# Absolute Agex - Groverworld

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22 Φεβ 2014 (πριν από 4 χρόνια και 4 μήνες)

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Absolute Age

Attempts at Absolute Age

Became more important in the age of Darwin.

Rate of Sedimentation

If the rate was constant over time, then we could
tell how old rocks are by their thickness

Isotopes

elements
with different mass
number (different
number of Neutrons)

These Isotopes break
down over time

Release of particles from the nucleus

This decay happens in a predictable way for
each element

Rates of Decay

Half Life
-

time required for half of the
radioactive isotope to decay.

Rate of decay are unchanged by environmental
conditions

This allows them to be a reliable source for dating

Active Element

Half Life

Carbon 14

5730 yrs

Uranium 238

4.5 billion years

Potassium
-
40

1.3 billion

years

The Rock Clock

decay to date rock
ages

Based on the
amount of
left in a rock

The math of radiometric dating

What percentage of a
would you have left
after 1 half life?

50%

What about 2 half lives?

25%

What about 3 half lives?

12.5%