Cosmogenic exposure age dating
To understand this situation, it is useful to imagine one in the place of a rock particle under an eroding surface.As the particle approaches the surface, it sees an exponentially increasing cosmic ray intensity and cosmogenic nuclide production rate.So in the case of an eroding surface, the cosmogenic nuclide content can be used not to measure an exposure age, but an erosion rate ( Let us now move on to a cosmogenic radionuclide in a surface that undergoes no erosion.Initially, the concentration of the nuclide increases almost linearly with time, but after a while, some of these nuclides are lost due to radioactive decay.
But some of the spallation products are very rare yet sufficiently long lived to accumulate in measurable quantities in terrestrial rocks.
When glacial striations can be observed on rock surfaces, this indicates that erosion has been negligible.
All those surfaces should plot on the zero erosion line of the banana plot.
This secondary cosmic ray shower is rapidly attenuated as it travels down into the atmosphere.
Only a very small fraction of the secondary cosmic rays, which mostly consist of neutrons, reach the surface of the Earth.