EARTH SCIENCE, 10E
EDWARD J. TARBUCK &
FREDERICK K. LUTGENS
EARTH’S HISTORY: A
BRIEF SUMMARY
CHAPTER 11
EARTH SCIENCE, 10E
PRECAMBRIAN ERA
4.5 billion to 540 million years ago
88% of Earth's history
Only sketchy knowledge
Most Precambrian rocks are devoid
of fossils
PRECAMBRIAN ERA CONT.
Precambrian rocks
•Most are buried from view
•Each continent has a "core area" of
Precambrian rocks called a shield
•Extensive iron ore deposits
•Absent are fossil fuels
PRECAMBRIAN SHIELDS
PRECAMBRIAN ERA CONT.
Earth's atmosphere
•Primitive atmosphere formed from volcanic gases
A process called outgassing
Water vapor, carbon dioxide, nitrogen, and several
trace gases
Very little free oxygen
•Water vapor condenses and forms primitive
oceans as Earth cools
PRECAMBRIAN ERA CONT
 Earth's atmosphere cont.
•Bacteria evolve, cynobacteria
•Plants evolve and photosynthesis
produces oxygen
•Increase in atmospheric oxygen
•By about 4 billion years after Earth
formed, abundant ocean-dwelling
organisms that require oxygen existed
PRECAMBRIAN ERA CONT.
 Precambrian fossils cont.
•Most common are stromatolites
Material deposited by algae
Common about 2 billion years ago
•Microfossils of bacteria and algae have been found
in chert
Southern Africa (3.1 billion years of age)
Lake Superior area (1.7 billion years of age)
•Plant fossils date from the middle Precambrian
•Animal fossils date from the late Precambrian
•Diverse and multicelled organisms exist by the close
of the Precambria
THE GEOLOGIC TIME SCALE
PALEOZOIC ERA
540 million years ago to about 248 million
years ago
First life forms with hard parts
Abundant Paleozoic fossils
Early Paleozoic history
•Southern continent of Gondwanaland exists
•Northern continent of Laurasia
Laurasia – North America, Europe, Asia, Greenland
Gondwanaland – South America, Africa, Antarctica, India, Australia
PALEOZOIC ERA
CONT.
Early Paleozoic history
•North America
A barren lowland
Seas move inland and recede several times and
shallow marine basins evaporate leaving rock
salt and gypsum deposits
Taconic orogeny, a mountain building event,
affects eastern North America
RECONSTRUCTION OF EARTH IN
EARLY PALEOZOIC TIME
PALEOZOIC ERA
Early Paleozoic life
•Restricted to seas
•Vertebrates had not yet evolved
•Life consisted of several invertebrate
groups
Trilobites
Brachiopods
Cephalopods
•First organisms with hard parts, such
as shells – perhaps for protection
NATURAL CAST OF A TRILOBITE
BRACIOPODS
APPEARANCE AND RELATIVE ABUNDANCE OF
MAJOR GROUPS OF ORGANISMS
PALEOZOIC ERA CONT.
Late Paleozoic history
•Supercontinent of Pangaea forms
•Several mountain belts formed during
the movements of the continents
•World's climate becomes very
seasonal, causing the dramatic
extinction of many species
FORMATION OF PANGAEA IN
LATE PALEOZOIC TIME
PALEOZOIC ERA CONT.
Late Paleozoic life
•Organisms diversified dramatically
•Land plants
•Fishes evolve into two groups of bony fish
Lung fish
Lobe-finned fish which become the
amphibians
•Insects invade the land
•Amphibians diversify rapidly
•Extensive coal swamps develop
MESOZOIC ERA
248 million years ago to about 65 million
years ago
Often called the “age of dinosaurs”
Mesozoic history
•Begins with much of the world's land above
sea level
•Seas invade western North America
•Breakup of Pangaea begins forming the
Atlantic Ocean
MESOZOIC ERA CONT.
Mesozoic history
•North American plate began to override the
Pacific plate
•Mountains of western North America
began forming
Mesozoic life
•Survivors of the great Paleozoic extinction
•Gymnosperms become the dominant trees
RECONSTRUCTION OF EARTH IN THE
LATE JURASSIC PERIOD
MESOZOIC ERA CONT.
Mesozoic life
•Reptiles (first true terrestrial animals)
readily adapt to the dry Mesozoic climate
•Reptiles have shell-covered eggs that can
be laid on the land
•Dinosaurs dominate
•One group of reptiles led to the birds
•Many reptile groups, along with many other
animal groups, become extinct at the close
of the Mesozoic
Archaeopteryx
had wings and
feathers like a
bird, but teeth,
claws and a tail
like a dinosaur.
MAJOR REPTILE GROUPS IN
THE MESOZOIC ERA
MESOZOIC ERA CONT.
Mesozoic life
•Many reptile groups, along with many other
animal groups, become extinct at the close
of the Mesozoic
One hypothesis is that a large asteroid or
comet struck Earth
Another possibility is extensive volcanism
CENOZOIC ERA
65 million years ago to the present
Often called the “age of mammals”
Smaller fraction of geologic time than
either the Paleozoic or the Mesozoic
North America
•Most of the continent was above sea
level throughout the Cenozoic era
CENOZOIC ERA CONT.
North America
•Many events of mountain building,
volcanism, and earthquakes in the West
•Eastern North America
Stable with abundant marine sedimentation
Eroded Appalachians were raised by
isostatic adjustments
CENOZOIC ERA CONT.
North America
•Western North America
Building of the Rocky Mountains was
coming to an end
Large region is uplifted
•Basin and Range Province formed
•Re-elevates the Rockies
•Rivers erode and form gorges (e.g.,
Grand Canyon and Black Canyon)
CENOZOIC ERA CONT.
North America
•Western North America
Volcanic activity is common
•Fissure eruptions form the Columbia
Plateau
•Volcanoes form from northern California
to the Canadian border
Coast Ranges form
Sierra Nevada become fault block
mountains
CENOZOIC ERA CONT.
Cenozoic life
•Mammals replace reptiles as the dominant
land animals
•Angiosperms (flowering plants with
covered seeds) dominate the plant world
Strongly influenced the evolution of both
birds and mammals
Food source for both birds and mammals
CENOZOIC ERA CONT.
Cenozoic life
•Two groups of mammals evolve
after the reptilian extinctions at the
close of the Mesozoic
Marsupials
Placentals
CENOZOIC ERA CONT.
Cenozoic life
•Mammals diversify quite rapidly and some
groups become very large
e.g., Hornless rhinoceros, which stood
nearly 16 feet high
Many large animals became extinct
•Humans evolve