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Transcript
Radiocarbon dating
AND
Uranium dating
-Lou Kimberly L. Colon
-Kaye Esperanza Elizalde
-Bunny Grace Escollar
• Another different use of radioactivity is
radioactive dating. Radioisotopes
decay, yielding their decay products.
• Using the decay curve and the
isotope’s known half-life, the age of
the sample can be estimated.
Radioisotopes are also called as
nuclear clocks.
•
Uranium Dating
• It is used to determine the age of
the earth, the moon or the solar
system.
• Uranium238 , Uranium 235, Th232,
K40, and Rb87 are used.
• With this method, scientists have
estimated the age of the oldest
rock on Earth to be 4 billion years
• uranium dating is a radiometric
dating technique which compares
two isotopes of uranium (U) in a
sample: 235U and 238U.235U/238U
dating is one of several radiometric
dating techniques exploiting the
uranium radioactive decay series, in
which 238U undergoes
14alpha and beta decay events while
decaying to the stable isotope 206Pb
and 207Pb.
For example:
• The half life of 238 Uranium is 4.5 X
10 raised to 8 years while that of
U235 is a little shorter. Both of them
decay into stable isotopes of lead:
238U to be 206Pb and 235U to
207Pb. Thus, any rock that
contains uranium will be rich in
206Pb and 207Pb.
• Using the same technique, the age
of the earth has been estimated to
be about 4.5 billion years .
• Rocks and soil from the moon when
examined using the 207Pb-206Pb
method, they found out that the
age of the rocks in the moon are
about 4.6 billion years.
• Since uranium has a very long life,, it is
used to measure the age of the older
objects in the earth such as rocks and
soil.
Rock from the Moon
Carbon Dating
•Uses the decay of the carbon14 isotope. The half-life of
carbon-14 is 5730 years. ]
• Radiocarbon dating (sometimes
simply known as carbon dating) is
a radiometric dating method that
uses the naturally occurring
radioisotope carbon-14 (14C) to
estimate the age of carbonbearing materials up to about
58,000 to 62,000 years
• One of the most frequent uses of
radiocarbon dating is to estimate the age of
organic remains from archaeological sites.
• When plants fix atmospheric carbon
dioxide (CO2) into organic material
during photosynthesis they incorporate a
quantity of 14C that approximately matches
the level of this isotope in the atmosphere.
After plants die or they are consumed by
other organisms the 14C fraction of this
organic material declines at a
fixed exponential rate due to
the radioactive decay of 14C
• The technique of radiocarbon dating
was developed by Willard Libby and
his colleagues at the University of
Chicago in 1949. . Libby estimated that
the steady state radioactivity
concentration of exchangeable
carbon-14 would be about 14
disintegrations per minute (dpm) per
gram.. He first demonstrated the
accuracy of radiocarbon dating by
accurately estimating the age of
wood from an ancient Egyptian royal
barge for which the age was known
from historical documents.
• The age of artifacts from
archaeological sites can be
determined using carbon-dating
techniques.
• The oldest caves in Palawan were
found to be 40,000 years.