 Objective
 To learn how the
geologic timeline was
made and how the
length of the various
periods are different
 Agenda
 Progress reports – need
to be signed by
Parent/guardian
 Geologic History Notes
 Project –highlights
 Lab: Geologic Timeline
Structure of the Time Scale
 Based on their interpretations of the rock
record, geologists have divided Earth’s 4.56billion-year history into units that represent
specific amounts of time. Taken together,
these time spans make up the geologic time
scale.
Structure of the Time Scale
 Eons represent the greatest expanses of time.
Eons are divided into eras. Each era is
subdivided into periods. Finally, periods are
divided into smaller units called epochs.
 There are three eras within the Phanerozoic
eon: the Paleozoic, which means “ancient
life,” the Mesozoic, which means “middle
life,” and the Cenozoic, which means “recent
life.”
 The Precambrian era lasted from Earth’s formation
4570 until 542 million years ago (mya).
 The first cells appeared in the Precambrian era.
 The Paleozoic era
lasted from 542 to
251 mya.
 Paleozoic is a Greek
word meaning
“ancient life.”
 Rocks from the Paleozoic Era contain fossils of
snails, clams, corals, and trilobites.
 Animals with backbones began
to appear.
 At the end of this era, the
continents that existed during
this time period collided to
form a new supercontinent,
Pangaea.
 The Mesozoic era lasted from 251 to 65 mya.
 This era is often called the Age of Reptiles.
 The Cenozoic era began 65 mya and is still going
on.
 The common name for the Cenozoic Era is the
Age of Mammals.
 Mammals diversified into a
variety of species including land
mammals, sea mammals, and
flying mammals.
 Cenozoic means “recent life.”
 Mastadon
 Ohmdenosaurus
 Stromatolites
 Zephyrosaur
 Apatosaurus (Brontosaurus)
 Wuerhosaurus
 Orthoceras Nautiloid
 Torosaurus latus
 Eurypterids
 Elasmosaurus platyurus
 Trilobites
 Manny: woolly mammoth
 Velociraptor
 Sid: ground sloth (Megalonyx)
 Chesapecten jeffersonius (
 Diego: saber-toothed tiger
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State Fossil)
Carcharodon Megalodon
Spinosaurus
Cave Bear (Ursus speleaus)
Ichthyodectes ctenodon
Coelophysis
Quagga
Giganotosaur
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(Smilodon)
Scrat: saber-toothed squirrel
(Leptictidium)
Dab: dodo
Carl: Embolotherium
Frank: Brontotherium