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USGS CMG InfoBank: Isotopes

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Comment: 18:55 - 19:37 (00:42)
Source: Annenberg/CPB Resources - Earth Revealed - 10. Geologic Time
Keywords: "radioactive decay", "radiometric age dating", "radiocarbon dating", isotope, element, "absolute age dating"

Our transcription: Grains of sand trickling through the narrow opening of an hourglass are somewhat analogous to isotopes decaying in a radioactive element.
The sand in the upper half of the hourglass represents a supply of parent isotope.
The sand in the lower half is its daughter product.
The proportion of parent to daughter depends upon how much time has elapsed.
This can be determined simply by measuring the ratio of parent to daughter sand.
This is how radioactive dating works.
The most familiar example is radiocarbon dating.

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