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Lichenometry
Lichenometry
Image of lichens on a rock from: https://willowhousechronicles.wordpress.com/2009/12/17/likin-lichens/
Lichenometry is the form of dating that I have chosen to look deeper into. Essentially the time of rock exposure can be determined by measuring the diameters of the lichens. From what I've read this technique works best in arctic environments. This graph shows that as the diameter goes up, the length of surface exposure does as well. This image is from https://www.ldeo.columbia.edu/~letour/research/lichens%20and%20landscapes/papers/lichens%20copy.pdf
This technique can be useful for geomorphologists for many reasons. This can give an indication on many different surface processes.
One article that I read discussed the link between lichenometry and proof of climate change. They studied the lichens on avalanche deposition to figure out if the avalanches were happening more frequently. They found that this was the case, which they attributed to climate change. They came to this conclusion because avalanches were happening during the spring melting period, which indicated higher temperatures. Armstrong, R. A. (2004). Lichens, lichenometry and global warming. Microbiologist, 5(32), e35.
My second article discusses dating rock falls on the San Andreas Fault. When a rock fall happens some of the rocks are exposed, which then grow lichens. It can then be figured out when the rock face fell and was exposed. This indicates when there has been an earthquake along the San Andreas. This means it can potentially help to prepare for future earthquakes. Bull, W. B. (1996). Dating San Andreas fault earthquakes with lichenometry. Geology, 24(2), 111-114.
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