Ch. 23.6: Earth’s History
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CPC 2016
Know the major divisions of time (biggest  smallest units): Eons, Eras, Periods
What determines or “punctuates” the cut-off dates for time units?
Know dates/cut offs for the following:
o Earth’s formation
o Precambrian Time
o Paleozoic Era
o Mesozoic Era
o Cenozoic Era
Describe overall climate conditions, dominant life forms, and big events of each ERA.
Earth’s Atmosphere: Where did Earth’s first atmosphere come from? What gases made up
Earth’s first atmosphere? How did these gases affect temperatures? What kind of organisms
could live in this atmosphere?
Name a greenhouse gas and explain how it works to increase global temperatures.
How did the evolution of cyanobacteria (blue-green algae) change the atmosphere?
Temperatures on the planet? How did this affect other organisms?
What is ozone? What benefit does it provide? Why was an ozone layer needed for life to live
on land?
How does volcanic activity affect global temperatures?
Explain how the following events can cause mass extinctions:
o Climate change
 Glaciation (Snowball Earth – what is it? When was it? What caused it? What
ended it?)
 Warming caused by ..
 Volcanic activity (How do volcanoes cause global warming?)
 Flood basalts (What are they? How are they different from today’s
volcanic activity?)
o Meteor (Asteroid) Impact
 How can a meteor impact cause a mass extinction?
o Growing Human Population
 What human activities might be responsible for a current mass extinction?