Earth’s History
How old is the Earth?
Standard 8.E.2
understand the age of Earth and
its life forms based on evidence of
change recorded in fossil records
and landforms.
Geologic time scale
• Record of all the major events and diversity of
life forms present in Earth’s history beginning
when the Earth formed until the present.
• As you move closer to present time on the
time scale, the diversity and complexity of life
forms increase.
• Time scale is divided into ERAS…..
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Precambrian Era
Paleozoic Era
Mesozoic Era
Cenozoic Era
Precambrian Era
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Earth’s 1st Era; began with the creation
of Earth
5 major events
1. Formation of Sun and light
2. Creation of the Earth
3. Creation of atmosphere from
volcanic activity
4. Creation of the oceans
5. Creation of life
• Simple forms of life like bacteria and
algae
• Rise of jellyfish and sea worms at end
of era
• Few fossils because most life was soft
body (no hard skeleton)
Paleozoic Era
• Begins with the early
invertebrates (trilobites and
brachiopods) and develops into
boney fish, spiders/insects, 1st
amphibians
• Reptiles dominate at end of this
era.
• Early land plants
(mosses/ferns/cones)
• Mass extinction at end of era
caused most water organisms
and amphibians to disappear.
Mesozoic Era (Age of Dinosaurs)
• Reptiles dominate this era,
including dinosaurs.
• Small mammals and birds
appear
• At end of era, flowering plants
and mammals increased.
• Mass extinction at end of era
caused dinosaur extinction.
Cenozoic Era
• New mammals appear
• Diversity of life increased
• Flowering plants most
common
• Humans are in most
recent part of this era.