第五章 风化作用

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1、第五章风化作用(Wethering)5.1地质作用概述•地质作用－在自然界中所发生的一切可以改变固体地球物质组成、构造和地表形态的作用•地质作用的三重概念：能、营力、作用方式•营力：由能量转化而成的，能够发生地质作用的力•作用方式：侵蚀、搬运、沉积5.1GeologicalProcess(地质作用)三个概念ExternalProcesses(外动力地质作用）•粒级反映碎屑物颗粒的大小•Erosion-rocksarebrokendown(weathered)into<0.005—0.05—0.5—2.0—5.0

2、dbywind,粘土粉砂细砂粗砂细砾粗砾water,iceandgravity.ExternalbecauseerosionoperatesattheEarth'ssurface.Theenergy•分选沉积物中碎屑的粒级方差越小，分sourceforthisprocessissolarandgravitational.选性越好InternalProcesses(内动力地质作用)•磨圆度碎屑物在搬运过程中棱角会逐渐•Processesthatproducemagmas,volcanoes,地磨损，使碎屑颗粒逐渐变圆，反映碎earthquakesandbuildmountain

3、ranges.Energy屑颗粒被磨圆的程度就是磨圆度comesfromtheinterioroftheEarth,Mostfromradioactivedecay-nuclearenergy.SomeGeologicRatesSomeGeologicRatesCuttingofGrandCanyonMovementofSanAndreasFault•2km/3m.y.=1cm/15yr•5cm/yr=7m/140yr.UpliftofAlpsGrowthofMt.St.Helens•5km/10m.y.=1cm/20yr.•3km/30,000yr=10cm/yr.Open

4、ingofAtlantic•5000km/180m.y.=2.8cm/yr.DepositionofNiagaraDolomiteUpliftofWhiteMtns.(N.H.)Granites•100m/1m.y.=1cm/100yr.•8km/150m.y.=1cm/190yr.1ProcessesrangefromthosethatoccurrapidlytothosethatoccurslowlyExamplesofslowprocesses•FormationofrocksExamplesoffasterprocesses•Chemicalbreakdownofro

5、cktoformsoil•Beacherosionduringastorm.(weathering)•Constructionofavolcaniccone•Chemicalcementationofsandgrainstogethertoformrock(diagenesis)•Landslides(avalanches)•Recrystallizationtorocktoformadifferentrock•DustStorms(metamorphism)•Constructionofmountainranges(tectonism)•mudflows•Erosionof

6、mountainranges•debrisflow(mud-rockflow)地质作用的方式5.2Weathering（风化作用特征）⎧⎧构造运动⎫Sincemanyrocksandmineralsareformedunderconditionspresentdeep⎪⎪⎪⎪⎪地震作用⎪withintheEarth,whentheyarrivenearthesurfaceasaresultofuplift内动力地质作用⎨⎪anderosion,theyencounterconditionsverydifferentfromthoseunder⎪岩浆作用⎪⎪⎪whichthey

7、originallyformed.Amongtheconditionspresentnearthe⎪⎪⎩变质作用⎪Earth'ssurfacethataredifferentfromthosedeepwithintheEarthare:⎪⎪•LowerTemperature(NearthesurfaceT=0-50oC)⎪⎪•LowerPressure(NearthesurfaceP=1toseveralhundred地质作用⎨重力作用⎬重力参与作用atmospheres)⎪⎪⎪⎪•Higherfree