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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.
题型分类:推理题
题干分析:关键词:Tokyo Bay
选项分析:此类题型分类,建议通过选项关键词定位原文信息进行判断。
选项A与原文第二句“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.”信息相反,原文说“在东京湾,绳纹时代的贝冢标记了被海水淹没的最高的海岸线位置,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。”而题干说“目前可用的沿海土地比Jomon时期的面积要小。”,注意原文是“maximum inundation by the sea”,题干信息是“coastal land”相反意思,因此选项错误;
选项B的raised beaches原段落并未提及;
选项C对应段落最后一句,软体动物的存在暗示着水温高,而Tokyo Bay是Jomon时期由软体动物组成的贝冢,故可以推出Tokyo Bay的水温在Jomon时期要比现在高。选项C正确。
选项D原文未提及Tokyo Bay’s raised beaches.
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