Download 2. Geologic History Agenda Physical Geographers Intro to Calif

Geog 106
2/18/2013
Agenda
Todaywewilldiscuss
2.GeologicHistory
 WhatPhysicalGeographyis
 BriefgeologichistoryofCalifornia
Geography106– CaliforniaGeography|M.Pesses|AntelopeValleyCollege
PhysicalGeographers
 Interestedinnatural
places &themobility
ofmatter&energy
 SynthesisofEarth’s
y
history&future
Uniformitarianism
 Thesameprocessesactive
todayhavebeenoccurring
throughoutgeologictime
 Invisibletous,but
unbelievablypowerful
Instructor: M. Pesses
IntrotoCalif.PhysicalGeography
NaturaldisastersleadtoCalifornia’sbeauty
TheoryofPlateTectonics
TheEarth’scrustisbrokenupintoaseriesof
“plates”
 ThesecrustalplatesfloatontopoftheAesthenosphere
intheUpperMantle
 Convectioncell
Convection cell
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“UnifyingTheory”
Tiestogetherearthquakes,
volcanoes,mountainranges,
pastclimates&fossil
evidence
PlateBoundaries
 Diverging
 Converging
 Sliding(Transform)
Diverging
 Platespulledapart
 Seafloorspreading
Instructor: M. Pesses
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Converging
 Platescollide
 Subductionzones
Terranes
 Crustalrockthatcame
fromanotherlocation
duetothemovement
ofplates
Sliding(Transform)
 Whereplatesslide
pasteachother
 Nodiverging,no
converging
 Usuallynovolcanic
activity
Instructor: M. Pesses
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ContinentalMargin
CaliforniaisNew
Rocks
Minerals
Minerals
Earth’scrust
feldspar
 8mainelements
 SiO2
 Resilient
Minerals
 Bondedelementswith
acrystallinestructure
 Thebuildingblocksof
rocks
Instructor: M. Pesses
Quartz
quartz
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Rocks
Anassemblageofminerals
Granite
 Quartz,feldspar,mica,
hornblende
Rocks
Categories
Exceptions
Allrockscanbesortedintooneofthree
categories
 Undifferentiated
material
 Organicmaterial
 Igneous
 Sedimentary
Sedimentary
 Metamorphic
Obsidian
IgneousProcesses
Formswhenmagmaorlava
solidifies
Magma
 Moltenrockunderneath
surfaceoftheEarth
f
f th E th
Lava
 Whenmagmareaches
surfaceoftheEarth
Instructor: M. Pesses
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IntrusiveIgneousRocks
 Termforrockformedbycoolingmagma
 Magmafillsincracks
 Slowcooling
 Largegrainsize
IntrusiveIgneousRocks
Massofintrusiverockcalledpluton
 Largeplutoncalledabatholith
Intrusiveigneousrocksalsocalledplutonic
rocks
ExtrusiveIgneousRocks
 Rocksformedby
coolinglava
 Coolsquickly
 Finegrained
g
 Alsocalledvolcanic
rocks
Granite
 Intrusive
 Mediumtocoarse
grained
 Felsic
 Richinfeldsparand
silica
Instructor: M. Pesses
Rhyolite




Extrusive
Finegrained
Felsic
Cools too quickly 
Coolstooquickly
Obsidian
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Basalt
 Extrusive
 Finegrained
 Mafic
SedimentaryRocks
Madefromlayeringofbrokendownrock&mineral
particles
 Sometimesorganicmaterial
 Rich
Richinironand
in iron and
magnesium
 Makesupmostof
oceanfloor
TheProcess
 Weatheringbreaksdownsurfacematerials
 Water,wind,orglacialicetransportsthese
sediments
 Burialofsedimentsleadstocompaction,
l f d
l d
cementation,&hardening
Subclasses
1. Clastic
2. ChemicallyPrecipitated
3. Organic
 Whichcreatesrocks
SedimentaryRocks
Examples
Clastic
 Madeoffragmentsofrock&minerals
 Layering
Instructor: M. Pesses
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SedimentaryRocks
Chemicallyprecipitated
 Dissolvedmineralsorhardpartsoforganisms
 Transportedinsolution,thenprecipitated
Evaporites
Waterevaporates,leavessalt
DeathValley,afterrain
OrganicSedimentaryRocks
Sedimentmadefrom
decayinganimal&
planttissue
DeathValley,afterwaterevaporates
Hydrocarbons
Solid
 Coal,Peat
Liquid
 Petroleum
Gas
 Naturalgas
Fossils
AlmostExclusivelyinSedimentaryRocks
 HeatofMeltingorMetamorphismWouldDestroy
AlmostEveryTypeofFossil
BuriedRapidlyAfterDeath,PreservedFromDecay
EnvironmentalClues
Fossils
 SaltWater– Corals,Echinoderms
 FreshWater– Insects,Amphibians
 Terrestrial– Leaves,LandAnimals
,
Color&Chemistry
 RedBeds– OftenTerrestrial
 BlackShale– OxygenPoor,OftenDeepWater
 Evaporites– AridClimates
Instructor: M. Pesses
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MetamporphicProcesses
Changesinsedimentaryorigneousrockduetoheat
orpressure
 Radioactivedecay
 PressuredeepwithinEarth
GeologicTime
GeologicTime
 15billionyears=15,000,000,000years
 15billionseconds=475years
 Considering1secondtocorrespondto1year:





BigBang‐ A.D.1526
Earth’ssFormation‐1858
Earth
Formation ‐1858
Dinosaurs‐ livedfrom1993‐1999
Humans‐ appeared2weeksago
IceAgeswouldhavehappenedeverydayforthelast2weeks.
 Thelastonewouldhaveended5hoursago
 JuliusCaesar‐ lived44minutesago
 UnitedStates– createdjustover3½minutesago
 WorldWarII‐ ended56secondsago
Instructor: M. Pesses
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GeologicTime
HistorybrokenupintoEons,Eras,&
Periods
 ChangebasedonchangeinEarth’sbiology,
atmosphere etc
atmosphere,etc.
Dating
 Absolute
 Relative
PrecambrianEon
ProterozoicEra (2.5bya– 545mya)
 Aneraisasubsectionofaneon
 MostofCaliforniaunderwater
 EvidenceinDeathValleyofshallowsea
PaleozoicEra
 (542mya– 251mya)
 MostofCaliforniastill
underwater
PrecambrianEon
 4.6billionyearsago
(bya)‐ 545million
yearsago(mya)
 Oldestrocksin
Californiajustunder2
billionyearsold
PhanerozoicEon
 (545mya– present)
 3eras
 Paleozoic
 Mesozoic
 Cenozoic
PaleozoicEra
 Pangaeastartingtoformatendofera
 Tectonicallyactive
 Terranesfromseafloorspreading
 Islandarcspushedupagainstcontinent
I l d
h d
i t
ti
t
 FossilscommontoEastAsia
 NorthAmericabeginstogrow
Instructor: M. Pesses
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MesozoicEra
 (251mya– 66mya)
MesozoicEra
Continuedterranebuild‐up
 FranciscanComplex
 Medleyofexoticrocksthat
makeuptheCoastRanges
MesozoicEra
GraniticPlutons
 Subductionofoceanplate
 Meltsrockintofelsicmagma
 Intrudesintoexistingrock,
cools
 Eventuallyexposedbyuplift
&erosion
MesozoicEra
Mountainbuilding
changedcoastline
 Nevadanorogeny
(approx.150mya)
 Pushedseainto
CentralValley
Instructor: M. Pesses
MesozoicEra
KlamathMountains
 Bothpluton&
blueschistaccretion
MesozoicEra
KeptoceanoutofBasin&Range
 Wedon’tfindmarinefossils,butdofindterrestrialred
sandstone
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MesozoicEra
Upliftacceleratederosion
 Exposedgranite
 filledCentralValley
withsediment
CenozoicEra
Volcanicactivity
 SubductionVolcanism
 Subducingplatemakes
felsicmagma,violent
volcanoes
 Responsibleforthe
Cascades
CenozoicEra
 (66mya– present)
 Continueduplift&sedimentdepositsinto
CentralValley
 Pushesseawestward
P h
d
CenozoicEra
PinnaclesNationalMonument
 ErodedvolcanothatoriginatedinwesternAntelopeValley
 SanAndreasmovedrock200milesNorth
CenozoicEra
 ModocPlateau
 Basin&
Range/Mojave
Instructor: M. Pesses
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CenozoicEra
Glaciallakes&inlandseas
NextTime
 ModernVolcanicLandscapes
 TronaPinnacles
Instructor: M. Pesses
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