Absolute Dating..POWERPOINT PRESENTATION

LESSON IN EARTH AND LIFE SCIENCE

1. RELATIVE AND
ABSOLUTE DATING

2. OBJECTIVES:
Differentiate relative and absolute
dating;
Describe the different methods (relative
and absolute dating) of determining the
age of stratified rocks; and
Understand and appreciate the
importance of the relative and absolute
dating in determining the age of
stratified rocks.

3. Earth’s history concealed in rocks
Goal of geology: unraveling Earth’s history
Principle time keeping devices:
Relative dating - putting rocks/events in proper order
Absolute dating - determining event’s actual time

4. Geologists often need to know the age of material that they find.
They use absolute dating methods, sometimes called numerical
dating, to give rocks an actual date, or date range, in number of
years. This is different to relative dating, which only puts geological
events in time order.

5. Relative dating of
fossils
(chronostratic)
is a system in which a
fossil is given an age
designation in terms of
epoch, period, or era
which can be compared to
other geologic units of
time as older or younger,
but without the burden of
assigning a specific
number.
Relative dating is best
explained when covering
the law of superposition
and a geologic time scale

6. Absolute dating of a fossil
(chronometric)
– numerical ages in millions
of years or some other
measurement. These are
most commonly obtained via
radiometric dating methods
performed on appropriate
rock types
- involves assigning a
specific quantity of age with
a fossil such as saying that
an echinoid, Hardouinia
bassleri, is 83 million years
old.

8. Half life – the amount of time it take for half a radioactive
substance to breakdown. Radioactive – a unstable substance
that breaks down or decays.
Ex: carbon 14 – 5,700 yrs, Calcium 41 – 130,000,Potassium 40 –
1,300,000yrs, Nitrogen 17 - 7 sec
EX: when a parent uranium 238 decays produces
Subatomic particles energy daughter lead 206

10. Dating Method Material Dated Age Range Dated
Carbon-14 to Nitrogen
(radiocarbon)
Organic remains, archeological
artefacts
Up to 60,000 years ago
Luminescence Tephra, loess, lake sediments Up to 100,000 years ago
Fission Track Tephra 10,000 to 400 million years ago
Potassium-40 to argon 40 Volcanic rocks 20,000 to 4.5 billion years ago
Uranium 238 to lead 206 Volcanic Rocks
1 million to 4.5 billion years
ago

11. Carbon Dating

14. Relative Dating: Key principles
Principle of Superposition
Principle of original horizontality
Principle of Original Lateral Continuity
Principle of cross-cutting relationships
Principle of Inclusions
Principle of Unconformities
Principle of Uniformitarianism

15. END OF THE LESSON