This can be done either by measuring growth rates from year to year (obviously, you will not have time for this!), or by measuring the size of colonies with known dates of origin.
With careful methodology, however, lichenometry can be a reliable method for dating rocks.Come back and tell us about your project using the “I Did This Project” link for the project you choose. Learn more about the News Feed The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources.You’ll find a link to “I Did This Project” on every project on the Science Buddies website so don’t forget to share your story! "Lichenometry: An Accessible Method for Dating Recent History (Geological and Manmade)." Science Buddies, 12 Apr. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help.If there is lichen growing on the wall, the lichen has most likely been living there since the time the wall was made, so if you could figure out how old the lichen is then you could deduce the age of the wall.Geologies use this method, called lichenometry, and other methods to establish dates and temporal sequences as they seek to construct a history from the available evidence.