Absolute Age

1
Absolute Age

• the age, in years, of a rock or other object

2
Atoms

• Everything is made up of atoms.
• Atoms have protons, neutrons and electrons.
• There are several different elements, such as
  mercury, helium, carbon, hydrogen, etc.
• Carbon is the element we will focus on today.

3
History of Carbon dating

• Archaeologists could date the past only by using
  recorded histories (Egyptian recorded history,
  Roman, etc.)
• They used pottery or other materials to date
  relatively
• Archaeologists needed a more accurate way to date
  the past.

4
Who developed radiocarbon dating?

• The radiocarbon method was developed by a team of
  scientists led by the late Professor Willard F.
  Libby, who won the Nobel Prize in Chemistry in
  1960 for the radiocarbon discovery.

5
How does it work?

• All plants and animals are made principally of
  CARBON.
• Most Carbon has 12 electrons (Carbon 12). An
  unstable version has 14 electrons (Carbon 14)
• Because it is unstable, it is called Radiocarbon

6
How does it work?

• 1940s- Scientists were sucessful in finding out
  how long it takes for a sample of Carbon14 to
  decay from a dead plant or animal
• Mr. Libby measured the Half-Life of Carbon 14,
  which was about 5568 years.

7
Half life

• Half Life is the amount of time it takes for half
  of the radiocarbon in a sample of plant or animal
  to decay.

8
What kind of samples can you date using
radiocarbon?

• Charcoal, wodd, twigs, seeds, bone, shell,
  leather, soil, pollen, hair, pottery, rock art,
  bird, eggshell, coral, blood residue, textiles,
  paper, fish remains, insect remains, resins,
  antlers
• Just to name a few.

9
How do we know it works?

• Scientists test radiocarbon dated samples against
  known dated material, such as Egyptian wood whose
  age is known, tree ring samples or other known
  dated objects.

10
How big of a sample do you need?

• Scientists can test a carbon sample that is as
  small as a grain of rice, pollen grains, seeds or
  tiny pieces of charcoal.

11
How much does it cost to date an object?

• About 250 for a single date on an object

12
What are the oldest things that can be
radiocarbon dated?

• Anything that is less than 50,000 to 60,000 years
  old. Beyond that other methods must be used
• REMEMBER the half life of carbon 14 is 5568 years

13
What are the some other methods?

• Uranium/Thorium dating (coral)
• Thermoluminescence (pottery,sediment)
• Obsidian Hydration
• Electron Spin Resonance (teeth)
• Amino Acid Racemisation dating (eggshell, bones)
• Many others!!!!!

14
What is the youngest thing that can be
radiocarbon dated?

• We can date pretty much anything from today or in
  modern times.

15
What kinds of famous things have been radiocarbon
dated?

• The Dead Sea Scrolls- correlated with writing
  styles used on the scrolls
• Iceman-(found in 1991 in northern Italy)

16
Why is this important?

• Instead of spending large amounts of time trying
  to figure out when something happened, we can
  focus on the how and why
• Scientists can more easily uncover the past

17
Principle of Uniformitarianism

• The Earths processes today give us clues to the
  past
• the present is key to the past