Absolute vs relative dating techniques
I also like this simple exercise, a spin-off from an activity described on the USGS site above.Take students on a neighborhood walk and see what you can observe about age dates around you.This was roughly the dating method used by scientists in the early days of palaeontology and archaeology, before the emergence of absolute radiometric dating methods (radiocarbon, potassium-argon, thermoluminescence, OSL, etc.)The relative dating method is still helpful, since basically it gives reasonably good results.And not every fossil or archaeological object can be dated, since radiometric dating methods are mostly rather costly, and the financial means of most research teams are limited.Relative dating is a method of dating fossils or archaeological objects according to the stratigraphical layer in which they are found.To tell it simply, fossils and archaeological objects are supposed to have the same age as the sediment in which they are embedded.
The half-life of carbon 14, for example, is 5,730 years.
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.
And in some cases older objects may be moved out of their original context and get mixed with younger objects, in a stratigraphically younger layer.
This is the reason why most palaeontologists and archaeologists collaborate with geologists, in order to explain the processes which were at the origin of the sedimentation of the layers.