This document discusses various methods of absolute dating used in geology to determine the age of rocks and materials. It explains key concepts like isotopes, radioactive decay, and different radiometric dating techniques including radiocarbon, luminescence, fission track, potassium-argon, and uranium-lead dating. Each method is suited to specific types of materials and age ranges. The document provides examples of how different techniques like mass spectrometry and measuring subatomic particle emission can be used to measure isotope amounts and decay products for absolute dating.

1. THE DISCUSSION ABOUT
ABSOLUTE DATING & ALL
THE METHODS ASSOCIATED
WITH IT
Earth & Life ScienceGroup 7 Presents:

2. What the topic is about…
 This discussion contains important
information about Absolute Dating. It
includes some process questions and a quiz
for you to complete.
At the end of said discussion, the students
shall be able to possess knowledge about the
said topic, and will be capable of answering
the process questions and the items on the
quiz.

3. Beginning Messages about the
topic
 Geologists often need to know the age of the
material the find.They use absolute dating
methods, sometimes called numerical dating,
to give rocks an actual date, or date range, in
numbers of years.This is different from
Relative Dating, which only puts geological
events in time order.

4. What is Absolute Dating?
 Absolute dating is the process of determining an age on a
specified chronology in archaeology & geology. Some
scientists prefer the terms chronometric or calendar dating, as
use of the word absolute implies a numerical age or range, in
contrast with relative dating, which places events in order
without any measure of the age between events. In
archaeology, absolute dating is usually based on the physical,
chemical and life properties of the materials of artifacts,
buildings, or other items that have been modified by humans
and by historical associations with materials with known dates
{such as coins and historical records}. For example, coins
found in excavations may have their production date written
on them, or there may be written records describing the coin
and when it was used, allowing the site to be associated with a
particular calendar year.

5. The Absolute Dating
Techniques
 Absolute dating techniques include radiocarbon dating of
wood or bones, potassium-argon dating, and trapped-
charged dating methods such as thermo-luminescence
dating of glazed ceramics. In historical geology, the
primary methods of absolute dating involve using the
radioactive decay of elements trapped in rocks or
minerals, including isotope systems from younger organic
remains {radiocarbon dating with 14C} to systems such as
uranium-lead dating that allow determination of absolute
ages for some of the oldest rocks on Earth.

6. Figure 6.1: The Radiocarbon Dating Method
Radiocarbon dating is a method that provides objective age estimates for carbon-based materials that
originated from living organisms. An age could be estimated by measuring the amount of carbon-14
present in the sample and comparing this against an internationally used reference standard.

7. Radiometric Dating; what are
those?
 Most absolute dates for rocks are obtained with
radiometric methods.These use radioactive
minerals in rocks as geological clocks.
 The atoms of some chemical elements have
different forms, called isotopes.These break down
over time in a process scientists call Radioactive
decay. Each original isotope, called the parent,
gradually decays to form a new isotope, called the
daughter. Each isotope is identified with what is
called a mass number.When 'parent' uranium-238
decays, for example, it produces subatomic
particles, energy and daughter lead-206.

8. What are isotopes?
 Each of two or more forms of the same element that contain
equal numbers of protons but different numbers of neutrons in
their nuclei, and hence differ in relative atomic mass but not in
chemical properties; in particular, a radioactive form of an
element.
Isotopes are important to geologists because each radioactive
element decays at a constant rate, which is unique to that
element.These rates of decay are known, so if you can measure
the proportion of parent and daughter isotopes in rocks now, you
can calculate when the rocks were formed.
 Because of their unique decay rates, different elements are used
for dating different age ranges. For example, the decay of
pottasium-40 to argon-40 is used to date rocks older than 20,000
years, and the decay of uranium-238 to lead-206 is used for rocks
older than 1 million years.

9. Figure 6.2: The Uranium-238 to Lead-206 Dating
Process
Uranium–Lead dating is the geological age-determination method that uses
the radioactive decay of uranium (U) isotopes (238U, 235U, and also in this entry 232Th)
into stable isotopes of lead (Pb) (206Pb, 207Pb, and 208Pb, respectively).

10. The Use of Radioactive
Isotopes
 Radiocarbon dating measures radioactive isotopes in once-living
organic material instead of rock, using the decay of carbo-14 to
nitrogen-14. Because of the fairly fast decay rate of carbon-14, it can
only be used on material up to 60,000 years old. Geologists uses
radiocarbon to date such materials as wood and pollen trapped in
sediment, which indicates the date of the sediment itself.
The table on the next slide, shows characteristics of some common
radiometric dating methods. Geologists choose a dating method that
suits the materials available to their rocks.There are over 30
radiometric methods available.

11. Dating Method Materials Dated Age Range Dated
1. Radiocarbon
{Otherwise known as the
Carbon-14 & Nitrogen-14
dating method}
Organic Remains &
ArchaeologicalArtifacts
Can age materials of up to
60,000 years ago.
2. Luminescence Tephra, Loess and Lake
Sediments
Can age materials of up to
100,000 years ago
3. FissionTrack OnlyTephra Can age materials from
10,000 to 400 million years
ago {mya}
4. Pottasium-40 to Argon-4o Volcanic Rocks Can age materials from
20,000 to 4.5 billion years ago
{bya}
5. Uranium-238 to Lead-206 Volcanic Rocks Can age materials from 1
million to 4.5 bya
Table 6.1: The Common Radiometric
Dating Methods

12. All radiometric dating methods measure isotopes in some way.
Most directly measure the amount of isotopes in rocks, using a
mass spectrometer. Others measure the subatomic particles
that are emitted as an isotope decays. Some measure the
decay of isotopes more indirectly. For example, a fission track
dating measures the microscopic marks left in crystals by
subatomic particles from decaying isotopes. Another example
is luminescence dating, which measures the energy from
radioactive decay that is trapped inside energy crystals.
Final words about Radiometric Dating

13. Figure 6.3: The Mass Spectrometer
A Mass Spectrometer is an apparatus for separating isotopes, molecules, and molecular fragments
according to mass.The sample is vaporized and ionized, and the ions are accelerated in an electric field
and deflected by a magnetic field into a curved trajectory that gives a distinctive mass spectrum.

14. Figure 6.4: The Luminescence Dating Process
Luminescence dating is an absolute radiometric method of determining the age of a material since a
key event in its history - typically burial (in the case of sediments) or firing (in the case of ceramics or
burnt stone).When a geological sediment is buried, the effects of the incoming solar radiation are
removed.

15. And we’re done!
 Thank you for listening and I hope you
understand our discussion..
However, before we leave…., do you have any
questions?
If not, time for us to test your knowledge…

16. Process Questions
 1.What is the difference between relative dating & absolute dating?
2.Why do some scientists use the terms chronometric or calendar
dating, over absolute dating?
3.What do you call the atoms of some chemical elements that have
different forms?
4.What do you call the dating method that can only date the tephra
material?
5.What do you call the dating method which measures the energy
from radioactive decay that is trapped inside energy crystals?