2. 外语
  3. EARTH’S ENERGY CYCLE (1) To understand most of the processes at work on Earth, it is useful to envisage interactions within

EARTH’S ENERGY CYCLE (1) To understand most of the processes at work on Earth, it is useful to envisage interactions within

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问题                                                 EARTH’S ENERGY CYCLE
    (1) To understand most of the processes at work on Earth, it is useful to envisage interactions within the Earth system as a series of interrelated cycles. One of these is the energy cycle, which encompasses the great "engines"—the external and internal energy sources—that drive the Earth system and all its cycles. We can think of Earth’s energy cycle as a "budget”: energy may be added to or subtracted from the budget and may be transferred from one storage place to another, but overall the additions and subtractions and transfers must balance each other. If a balance did not exist, Earth would either heat up or cool down until a balance was reached.
    (2) The total amount of energy flowing into Earth’s energy budget is more than 174,000 terawatts (or 174,000 x 1012 watts). This quantity completely dwarfs the 10 terawatts of energy that humans use per year. There are three main sources from which energy flows into the Earth system.
    (3) Incoming short-wavelength solar radiation overwhelmingly dominates the flow of energy in Earth’s energy budget, accounting for about 99.986 percent of the total. An estimated 174,000 terawatts of solar radiation is intercepted by Earth. Some of this vast influx powers the winds, rainfall, ocean currents, waves, and other processes in the hydrologic (or water) cycle. Some is used for photosynthesis and is temporarily stored in the biosphere in the form of plant and animal life. When plants die and are buried, some of the solar energy is stored in rocks, when we burn coal, oil, or natural gas, we release stored solar energy.
    (4) The second most powerful source of energy, at 23 terawatts or 0.013 percent of the total, is geothermal energy, Earth’s internal heat energy. Geothermal energy eventually finds its way to Earth’s surface, primarily via volcanic pathways. It drives the rock cycle and is therefore the source of the energy that uplifts mountains, causes earthquakes and volcanic eruptions, and generally shapes the face of the Earth.
    (5) The smallest source of energy for Earth is the kinetic (motion) energy of Earth’s rotation. The Moon’s gravitational pull lifts a tidal bulge in the ocean; as Earth rotates, the tidal bulge runs into the coastlines of continents and islands, causing high tides. The force of the tidal bulge piling up against landmasses acts as a very slow brake, actually causing Earth’s rate of rotation to decrease slightly. The transfer of tidal energy accounts for approximately 3 terawatts, or 0.002 percent of the tidal energy budget.
    (6) Earth loses energy from the cycle in two main ways: reflection, and degradation and reradiation. About 40 percent of incoming solar radiation is simply reflected, unchanged, back into space by the clouds, the sea, and other surfaces. [A] For any planetary body, the percentage of incoming radiation that is reflected is called the "albedo" . [B] Each different material has a characteristic reflectivity. [C] For example, ice is more reflectant than rocks or pavement; water is more highly reflectant than vegetation; and forested land reflects light differently than agricultural land. [D] Thus, if large expanses of land are converted from forest to plowed land, or from forest to city, the actual reflectivity of Earth’s surface, and hence its albedo, may be altered. Any change in albedo will, of course, have an effect on Earth’s energy budget.
    (7) The portion of incoming solar energy that is not reflected back into space, along with tidal and geothermal energy, is absorbed by materials at Earth’s surface, in particular the atmosphere and hydrosphere. This energy undergoes a series of irreversible degradations in which it is transferred from one reservoir to another and converted from one form to another. The energy that is absorbed, utilized, transferred, and degraded eventually ends up as heat, in which form it is reradiated back into space as long-wavelength (infrared) radiation. Weather patterns are a manifestation of energy transfer and degradation.
In paragraph 1, the author introduces the concept of a budget in order to________.
选项 A、indicate how different cycles in the Earth system relate to each other
B、illustrate how Earth’s energy cycle must maintain an overall balance
C、show that Earth gains energy from both external and internal sources
D、explain how energy is transferred from one storage place to another
答案B
解析 本题询问在第1段中，作者介绍“预算”这一概念的目的，属于修辞目的题，budget出现在第1段倒数第2句，budget后是对这个单词的解释：地球的能量有增有减，也会从一个储藏地转移至另一个储藏地，但总的来说应达到平衡。这其实就同经济生活中的预算有着同样特征：有收入有支出，但总体上收支平衡，因此，作者引入“预算”这一经济学概念，是为了让读者更好地理解地球能量循环需达到平衡，故选B项“为了阐述地球的能量循环如何维持整体平衡”。A项“为了表明地球系统中的不同循环之间如何相互作用”，原文并没有提到地球系统中不同的循环之间如何相互作用。C项“为了表明地球从内部和外部能量来源中获取能虽”可定位至原文第1段第2句，该句提到的地球外部和内部的能量来源是对巨大“引擎”的定义的补充说明，与第3句中的budget并无承接的逻辑关系。D项说“为了解释能量如何从一个储藏地转移至另一个储藏地”，第1段第3句只提到了能量的储藏地可改变，并没有解释原理。
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