Cosmogenic exposure age dating

The accumulation of cosmogenic nuclides in minerals at or near the earth's surface provides a basis for exposure 'dating' of landforms, the quantification of erosion rates, and other geologic applications (Bierman, 1994; Cerling and Craig, 1994; Gosse and Phillips, 2001).Independent evidence discussed below strongly suggests that production rates of these nuclides have remained constant or nearly so, validating their use in geochronometry.Each nuclide is useful for dating some target minerals, but not for others, for various reasons.For example, Note: The actual cosmic radiation flux, and hence TCN production rate, varies with geomagnetic latitude and altitude.This essay focuses on cosmogenic exposure dating, a method of dating rock surfaces which has been compared to using the redness of someone's skin in order to estimate the duration of exposure to sunlight (an analogy attributed to Edward Evenson; Gosse and Phillips, 2001).Such analyses show that many landform surfaces have been exposed to cosmic radiation for at least 10Be).Concentrations of actual radionuclides may or may not have been increased; if they have, the term Technologically-Enhanced (TENORM) may be used.

Furthermore, it is also often claimed that before the moon landings there was considerable fear that astronauts would sink into a very thick dust layer, but subsequently scientists have remained silent as to why the anticipated dust wasn’t there.However, certain work activities can give rise to significantly enhanced exposures that may need to be controlled by regulation.Material giving rise to these enhanced exposures has become known as naturally occurring radioactive material (NORM).Thus the different measurement techniques cover different size and mass ranges of particles, so that to obtain the most reliable estimate requires an integration of results from different techniques over the full range of particle masses and sizes.When this is done, most current estimates of the meteoritic dust influx rate to the earth fall in the range of 10,000-20,000 tons per year, although some suggest this rate could still be as much as up to 100,000 tons per year.

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