Geological Time Scale

1. Geologic
TimeScale
A BRIEF HISTORY OF
EARTHSINCE 4.6BILLION
YEARS.

2. GEOLOGIC TIME SCALE
MYA ERA PERIOD EPOCH PLATE TECTONICS LIFE
0.01
Cenozoic
“Age of
Mammals”
Quaternary
Holocene Beaches and barrier islands form
-Mastadons become extinct
-Human culture flourishes
-Accelerating extinction of many
species
1.8 Pleistocene Ice sheets form
-Modern humans develop
-Asians arrive and settle the
Americas
5.3
Tertiary
Pliocene
-Volcanic activity in North
America and Africa
-Grand Canyon forms
Hominids develop
23.8 Miocene Sandhills form in S.C.
Horses, mastadons, mammoths,
tigers, and camels live in South
Carolina
33.7 Oligocene
Appalachians uplift; erosion
increases
Cats, dogs, and apes appear
54.8 Eocene
Sea levels rise; deposits of marine
sediments – limestone in S.C.;
land bridges form
-Grass spreads widely
-Diverse array of animals develop,
including whales, rhinos, and
elephants
65.0 Paleocene
Earthquakes common; Georgia
Embayment, Cape Fear Arch
forms in Southeast
-First horses appear (size of a cat)
-Tropical plants dominate
144
Mesozoic
“Age of
Reptiles”
Cretaceous
Mass extinction occurs at the end
of the period caused by a
meteorite impact (Dinosaurs,
ammonites and 25% of marine life
become extinct)
-T-Rex develops but number of
dinosaur species decline
-Snakes appear and first primates
appear
-Angiosperms appear
206 Jurassic
Western US: orogeny of Rockies;
North America continues to rotate
away from Africa
-First birds appear
-Golden age of dinosaurs
248 Triassic
-Pangea begins to break apart
-Rocky Mountains and Sierra
Nevada form
First dinosaurs, mammals,
crinoids, and modern echinoids
appear
290 Permian
-Pangea forms
-Appalachians rise
-90% of Earth’s species become
extinct, including trilobites,
blastoids, fish and amphibians
because of heavy volcanism in
Siberia
2
Table of Contents

3. 320
Carboniferous
Pennsylvanian
Great swamps develop (future
coal deposits
-Reptiles develop from
amphibians
-Flying insects appear
354 Mississippian
Much of North America is under
water
-First seed plants appear
-Sea life flourishes including
coral, brachiopods, blastoids, and
bryozoa
417 Devonian
Acadian Orogeny – SC
metamorphism
-Dominant animals: fish
-Amphibians, evergreens and
ferns appear
443 Silurian Extensive erosion
First land plants appear and land
animals follow
490 Ordovician
-Beginning of the construction of
South Carolina
-Great extinction due to growth of
ice caps including in what is now
northern Africa
-First animals with bones appear
-Dominant animals: marine
invertebrates including corals and
trilobites
540 Cambrian
S.C. near the equator; island arc
continues to move toward North
America
-Explosion of life
-All existing phyla came into
being here
-Life forms in warm seas as
oxygen levels rose enough to
support life
-Dominant animals: trilobites and
brachiopods
4600
Precambrian
(Hadean, Archean, and Proterozoic Ages)
Earth takes 10 million years to
cool: initial atmosphere escapes
into space (H&He) and the core
forms (Fe&Ni)
Volcanic outgassing of water and
carbon dioxide occurred for
millions of years, helping to build
atmosphere and then oceans
At 3 billion years ago, banded
iron formation rocks appear due
to rising oxygen levels in the
atmosphere and sea
No life possible as the Earth
initially forms 4.6 billion years
ago.
Simple, single-celled forms of life
appear 3.8 billion years ago.
They will become more complex
and successful over the next 3
billion years: Prokaryotes then
Eukaryotes
Cyanobacteria begins producing
free oxygen (photosynthesis)
Paleozoic
“Age of
Invertebrates”
Modified after Carolina Rocks, contributed by J. Westmoreland

4. Measuring Time
•
•
•
TheGeological time
scale is arecord of the
life forms and geological
events in Earth’shistory.
Scientists developedthe
time scaleby studying
rock layers and
fossils world wide.
Radioactive dating
helped determine the
absolute divisions inthe
time scale.

5. Giving Time aName
• Thelargest sectionsare called “eons”.
• “Eons” are divided into “eras” (the 2ndlargest
section).
• “Eras” are divided into
“periods”.
• ‘Periods’ are
divided into ‘epochs”.

6. Eons
• Largest, most generaldivision
of time.
• 2 Eons
• Theeons are: Cryptozoic
(Precambrian) eon and
Phanerozoic eon.
• Precambrian and
Phanerozoic eon both
consists of three erasas
shown in the figure.

7. Eras
•
•
EachEonis broken up into Eras.
Major eras in Earth’shistory:
• Archean (4600 mya - 2500mya)
• Proterozoic (2500 mya - 540mya)
• Paleozoic (540mya - 250mya)
• Mesozoic (250 mya - 65.5mya)
• Cenozoic (65.5 mya – present)
*mya refers to million years ago.

8. Periods
• EachErais divided into
even more specificblocks
of time calledperiods.
• Various geologic events
are associated with each
period.
• Eachperiod is again
classified into different
epochs.

9. How is Time Divided?
•
•
Major changesin Earth’s history mark theboundaries
between the sections.
Most sections have been divided becauseamajor
organism developed or went extinct ineach section.

10. Cryptozoiceon(Precambrian time)
•
•
•
•
•
Lastedfrom 540 million years agoto
4600 million yearsago.
Oldest and longest (covers almost 90%
of earth’shistory).
simple organisms- bacteria, algae,
protozoa wasborn.
Oldest rocks that we know werefound
in this eon which dates to about 3.5
billion yearsold.
Divided into 2 eras: Proterozoicand
Archean era.

11. Archean era
• Lastedfrom 2500 million years
ago– 4600 million yearsago.
• Earliest plants (marine algae)
developed.
• Thefirst life bacteria cameinto
existence (3800 million years
ago).
• The oldest rocks (3500 million
years ago) were formed in this
era.

12. Proterozoic era
• Lasted from 540 million years
ago to 2500 million yearsago.
• Marine invertebrates were
probably common, few with
shells.
• Glaciations took place inthis
era, probably worldwide.

13. Phanerozoic eon
• Beganfrom 540 million years
agoand is still continuingtoday.
• Divided into threeeras:
i) Paleozoic era (Past life)
ii)Mesozoic era (Middle life)
iii)Cenozoic era (Present life)

14. Palaeozoic Era
•
•
•
•
Began 570 million years ago and
ended 250 million yearsago.
Divided into 6 periods (Permian,
Carboniferous period, Devonian,
Silurian, Ordovician,Cambrian).
For the first time on Earth,
organisms had hard parts (shells,
exoskeletons).
Evolution and development of
pteridophytes, amphibians, reptiles,
fishes, wing bearing insects,
trilobites etc.

15. Mesozoic era
• Lastedfrom 250 millionyears
agoto 65 million yearsago.
• Popularly known asTime of
Reptiles.
• Divided into three periods:
Triassic, Jurassicand Cretaceous.
• Dinosaurs, mammals and
gymnosperms appeared.

16. Cenozoicera
• From 65 million yearsago
to presentdays.
• Divided into twoperiods:
Tertiary andQuarterny.
• Development of modern
mammals, angiosperms
and human beings.

17. Phanerozoic Eonin brief:

18. IMPORTANTPERIODSIN THEHISTORY
OFEARTH
i) Carboniferous Period
It lasted from 360 millionyears to
300 Million years. It is animportant
period of Paleozoicera.
During this period, first reptiles
and pteridophytes wereformed
and coal plants got spread. The
dead bodies got buried inthis
period forming the coals that weuse
today.

19. ii)
Permian
It lied between 300 million years
to 250 million years. It is also an
important period ofPalaeozoic
era. Largest massextinction
happened in thisperiod.
Scientists are not surewhat
causedthis massextinction
(maybe climate change &
volcanoes). 90%of oceanlife
and 78%of land life died.

20. iii)
Jurassic
Jurassic is an important
period of Mesozoic era. It
lasted from 250 millionyears
ago to 200 million years ago.
During this period, first birds
and mammals were formed.
Gymnosperms were dominating
plants. Thedinosaurs were
formed in Triassic period
reached at their peak in this
period.

21. iv)
Cretaceous
It is aperiod of Mesozoic era
which lasted from 150 million
years agoto 65.5 million years
ago. It marked the end of the
Mesozoic Eraand the beginning
of the Cenozoic Era.All of the
dinosaurs and half of the other
animals & plants went extinct in
this period. Scientists think an
asteroid hit Earth, the dustclouds
blocked out the sun.Asaresult,
plants died, then herbivores,then
carnivores.

22. v)Quarternery
period
It is aperiod of Cenozoicera
which hasbeen lasting from
1.8 million years agoto
present days. In thisperiod,
the humans evolved asthe
most intelligent creature of
earth and took over. It is
divided into 2 epochs
namely: Pleistocene and
Holocene.