Other radioactive dating methods

From the mapped field relationships, it is a simple matter to work out a geological cross-section and the relative timing of the geologic events.

His geological cross-section may look something like Figure 2.

Someone may ask, ‘Why do geologists still use radiometric dating?The field relationships are generally broad, and a wide range of ‘dates’ can be interpreted as the time when the lava solidified.What would our geologist have thought if the date from the lab had been greater than 200 million years, say 350.5 ± 4.3 million years?He may suggest that some other very old material had contaminated the lava as it passed through the earth.Or he may suggest that the result was due to a characteristic of the lava—that the dyke had inherited an old ‘age’. 200.4 ± 3.2 million years) implies that the calculated date of 200.4 million years is accurate to plus or minus 3.2 million years.

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