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THE GEOLOGIC TIME SCALE

Objectives:1.To trace the geologic time scale from the

earliest forms up to humans;

2.To analyze the chronological sequenceof rock units etermine using si!

funamental principles; an

".To compare the methos bet#eenrelative an absolute ating.

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Geologic age of Earth about 4.6

billion years

Very difficult to appreciate from our

human perspective

Two basic ways to mae sense of

geologic time!

"elative #ges

#bsolute #ges

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"elative dating $lacing geologic events in se%uential

order as determined by their position ingeologic record

&as resulted in the Geologic Time 'cale

#bsolute dating Gives specific dates for events and

materials e(pressed in years before

present "adiometric dating most common

method used to obtain absolute dates

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At Present

$istribution of lan masses favors high

bioiversity

Tropical forests are richest ecosystems

%n mist of #hat may be a great mass

e!tinction

&uman hunters an human activities have

increase the pace of e!tinction