Did geologists determine the age of rocks and fossils before the advent of modern scientific dating methods such as radiometric, electron spin resonance and thermoluminescence?
If they did, does anyone know how they went about it?
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1$\begingroup$ There was not an absolute method before radiometric dating, as far as I know. They used relative methods, but physicists had estimated the age of the Earth to be much less than the current accepted value... so the estimated ages were not good. en.wikipedia.org/wiki/Age_of_Earth#Early_calculations $\endgroup$– f.thorpe ♦Jul 30, 2021 at 16:51
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1$\begingroup$ very relevant link en.wikipedia.org/wiki/Relative_dating $\endgroup$– JohnJul 31, 2021 at 15:19
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$\begingroup$ What time frame do you consider to be "modern"? I would consider "modern" to mean techniques developed in the last 100 years or so. If that's the case, every currently used dating technique is "modern". $\endgroup$– David HammenAug 1, 2021 at 11:42
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1$\begingroup$ @David Hammen Radiometric dating started in 1905 so anything before that. en.m.wikipedia.org/wiki/Radiometric_dating $\endgroup$– RickAug 1, 2021 at 14:50
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The approach adopted by Charles Lyell (and other writers in a similar timeframe), in his book 'Principles of Geology' which was first published in the 1830s was to look at processes in the modern landscape where the rate of change could be determined by observation or from historical evidence, and assuming that similar processes operated at similar rates in the geological past. So, for instance, if you measure the amount of sediment transported by a river today, and you measure the volume of sediment in that river's delta, you can estimate how long that delta took to form. If you see a similar delta in the geological record, you can assume it took a similar time to form. Lyell's estimates of the age of the earth were low, but as the concept of plate tectonics, with it's progressive recycling of rocks through subduction wasn't recognised, it was remarkably prescient.
