关注微信领¥50

百门课程¥0元


50万+已关注

2018年4月21日托福阅读机经预测

2018-04-04 09:52:00来源:网络

  2018年4月21日托福阅读机经预测!4月21日的托福考试即将来临,大家在考试前夕,应该重点备考哪些知识呢?新东方在线托福网为大家汇总了相关的内容,供大家参考。更多精彩尽请关注新东方在线托福网(http://toefl.koolearn.com)!

  How Soil is Formed

  Soil formation is a dynamic process that takes place in different environments. It is strongly influenced by the parent material, climate (largely vegetation and temperature and water exchanges), topography (the elevations, depressions, directions and angles of slopes, and other surface features of the landscape), and time.

  The parent material is the unconsolidated mass on which soil formation takes place. This material may or may not be derived from the on-site geological substrate or bedrock on which it rests. Parent materials can be transported by wind, water, glaciers, and gravity and deposited on top of bedrock. Because of the diversity of materials involved, soils derived from transported parent materials are commonly more fertile than soils from parent materials derived in place. Whatever the parent material, whether derived in place from bedrock or from transported material, it ultimately comes from geological materials, such as igneous, sedimentary, and metamorphic rocks, and the composition of the rocks largely determines the chemical composition of the soil.

  Climate is most influential in determining the nature and intensity of weathering and the type of vegetation that further affects soil formation. The soil material experiences daily and seasonal variations in heating and cooling. Open surfaces exposed to thermal radiation undergo the greatest daily fluctuations in heating and cooling, soils covered with vegetation the least. Hill slopes facing the sun absorb more heat than those facing away from the sun. Radiant energy has a pronounced effect on the moisture regime, especially the evaporative process and dryness. Temperature can stimulate or inhibit biogeochemical reactions in soil material.

|

|

|

》》》2018年4月托福预测考前点题【直播课】《《《

》》》2018年4月21日托福机经预测汇总《《《

为你特别匹配的托福超值课程,快速提分先人一步!
  • 新东方托福1月公益课(第1期)

    新东方托福1月公益课(第1期)

    特点1天1节公益课,给2019来点托福备考新鲜货!

    课时:10小时

    查看详情
  • 【活动价】新东方托福名师在线一对一(体验课)

    【活动价】新东方托福名师在线一对一(体验课)

    适合人群:想体验新东方在线致赢托福1对1辅导冲分课程的同学

    体验课时:30分钟

    查看详情
  • 大学生旗舰直达班 (冲110分)

    【知心托福】大学生旗舰直达班 (冲110分)

    适合人群:托福目标分数110分!

    课时:343

    查看详情
  • 大学生旗舰直达班 (冲100分)

    【知心托福】大学生旗舰直达班 (冲110分)

    适合人群:托福目标分数100分!

    课时:331

    查看详情
  • 大学生旗舰直达班 (冲90分)

    【知心托福】大学生旗舰直达班 (冲90分)

    适合人群:托福目标分数90分!

    课时:310

    查看详情
全部课程>>
单项突破
直播课堂

更多托福课程
新东方25年教学经验沉淀
托福考生必修课
托福考生,高效提分,安心之选

查看详情>>
更多>>
更多课程>>
更多>>
更多内容
更多>>
更多公开课>>
更多>>
更多课程>>