2018年5月19日托福阅读机经

-本文为网络收集精选范文、公文、论文、和其他应用文档，如需本文，请下载-2018年5月19日托福阅读机经本文从网络收集而来，上传到平台为了帮到更多的人，如果您需要使用本文档，请点击下载按钮下载本文档（有偿下载），另外祝您生活愉快，工作顺利，万事如意！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2019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 planets 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 Suns 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 SystemComets文化艺术类The Origins of WritingLive PerformanceThe Origins of TheaterThe Development of Printing地质类Early Theories of Continental DriftAttempts at Determining Earths AgeHow Soil is FormedEarths Energy CycleThermal Stratification环境类The Climate of JapanThe Role of the Ocean in Controlling Climate经济类Effects of the Commercial RevolutionSeventeenth-Century European Economic Growth考古类Environmental Impact of the AnasaziThe Collapse of the MaysThe Chaco Phenomenon科学类The Birth of PhotographyEarly American Printing Industry农业类Agricultural Society in Eighteenth- Century British AmericaWater Management in Early Agriculture社会类Population Growth in Nineteenth-Century EuropeHunting and the Setting of Inner Eurasia生物类Extinctions at the End of the CretaceousThe Cambrian ExplosionThe Extinction of the DinosaursHow Animals in Rain Forests Make Themselves HeardSociality in AnimalsDinosaurs and Parental CareHabitat SelectionTemperature Regulation in Marine OrganismsCell TheoryPoikilothermsForest SuccessionThe Role of DiapauseThe Identification of the Genetic Mater