Grade 7 Science
GEOLOGIC TIME
PRE-CAMBRIAN TIME

3 very long Eons:
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Hadean,
Archean and
Proterozoic;
Covers 87% of
earth’s history;
Formation of earth,
volcanic activity;
Atmosphere and
oceans formed;
PRE-CAMBRIAN TIME
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A thick, stable crust was
formed;
Oldest rock evidence =
4.3 billion years old;
Algae and bacteria were
the first life forms;
Jellyfish and worms
evolved towards the end
of this time period.
PHANEROZOIC EON
Latest 13% of earth’s history;
 3 smaller periods called “Era’s”

 Paleozoic:
 Mesozoic:
 Cenozoic:
“Age of Fishes” or “Age of Ancient
Life”
“Age of Dinosaurs” or “Age of
Medieval Life”
“Age of Mammals” or “Age of
Recent Life”
PHANEROZOIC EON
PALEOZOIC ERA

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“Age of Fishes” or
“Age of Ancient Life”;
7 “Periods”, first is
called the Cambrian,
hence, all previous
time is called the
“Pre-Cambrian”
This first Era covers
over half of the
Phanerozoic Eon.
PHANEROZOIC EON
PALEOZOIC ERA


“Pangea” forms:
Motion of the earths
crustal plates brought
much of the total land
together and fused
into a super-continent.
Era begins when
animals first
developed skeletons
(exo-)
PHANEROZOIC EON
PALEOZOIC ERA
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Ends with major
catastrophe that wiped
more species off the face
of the earth than at any
other time in history
(Permian extinction: 95%
of all species)
Scorpions and centipedes
were the first animal to
live on land.
Insects, fern-like plants
and conifers (trees that
have cones) developed.
PHANEROZOIC EON
MESOZOIC ERA


“Age of Dinosaurs” or “Age of Medieval
Life”;
3 “Periods”:



Triassic
Jurassic
Cretaceous
PHANEROZOIC EON
MESOZOIC ERA
Triassic Period:
 Pangea
breaks
apart;
 Dinosaurs and
mammals first
appeared.
PHANEROZOIC EON
MESOZOIC ERA
Jurassic Period:
 Rocky
Mountains form;
 First birds
appear.
PHANEROZOIC EON
MESOZOIC ERA
Cretaceous Period
 Flowering
plants
appeared;
 Period ends in a
mass extinction
(by an asteroid???)
PHANEROZOIC EON
CENOZOIC ERA


“Age of Mammals” or “Age of Recent Life”;
2 “Periods”:


Tertiary and
Quaternary.
PHANEROZOIC EON
CENOZOIC ERA
Tertiary Period:
 Mountain
 Andes,
building:
Alps,
Himalayan and
Western North
America
PHANEROZOIC EON
CENOZOIC ERA
Tertiary Period:
 Modern
mammals,
new birds, first
horses, sabertooth tiger, whales,
first elephants and
mastodons.
PHANEROZOIC EON
CENOZOIC ERA
Tertiary Period:
 First
Humans
 “Ardi”
(4.4 mya)
 (Ardipithecus
ramidus)
??? Ardipithecus kadabba
5.6 mya
PHANEROZOIC EON
CENOZOIC ERA
Quaternary Period:
 Ice
Ages to the
present;
 Extinction of large
mammals such as
wooly mammoths;
 Modern humans
appear and
dominate.