Teaching relative age dating
Free 5-day trial Geologic time extends back 4.6 billion years.Because the earth is so old and rocks formed millions of years ago, geologists needed a way to date rocks and rock units called strata.To understand this better, consider a four-layer cake. It wouldn't be possible for the other layers to be added without the bottom layer first.This same process applies with each layer to the cake added.To think of it another way, the chocolate chips found in chocolate chip cookies must be made first before they are added to the cookie, right?
Principle of original horizontality: This principle simply states that deposition of rocks occurs horizontally or nearly horizontally. Most deposition occurs as the ocean deposits sediment flat and horizontally on existing rock, either on the ocean floor or on the continent.Principle of cross-cutting relations: The principle is another example of which came first.Instead of using layers, it involves features that cut through the rock, like a fault or a dike.This allows geologists to determine the age of a rock or strata relative to another rock or strata.
So, instead of saying when something happened, it puts events in the order they happened.Law of superposition: This is one of the most basic techniques of relative dating geologists use.