Erosion and Landscape Evolution.ppt

8/18/2019 Erosion and Landscape Evolution.ppt

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Erosion and LandscapeEvolution


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How Do We Know Rivers Cut Their Valleys?

John Play air! "#$$• Tri%utary valleys al&ost always 'oin

the &ain valley at e(actly the sa&eelevation! even thou)h the valleys&ay %e)in &any &iles apart* This isvery unli+ely unless the rivers havecut the valleys*

• How Rivers Widen Valleys


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Constructive and DestructiveProcesses

Hi)hlands• Erosion Do&inates• Destructive Processes• History not Preserved• Little ,eolo)ical Record

TransportLowlands! Coastal Plain! La+es and -ea s• Deposition Do&inates• Constructive Processes• History Preserved• ,ood ,eolo)ical Record


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-trea& .%rasion! /arathonCounty


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/e)a0Potholes! -t* Croi(Valley


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.nato&y

o aDraina)e-yste&


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TheContinental

Divide!Colorado


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-trea& 1rder


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The River That Did This2*


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Loo+s Li+e This 3ear 4ts-ource


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The 4deal -trea& Cycle5W*/* Davis! "##$6

3ot a Literal Ti&e-e7uence

• 8outh• /aturity•

1ld .)e• Re'uvenatio n


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8outh • V0-haped Valley• Rapids• Water alls• 3o :lood Plain• Draina)e

Divides ;road

and :lat!


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8outh ul Landscape! .ri=ona


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/aturity

5Early6

• V0-haped Valley• ;e)innin)s o :lood

Plain• -and and ,ravel

;ars• -harp Divides• Relie Reaches

/a(i&u&• Valleys stop

deepenin)• ,eneral .)ree&ent

on this sta)e! lotso e(a&ples


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8oun)0/ature Landscape! Cali ornia


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/ature Landscape!Kentuc+y


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/aturity

5Late6

• Valley has >at%otto&

•

3arrow :lood Plain• Divides %e)in toround o

• Relie di&inishes•

-edi&ent %uildsup! >ood plainwidens

• River %e)ins to&eander

• /any )eolo)ists%elieve slopesstay steep %utsi&ply retreat*


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1ld /ature Landscape! Tennessee


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1ld

.)e

• Land worn tonearly >at sur ace5peneplain6

• Resistant roc+sre&ain aserosionalre&nants5&onadnoc+s6

• Rivers &eander

across e(tre&elywide! >at >oodplains


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/onadnoc+! Colorado


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/onadnoc+s! /aine

ld ) d h


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1ld .)e Landscape! -outh.&erica


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The 1nset o 1ld .)e?4ndiana


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1ld .)e? 1r /ay%e 3ot@ 3e%ras+a


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1ld .)e? 3oA 5Wisconsin6


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Re'uvenation• -o&e chan)e causes strea& to

speed up and cut deeper* – ow

• -trea& valley ta+es on youth ul

characteristics %ut retains eatures oolder sta)es as well*• Can happen at any point in the cycle*


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Re'uvenation!


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Re'uvenation o an old0a)elandscape


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Re'uvenation o an early&ature landscape


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/achu Pichu! Peru


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/achu Pichu! Peru


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Why the -trea& Cycle DoesnBtE(plain Everythin)

• Rises and alls in sea level durin) the ice a)esre'uvenated &ost landscapes to so&e e(tent*

• Cli&ate chan)es &ean that &ass0wastin)

processes in te&perate re)ions &ay haveunder)one radical chan)es repeatedly in thelast ew &illion years*

• 4n places where conditions have re&ained

uni or& or lon) ti&es! li+e the sta%leinteriors o . rica! .ustralia and -outh.&erica! the ideal strea& cycle see&s towor+ %est*


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-ea Level and River Pro le

uperpose n ece en


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uperpose n ece enDrainage

Streams Cut Right Through HighTopography


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Re'uvenatedPeneplain@

the3ortheaste

rn


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Re uvenated

Peneplain


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edDraina)e!Delaware

Water,ap


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C &% l d / t i !


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Cu&%erland /ountains!Vir)inia


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Cu&%erland ,ap


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Devil s ,ap! Wyo&in)


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Riversand

Crustal/ove&en

t!Cali ornia


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Tectonic


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Tectonic


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The


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Draina)e Diversion


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TheHuan) He@

China s-orrowF

• "##G@ !$$$!$$$dead

• "I "@ !G$$!$$$dead

•

"I #@ The Chinesedyna&ite levees toslow the Japanesehal a &illionChinese died*

Ri Di i i h C i


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River Diversions in the CaspianRe)ion


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-trea&Piracy@3orthea

stEn)land


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Why is the Danu%e ;lue?


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Piracy on the Danu%e


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:lood! Ecuador

:lood! reen ;ay! June


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:lood! ,reen ;ay! June"II$


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:lood! ,reen ;ay! June "II$

;uildin) -&art in a :lood


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;uildin) -&art in a :loodPlain

Channeled -ca%lands!


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Channeled ca%lands!Washin)ton

: u : ow s -ca e0


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: u : ow s ca e04nvariant

Erosion o ;edroc+ River


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Erosion o ;edroc+ River;eds


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-ca%land Terrain! 1re)on


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Erosiono -o tRiver;eds

/e)a0 ravel ;ar!


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/e)a0,ravel ;ar!Washin)ton


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/e)a0:lood

Deposits!Washin)to

n

Erosion and Landscape Evolution.ppt

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