Absolute and relative dating methods

Dendrochronology: Also known as tree-ring dating, the science concerned with determining the age of trees by examining their growth rings.

Half-life: Measurement of the time it takes for one-half of a radioactive substance to decay.

These include the uranium-thorium method, the potassium-argon method, and the rubidium-strontium method. Thermoluminescence (pronounced ther-moeloo-mi-NES-ence) dating is very useful for determining the age of pottery.

When a piece of pottery is heated in a laboratory at temperatures more than 930°F (500°C), electrons from quartz and other minerals in the pottery clay emit light.

When carbon-14 falls to Earth, it is absorbed by plants.

These plants are eaten by animals who, in turn, are eaten by even larger animals.

Since certain species of animals existed on Earth at specific times in history, the fossils or remains of such animals embedded within those successive layers of rock also help scientists determine the age of the layers.

Similarly, pollen grains released by seed-bearing plants became fossilized in rock layers.

The successive layers of rock represent successive intervals of time.With sensitive instrumentation, this range can be extended to 70,000 years.In addition to the radiocarbon dating technique, scientists have developed other dating methods based on the transformation of one element into another.Eventually, the entire ecosystem (community of plants and animals) of the planet, including humans, is filled with a concentration of carbon-14.As long as an organism is alive, the supply of carbon-14 is replenished.

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