Relative and absolute dating lessons
Electronic course reserves, or "e-Reserves," are articles and book chapters that are available online through the University Libraries.If you have any questions about the lesson materials or assignments, post them to our online discussion forum (not e-mail). While you are there, feel free to post your own responses if you, too, are able to help out a classmate!In a way this field, called geochronology, is some of the purest detective work earth scientists do.
No bones about it, fossils are important age markers.
Crests of the first set are preserved in the troughs of the second set, hence, the ladderback appearance.