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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.Uranium is present in many different rocks and minerals, usually in the form of uranium-238.Despite seeming like a relatively stable place, the Earth's surface has changed dramatically over the past 4.6 billion years.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.Different methods have their own limitations, especially with regard to the age range they can measure and the substances they can date.This is because new sediments are always laid down on top of sediments that have already been deposited.So, when looking at the history of a cliff face, it is important to read the story it tells from the bottom layer up.

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Geologists call this the principle of lateral continuity. This is an informational tour in which students gain a basic understanding of geologic time, the evidence for events in Earth’s history, relative and absolute dating techniques, and the significance of the Geologic Time Scale.Instead, other methods are used to work out a fossil’s age.Early geologists, in the 1700s and 1800s, noticed how fossils seemed to occur in sequences: certain assemblages of fossils were always found below other assemblages. Since 1859, paleontologists, or fossil experts, have searched the world for fossils.In the past 150 years they have not found any fossils that Darwin would not have expected.New discoveries have filled in the gaps, and shown us in unimaginable detail the shape of the great ‘tree of life’.