Lichenometry

In <a href="/facts/Archaeology/K3Q5P38R">archaeology</a>, <a href="/facts/Palaeontology/60n5yldd">palaeontology</a>, and <a href="/facts/Geomorphology/MDf2I2h5">geomorphology</a>, lichenometry is a geomorphic method of <a href="/facts/Geochronologic/U8hRTGwL">geochronologic</a> dating that uses <a href="/facts/Lichen/cfbt9vjj">lichen</a> growth to determine the <a href="/facts/Surface_exposure_dating/HKFzxr4x">age of exposed rock</a>, based on a presumed specific rate of increase in radial size over time.: 9  Measuring the diameter of the largest lichen of a species on a rock surface can therefore be used to determine the length of time the rock has been exposed. Lichen can be preserved on old rock faces for up to 10,000 years, providing the maximum age limit of the technique, but it is most accurate (within 10% error) when applied to surfaces that have been exposed for less than 1,000 years. (The practical limit of the technique might be 4,000 to 5,000 years.)
Lichenometry is especially useful for dating surfaces less than 500 years old, as radiocarbon dating techniques are less accurate over this period. The lichens most commonly used for lichenometry are those of the genera <a href="/facts/Rhizocarpon/77hLPXfz">Rhizocarpon</a> (such as the species <a href="/facts/Rhizocarpon_geographicum/JFjkpUCu">Rhizocarpon geographicum</a>) and <a href="/facts/Xanthoria/3aGzgkVb">Xanthoria</a>. The measured growth rates of R. geographicum tends to fall within the range of 0.9–0.3 millimeter per year, depending on several factors, including the size of the lichen patch.
The technique was first employed by <a href="/facts/Knut_F%C3%A6gri/kfTYmzNc">Knut Fægri</a> in 1933, though the first exclusively lichenometric paper was not published until 1950, by Austrian <a href="/facts/Roland_Beschel/GI0c5jRb">Roland Beschel</a>, in a paper concerning the European <a href="/facts/Alps/Q3zdQId4">Alps</a>.

Lichenometry open-in-new

Lichenometry