Of thermoluminescence dating

Posted by / 25-Jan-2015 20:02

Of thermoluminescence dating

Minerals, in fact, everything in our planet, are exposed to cosmic radiation: luminescence dating takes advantage of the fact that certain minerals both collect and release energy from that radiation under specific conditions.

Crystalline rock types and soils collect energy from the radioactive decay of cosmic uranium, thorium, and potassium-40.

Luminescence dating is good for between a few hundred to (at least) several hundred thousand years, making it much more useful than carbon dating.

The term luminescence refers to the energy emitted as light from minerals such as quartz and feldspar after they've been exposed to an ionizing radiation of some sort.

Electrons from these substances get trapped in the mineral's crystalline structure, and continuing exposure of the rocks to these elements over time leads to predictable increases in the number of electrons caught in the matrices.

TL dating is a matter of comparing the energy stored in a crystal to what "ought" to be there, thereby coming up with a date-of-last-heated.

In the same way, more or less, OSL (optically stimulated luminescence) dating measures the last time an object was exposed to sunlight.

Luminescence dating (including thermoluminescence and optically stimulated luminescence) is a type of dating methodology that measures the amount of light emitted from energy stored in certain rock types and derived soils to obtain an absolute date for a specific event that occurred in the past.The method is a direct dating technique, meaning that the amount of energy emitted is a direct result of the event being measured.Better still, unlike radiocarbon dating, the effect luminescence dating measures increases with time.As a result, there is no upper date limit set by the sensitivity of the method itself, although other factors may limit the method's feasibility.Two forms of luminescence dating are used by archaeologists to date events in the past: thermoluminescence (TL) or thermally stimulated luminescence (TSL), which measures energy emitted after an object has been exposed to temperatures between 400 and 500°C; and optically stimulated luminescence (OSL), which measures energy emitted after an object has been exposed to daylight.

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To put it simply, certain minerals (quartz, feldspar, and calcite), store energy from the sun at a known rate.

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