Principle of Inclusions If we find a rock fragment enclosed within another rock, we say the fragment is an inclusion.

numerical dating-77

He concluded that process that are currently operating on the Earth must be the same processes that operated in the past.

This principle is often stated as "the present is the key to the past".

Principle of Original Continuity If layers are deposited horizontally over the sea floor, then they would be expected to be laterally continuous over some distance.

Thus, if the strata are later uplifted and then cut by a canyon, we know that the same strata would be expected to occur on both sides of the canyon.

Sediment deposited on steep slopes will be washed away before it is buried and lithified to become sedimentary rock, but sediment deposited in nearly horizontal layers can be buried and lithified.

Thus rocks that we now see inclined or folded have been disturbed since their original deposition.Look at the many photographs of the Grand Canyon in your textbook.Note that you can follow the layers all along the walls of the canyon, and you can find the same layers on both sides of the canyon.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.Prior to the late 17th century, geologic time was thought to be the same as historical time.