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Postby a_haworthroberts » Mon Nov 07, 2016 11:52 pm ... -year.html

What I found of greater interest was not the faster recent rates of coastal erosion of cliffs near to Beachy Head in Sussex but rather how the scientists deduced that the cliffs are now eroding faster than previously (I mean historically when observations by scientists were not taking place).

As outlined in the Daily Mail's report (they should stick to science instead of being pro-Brexit whingers imho):
"The cliffs in East Sussex have only been documented for the past 150 years, but researchers were able to look back much further by dating samples of the rocks.
Cosmic rays penetrate through the atmosphere and collide with atoms in rocks, resulting in the production of rare isotopes such as beryllium-10 in the upper few metres of the Earth's surface.
The researchers counted the number of beryllium-10 isotopes in our shore platform rock samples to work out how long the shore platform had been exposed to cosmic radiation, and therefore how long it has been since cliff retreat uncovered that section of platform.
They found the erosion rate of the cliffs was slow, around 0.8 inches (2 cm) a year, up until a few hundred years ago."

The BBC report explains that beryllium-10 "is produced when cosmic rays - that constantly shower the Earth - hit oxygen atoms in the flints' quartz minerals.
The longer the nodules have been exposed, the greater their build-up of beryllium-10".

Thus scientists can deduce when different rock/mineral samples were first exposed by coastal erosion and thus uncover any variations within the rate of erosion during past
centuries or millennia. If past erosion rates were slower than today's (today's are nearly tenfold faster it would appear) then the time at which older rock/mineral samples were first exposed to cosmic rays was longer ago than might be assumed from direct observations (only) in the here and now.

And the notion that these cliffs have been in existence for much more than just 4,500 or 6,000 years has not been overturned. And NO strict unbending uniformitarianism is required in order to reach that conclusion. Cosmic rays (or Earth's magnetic field) do vary to some extent over time - but not significantly enough to undermine the PNAS conclusions.
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