2017年10月14日托福閱讀考試預(yù)測(cè)

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      2017年10月14日托福閱讀考試預(yù)測(cè)
      天文類(lèi)Surface Fluids on Venus and Earth
      參考閱讀:
      A fluid is a substance, such as a liquid or gas, in which the component particles (usually molecules) can move past one another. Fluids flow easily and conform to the shape of their containers. The geologic processes related to the movement of fluids on a planet’s surface can completely resurface a planet many times. These processes derive their energy from the Sun and the gravitational forces of the planet itself. As these fluids interact with surface materials, they move particles about or react chemically with them to modify or produce materials. On a solid planet with a hydrosphere and an atmosphere, only a tiny fraction of the planetary mass flows as surface fluids. Yet the movements of these fluids can drastically alter a planet. Consider Venus and Earth, both terrestrial planets with atmosphere.
      Venus and Earth are commonly regarded as twin planets but not identical twins. They are about the same size, are composed of roughly the same mix of materials, and may have been comparably endowed at their beginning with carbon dioxide and water. However, the twins evolved differently, largely because of differences in their distance from the Sun. With a significant amount of internal heat, Venus may continue to be geologically active with volcanoes, rifting, and folding. However, it lacks any sign of a hydrologic system (water circulation and distribution): there are no streams, lakes, oceans, or glaciers. Space probes suggest that Venus may have started with as much water as Earth, but it was unable to keep its water in liquid form. Because Venus receives more heat from the Sun, water released from the interior evaporated and rose to the upper atmosphere where the Sun’s ultraviolet rays broke the molecules apart. Much of the freed hydrogen escaped into space, and Venus lost its water. Without water, Venus became less and less like Earth and kept an atmosphere filled with carbon dioxide. The carbon dioxide acts as a blanket, creating an intense greenhouse effect and driving surface temperatures high enough to melt lead and to prohibit the formation of carbonate minerals. Volcanoes continually vented more carbon dioxide into the atmosphere. On Earth, liquid water removes carbon dioxide from the atmosphere and combines it with calcium, from rock weathering, to form carbonate sedimentary rocks. Without liquid water to remove carbon from the atmosphere, the level of carbon dioxide in the atmosphere of Venus remainshigh.
      Origin of the Solar System
      Comets
      文化藝術(shù)類(lèi)
      The Origins of Writing
      Live Performance
      The Origins of Theater
      The Development of Printing
      地質(zhì)類(lèi)
      Early Theories of Continental Drift
      Attempts at Determining Earth’s Age
      How Soil is Formed
      Earth’s Energy Cycle
      Thermal Stratification
      環(huán)境類(lèi)
      The Climate of Japan
      The Role of the Ocean in Controlling Climate
      經(jīng)濟(jì)類(lèi)
      Effects of the Commercial Revolution
      Seventeenth-Century European Economic Growth
      考古類(lèi)
      Environmental Impact of the Anasazi
      The Collapse of the Mays
      The Chaco Phenomenon
      科學(xué)類(lèi)
      The Birth of Photography
      Early American Printing Industry
      農(nóng)業(yè)類(lèi)
      Agricultural Society in Eighteenth- Century British America
      Water Management in Early Agriculture
      社會(huì)類(lèi)
      Population Growth in Nineteenth-Century Europe
      Hunting and the Setting of Inner Eurasia
      生物類(lèi)
      Extinctions at the End of the Cretaceous
      The Cambrian Explosion
      The Extinction of the Dinosaurs
      How Animals in Rain Forests Make Themselves Heard
      Sociality in Animals
      Dinosaurs and Parental Care
      Habitat Selection
      Temperature Regulation in Marine Organisms
      Cell Theory
      Poikilotherms
      Forest Succession
      The Role of Diapause
      The Identification of the Genetic Material
      How Plants and Animals Arrived in the Hawaiian Islands
      Constraints on Natural Selection