Lichenometry

Lichenometry estimates how long a surface has been exposed by measuring the size of lichens growing on it and applying a growth-rate calibration.

Lichen growth curve: A relationship between lichen size and the time elapsed since growth began. Lichenometry uses a calibrated growth curve to translate thallus measurements into exposure ages.
Glacial geomorphology: The study of landforms produced by glaciers and the processes that shape them. Lichenometry can estimate when glacial deposits or newly exposed rock surfaces formed.
Lichen: A stable association in which a fungus lives with an alga, cyanobacterium, or both. Lichenometry relies on lichens’ slow growth on exposed mineral surfaces.
Cosmogenic nuclide dating: A method that dates rock exposure by measuring nuclides produced by cosmic-ray interactions. It can provide an independent exposure age for checking lichenometric estimates.
Lichenometry calibration: The process of establishing local lichen growth rates against surfaces of known age. Calibration supplies the rate needed to turn lichen size into a date.
Moraine: An accumulation of rock and sediment transported and deposited by a glacier. Lichen-covered moraine boulders can preserve evidence of glacier advances and retreats.
Rhizocarpon geographicum: A yellow-green map lichen widely used in lichenometric studies. Its conspicuous growth and measurable thalli make it a common target for dating.
Radiocarbon dating: A dating method based on the radioactive decay of carbon-14 in once-living material. Unlike lichenometry, it dates organic remains rather than lichen size on a surface.
Lichen thallus: The vegetative body of a lichen, formed by a fungus living with a photosynthetic partner. Its measurable diameter is the basic observation used in many lichenometric studies.
Rockfall: The sudden detachment and descent of rock from a steep slope or cliff. Lichen sizes on deposited blocks can help constrain when a rockfall occurred.

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