Relative dating means placing rocks in their proper sequence of formation, first, second, third, and so on. Relative dating cannot tell us how long ago something took place, only that it followed one event and preceded another. The relative dating techniques that were developed are valuable and still widely used. Numerical dating methods did not replace these techniques; they simply supplemented them. To establish a relative time scale, a few basic principles or rules had to be dis- covered and applied Although they may seem obvious to today, they were major breakthroughs in thinking at the time, and their discovery and acceptance was an important scientific achievement.
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