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These reasons will work from the general to the specific.
The goal of this lecture is come to come to a scientific understanding of geologic time and the age of the Earth.
In order to do so we will have to understand the following: To better understand these concepts, let's look at an archeological example: Imagine we are a group of archeologists studying two different trash pits recently discovered on the Tulane University campus and at the Audubon Zoo (where they all aksed for you).
The diagram right shows two distinct faunal assemblages.
Although the types of trash in each pit is quite variable, each layer has a distinctive kind of trash that distinguishes it from other layers in the pits.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.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.These ages have been derived from relative dating and absolute dating (radiometric dating) of rock layers and fossils.