RE: Hugh Ross meets Mungo man

Glenn R. Morton (
Sat, 29 May 1999 08:04:47 -0500

Adrian Teo wrote:

>I've had several discussions with others (outside of this listserv) on >the accuracy and validity of dating methods. Can anybody explain each >of the three methods used in Glenn's post? Thanks!

Since no one else did, here is the explanation of uranium series,
electron spin resonance and optically stimulated luminescence.

Uranium series dating dates the uranium and thorium which is
incorporated into travertine (cave limestone) deposits. Ground water,
seeping into caves, contains uranium 238 and 234, which are highly
soluble in water, but not daughter elements such as thorium 230 which is
insoluble. After the uranium is deposited in the limestone, the uranium
238 and 234 decays to thorium -230 and then this on to other isotopes.
By measuring the ratios, and knowing the half-lives of the radioactive
series, one can date the travertine and thus anything it covers. All
the thorium and below must have originally been uranium. The method is
good from 5000 years ago back to about 1 million years

Electron spin resonance (ESR) measures damage to crystaline material
such as tooth enamel. As a tooth lies in the earth it is bombarded by
natural radioactivity. This disrupts the crystal displacing electrons
in the crystal lattice. By bombarding the crystal with microwaves, a
some of the energy is absorbed by the trapped electrons indicating the
extent of the radiation damage. By knowing the ambient radiation level
in the deposite a tooth came from, one can calculate how long the thing
has been lying there. ESR works from the present to more than a million
years ago.

Thermoluminescence is similar to ESR. When a mineral like flint or
quarts is heated or exposed to sunlight the crystal lattice is annealed
a bit and displaced electrons are 'neutralized'. When the object is
buried it does not see the sun but radiation damage once again
accumulates, causing displaced electrons.. By stimulating the object
with light, there is a glow which eminates from the object which can be
measured. This glow indicates how much damage the flint has suffered.
ONce again by knowing the ambient radiation level, one can calculate how
long it has been since the mineral saw sunlight or how long since it was
heated. The range is from 5000 to 500,000 years for this method.

Info can be found in Encylcopedia of Human Evolution S. Jones ed. p.

BTW Thermoluminescence was discovered by either Boyle or Hooke who took
a crystal to bed with him and placed it next to his body. In the dark
the crystal glowed. No one knows what he was really doing with the


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