1 8 3 0 ▁birth s ▁Category : 1 9 1 5 ▁death s ▁Category : Can ad ian ▁printer s ▁Category : Can ad ian ▁invent ors <0x0A> </s> ▁In ▁arch ae ology , ▁p ala e ont ology , ▁and ▁ge omorph ology , ▁l ichen ometry ▁is ▁a ▁ge omorphic ▁method ▁of ▁ge och ron olog ic ▁d ating ▁that ▁uses ▁l ichen ▁growth ▁to ▁determine ▁the ▁age ▁of ▁exposed ▁rock , ▁based ▁on ▁a ▁pres umed ▁specific ▁rate ▁of ▁increase ▁in ▁radial ▁size ▁over ▁time . ▁Me as uring ▁the ▁diameter ▁of ▁the ▁largest ▁l ichen ▁of ▁a ▁species ▁on ▁a ▁rock ▁surface ▁can ▁therefore ▁be ▁used ▁to ▁determine ▁the ▁length ▁of ▁time ▁the ▁rock ▁has ▁been ▁exposed . ▁L ichen ▁can ▁be ▁preserved ▁on ▁old ▁rock ▁faces ▁for ▁up ▁to ▁ 1 0 , 0 0 0 ▁years , ▁providing ▁the ▁maximum ▁age ▁limit ▁of ▁the ▁technique , ▁though ▁it ▁is ▁most ▁accurate ▁( with in ▁ 1 0 % ▁error ) ▁when ▁applied ▁to ▁surfaces ▁that ▁have ▁been ▁exposed ▁for ▁less ▁than ▁ 1 , 0 0 0 ▁years . ▁( The ▁practical ▁limit ▁of ▁the ▁technique ▁might ▁be ▁ 4 , 0 0 0 ▁to ▁ 5 , 0 0 0 ▁years .) ▁L ichen ometry ▁is ▁especially ▁useful ▁for ▁d ating ▁surfaces ▁less ▁than ▁ 5 0 0 ▁years ▁old , ▁as ▁radi oc ar bon ▁d ating ▁techniques ▁are ▁less ▁accurate ▁over ▁this ▁period . ▁The ▁l ich ens ▁most ▁commonly ▁used ▁for ▁l