Cosmogenic dating techniques jason wade dating


02-Aug-2017 12:25

Although dating with this method is expensive and the entire process takes a long time, TCN dating has the advantage that the dateable material is produced by the rockslide event itself by exposing fresh material surfaces to the cosmic rays.

With the accuracy of modern instruments general every surface older than about 1000 years can be dated and the uncertainty limits today lie below 10% of the age.

Earth is assaulted with high energy particles every day, (ex: protons and alpha particles). When the primary cosmic rays interact with atoms in gasses from the atmosphere, there are secondary particles that are produced and provide energy for many different reactions in the atmosphere.

These rays reach the earth’s surface are mostly composed of neutrons When the particle rays strike an atom on the earth’s surface, they can dislodge protons from an atom or add/dislodge neutrons in a process called spallation.

These nuclides are generally referred to as naturally occurring radioactivity and are derived from the radioactive decay of thorium and uranium.

Cosmogenic nuclides are atoms that are constantly being synthesized from the bombardment of planetary surfaces by cosmic particles (primarily protons ejected from the Sun), and are also considered natural in their origin.

These particles interact with atoms in atmospheric gases (and thereby producing northern lights) and the surface of Earth.

Periods of heavy rain and lots of sunshine will make larger gaps of growth in the rings, while periods of drought might make it difficult to count individual rings. When a given quantity of an isotope is created (in a supernovae, for example), after the half-life has expired, 50% of the parent isotope will have decomposed into daughter isotopes.

The basic principle is that these radionuclides are produced at a known rate, and also decay at a known rate.

Accordingly, by measuring the concentration of these cosmogenic nuclides in a rock sample, and accounting for the flux of the cosmic rays and the half-life of the nuclide, it is possible to estimate how long the sample has been exposed to cosmic rays.

Spallation is a process in which a heavy nucleus emits a large number of nucleons as a result of being hit by a high-energy particle, thus greatly reducing its atomic weight This will produce a different isotope of the atom or producing a completely different element all together.

These new isotopes are called cosmogenic nuclides With rocks, usually only the first meter of the material is affected.

These ions are accelerated in an electric field through collimating slits and subject to a magnetic field which causes the ions to follow a curved path. By adjustment of the strength of the magnetic field and suitable placement of an ion collector, the different isotopes can be measured with precision.