Realitive and absolute dating

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.

It’s based either on fossils which are recognized to represent a particular interval of time, or on radioactive decay of specific isotopes. Based on the Rule of Superposition, certain organisms clearly lived before others, during certain geologic times.

After all, a dinosaur wouldn’t be caught dead next to a trilobite.

The narrower a range of time that an animal lived, the better it is as an index of a specific time.

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.

Last modified 27-Aug-2015 13:38