Though using similar methods, these two techniques differ in certain ways that will be discussed in this article.As the name implies, relative dating can tell which of the two artifacts is older.But the most accurate forms of absolute age dating are radiometric methods. Sedimentary rocks in particular are notoriously radioactive-free zones.This method works because some unstable (radioactive) isotopes of some elements decay at a known rate into daughter products. Half-life simply means the amount of time it takes for half of a remaining particular isotope to decay to a daughter product. Good discussion from the US Geological Survey: geochronolgists just measure the ratio of the remaining parent atom to the amount of daughter and voila, they know how long the molecule has been hanging out decaying. So to date those, geologists look for layers like volcanic ash that might be sandwiched between the sedimentary layers, and that tend to have radioactive elements.The narrower a range of time that an animal lived, the better it is as an index of a specific time.No bones about it, fossils are important age markers.Pretty obvious that the dike came after the rocks it cuts through, right?
There are many methods employed by these scientists, interested in the old, to get to know the age of items.Unlike people, you can’t really guess the age of a rock from looking at it.Yet, you’ve heard the news: Earth is 4.6 billion years old. That corn cob found in an ancient Native American fire pit is 1,000 years old. Geologic age dating—assigning an age to materials—is an entire discipline of its own.Relative age dating also means paying attention to crosscutting relationships.Say for example that a volcanic dike, or a fault, cuts across several sedimentary layers, or maybe through another volcanic rock type.Like the other kind of dating, geologic dating isn’t always simple.