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Text 2

http://www.sina.com.cn 2006/09/25 19:57 东方飞龙

　　Text 2

　　Today, the Black Sea is a brackish inland sea, fed by fresh water from European rivers and saltier, Mediterranean seawater flowing in through the Bosporus strait. In the 1970s and 1980s, cores through nowsubmerged sediments off the northern and western coasts revealed the remains of a coastal plain that was e

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xposed late in the last ice age and into the interglacial warmth of the past 10,000 years. Long after glacial melt waters began raising world sea levels, it seems, the Black Sea was a freshwater lake, much smaller and lower than todays sea; it was cut off from the Mediterranean because the level of that sea was even lower than the Bosporus.

　　Evidence that a rising Mediterranean suddenly refilled this lowered Black Sea emerged from a joint RussianUS expedition in 1993, during which researchers used seismic waves to image the layers of sediment at the bottom of the Black Sea. If rising waters had crept slowly across the coastal plain, they would have deposited a wedge of sediment as they went. But as Ryan, Pitman, and colleagues reported in Marine Geology last year, they saw no sign of that. Instead they found a thin, uniform dusting of sediment, consistent with a geologically instantaneous refilling of the Black Sea.

　　In addition, radiocarbon dating of the shells of the first salttolerant molluscan invaders from the Mediterranean yielded the same age—7550 years before present, plus or minus 100 years—regardless of whether the shells came from deep, permanently flooded sediments or from the shallow shelf. If the refilling had been gradual, the team reasoned, the shells in deeper water would have been laid down first.

　　Finally, seismic probing has shown that the hardrock basement beneath the sediments filling the Bosporus channel lies at a depth of nearly 100 meters, rather than 35 meters, as had been thought. So the floodwaters could have cut a very deep channel through the sediments and down to bedrock, letting the water spill through far faster.［329 words］

　　1. The purpose of the author in writing the text is to (此题与2006年大纲样题第35题相仿)

　　［A］ outline the geographical features of the Bosporus.

　　［B］ explain why the Black Sea was a freshwater lake.

　　［C］ describe a joint RussianUS expedition to the Black Sea.

　　［D］ provide new evidence that a rising Mediterranean suddenly refilled the lowered Black Sea.

　　2. By referring to the report of the expedition team, the author shows that

　　［A］　the Black Sea was gradually refilled 10,000 years ago.

　　［B］　a wedge of sediment was found at the bottom of the Black Sea.

　　［C］　the hardrock basement beneath the sediments filling the Bosporus channel lies at a depth of nearly 35 meters.

　　［D］　a thin and uniform dusting of sediment with a geologically instantaneous refilling of the Black was found.

　　3. “Brackish” water (Line 1, Para.1) is not pure because it is(此题与2006年第29题相仿)

　　［A］　slightly salty. ［B］　unclear.

　　［C］　polluted. ［D］　not fresh.

　　4. The text is most likely a part of a

　　［A］　journalist interview. ［B］　book review.

　　［C］　scientific report. ［D］　narrative story.

　　5. If a rising Mediterranean had gradually refilled the lowered Black Sea,

　　［A］ the floodwaters would have left a thicker, uniform dusting of sediment.

　　［B］ the Black Sea would have become a much smaller freshwater lake.

　　［C］ radiocarbon dating of the shells from deeper sediments would have yielded older age than those from shallow shelf.

　　［D］ the hardrock basement beneath the sediments filling the Bosporus would have lain at a depth of 35 meters.

　　-核心及超纲词汇

　　1.brackisha.(指水)略咸的［同义］ saltish, somewhat salt

　　2.flow in through不断涌入

　　3.coastal plain沿海平原

　　4.refillv.再装满，再充满

　　5.seismica.

地震的［例］ seismic research 地震研究

　　6.sedimentn.沉淀物［同义］ dregs, lees, settlings, grounds

　　7.radiocarbonn.放射性炭

　　8.molluscann.软体动物

　　-全文精译

　　自然地理的开发

　　今天，黑海(the Black Sea)是一个略带咸味的(brackish)内陆海(inland sea)，由来自欧洲河流的淡水和穿越博斯普鲁斯海峡的地中海海水汇集而成。20世纪70、80年代，从北部及西部的海岸沉积提取的岩芯表明了一处沿海平原遗址。这个平原从上个冰川期末到过去10，000年的间冰期温暖期的这段时间内开始暴露出来，冰川融化后的水大大抬高了(raise)海平面，此后很久，黑海仍是淡水湖，并且比今天的黑海要小要低，因为黑海比博斯普鲁斯海峡还要低，所以它与地中海是分开的。

　　1993年，俄美联合考察找到了地中海上升并突然注入(refill)黑海的证据，考察中，研究人员用“地震波”绘制了黑海底部的沉积层的图形。如果上涨的水蔓延并覆盖了沿海平原，肯定会在沿途留下(deposit)楔型沉积层。但Ryan、 Pitman以及同事们在去年的《海洋地理》中却称没有发现这种迹象，相反，他们发现了一种很薄的、均匀的覆盖型沉积，这与地理上的黑海瞬间注入相一致。

　　另外，采用放射性碳对来自地中海流域的第一批耐盐性(salttolerant)软体动物的壳进行年代测定，结果显示，不管这些壳体是采自永久被洪水淹没的深水沉淀还是较浅的大陆架(shallow shelf)，它们都源自同样的年代——距今7550+/-100年。该小组判断，如果注入是渐进的，深水里的贝壳会首先沉淀下来。

　　最后，地震探测显示：坚硬的基岩层位于填补博斯普鲁斯海峡的沉积物下面，约在水深100米处，而不是以前所认为的35米深处。所以洪水完全可以在沉积岩层上方切开一条通道，直达基岩，这样就可以使水以更快的速度注入。

　　-答案详解

　　1. 【正确答案】［D］ provide new evidence that a rising Mediterranean suddenly refilled the lowered Black Sea.

　　【本题考点】主旨大意题。

　　【试题精解】本文主要依据1993年俄美联合考察队提供的新证据，证明上升的地中海海水突然充入地势低的黑海。

　　【考点出处】本题是主旨题，需对文章作整体性把握方可正确解答。

　　2. 【正确答案】［D］ a thin and uniform dusting of sediment with a geologically instantaneous refilling of the Black was found.

　　【本题考点】细节判断题。

　　【试题精解】参见第二段有关考察队报告的相关内容，可排除选项［A］、［B］。根据文章末段第一句话可知，［C］错误。只有［D］符合题意。“Instead they found a thin, uniform dusting of sediment, consistent with a geologically instantaneous refilling of the Black Sea.”(第二段末句)。

　　【考点出处】宜用排除法。四个选项均可通过在全文中的查证鉴别正误。

　　3. 【正确答案】［A］ slightly salty.

　　【本题考点】推理暗示题。

　　【试题精解】 Brackish water 不纯，是由于略带咸味，参见第一段的内容。

　　【考点出处】第一段。

　　4. 【正确答案】［C］ scientific report.

　　【本题考点】推理暗示题。

　　【试题精解】本文可能是科技报道类文章的一部分。 a journalist interview: 新闻采访； a book review:书评；a narrative story:叙述故事。

　　【考点出处】通过对文章内容的了解可知，本文是一篇科学说明文，“科学报告”与文章类型一致。

　　5. 【正确答案】［C］ radiocarbon dating of the shells from deeper sediments would have yielded older age than those from shallow shelf.

　　【本题考点】段落语义推断题。

　　【试题精解】参考文章第二段内容可以推断，如果上涨的地中海海水是逐渐流入地势低的黑海，应留下一层楔形的沉淀物，而不应为均匀(uniform)厚度，因此答案［A］错误；答案［B］、［D］在文中找不到推理依据，根据第三段的叙述，可以推知［C］。

　　【考点出处】此题宜用排除法，［C］项与第三段意思一致。