What is relative dating and how is it used
Knowing when a dinosaur or other animal lived is important because it helps us place them on the evolutionary family tree.Accurate dates also allow us to create sequences of evolutionary change and work out when species appeared or became extinct. These are: Where possible, several different methods are used and each method is repeated to confirm the results obtained and improve accuracy.This image from Lake Mead NRA shows a sequence of sedimentary rock layers.The oldest layers, Cambrian (570-505 million years ago) are at the base, with younger layers piled on top.Relative dating methods allow one to determine if an object is earlier than, later than, or contemporary with some other object.It does not, however, allow one to independently assign an accurate estimation of the age of an object as expressed in years.Concealed within the rocks that make up the Earth's crust lies evidence of over 4.5 billion years of time.
Volcanic rocks – such as tuff and basalt – can be used in dating because they are formed at a particular moment in time, during an eruption.
Cultural seriations are based on typologies, in which artifacts that are numerous across a wide variety of sites and over time, like pottery or stone tools.
If archaeologists know how pottery styles, glazes, and techniques have changed over time they can date sites based on the ratio of different kinds of pottery.
In the past, relative dating methods often were the only ones available to paleoanthropologists.
As a result, it was difficult to chronologically compare fossils from different parts of the world.However, the assumption of contemporaneity may not always be correct.