nearbycontinent. In the days following, samples of solid gypsum were repeatedly brought on deck asdrilling operations penetrated the seafloor. Furthermore, the gypsum was found to possesspeculiarities of composition and structure that suggested it had formed on desert flats.Sediment above and below the gypsum layer contained tiny marine fossils, indicating open-ocean conditions. As they drilled into the central and deepest part of the Mediterranean basin,the scientists took solid, shiny, crystalline salt from the core barrel. Interbedded with the saltwere thin layers of what appeared to be windblown silt.

　　The time had come to formulate a hypothesis. The investigators theorized that about 20million years ago, the Mediterranean was a broad seaway linked to the Atlantic by two narrowstraits. Crustal movements closed the straits, and the landlocked Mediterranean began toevaporate. Increasing salinity caused by the evaporation resulted in the extermination ofscores of invertebrate species. Only a few organisms especially tolerant of very saltyconditions remained. As evaporation continued, the remaining brine (salt water) became sodense that the calcium sulfate of the hard layer was precipitated. In the central deeper part ofthe basin, the last of the brine evaporated to precipitate more soluble sodium chloride (salt).Later, under the weight of overlying sediments, this salt flowed plastically upward to form saltdomes. Before this happened, however, the Mediterranean was a vast desert 3,000 metersdeep. Then, about 5.5 million years ago came the deluge. As a result of crustal adjustmentsand faulting, the Strait of Gibraltar, where the Mediterranean now connects to the Atlantic,opened, and water cascaded spectacularly back into the Mediterranean. Turbulent waters toreinto the hardened salt flats, broke them up, and ground them into the pebbles observed in thefirst sample taken by the Challenger. As the basin was refilled, normal marine organismsreturned. Soon layer of oceanic ooze began to accumulate above the old hard layer.

　　The salt and gypsum, the faunal changes, and the unusual gravel provided abundantevidence that the Mediterranean was once a desert.

　　gypsum: a mineral made of calcium sulfate and water

　　Paragraph 1 In 1970 geologists Kenneth J. Hsu and William B.F. Ryan were collecting researchdata while aboard the oceanographic research vessel Glomar Challenger. An objective of thisparticular cruise was to investigate the floor of the Mediterranean and to resolve questionsabout its geologic history. One question was related to evidence that the invertebrate fauna(animals without spines) of the Mediterranean had changed abruptly about 6 million years ago.Most of the older organisms were nearly wiped out, although a few hardy species survived. Afew managed to migrate into the Atlantic. Somewhat later, the migrants returned, bringing newspecies with them. Why did the near extinction and migrations occur?

　　1.The word “objective” in the passage is closest in meaning to

　　○achievement

　　○requirement

　　○purpose

　　○feature

　　2.Which of the following is NOT mentioned in paragraph 1 as a change that occurred in thefauna of the Mediterranean?

　　○Most invertebrate species disappeared during a wave of extinctions.

　　○A few hardy species wiped out many of the Mediterranean’s invertebrates.

　　○Some invertebrates migrated to Atlantic Ocean.

　　○New species of fauna populated the Mediterranean when the old migrants returned.

　　Paragraph 3 With question such as these clearly before them, the scientists aboard the GlomarChallenger processed to the Mediterranean to search for the answers. On August 23, 1970,they recovered a sample. The sample consisted of pebbles of gypsum and fragments ofvolcanic rock. Not a single pebble was found that might have indicated that the pebbles camefrom the nearby continent. In the days following, samples of solid gypsum were repeatedlybrought on deck as drilling operations penetrated the seafloor. Furthermore, the gypsum wasfound to possess peculiarities of composition and structure that suggested it had formed ondesert flats. Sediment above and below the gypsum layer contained tiny marine fossils,indicating open-ocean conditions. As they drilled into the central and deepest part of theMediterranean basin, the scientists took solid, shiny, crystalline salt from the core barrel.Interbedded with the salt were thin layers of what appeared to be windblown silt.

　　3.What does the author imply by saying “Not a single pebble was found that might haveindicated that the pebbles came from the nearby continent”?

　　○The most obvious explanation for the origin of the pebbles was not supported by theevidence.

　　○The geologists did not find as many pebbles as they expected.

　　○The geologists were looking for a particular kind of pebble.

　　○The different pebbles could not have come from only one source.

　　4.Which of the following can be inferred from paragraph 3 about the solid gypsum layer?

　　○It did not contain any marine fossil.

　　○It had formed in open-ocean conditions.

　　○It had once been soft, deep-sea mud.

　　○It contained sediment from nearby deserts.

　　5. Select the TWO answer choice from paragraph 3 that identify materials discovered in thedeepest part of the Mediterranean basin. To receive credit you must select TWO answers.

　　○Volcanic rock fragments.

　　○This silt layers

　　○Soft, deep-sea mud

　　○Crystalline salt

　　6. What is the main purpose of paragraph 3?

　　○To describe the physical evidence collected by Hsu and Ryan.

　　○To explain why some of the questions posed earlier in the passage could not be answered bythe findings of the Glomar Challenger.

　　○To evaluate techniques used by Hsu and Ryan to explore the sea floor.

　　○To describe the most difficult problems faced by the Glomar Challenger expedition.

　　1.○ 3

　　2.○ 2

　　3.○ 1

　　4.○ 1

　　5.○ 2 4

　　6.○ 1

　　参考译文

　　地中海的地质历史

　　1970年，地理学家Kenneth J. Hsu 和 William B.F. Ryan曾在海洋调查船Glomar Challenger号上致力收集调研资料。这次特别巡航的一个目的是调查地中海的地层以及解决关于其地质历史的问题。其中一个问题是有关地中海地区无脊椎动物(没有脊椎的动物)600百万年前发生剧变的证据。大部分古老的生物都几乎灭绝了，尽管一些顽强的种类得以生存。一些动物成功地迁移到了大西洋。不久后，这些动物又回来了，并带回来新的物种。为什么这最近的动物灭绝和迁移会发生呢?

　　Glomar Challenger号上科学家们的另一个任务是尝试去确定深埋在地中海海底穹顶状巨块的起源。这些结构在早些年被回声探测器探测过，但是它们在探测过程中从未被穿透。它们是像美国海湾海岸一带的含盐圆顶状巨块吗?如果是的话，为什么在地中海海底之下会有这么多坚硬的结晶盐呢?

　　带着这些清楚摆在他们面前的问题，科学家们登上Glomar Challenger号前往地中海寻找答案。1970年8月23日，他们恢复了一个样本。这个样本由石膏鹅卵石和火山岩碎块组成。周围没有鹅卵石被发现，这可能说明这些小石头不来自附近的大陆。接下来的日子里，随着海底岩层穿透实验的进行，石膏固体样本被不断地放在甲板上。而且，这些膏状物的组成和结构特性表明它们形成于沙漠。在石膏层上下的沉积物中包含了微小的海洋生物化石，这说明了是开放性的海洋环境。当钻到地中海盆地中心的最深处时，科学家们从钻管中获得了坚实的、光亮的结晶盐。跟结晶盐相互嵌在一起的薄层像是被风吹起的泥沙层。

　　时间明确地阐明了一个假设。调查者们构思了这样的理论：大约2000万年前，地中海是一条宽阔的航道，它通过两条狭窄的海峡与大西洋连接。地壳运动封闭了海峡，被陆地包围的地中海也开始蒸发。由蒸发引起的越来越高的盐度造成无脊椎动物种类的灭绝。只有一些能抵抗高盐度条件的物种保留下来。随着蒸发的继续进行，盐水浓度太高以致硬地层的硫酸钙发生沉淀。在盆地的中间深处，剩余盐水的持续蒸发形成更多的可溶的氯化钠(盐)。后来，在上层沉淀物的重压下，盐向上形成了含盐的圆顶。然而在这之前，地中海是一个3000米深的大沙漠。然后，550万年前发生了洪水。作为地壳调整和断层作用的结果，现在连接地中海和大西洋的直布罗陀海峡打开了，水流像瀑布一样壮观地涌回地中海。湍急的水流冲击并摧毁了坚硬的含盐层，使把它们磨成了Challenger号获得的**份样品中所观察到的鹅卵石。随着盆地的填充，普通的海洋生物又回来了。不久后海洋软泥层开始在老的硬地层上堆积。

　　盐、石膏、动物区系的变更，还有不寻常的沙砾层都为地中海曾经是块沙漠的理论提供了充分的证据。