Can relative dating always be used

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The Age of Dinosaurs was so many millions of years ago that it is very difficult to date exactly.

Scientists use two kinds of dating techniques to work out the age of rocks and fossils. This considers the positions of the different rocks in sequence (in relation to each other) and the different types of fossil that are found in them.

Your goal is to study the smooth, parallel layers of rock to learn how the land built up over geologic time.

Now imagine that you come upon a formation like this: What do you think of it? How can you make any conclusions about rock layers that make such a crazy arrangement?

A fossil will always be younger than fossils in the beds beneath it and this is called the principle of superposition.

In an undisturbed sequence of rocks, such as in a cliff face, it is easy to get a rough idea of the ages of the individual strata – the oldest lies at the bottom and the youngest lies at the top.

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Learn how inclusions and unconformities can tell us stories about the geologic past.

Sometimes, scientists already know the age of the fossil because fossils of the same species have been found elsewhere and it has been possible to establish accurately from those when the dinosaur lived.

Geologists call this the principle of lateral continuity.

The atoms of some chemical elements have different forms, called isotopes.

These break down over time in a process scientists call radioactive decay.

Relative dating cannot establish absolute age, but it can establish whether one rock is older or younger than another.

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