First of all, what is lichen?
Lichen is a fungus that is associated with another living organism such as an alga, the bark of a tree … It is said to live in symbiosis. That is to say, both help each other to survive.
Lichen grows where other plants cannot live: on top of the mountains, on rocks by the sea, on cooled lava and sometimes on sidewalks. They are easily recognized by their yellow/green color and their round shape is flattened.
How to date with lichen?
It is also thanks to this round shape that researchers can get an idea of the period of history to which an object belongs.
Indeed, the Arctic lichen, which can live for more than 10,000 years, grows by 1 mm every 50 years. This is how the stone statues of Easter Island (South Pacific) could be dated.