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  3. The climate of earth has fluctuated quite a bit over the last 4.6 billion ye

The climate of earth has fluctuated quite a bit over the last 4.6 billion ye

游客2024-05-08  4
问题     The climate of earth has fluctuated quite a bit over the last 4.6 billion years of our planet’s history and it can be expected that the climate will continue to change. One of the most intriguing questions in earth science is whether the periods of ice ages are over or arc we living in an "interglacial" period of time between ice ages?
    The geologic time period we are now living in is known as the Holocene (全新世). This epoch began about 11,000 years ago which was the end of the last glacial period and the end of the Pleistocene (更新世) epoch. The Pleistocene was an epoch of cool glacial and warmer interglacial periods which began about 1.8 million years ago.
    Since the glacial period known as the "Wisconsin" in North America and "Wrm’ in Europe when over 10 million square miles (about 27 million km2 ) of North America, Asia, and Europe were covered by ice, almost all of the ice sheets covering the land and glaciers in the mountains have retreated. Today, about ten percent of the earth’s surface is covered by ice; 96% of this ice is located in Antarctica and Greenland. Glacial ice is also present in such diverse places as Alaska, Canada, New Zealand, Asia, and California.
    As only 11,000 years has passed since the last Ice Age, scientists can not be certain that we are indeed living in a post- glacial Holocene epoch instead of an interglacial period of the Pleistocene and thus due for another ice age in the geologic future. Some scientists believe that an increase in global temperature, as we are now experiencing, could be a sign of an impending ice age and could actually increase the amount of ice on the earth’s surface.
    The cold, dry air above the Arctic and Antarctica carries little moisture and drops little snow on the regions. An increase in global temperature could increase the mount of moisture in the air and increase the amount of snowfall. After years of more snowfall than melting, the Polar Regions could accumulate more ice.
    An accumulation of ice would lead to a lowering of the level of the oceans and there would be further, unanticipated changes in the global climate system as well. Our short history on earth and our shorter record of the climate keeps us from fully understanding the implications of global warming. Without a doubt, an increase in the earth’s temperature will have major consequences for all life on this planet.  [br] Which of the following statements is TRUE according to the passage?
选项 A、96 percent of the earth’s surface is covered by ice.
B、Over 10 million square miles of the earth’s surface are covered by ice now.
C、Almost all of the ice sheets coveting the land and glaciers in the mountains have been hidden.
D、Most of the ice on the earth’s surface is located in Antarctic and Greenland for the time being.
答案 D
解析 细节题。文章第三段倒数第二句指出，如今地球表面的10%被冰覆盖，其中的96%分布在南极洲和格陵兰岛，所以D正确。
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