Deep Time and the Geologic Time Scale

Prior to the 1700’s deep time did not exist ...

According to Genesisthe Earth was created in 6 days about 6000 years ago.

Earth history = Biblical history

Dinosaurs did not exist.

Cuvier (1769-1832) Hutton (1726-1797)

The Geologists (1700’s)

Rock layers show that the Earth is ancient and has a long pre-human history, including extinct species preserved as fossils.

Seco

ndar

yPrimary

Secondary

Transitional

Tertiary

Diluvialpost-Diluvial

circa 1790

Flood GravelsLayers composed of unconsolidated sediment

Hard rock layers with abundant fossils

Hard rock layers with sparse fossils

Crystalline rock

Earth History, 1700’s

Tertiary

Trans.

Primary

Seco

ndar

y

Fossil Reptiles

Dinosaur fossils were found in the upper part of the Secondary rock layers.

Earth Forms

Now

The Age of the Earth

4,600,000,000 years ago4.6 Ga

January 1st

December 31st

One Year

The Earth is 4.6 billion years old

January

Februa

ry

Mar

ch

Apr

il

MayJune

July

August O

ctoberNovember

December

Major Subdivisions of Geologic Time

3.45 Ga

2.3 Ga

1.15 Ga

0 Ga4.6 Ga

Sept

embe

r

January

Februa

ryMar

ch

Apr

il

MayJune

July

August O

ctoberNovember

December

3.45 Ga

2.3 Ga

1.15 Ga

4.6 Ga

Earth is cooling.Heavy meteoric bombardment.

Crust, oceans, and atmosphere are forming and reforming.

No surviving rock.

Sept

embe

r

Origin of life?

January

Februa

ryMar

ch

Apr

il

MayJune

JulyAug

ust October

November

December

2.3 Ga

1.15 Ga

4.6 Ga

Hadean Eon

Sept

embe

r

3.8 Ga

January

Februa

ryMar

ch

Apr

il

MayJune

July

August O

ctoberNovember

December

3.45 Ga

2.3 Ga

1.15 Ga

4.6 Ga

Formation of large continents.Oxygenation of the atmosphere.

Oldest rock formations.

Sept

embe

r

Evolution of Bacterial Life!

January

Februa

ryMar

ch

Apr

il

MayJune

July

August O

ctoberNovember

December

2.5 Ga

1.15 Ga

4.6 Ga

Hadean Eon

Archean Eon 3.8 Ga

Sept

embe

r

January

Februa

ryMar

ch

Apr

il

MayJune

JulyAug

ustSe

ptem

ber O

ctoberNovember

December

3.45 Ga

2.3 Ga

1.15 Ga

4.6 Ga

First animal fossils.Evolution of most animal phyla.

Evolution of

Eucaryotic Life

January

Februa

ryMar

ch

Apr

il

MayJune

July

August O

ctoberNovember

December

2.5 Ga

540 Ma

4.6 Ga

Hadean Eon

Archean Eon 3.8 Ga

Sept

embe

r

Proterozoic Eon abundant fossils of animals with shells

January

Februa

ryMar

ch

Apr

il

MayJune

JulyAug

ust October

November

December

2.5 Ga

4.6 Ga

Archean Eon 3.8 Ga

Sept

embe

r

Proterozoic Eon

Phanerozoic Eon

evolution of vertebrateslate Nov. - December

Haikouichthys

Acanthostega

December

1 5 10 15 20 25 31

first tetrapods

first amniotes

Didecte

s

synapsids rule

Dimetrodon

formation of Pangea

largest mass extinction

Permian - Age of Synapsids (pre-mammals)

December

1 5 10 15 20 25 31

first tetrapodscoal swamps

formation of Pangea

Age of Dinosaurs

first birds

continents drift into their modernpositions

first amniotes

largest mass extinction

December

1 5 10 15 20 25 31

first tetrapodscoal swamps

formation of Pangea

Age of Dinosaurs

first birds

continents drift into their modernpositions

first amniotes

largest mass extinction

evolutionof modernmammals

formation of the Alps and Himalayas

What about us?D

ecem

ber 3

1st

noon

midnight

Ice Ages

11:48 pm - First modern humans evolve11:59 pm - Agriculture develops11:59:45 pm - Roman Empire11:59:57 - Columbus sets sail11:59:59 - First Geologists

10:00 pm - Hominids migrate out of Africa5:00 pm - First hominids evolve

Hominids evolve

MillenniumCentury

Decade Year

Month Day

Subdivisions of Human Time

longer shorter

EonEra

Period Epoch

Stage Substage

Subdivisions of Geologic Time

longer shorter

Modern Geologic Time Scale

Hadean

Archean

Proterozoic

Phanerozoic

3800 Ma

4600 Ma

2500 Ma

540 Ma

0 MaM

C

P

January

Februa

ryMar

ch

Apr

il

MayJune

July

August O

ctoberNovember

December

2.5 Ga

540 Ma

4.6 Ga

Hadean Eon

Archean Eon 3.8 Ga

Sept

embe

r

Proterozoic Eon

Phanerozoic Eon

Modern Geologic Time Scale

Pale

ozoi

c

Ordovician

Cambrian

Silurian

Devonian

Mississippian

Pennsylvanian

Permian

Mes

ozoi

cTriassic

Jurassic

Cretaceous

Paleocene

Eocene

Oligocene

Miocene

Pliocene

Pleistocene

Cen

ozoi

c

Terti

ary

Holocene

Qua

t.

Pale

ogen

eN

eoge

ne

540

510

439

408

360

323

290

245

208

146

57

35

23

5

1.6

.01

0

Car

b.

Quat. = QuaternaryCarb. = Carboniferous

Ma

65RIP

Hadean

Archean

Proterozoic

Phanerozoic

3800 Ma

4600 Ma

2500 Ma

540 Ma

0 MaM

C

P

Eras

Modern Geologic Time Scale

Pale

ozoi

c

Ordovician

Cambrian

Silurian

Devonian

Mississippian

Pennsylvanian

Permian

Mes

ozoi

c

Triassic

Jurassic

Cretaceous

Paleocene

Eocene

Oligocene

Miocene

Pliocene

Pleistocene

Cen

ozoi

c

Terti

ary

Holocene

Qua

t.

Pale

ogen

eN

eoge

ne

540

510

439

408

360

323

290

245

208

146

57

35

23

5

1.6

.01

0

Car

b.

Quat. = QuaternaryCarb. = Carboniferous

Ma

65RIP

Hadean

Archean

Proterozoic

Phanerozoic

3800 Ma

4600 Ma

2500 Ma

540 Ma

0 MaM

C

P

Periods

Modern Geologic Time Scale

Pale

ozoi

c

Ordovician

Cambrian

Silurian

Devonian

Mississippian

Pennsylvanian

Permian

Mes

ozoi

c

Triassic

Jurassic

Cretaceous

Paleocene

Eocene

Oligocene

Miocene

Pliocene

Pleistocene

Cen

ozoi

c

Terti

ary

Holocene

Qua

t.

Pale

ogen

eN

eoge

ne

540

510

439

408

360

323

290

245

208

146

57

35

23

5

1.6

.01

0

Car

b.

Quat. = QuaternaryCarb. = Carboniferous

Ma

65RIP

Hadean

Archean

Proterozoic

Phanerozoic

3800 Ma

4600 Ma

2500 Ma

540 Ma

0 MaM

C

P

Epochs

What records the passing of geologic time?

• Formation of rock layers• Sediments are deposited over time in

layers.• Each layer traps and records information

about the time during which it formed.• Sedimentary layers are analogous to the

pages that compose the book of Earth History.

East Devonshire

Problem - how do you determine the order in which rock layers formed?

At a single place, layers can be ordered using the law of Superposition.

oldest

less old

even less old

younger

youngest

time

The same rock type repeats through time.

Seco

ndar

y

Primary

Secondary

Transitional

Tertiary

Diluvialpost-Diluvial

circa 1790

Flood GravelsLayers composed of unconsolidated sediment

Hard rock layers with abundant fossils

Hard rock layers with sparse fossils

Crystalline rock

Earth History, 1700’s

Tertiary

Trans.

Primary

Cretaceous SystemD’Omalius d’Halloy, 1822

Primary

Secondary

Transitional

Tertiary

Diluvialpost-Diluvial

circa 1790

Parisian gypsum beds

London clay

alluvium

Sicilian strata

English chalk

OolitesLias

New Red Sandstone

Muschelkalk - TriasMagnesian Limestone

Coal Measures

Mountain Limestone

Old Red SandstoneDevonshire strata

Wenlock Limestone

Welsh Greywackes

Parisian chalk

Jura Mt. strataPerm strata

circa 1820

gravels

Crystalline (metamorphic) strata

British Isles Continental Europe

GeologicSystems

East Devonshire

Within a local region, rock layers can be correlated on the basis of their lithology (physical characteristics) to define a geologic system.

West Devonshire

Correlation - the matching-up of rock layers between different places.

• We can put local rock layers in the correct time order because we can see how they are stacked on each other.

• We can use the physical features of rock layers to correlate them into a regional system.

• The Problem: How can we correlate different regional systems so that they are in the correct time order if we can’t directly match their layers?

Great Britain Continental Europe

?

?

How can we correlate different systems if the layers cannot be correlated based on their physical features?

William Smith (1769-1839)surveyor, civil engineer

Smith made the first large scale geologic map showing the distribution and order of rock layers in Great Britain.

In his work as a surveyor, Smith noticed that the rock layers seemed to contain a unique sequence of fossil species that appear and disappear through time.

Even when the rocks look different, the sequence of fossils is always the same.

Location A Location B

Location A

Location B

Fossils provide the key tocorrelating rock strata.

Location A

Location C

Location B

TI

ME

Evolves

Goes Extinct

Unique interval of time

Exists

The evolution and extinction of species define unique intervals of time.

TI

ME

Evolves

Exists

Goes Extinct

TI

ME

TI

ME

TI

ME

Great Britain Continental Europe

Fossils are the key to correlating regional systems

•Once a particular regional system was formally named and its fossils described, other regional systems with the same fossils were correlated to it and given the same name.

•The original system names thus came to stand for particular intervals of geologic time.

Geologic Systems and Geologic Time

•For example, the Jurassic System was originally named for the rocks and fossils of the Jura Mountains between France and Switzerland.

•Now the Jurassic Period refers to the time interval during which the fossil species of the Jurassic System lived.

•Any rock layers with these fossils can be identified as Jurassic in age.

Geologic Systems and Geologic Time

Primary

Secondary

Transitional

Tertiary

Diluvialpost-Diluvial

Parisian gypsum bedsLondon clay

alluvium

Sicilian strata

English chalk

OolitesLias

New Red Sandstone Muschelkalk - Trias

Magnesian Limestone

Coal MeasuresMountain Limestone

Old Red Sandstone Devonshire strata

Wenlock Limestone

Welsh Greywackes

Parisian chalk

Jura Mt. strata

Perm strata

circa 1790 circa 1870

Modern Time Scale

Tertiary

Cretaceous

Jurassic

Triassic

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

Precambrian

Quaternarygravels

Crystalline (metamorphic) strata

British Isles Continental Europe

How do we subdivide geologic time and assign sedimentary layers to their correct position in time?

• fossils• each time interval in Earth history is defined by a unique set of species that existed at that time.

•Species evolve, live for a short time, and go extinct.

•The same species never evolves twice (extinction is forever).

•Evolution provides a “biological calendar” that geologists use to keep track of time.

•Mass extinctions create the boundaries that define most geologic time intervals.