Description of absolute dating and numerical age

Principle of Uniformitarianism The principle of Uniformitarianism was postulated by James Hutton (1726-1797) who examined rocks in Scotland and noted that features like mudcracks, ripple marks, graded bedding, etc.where the same features that could be seen forming in modern environments.

For example, the mudstone, sandstone and shale are cut by the basalt dike, so we know that the mudstone, sandstone, and shale had to be present before the intrusion of the basalt dike.From the beginning of this course, we have stated that the Earth is about 4.6 billion years old.How do we know this and how do we know the ages of other events in Earth history?In the diagram to the right,the fault cuts the limestone and the sandstone, but does not cut the basalt.Thus we know that the fault is younger than the limestone and shale, but older than the basalt above.

In fact, sedimentary rocks are, in a sense, trash from the Earth's surface deposited in basins.