Transcript Absolute Age

Absolute Age
Actual Age
Radioactive Decay
• Nuclei of unstable atoms break down or
decay, giving off particles and energy
• Process continues until the atoms are
stable
• Predictable
Parent
Unstable Radioactive Isotope
Daughter
Stable Decay Product
Carbon 14 (C14)
Nitrogen 14 (N14)
Uranium 238 (U238)
Lead 206 (Pb206)
Half life: The time required for 1/2 of a parent
material to break down to daughter (stable)
material
• Another
look
Half life
remains
constant,
does not
change if
rock changes
size
# of Half Lives
Gone By
0
Parent
Remaining
100
1
Daughter
Remaining
1
0
0
50
1/2
50
1/2
2
25
1/4
75
3/4
3
12.5
1/8
87.5
7/8
4
6.25
1/16
93.75
15/16
Lets graph it!!
100%
50%
25%
1
2
3
Number of ½ lives
4
Radiometric Dating
Knowing the amounts of parent and
daughter atoms and the half life of the
radioactive atoms, you can determine the
age of the object
ESRT Page 1
To determine the age
• AGE of ROCK/ = number of
FOSSIL
½ lives
•
X
the half-life of the
radioactive isotope
(ESRT p1)
Carbon 14
- Shorter ½ life
- Used to date plants and animals of past
40,000 years
- Carbon is incorporated into the cells of
living organisms and begins to decay
when the organism dies
Uranium 238
Used to date older rocks
Has a larger half life