Weathering & Sediment

Weathering & Sediment -...

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Unformatted text preview: !""#$"%&'&"()* •  +,-*./%&*0#$1)*(23)*4&&5* •  678*9$3:*(23)*4&&5;*<&(,3=)*(#*-&*,""#$"%&>*#"*!?&"$&*,">*3"* %=,))*@2$1)>,A* •  B2,"C&*3"*(2&*+&%($1&*8%2&>$=&D* –  –  –  –  –  –  –  –  –  .%(*EF*G*H&,(2&13"C* .%(*IJ*K*L3?&1)*#M*8,">D*8&>3'&"(*N#?&'&"(* .%(*IE*K*@,5&*$O*'3>(&1'* .%(*IP*K*L3?&1)*,">*Q=##>)* .%(*IR*K*N3"&1,=*L&)#$1%&)* .%(*IF*K*7"(1#*(#*@#O#*N,O)* S#?*E*K*Q1#:&"*H#1=>D*6=,%3&1)* S#?*T*K*B,1&&1)*(,=5* S#?*U*K*V3>&#K*9$&&")*#M*<3,'#">)* started October 18th, 2011 Envir/Earth Sc 1G03 Earth & the Environment OUTLINE Rocks to sediments: Weathering! What is weathering? Mechanical weathering Chemical weathering Weathering and climate What is sediment? What is weathering? •  Weathering: – Processes that change the physical and chemical character of rock at or near the Earth's surface •  Erosion –  Physical removal of rock particles by an agent such as a stream or glacier H&,(2&13"CW*X1#)3#"*Y*8=#O&)* •  O1#>$%&)*** LANDSCAPES •  ',>&*$O*#M*** LANDFORMS !"#$%&'()*+& erosion transport deposition Landform (arete) little point on top of the mountain Landscape (entire mountain range) Stock image of landscape with aretes e.g. alpine valley Corbis Digital Stock What does weathering do? •  Mechanical weathering –  –  B reaks rocks into smaller pieces Physical change •  Chemical weathering –  Decomposition of rock from exposure to water and atmospheric gases (CO2,O2) –  Chemical change - new compounds form What causes rocks to physically break? Mechanical weathering: FROST ACTION –  expansion of water as it freezes in joints/cracks –  breaks rock apart –  effective in high latitude areas (freezethaw cycles) Fig. 8.5 Pressure release •  –  rocks formed deep underground, –  pressure release - "unloading" –  rocks crack along "sheet joints" Process called "exfoliation" Fig. 8.8 then exposed by erosion 8,=(*H&>C3"C* salt •  61#4(2*#M*** crystals in spaces in rocks arid •  7"*** regions, as water evaporates What else can cause rocks to break? •  plant growth, burrowing animals •  Mechanical weathering breaks rocks into smaller pieces - increases surface area Allows more extensive chemical weathering by water and air Fig. 8.11 What is chemical weathering? •  Rock decomposition –  Transforms rocks and minerals into new chemical products –  OXYGEN - combines with minerals and elements = oxidation Iron oxidizes – forms iron oxide - red coloured soils ,-".&%)&"/0%#&%)&.)&1)/2#3& •  solution weathering ** carbonic acid •  ** –  ** rainwater + carbon dioxide (H2CO3) –  '#)(*&Z&%[?&*,C&"(*#M* chemical weathering –  %,"*>3))#=?&* limestones sinkholes caves ,-".&0#&"/0%&1"0*3& very •  L,3"4,(&1*43(2*** low pH (<5.5) –  carbonic acid, sulphuric acid, nitric acid ** –  3"%1&,)&)*1,(&*#M* >3))#=$[#"*#M*1#%5)W* )(,($&)W*-$3=>3"C)*&(%;* XZ&%()*#M*,%3>)\* ACID MINE DRAINAGE –  )$=O2$1K%#"(,3"3"C*'3"&1,=)*** oxidize in mine tailings (waste rocks) acids –  M#1'*** at sruface –  &;C;***nickel mines, Sudbury 0A>1#=A)3)* •  7M*4,(&1*3)*,>>&>W*** some minerals expand •  !=(&1&>*?&1)3#"*3)*** softer & weaker • Feldspars weathered to clays ** •  SPHEROIDAL weathering may result from hydrolysis •  Outer layers of flake off 8.*H0!@*78*@0X*LX+!@7.S807]*^X@HXXS* B+7N!@X*!S<*HX!@0XL7S6_* Average number of freeze-thaw cycles per year in Canada (Fraser 1959). 4)5&%)$#&/607".$&"8$/.&5$".-$10*9& (1)/$##$#3& •  B2&'3%,=* 4&,(2&13"C*'#)(* 3"(&")&*3"*4,1'W* '#3)(*%=3',(&)* •  N&%2,"3%,=* 4&,(2&13"C* 3'O#1(,"(*3"*%#=>* %=3',(&)* ,-".&"1$&#$%07$*.#3&:"&;0.&)<&1$=0$5>& •  Loose solid particles formed by **eathering or erosion of prew existing rocks chemical •  .1*-A***precipitation from solution •  8&>3'&"()*,1&*!! UNCONSOLIDATED •  8&>3'&"(,1A*1#%5)*,1&*! LITHIFIED –  C1,3")*2&=>*(#C&(2&1*-A*** cementation or crystallization, packed tightly by compaction !"#$%&$'($)((%$*&$+)%(,-*.)%$-(%/0()*-$ .)%$-(%/0()*$0&1(0()*2$ RECONSTRUCTION of past environmental •  !* conditions, past climates, paleogeographies, changes through time H2A*>#*4&*"&&>*(#*$">&1)(,">*)&>3'&"()_* •  !* - oil & RESOURCE EXPLORATION gas, gypsum, salt, construction materials ,-?&%)&5$&*$$%&.)&'*%$1#."*%&#$%07$*.#3& ISSUES •  !* - ENVIRONMENTALsediment Coastal erosion, movement, aquifer characteristics stopped october 18th, 2011 Started October 20th, 2011 4)5&/"*&5$&/6"##0<?@%$#/10;$&#$%07$*.#3& •  ** •  ** Composition and grain size Composition –  !* CLASTIC sediments made of loose •  ** particles (clasts) - Clasts - Matrix between large grains - Cement NON-CLASTIC - made of chemical precipitates such as phosphates, evaporites, some carbonates •   !* Calcium sulphate, sabkha, Qatar 9$&)[#"* •  H2,(*3)*,"*,`$3M&1_* ...
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