07 Geology: Ice Age
地质学：关于更新世时期冰期的研究
导读
冰期（Ice Age）是地球上气候寒冷、具有强烈冰川作用的地质时期。大冰期、冰期和间冰期都是根据气候划分的地质时间单位。
放射性元素的衰变有一定的速率（the rates of decay of various radioactive elements）。半衰期是放射性元素的原子核有半数发生衰变需要的时间。每一种放射性元素的原子核有一定的半衰期，不同的放射性元素半衰期不同。
The term “Ice Age” may give a wrong impression. The epoch that geologists know as the Pleistocene and that spanned the 1.5 to 2.0 million years prior to the current geologic epoch was not one long continuous glaciation![glaciation: the condition of being covered with glaciers or masses of ice; the result of glacial action[地质]冰川作用](https://epubservercos.yuewen.com/9A4043/14676543005843806/epubprivate/OEBPS/Images/note.png?sign=1736254416-AFhcJ5QwDLbBNeka1QzySfq8bwjnw3UF-0-d35bb2205ae9ed2407968bf7dbcfcbe3)
, but a period of oscillating climate with ice advances punctuated by times of interglacial climate not very different from the climate experienced now. Ice sheets that derived from an ice cap centered on northern Scandinavia reached southward to Central Europe. And beyond the margins of the ice sheets, climatic oscillations affected most of the rest of the world; for example,in the deserts, periods of wetter conditions (pluvials) contrasted with drier, interpluvial periods. Although the time involved is so short, about 0.04 percent of the total age of the Earth, the amount of attention devoted to the Pleistocene has been incredibly large, probably because of its immediacy, and because the epoch largely coincides with the appearance on Earth of humans and their immediate ancestors.
There is no reliable way of dating much of the Ice Age. Geological dates are usually obtained by using the rates of decay of various radioactive elements found in minerals. Some of these rates are suitable for very old rocks but involve increasing errors when used for young rocks; others are suitable for very young rocks and errors increase rapidly in older rocks. Most of the Ice Age spans a period of time for which no element has an appropriate decay rate.
Nevertheless, researchers of the Pleistocene epoch have developed all sorts of more or less fanciful model schemes of how they would have arranged the Ice Age had they been in charge of events. For example, an early classification of Alpine glaciation suggested the existence there of four glaciations, named the Gunz, Mindel, Riss, and Wurm. This succession was based primarily on a series of deposits and events not directly related to glacial and interglacial periods, rather than on the more usual modern method of studying biological remains found in interglacial beds themselves interstratified within glacial deposits. Yet this succession was forced willy-nilly onto the glaciated parts of Northern Europe, where there are partial successions of true glacial ground moraines and interglacial deposits, with hopes of ultimately piecing them together to provide a complete Pleistocene succession. Eradication of the Alpine nomenclature is still proving a Herculean task.
There is no conclusive evidence about the relative length, complexity, and temperatures of the various glacial and interglacial periods. We do not know whether we live in a postglacial period or an interglacial period. The chill truth seems to be that we are already past the optimum climate of postglacial time. Studies of certain fossil distributions and of the pollen of certain temperate plants suggest decreases of a degree or two in both summer and winter temperatures and, therefore, that we may be in the declining climatic phase leading to glaciation and extinction.
“冰期”这个术语可能引起一种错误的印象。地质学家称更新世的、在当今地质时期以前跨越150万到200万年的那个时期，并不是一个漫长的、不间断的冰川作用时期，而是一个冰河进展不时被同当前气候相差无几的间冰期气候所打断的气候上下变动的时期。源出于集中在北斯堪的纳维亚半岛的冰帽的大片冰层，向南流到欧洲中部。而在大片冰层外缘，气候的变动影响地球其余大部分地区。例如，在沙漠中，洪水（洪积世）时期同洪水期之间的干旱时期形成对照。更新世期占的时间虽然很短，大约占地球全部年龄的0.04%，但是用于研究这个时期的精力却是大得惊人，也许是因为更新世时期跟当今地质时期直接相连，也许是因为更新世时期大致同地球上出现人类及其最接近的祖先的时间相一致的缘故。
还没有可靠的方法来充分确定冰期的年龄。地质年龄通常用矿石中发现的各种放射性元素的衰变率来算得的。有些衰变率适合于测定老年岩石的年龄，但用于年轻岩石则发生愈来愈大的误差；有些则适合于极其年轻的岩石，用于老年岩石则误差迅速增加。大部分冰期跨越一个没有合适衰变率元素的时期。
然而，更新世时期的研究者们提出了各种各样多少有点怪异的模式方案，说假如过去让他们负责的话，他们早就把冰期的时期作如何如何的划分了。例如对阿尔卑斯山脉的冰蚀的早期分类，提出存在名为恭兹冰期、民德尔冰期、里斯冰期以及玉木冰期的四个冰蚀期。这个冰期系列主要的根据是同冰河期和间冰期没有直接关系的一系列沉积矿床和地质活动，而不是根据更为常用的现代方法，即研究夹在冰川沉积物层之间的在间冰期矿床中发现的生物遗体。但是，这个冰期系列是勉勉强强纳入北欧冰河覆盖地区，那里有真正冰河地区的冰碛层和间冰期的沉积矿床的部分系列，希望最终能把这些连在一起，构成一个完整的更新世系列。要根除关于阿尔卑斯山脉冰河期的陈旧的名词术语至今仍将是一个艰巨任务。
关于各种冰期和间冰期的相对长度、复杂性和温度还没有确定性的证据。我们并不知道，我们现在是生活在冰后期，还是生活在间冰河期。使人寒心的事实似乎是我们已经过完了冰后期的最佳气候时期。研究某些化石分布和某些温带植物的花粉表明地球夏季和冬季的温度各降低了一度或两度，因而表明我们可能处在引向冰川作用和灭绝的下降气候阶段。
Sentence Translation
句子翻译
1. And beyond the margins of the ice sheets, climatic oscillations affected most of the rest of the world; for example, in the deserts, periods of wetter conditions (pluvials) contrasted with drier, interpluvial periods.
2. Nevertheless, researchers of the Pleistocene epoch have developed all sorts of more or less fanciful model schemes of how they would have arranged the Ice Age had they been in charge of events.
Key
1．而在大片冰层外缘，气候的变动影响地球其余大部分地区。例如，在沙漠中，洪水（洪积世）时期同洪水期之间的干旱时期形成对照。
2．然而，更新世时期的研究者们提出了各种各样多少有点怪异的模式方案，说假如过去让他们负责的话，他们早就把冰期的时期作如何如何的划分了。
Emulation美文自己写得出——学生仿写
仿写范例
Self-reliance
Goethe once said that whoever is always paying nothing all the life will achieve nothing, and whoever can not dominate oneself will be a slave forever. Indeed, I can not imagine anything we can not do so long as we are self-reliant. As far as my own experience as a student is concerned, nothing is more important than self-reliance in achieving success.
First things first, life is a journey full of stumbling blocks, dangerous traps and unexpected crises. If you have known clearly what you want your life to be, it is self-reliance that carries you there. Moses was a stutterer, yet he was called on to be the voice of God; Abraham Lincoln overcame a difficult childhood, depression, the death of two sons, and constant ridicule during the Civil War to become unarguably the greatest President ever; Helen Keller made an impact on the world despite being deaf, dumb and blind from an early age. These examples prove that there is no better royal road to great accomplishment than self-reliance.
Second, it goes without saying that self-reliance forces us to set a higher goal in our daily existence. Just as a famous man put it, “living without an aim is like sailing without a compass.” The society is full of competition which is becoming more and more intense, what we can get often depends not on how much we have done but how much better we have done than others. Without self-reliance, we would probably be satisfied with and remain what we are, leaving our potentials to go to waste.
Last but not least, self-reliance can banish the greatest evil in the world: laziness. Take myself for example, I was born in a small village where many parents were illiterate, few children could pursue fundamental education, let alone college. So this is why I so cherish the college time. College time can fly away as quick as a wink. Many of my classmates squander their time by indulging in computer games, hanging around and sleeping in dorm. On the contrary, I spared no effort to learn and worked harder than any classmate, because I knew that it will never rain rose, when we want to have more roses, we must plant trees. When I enjoy the fruits of my labor, I believe more firmly that self-reliance makes perfect.
As an old Latin American saying goes: “Self-reliance is superior to the hand of God.” Indeed, no pain, no palm; no thorns, no throne; no gall, no glory; no cross, no crown. What we sow at present shall be reap in the future, so our future is determined by our present actions—self-reliance.