Unit 3Chapter 9

A View of the Earths Past

Section 1. Geologic Time

The scale outlines the development of Earth and life on Earth. It is the summary of major events in Earth’s past that are preserved in the rock record. Fossils are an important part of this scale.

Geologic ColumnNo single rock layer on Earth contains a record of all of the

geologic events, so scientists combine their observations to create standard arrangement of rock layers.

Using a Geologic ColumnScientists use the rock layers to date rock layers that can not be

dated radio metrically. They compare fossils in similar rock layers or that is relatively the same time period. If they match, than the rocks were likely formed around the same time.

Division of Geologic TimeDivision of Geologic Time

IIt is usually broken down by fossils of a t is usually broken down by fossils of a dominate life form.dominate life form.

Eons and Era’sEons and Era’s

EonsEons – Longest segment of time – Longest segment of time

Haden and Achaean EonHaden and Achaean Eon**

4.6 billion years ago to 2.5 billion4.6 billion years ago to 2.5 billion

Earths formation to first fossilsEarths formation to first fossils

Proterzoic EonProterzoic Eon**

2.5 billion years ago to 570 million2.5 billion years ago to 570 million

No life on land No life on land

Fossils of simple plants & animalsFossils of simple plants & animals

* Also called * Also called Precambrian EonPrecambrian Eon

Phanerozic EonPhanerozic Eon

About 570 to presentAbout 570 to present

EraEra- a long period of time that is further divided- a long period of time that is further divided

Paleozoic EraPaleozoic Era

Age of InvertebratesAge of Invertebrates

543 million years ago543 million years ago

Mesozoic EraMesozoic Era

Age of ReptilesAge of Reptiles

248 million years ago248 million years ago

CenozoicCenozoic EraEra

Age of MammalsAge of Mammals

65 million years ago to present65 million years ago to present

Periods and EpochsPeriods and EpochsPeriod Period – are a shorter period of time further divided usually named for the place where a fossil – are a shorter period of time further divided usually named for the place where a fossil

was found.was found.CambrianCambrian

543 million years ago543 million years agoOrdovicianOrdovician

490 million years ago490 million years agoSilurianSilurian

443 million 443 million years agoyears agoDevonianDevonian

417 million years ago417 million years agoCarboniferousCarboniferous

Mississippian 354 million years agoMississippian 354 million years agoPennsylvanian 323 million years agoPennsylvanian 323 million years ago

PermianPermian290 million years ago290 million years ago

TriassicTriassic248 million years ago248 million years ago

JurassicJurassic206 million years ago206 million years ago

CretaceousCretaceous144 million years ago144 million years ago

TertiaryTertiaryPaleocene Paleocene 65 million years ago65 million years agoNeoceneNeocene 24 million years ago 24 million years ago

QuaternaryQuaternary2 million years ago to present2 million years ago to present

EpochsEpochs – the next smallest time division – the next smallest time divisionEarly, Middle & LateEarly, Middle & Late

Cenozoic EraCenozoic Era is the only one with names is the only one with namesPaleocene 65 million years agoPaleocene 65 million years agoEocene 54.8 million years agoEocene 54.8 million years agoOligocene 33.7 million years agoOligocene 33.7 million years agoMiocene 24 million years agoMiocene 24 million years agoPliocene 5 million years agoPliocene 5 million years agoPleistocene about 2 million Pleistocene about 2 million Holocene started about 10 thousand years ago to Holocene started about 10 thousand years ago to

presentpresent

AgeAge- even a smaller division – usually a new fossil - even a smaller division – usually a new fossil was introduced.was introduced.

Section 2 Precambrian Time and the Section 2 Precambrian Time and the Paleozoic EraPaleozoic Era

Evolution Evolution The process of change that produces new life formsThe process of change that produces new life forms

  Charles Darwin (1859)Charles Darwin (1859)

Proposed:Proposed:Surviving offspring inherited favorable traits toSurviving offspring inherited favorable traits to

further survive the environmentfurther survive the environmentAn organism adapts to the environment orAn organism adapts to the environment or

becomes extinctbecomes extinctNatural Selection which is the processes thatNatural Selection which is the processes thatallows animals and plants that are best suited to survive to allows animals and plants that are best suited to survive to

reproduce and pass on their traitsreproduce and pass on their traitsTime can create new speciesTime can create new species

Species – a group of organisms that can Species – a group of organisms that can reproduce fertile offspringreproduce fertile offspring

There is tremendous amount of debate over whether the There is tremendous amount of debate over whether the changes in evolution take place quickly or if they are changes in evolution take place quickly or if they are slow and steady. The best scientific evidence now slow and steady. The best scientific evidence now points to Punctuated Equilibrium. Which involves a points to Punctuated Equilibrium. Which involves a slow natural process then some kind of change slow natural process then some kind of change happens to the environment and there is a series of happens to the environment and there is a series of very rapid changes or Bursts of Evolution.very rapid changes or Bursts of Evolution.

Precambrian LifePrecambrian Life

It is the time period from 4.6 billion to 542 million years It is the time period from 4.6 billion to 542 million years ago. This includes about 88% of Earth’s history ago. This includes about 88% of Earth’s history occurred during this time. The rock record has been occurred during this time. The rock record has been deformed so much that scientists can not interpret what deformed so much that scientists can not interpret what took place and when it took place.took place and when it took place.

  Precambrian RocksPrecambrian RocksShields – large areas of Precambrian exposed rocksShields – large areas of Precambrian exposed rocks  Precambrian LifePrecambrian LifeVery little life has been discovered. The life forms that Very little life has been discovered. The life forms that

were mostly found were cyanobactria in stromatolites were mostly found were cyanobactria in stromatolites or layered reef like deposits.or layered reef like deposits.