GeologicalTime

Thereare2basicwaysyoucantellhowoldsomethingis

1.  Absolute,me‐iden8fiestheactualdateofanevent

2.  Rela,ve,me‐doesnotiden8fytheexact8me,buttheorderinwhichthingshappened.

AbsoluteTime

•  Treerings‐youcantellhowoldatreeisbycoun8ngtheringswhichareimbeddedinit.

•  Bystudyingthesizeoftheringsyoucandeterminewhattheclimatewaslikewhenitwasoncealive.

•  Thickerringsmeanmoreprecipita8on.

•  Varves‐anysedimentsthatshowayearlycycle.

•  Eachseasonproducesmoreorlesssedimentdeposits.

•  Radioac,veElements‐rocks&fossilsofallkindhaveradioac8veelementsintheirmakeup.

•  Whentheseelementsbreakdowntheybecomesomethingelse.

•  Whenwestudythem&findlessoftheradioac8veelementweknowthatitisolder.

•  HalfLife‐whentheseradioac8veelementsdecaytheydosoinhalvesorhalflives.

•  Donotcopy.•  Takeapieceofpaper•  KeepRippingitinhalfevery5seconds.•  Bylookingatthesizeofthepaperyoucanfindouthowlongyouhavebeenrippingitfor.

•  Radio‐CarbonDa8ng‐alllivingthingscarbon‐14inthem.

•  ALeralivingthingdiesitwillbegintoloseitscarbon‐14.

•  ThepercentageleLinthefossilwilltellushowoldthefossilis.

Relative Time

•  LawofSuperposi,on‐Whenlayersoftheearthgoundisturbedtheywillhavetheyoungestrocksontop&theoldestrocksontheboMom.

e d b

a

Layer (e) is the youngest layer

Layer (a) would be the oldest layer

Layer (c) formed before layer (d) and (e) c

GeologicalTimetable

AsummaryofmajoreventsthathappenedinourEarth’shistory

•  Era‐averylargepor8onof8meinhistory

•  Period‐por8onof8methatoccurredinanera.(shorterthananera)

•  Epoch‐por8onof8methatoccurredinaperiod(shorterthanaperiod)

Thereare4mainera’sinourEarth’sHistory

Precambrian

Cenozoic

Mesozoic

Paleozoic

PrecambrianEra

Age

•  Allofearth’shistoryfromthebirthoftheearthun8labout570millionyearsago

Life

•  Themajorcharacteris8csofrocksfromthiseraisthattherearefewfossilsoflivingorganisms

•  Lifeduringthiserawasmainlybacteria&simpletypesofsingle&mul8‐cellularorganisms.

•  Stromatolites‐typeofalgaethatflourishedduringthis8me.

Otherlifethatlivedduringthis8mewere:

•  Jellyfish•  Simplefungi

•  Marineworms

•  Ancestorsofstarfish&coral

Geology

•  MuchofthePrecambrianrockhasbeeneitherburieddeepintheearth,changedbyheatandpressure,eithermeltedormetamorphosed.

•  Thisiswhyitisdifficulttolocateanyfossils.•  Foralongperiodof8metheearth’scrustwasmoltenrock

•  Shields‐rockthatformedfromthePrecambrianeraandareexposeds8lltoday.

MineralDeposits

•  AbouthalfoftheworldsmetallicmineraldepositsoccurinPrecambrianrocks.

Herearejustafew:

•  Iron•  Copper•  Gold•  Nickel

PaleozoicEra

Age

•  570millionyearsago‐250millionyearsago

periods

•  Cambrian–1st•  Ordovician•  Silurian•  Devonian•  Mississippian

•  Pennsylvanian•  Permian‐Last

Life

•  Therewasanexplosionoflife•  Firstanimalswithhardparts(shells,teeth,bones)begantoform

•  Fishesdominatedthisera

•  Clams,snails,sponges,amphibians,spiders

•  Landplantsbegantoform(ferns)

•  Rep8lesappeared

Geology

Beginningofera•  AppalachianMountainsbegantoform

Towardstheendoftheera

•  Coalformingswampsbeganforming

•  AppalachianMountainsstoppedrising

MassEx8nc8on

•  96%ofalllifehaddied•  1/2ofallknownspeciesbecameex8nct•  Mostwaterinvertebratesnolongerexist•  Ex8nc8onisbelievedtohaveoccurredin3majorstagesgradualatfirst,cappedoffbyamajorcatastrophicevent.

•  Greatestmassex8nc8ononourearth’shistory

MesozoicEra

Age

•  250millionyearsago‐65millionyearsago•  Shortestofalltheera’s

Periods

•  Triassic–first•  Jurassic•  Cretaceous‐last

Life

•  Dinosaursbecamethedominantlandanimals•  IntheU.S.wecanfindfossilsprimarilyin:

•  Montana Utah

•  Colorado Kansas

•  Texas Oklahoma

•  NewMexico

•  Firstdinosaursweresmallnolargerthanrabbits

•  As8mewentontheygrewlarger

•  Mammalsfirstappearedonearth

•  Birdsfirstappearedonearth•  Rep8les(dinosaurs)livedintheseas,land,&skies.

•  Coniferswerethedominanttrees

•  Floweringplantssuchasdeciduoustreesappearedduringthisera.

Geology

•  AppalachianMountainsbegantoweardown

•  RockymountainsbegantoformBeginningoftheera•  Onesupercon8nentonearthcalledPangaeaEndoftheera•  Con8nentssplitapartalmosttowheretheyaretoday.(PlateTectonics)

Endofanera

MassEx8nc8on•  50%ofallplant&animallifebecameex8nct•  Mostrep8lesbecameex8nct•  Mammalssurvived•  Majorchangeinclimateoccurred•  Earthwasbelievedtobestruckbyanasteroid(YucatanPenninsula)

Evidencethatsupportsthisimpactidea

•  Tek8tes‐rocksthatformwhendebrisfromanimpactissprayedintotheairmeltedandcooled.

•  Thereisathinrocklayer(tek8tes)coveringtheearth.Thislayerisfoundallovertheearth.

•  Thislayerisfoundatacertaindepth.ThisdepthseparatestherocklayerbetweentheMesozoic&CenozoicEra’s

•  Inthislayeryoucanfindanelementwhichoriginatedfromouterspace.

•  ThereisanextremelylargecraterfoundintheYucatanPeninsula,whichwasformedattheendoftheMesozoiclayer.

CenozoicEra

Age

•  65millionyearsagotothepresent

Periods

•  Ter8ary•  Quaternary

Epochs

•  7epochs

Life

Maintypesofplantlife:•  Grasses‐new•  DeciduousTrees•  Tropicalplants•  Conifers

Maintypesofanimallife•  Mammalsarethedominantspecies

•  Insects•  Birds•  Fish•  Rep8les

Humans‐new

•  Humanlikespeciesneededtohave2mainfactorstobedis8nguishedfromapes:– Walkupright(ratherthanonall4’s)– Largerbrainmass

•  As8mewentonhominidsbeganhavingmorebrainmass

Geology

•  Con8nentsarewheretheyaretoday.•  Rockymountainscon8nuedtoupliL

•  Greatlakesformed

•  CoalbeginsformingintheU.S.

NextEra???

•  AnewErabeginsaLersomethingmajoroccursinthelifeandgeology.

•  MassEx8nc8ons‐endofPaleozoiceraandMesozoicera

•  Explosionofnewlife‐BeginningofPaleozoicera

PossibleWaysourownEracanend

•  Diseasethatcouldwipeoutlife•  Climac8cchange

•  Nuclearwar•  Impactfromouterspace(comet,asteroid)

•  GammaRays

•  Newdominantspeciesintroduced

•  LowTestGrades