The document discusses key events in Earth's history from the formation of the planet 4.6 billion years ago through the present day. It outlines the major eons, eras, periods, and epochs of the geologic time scale and describes some of the life forms, tectonic events, and environmental conditions that characterized each period. Radiometric dating methods are also introduced that allow scientists to determine absolute dates for rocks and fossils.

2. IT IS ESTIMATED THAT THE EARTH FORMED
ALONG WITH THE SOLAR SYSTEM 4.6 BILLION
YEARS AGO (4,600 MYA)
THE GEOLOGIC TIME SCALE IS
A SUMMARY OF THE MAJOR EVENTS IN EARTH’S HISTORY
EON – largest segment of geologic time
ERA
PERIOD
EPOCH – smallest segment of geologic time

4. Two Kinds of Ages
Relative - Know Order of Events But Not
Dates
• Civil War Happened Before W.W.II
• Bedrock in Wisconsin Formed Before The
Glaciers Came
Absolute - Know Dates
• Civil War 1861-1865
• World War II 1939-1945
• Glaciers Left Wisconsin About 11,000 Years
Ago

5. LAW OF SUPERPOSITION-
IN UNDISTURBED
SEDIMENTARY ROCKS THE
OLDEST ROCK LAYERS
ARE AT THE BOTTOM AND
THE YOUNGEST ARE AT
THE TOP.

6. LAW OF INCLUDED FRAGMENTS - IF FRAGMENTS
OF ONE TYPE OF ROCK ARE FOUND IN ANOTHER
ROCK LAYER THE ROCK FRAGMENTS MUST BE
OLDER THAN THE ROCK LAYER IN WHICH THEY
ARE FOUND
FAULTED AND FOLDED LAYERS - LAYERS OF
ROCK THAT HAVE BEEN FAULTED OR FOLDED
MUST HAVE BEEN PRESENT BEFORE THE ACTIONS
OF FAULTING OR FOLDING TOOK PLACE
FOLDING FAULTING

7. UNCONFORMITY- A PLACE IN THE ROCK RECORD WHERE
LAYERS OF ROCK ARE MISSING BECAUSE OF UPLIFT AND
EROSION. THE RESULT CAN BE A LARGE AGE
DIFFERENCE BETWEEN THE ROCKS ABOVE AND THOSE
BELOW THE EROSIONAL SURFACE (IT APPEARS LIKE A
SQUIGGLY LINE IN A CROSS-SECTION)

8. MATCHING OF ROCK
LAYERS THAT CAN BE SEEN
AT THE EARTH’S SURFACE,
OVER A LARGE AREA
AN OUTCROP IS EXPOSED
ROCK LAYERS AT THE
EARTH’S SURFACE
A KEY BED IS A THIN, WIDESPREAD LAYER, USUALLY OF
VOLCANIC ASH, THAT CAN BE USED TO CORRELATE AN
EXACT POINT OF TIME

9. RADIOACTIVE DATING
RADIOACTIVE ISOTOPES ARE ATOMS OF
ELEMENTS THAT GIVE OFF RADIATION FROM
THEIR NUCLEI
RADIOACTIVE DECAY IS THE PROCESS BY
WHICH A RADIOACTIVE ISOTOPE CHANGES
INTO A NEW STABLE ELEMENT
USED TO DATE FAR BACK IN TIME. CERTAIN ROCKS CONTAIN
RADIOACTIVE ISOTOPES

10. THE RATE AT WHICH A RADIOACTIVE ELEMENT DECAYS. IT
IS THE TIME IT TAKES FOR HALF OF THE ATOMS OF THE
RADIOACTIVE ELEMENT TO DECAY TO A STABLE END
PRODUCT (SEE PAGE 1 OF THE ESRT)
AT THE END OF EACH HALF-LIFE, HALF OF THE
RADIOACTIVE MATERIAL REMAINS
DAUGHTER ISOTOPE = THE STABLE ISOTOPE THAT HAS BEEN CHANGED
PARENT ISOTOPE = THE RADIOACTIVE ISOTOPE THAT BEGINS

11. RADIOCARBON DATING USES THE RADIOACTIVE
ISOTOPE CARBON-14 FOUND IN ALL LIVING THINGS.
BECAUSE CARBON-14 IS CONTINUALLY ABSORBED BY FOOD
AND WATER IT STAYS CONSTANT IN LIVING THINGS. WHEN
THE LIVING THING DIES THE PERCENTAGE OF CARBON-14
DECREASES AT THE RATE OF ITS HALF-LIFE. CAN BE USED
TO DATE BACK ABOUT 100,000 YEARS

12. URANIUM LEAD METHOD IS USEFUL TO DATE ROCKS
OLDER THAN 10 MILLION YEARS. CAN BE USED ONLY ON
IGNEOUS ROCKS THAT CONTAIN THE RIGHT KIND OF
URANIUM
RUBIDIUM-STRONTIUM METHOD CAN ALSO BE USED
TO DATE OLDER ROCKS BECAUSE OF ITS LONG HALF-LIFE. IT
IS ALSO VERY COMMONLY FOUND IN IGNEOUS ROCKS.
POTASSIUM-ARGON METHOD IS VERY USEFUL SINCE
POTASSIUM-40 CAN BE FOUND IN METAMORPHIC,
SEDIMENTARY, AND IGNEOUS ROCKS. IT CAN DATE OLDER
ROCKS BUT MAY ALSO DATE ROCKS AS YOUNG AS 50,000
YEARS

13. Eons:
Precambrian: Earliest span
of time
Phanerozoic: Everything
since
Eras:
Paleozoic
Mesozoic
Cenozoic
Periods:
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
(Missipp. & Pennsylvanian)
Permian
Triassic
Jurassic
Cretaceous
Paleogene
Neogene
Quaternary
Epochs:
Paleocene
Eocene
Oligocene
Miocene
Pliocene
Pleistocene
Holocene
We are living in the Phanerozoic Eon, Cenozoic Era,
Quaternary Period, Holocene Epoch……..BUT
Paleozoic
“Age of
Invertebrates”
Mesozoic
“Age of Reptiles”
Cenozoic
“Age of Mammals”
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14. The Earth Through Time
Standard 8-2.5: Illustrate the vast diversity of life that has been present on Earth over time by using the geologic time scale.
 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, becoming more complex and
successful over the next 3 billion years:
Prokaryotes then Eukaryotes
 Cyanobacteria begins producing free oxygen
(photosynthesis)
 Land masses gather to make up a continent
called “Rodinia”
Cambrian:
 Explosion of life
 All existing phyla come into being at this time
 Life forms in warm seas as oxygen levels rise
enough to support life
 Dominant animals: Marine invertebrates
(trilobites and brachiopods)
 Supercontinent Gondwana forms near the South
Pole (note position of present-day Florida)
The Proterozoic:
PaleoMaps used with permission from Christopher Scotese and are under
copyright of C.R. Scotese, 2002
14
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15. Ordovician:
Silurian:
 The 1st animals with bones appear, though
dominant animals are still trilobites, brachiopods
and corals
 The beginning of the construction of South
Carolina
 A very cold time in Earth’s history: there was a
great extinction due to ice caps in present-day
Africa
 Four main continents: Gondwana, Baltica,
Siberia and Laurentia
 First land plants appear and land animals follow
 Laurentia collides with Baltica and closes
Iapetus Sea.
 Coral reefs expand and land plants begin to
colonize barren land.
 First millipede fossils and sea scorpions
(Euryptides) found in this period
PaleoMaps used with permission from Christopher
Scotese and are under copyright of C.R. Scotese, 2002
15
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16. Devonian (Age of the
Fish)
Mississippian:
 First seed plants appear
 Much of North America is
covered by shallow seas and sea
life flourishes (bryoza, brachipods,
blastoids)
Pennsylvanian:
 Modern North America begins
to form
 Ice covers the southern
hemisphere and coal swamps
formed along equator.
 Lizards and winged insects first
appear.
 Pre-Pangea forms. Dominant animal:
fish
 Oceans still freshwater and fish
migrate from southern hemisphere to
North America.
 Present-day Arctic Canada was at the
equator and hardwoods began to grow.
 Amphibians, evergreens and ferns
appear
 The Acadian Orogeny, leading to S.C.
metamorphism
PaleoMaps used with permission from Christopher Scotese and are under
copyright of C.R. Scotese, 2002
16
21
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17. Permian:
 Last period of the Paleozoic
 Pangea forms. Reptiles spread
across continents.
 The Appalachians rise
 90% of Earth’s species become
extinct due to volcanism in Siberia.
This marks the end of trilobites,
ammonoids, blastoids, and most
fish.
Triassic:
 First dinosaurs appear
 First mammals- small rodents appear
 Life and fauna re-diversify
 Rocky Mountains form.
 First turtle fossil from this period
 Pangea breaks apart
PaleoMaps used with permission from Christopher Scotese and are under
copyright of C.R. Scotese, 2002
22
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18. Jurassic:
 Pangea still breaking apart
 Dinosaurs flourish “Golden age of
dinosaurs”
 First birds appear
 North America continues to rotate away
from Africa
Cretaceous:
 T-Rex develops
 First snakes and primates appear
 Deciduous trees and grasses
common
 First flowering plants
 Mass extinction marks the end of
the Mesozoic Era, with the demise
of dinoaurs and 25% of all marine
life.
PaleoMaps used with permission from Christopher Scotese and are under copyright of
C.R. Scotese, 2002 18
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19. Tertiary:
 First horses appear and tropical
plants dominate (Paleocene)
 Grasses spread and whales, rhinos,
elephants and other large mammals
develop. Sea level rises and
limestone deposits form in S.C.
(Eocene)
 Dogs, cats, and apes appear
(Oligocene)
 Horses, mastadons, camels, and
tigers roam free in S.C. (Miocene)
 Hominids develop and the Grand
Canyon forms (Pliocene)
Quaternary:
 Modern humans develop and ice
sheets are predominant- Ice age
(Pleistocene)
 Holocene Humans flourish
(Holocene)
PaleoMaps used with permission from Christopher Scotese and are under
copyright of C.R. Scotese, 2002
19
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20. • Specific conditions are needed for fossilization.
• Only a tiny percentage of living things became fossils.
Fossils: Remains of Ancient Plants And
Animals, Evidence of Life

21. Ripple Marks, Bay Beach

22. Fossil Ripple Marks, Baraboo Range

23. Modern Mud Cracks

24. Fossil Mud Cracks, Virginia

25. Commonly Preserved:
Hard Parts of Organisms:
• Bones
• Shells
• Hard Parts of Insects
• Woody Material
Soft or Easily Decayed Parts of
Organisms:
Internal Organs
Skin
Hair
Feathers

26. Types of Fossils
• Original Material (Preserved)
• Casts & Molds
• Replacement (Petrified Wood)
• Carbonized Films (Leaves)
• Footprints, Tracks, Etc.
– “Trace Fossils” – Our only preserved record of
behavior of fossil organisms

27. • Amber-preserved fossils are organisms that
become trapped in tree resin that hardens after
the tree is buried.

28. Dinosaur
Tracks,
Texas

29. Where Fossils Occur
Almost Exclusively in Sedimentary Rocks
• Heat of Melting or Metamorphism Would Destroy
Almost Every Type of Fossil
• Rare Exceptions:
– Some Fossils in Low-grade Metamorphic Rocks
– Trees Buried by Lava Flow
To Be Preserved, Organisms Have to Be:
• Buried Rapidly After Death
• Preserved From Decay

30. INDEX FOSSIL
EASILY IDENTIFIABLE
WIDESPREAD OCCURRENCE
SHORT-LIVED

31. Two Conceptions of Earth History:
Catastrophism
• Assumption: Great Effects Require Great Causes
• Earth History Dominated by Violent Events
Uniformitarianism
• Assumption: We Can Use Cause And Effect to
Determine Causes of Past Events
• Finding: Earth History Dominated by Small-scale
Events Typical of the Present.
• Catastrophes Do Happen But Are Uncommon

32. Summarize the factors, both natural and man-made, that can contribute to the extinction of a species.
Why Extinction?
 Extinction of a species occurs when no more members of a particular species remains. Extinction
through time is very common, and, in fact, nearly 90 percent of all species that ever lived on Earth
are now extinct.
 Organisms that cannot survive a catastrophic or significant change in earth’s climate usually
become extinct. Extinctions are a way of clearing the path for new kinds of life that is potentially
more advanced. This is a natural part of life’s process.
 Natural phenomena that can contribute to the extinction of a species include global climate
changes, volcanic explosions, and celestial impacts.
 The influence of humans on the environment do not
include comet impacts or volcanism; however, man has
caused extinctions all the same. Over the past few
hundred years, man has cut rainforests and woodland
forests, destroying natural habitats. Pollution from
industrial plants and vehicles has also affected the air
we breath and contributed to greenhouse gases, which
drive global warming. We are looking at the potential
extinction of many species due to this warming trend.
 In addition to threatening less-adaptive creatures
than ourselves, man is negatively impacting biological
resources that our own species need. Man can adapt to
many things with the help of technology. 32
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