Absolute Dating Notes

Absolute Dating:
How do we calculate this?

Radioactive Decay:
o Helpful for dating igneous and metamorphic rocks
o When atoms break down, they give off
and
o When the original element breaks down, it becomes an
.
.
How do we measure radioactive decay?

Half Life:
o The half life is
for an element
o The half life is different for each element
o At the end of one half life,
of the atoms will remain.

Common Radioactive Elements: used in radioactive dating
o
– short half life (5700 years), good for dating recent objects
o Potassium
o Rubidium
o Thorium
o
– long half life (4.5 billion years), good for dating old objects
How do we use this to date rocks?

Dating Objects:


Parent Atom:
Daughter Atom:
o Ex. We started with 50g of potassium (Parent). We now have 25g of potassium
(Parent) and 25g of argon. (Daughter)
25g / 50g
1/2
One half life has passed!