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2018年5月19日托福阅读机经

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2018-05-14 15:26

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【 liuxue86.com - 托福机经 】

  需要考托福的同学对于机经都有一种信任感,那么大家应该如何进行托福机经的学习呢,下面和出国留学网小编一起来看看2018年5月19日托福阅读机经。

  天文类Surface Fluids on Venus and Earth

  参考阅读:

  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.

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  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

  文化艺术类

  The Origins of Writing

  Live Performance

  The Origins of Theater

  The Development of Printing

  地质类

  Early Theories of Continental Drift

  Attempts at Determining Earth’s Age

  How Soil is Formed

  Earth’s Energy Cycle

  Thermal Stratification

  环境类

  The Climate of Japan

  The Role of the Ocean in Controlling Climate

  经济类

  Effects of the Commercial Revolution

  Seventeenth-Century European Economic Growth

  考古类

  Environmental Impact of the Anasazi

  The Collapse of the Mays

  The Chaco Phenomenon

  科学类

  The Birth of Photography

  Early American Printing Industry

  农业类

  Agricultural Society in Eighteenth- Century British America

  Water Management in Early Agriculture

  社会类

  Population Growth in Nineteenth-Century Europe

  Hunting and the Setting of Inner Eurasia

  生物类

  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

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  想了解更多托福机经网的资讯,请访问: 托福机经

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