ABSTRACT
The technique that has become known as lichenometry has been adopted by geomorphologists, glacial workers in particular, since its introduction by R. E. Beschel in a series of papers dating from 1950. Once the lichen is established an initial period of rapid growth ensues but soon this gives way to a regular progressive enlargement of the thallus diameter over time. The sizes of the largest thalli found on a series of surfaces will hence indicate the order in which these became exposed, and a relative chronology may thus be established. A way round the problem that surfaces of interest will vary widely in size and hence influence the chances of finding a lichen of specified size is that the search areas should be proportional to the area of each feature, so that the number of observations from different populations should be the same wherever possible.
