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The methods are all based on radioactive decay: The first radiometric dates, generated about 1920, showed that the Earth was hundreds of millions, or billions, of years old.Since then, geologists have made many tens of thousands of radiometric age determinations, and they have refined the earlier estimates.
online directory of dinosaur exhibits fro around the world. t=sub_pages&cat=8 Many natural history museums and universities worldwide offer public participation programs in dinosaur events, such as fossil hunting or fossil cataloguing. The list is too long to mention here, so a couple of examples are provided to get you going on your search for programs in your area: Explore U. fossil collecting locations that are detailed on this site.
New discoveries have filled in the gaps, and shown us in unimaginable detail the shape of the great ‘tree of life’.
Darwin and his contemporaries could never have imagined the improvements in resolution of stratigraphy that have come since 1859, nor guessed what fossils were to be found in the southern continents, nor predicted the huge increase in the number of amateur and professional paleontologists worldwide.
A key point is that it is no longer necessary simply to accept one chemical determination of a rock’s age.
Age estimates can be cross-tested by using different isotope pairs.