Official 49 Passage 1

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Ancient Coastlines

纠错

The word crucial in the passage is closest in meaning to

Click on an oval to select your answer. To choose a different answer,

click one different oval.

  • A
    Interesting
  • B
    Important
  • C
    Established
  • D
    Understood
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正确答案: B

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  • 原文
  • 译文
  • Information on past climates is of primary relevance to archaeology because of what it tells us about the effects on the land and on the resources that people needed to survive. The most crucial effect of climate was on the sheer quantity of land available in each period,measurable by studying ancient coastlines. These have changed constantly through time,even in relatively recent periods,as can be seen from the Neolithic stone circle of Er Lannic,in Brittany,France(once inland but now half submerged on an island)or medieval villages in east Yorkshire,England,that have tumbled into the sea in the last few centuries as the North Sea gnaws its way westward and erodes the cliffs. Conversely,silts deposited by rivers sometimes push the sea farther back,creating new land,as at Ephesus in western Turkey,a port on the coast in Roman times but today some five kilometers inland.



    Nevertheless,for archeologists concerned with the long periods of time of the Paleolithic period there are variations in coastlines of much greater magnitude to consider. The expansion and contraction of the continental glaciers caused huge and uneven rises and falls in sea levels worldwide. When the ice sheets grew,the sea level would drop as water became locked up in the glaciers;when the ice melted,the sea level would rise again. Falls in sea level often exposed a number of important land bridges,such as those linking Alaska to northeast Asia and Britain to northwest Europe,a phenomenon with far-reaching effects not only on human colonization of the globe but also on the environment as a whole-the flora and fauna of isolated or insular areas were radically and often irreversibly affected. Between Alaska and Asia today lies the Bering Strait,which is so shallow that a fall in sea level of only four meters would turn it into a land bridge. When the ice sheets were at their greatest extent some 18,000 years ago (the glacier maximum),it is thought that the fall was about 120 meters,which therefore created not merely a bridge but a vast plain,1,000 kilometers from the north to the south,which has been called Beringia. The existence of Beringia(and the extent to which it could have supported human life)is one of the crucial pieces of evidence in the continuing debate about the likely route and date of human colonization of the New World.



    The assessment of past rises and falls in sea level requires study of submerged land surfaces off the coast and of raised or elevated beaches on land. Raised beaches are remnants of former coastlines at higher levels relative to the present shoreline and visible,for instance,along the Californian coast north of San Francisco. The height of a raised beach above the present shoreline,however,does not generally give a straightforward indication of the height of a former sea level. In the majority of cases,the beaches lie at a higher level because the land has been raised up through isostatic uplift or tectonic movement. Isostatic uplift of the land occurs when the weight of ice is removed as temperatures rise,as at the end of an ice age;it has affected coastlines,for example,in Scandinavia,Scotland,Alaska,and Newfoundland during the postglacial period. Tectonic movements involve displacements in the plates that make up Earth`s crust. Middle and Late Pleistocene raised beaches in the Mediterranean are one instance of such movements.



    Raised beaches often consist of areas of sand,pebbles,or dunes,sometimes containing seashells or piles of debris comprising shells and bones of marine animals used by humans. In Tokyo Bay,for example,shell mounds of the Jomon period(about 10,000 to 300 B.C.E.)mark the position of the shoreline at a time of maximum inundation by the sea(6,500-5,500 years ago),when, through tectonic movement,the sea was three to five meters higher in relation to the contemporary landmass of Japan than at present. Analysis of the shells themselves has confirmed the changes in marine topography,for it is only during the maximum phase that subtropical species of mollusc are present,indicating a higher water temperature.


  • 过去的气候信息和考古学有着密切的关联,因为这些信息告诉我们气候对人类生存所需的土地和资源产生的影响。 气候最关键的影响是对于各个时期可使用土地的数量,这可以通过研究古海岸线来测算。 即使是相对较近的年代,海岸线也一直在不断地改变着,这可以从法国布列塔尼地区的Er Lannic的新石器时代的巨石阵得到证实(曾经是内陆,现在半埋在一个岛上);也可以从英国东约克郡中世纪的村庄得到证实,在过去的几个世纪里,随着北海一路向西侵入并侵蚀悬崖,这个村庄已没入大海。 相反,沉积在河流旁的淤泥有时会将大海推回到更远的地方,创造出新的土地,这就和土耳其西部以弗所一样,(这个地方)在古罗马时代是一个港口海岸,但今天位于距离海洋约5公里的内陆。

    然而,对于那些关注漫长的旧石器时代的考古学家来说,他们需要研究的海岸线有着更大的变化性。 大陆冰川的膨胀和收缩引起全球海平面巨大且不平稳地上升和下降。 当冰盖增长,海平面就会下降,这是因为水被封锁在冰川内;当冰融化,海平面会再次上升。 当海平面下降时,一些重要的陆桥会暴露出来,比如连接阿拉斯加与亚洲东北部的陆桥,以及连接英国和西北部欧洲的陆桥,这一现象不仅对人类的殖民,而且对整个环境都有着深远的影响——对于孤立或隔绝区域的植物群或动物群有着彻底的不可逆的影响。 如今,在阿拉斯加和亚洲之间的是白令海峡,这个海峡很浅,只需要四米的海平面下降就可以把它变成一个陆桥。 大约18000年前,当冰盖达到巅峰(冰川最大化),(人们推断)当时海平面下降大约有120米,因此创造的不仅仅是一个桥,而是一个广阔的平原,从北到南1000公里,被称为白令陆桥。 对于人类殖民新大陆的可能路径和可能日期的争论来说,白令陆桥的存在(以及它可以支持人类生存的程度),是至关重要的依据。

    针对过去海平面上升和下降的估算,是需要通过研究沿海下沉地表以及陆地上上升的海滩来实现的。 海滩高地是相较于现在的海岸线来说,过去较高海岸线的遗迹,例如,旧金山北部的加利福尼亚海岸就可以看得见。 但是,现在沿海地带上的海滩高地的高度,并不能为过去海平面的高度(估算)提供直接的线索。 在大多数情况下,海滩高地是陆地通过均衡隆起或地壳运动而抬升的。 随着温度上升,当冰块的重量减轻,比如在某个冰河时期末期,土地的均衡隆起就会发生;它对冰河时期后的斯堪的纳维亚、苏格兰、阿拉斯加和纽芬兰岛海岸线都产生了影响。 地壳运动是构成地球地壳的版块的移动。 更新世中晚期的海滩高地是这种运动的一个实例。

    海滩高地通常由含有沙地、卵石、或沙丘的地区构成,有时(这些区域)还包含贝壳或者碎片堆,包括贝壳和被人类使用过后的海洋动物的骨头。 例如,在东京湾,绳纹时代的贝冢(约公元前10000至300年)标记了被海水淹没的最高的海岸线位置(6500-5500年前),当时通过地壳运动,海平面比现在的日本陆地高出三米到五米。 对贝壳的分析证实了海洋地势的改变,因为只有当海平面达到最高水平时,亚热带的软体动物才出现,这表明了(当时)较高的水温。
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    3 感谢 不懂
    解析

    题型分类:词汇题

    原文定位:词汇所在句The most crucial effect of climate was on the sheer quantity of land available in each period”即“气候对于各个时期可使用土地的数量有着至关重要的影响”,crucial: 至关重要的。

    选项分析:Interesting:有趣的;important:重要的;established:建立的;understood:理解的。因此,选项B符合题干词意。

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