Scientists determine the age of fossils using two methods: relative dating and absolute dating. Relative dating involves principles such as superposition and faunal succession to establish a sequence of events, while absolute dating uses techniques like carbon-14 and potassium-argon dating to ascertain specific ages based on radioactive decay rates. Carbon-14 is used for organic remains, and potassium-argon is used for inorganic substances.

4. HOW DO WE KNOW THE AGE OF FOSSIL?
Scientist use two methods
to determine the age of
fossils
1.Relative Dating
2. Absolute Dating

6. RELATIVE DATING TECHNIQUES
PRINCIPLE OF SUPERPOSITION
“In a vertical sequence, the youngest rocks are on
the top and the oldest are on the bottom.”

7. RELATIVE DATING TECHNIQUES
PRINCIPLE OF CROSS-CUTTING RELATIONSHIP
“A rock layer is always older than a feature that cuts
through it.”

8. RELATIVE DATING TECHNIQUES
PRINCIPLE OF INCLUSION
“Inclusions found in other rocks (or formations) must
be older than the rock that contain them.”

9. RELATIVE DATING TECHNIQUES
PRINCIPLE OF ORIGINAL HORIZONTALITY
“Sediments are deposited in nearly horizontal
layers.”

10. RELATIVE DATING TECHNIQUES
PRINCIPLE OF LATERAL CONTINUITY
“layers of sediment initially extend laterally in all
directions.”
CONNECTING WIDELY SEPARATED EVENTS

11. RELATIVE DATING TECHNIQUES
PRINCIPLE OF FAUNAL SUCCESSION
“states that groups of fossil plants and animals occur in the
geologic record in a definite and determinable order. A
period of geologic time can be recognized by its respective
fossils.”

13. • Determines the specific age of a fossil
• Looks at chemical Properties
• Potassium-Argon
2 TYPES
• Carbon-14 (Radiocarbon)

14. RADIOMETRIC TECHNIQUES
• It is based on the known and constant
rate of decay of radioactive isotopes into
their radiogenic daughter isotopes.
• Particular isotopes are suitable for
different application due to the type of
atoms present in the mineral or other
material and its approximate age

15. ABSOLUTE DATING TECHNIQUES
CARBON-14 DATING
• Also known as Radiocarbon dating
• Used to date organic remains
• Scientist measure the radiocarbon in the
fossil to determine its age
5,730
years
½ of
C-14
Nitrogen
5,730
years
¼ of
C-14
remain
5,730
years
1/8 of
C-14
left
Half life
of C-14
• Determine the date of death of the
organic matter in an artifact or ecofact.

17. ABSOLUTE DATING TECHNIQUES
POTASSIUM-ARGON DATING
• Potassium-40 is a radioactive isotope of
potassium that decayed into Argon-40.
• Scientists measure the amount of argon
in the rock to determine its age
• Argon: is not commonly incorporated into such
samples except when produced “in situ” through
radioactive decay.
• Used only for inorganic substances
(rocks and minerals)
• Used to calibrate the geometric polaity
time scale.

18. REFFERENCES:
 http://maps.unomaha.edu/maher/geo117/part2/117historical.html
 http://www.oldearth.org/curriculum/geology/images/Xenolith.jpg
 http://geologylearn.blogspot.com/2015/05/geologic-principles-for-dening-
relative.html
 http://www.nature.com/scitable/knowledge/library/dating-rocks-and-fossils-
using-geologic-methods-107924044
 https://www.fossilera.com/pages/dating-fossils