Relative age dating principles
Relative dating does not provide actual numerical dates for the rocks.
Fossils are important for working out the relative ages of sedimentary rocks.
where the same features that could be seen forming in modern environments.
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".
A more modern way of stating the same principle is that the laws of nature (as outlined by the laws of chemistry and physics) have operated in the same way since the beginning of time, and thus if we understand the physical and chemical principles by which nature operates, we can assume that nature operated the same way in the past.
Some fossils, called index fossils, are particularly useful in correlating rocks.
For a fossil to be a good index fossil, it needs to have lived during one specific time period, be easy to identify and have been abundant and found in many places. If you find ammonites in a rock in the South Island and also in a rock in the North Island, you can say that both rocks are Mesozoic.
That fossil species may have been dated somewhere else, so you can match them and say that your fossil has a similar age.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.Principles of Stratigraphy Stratigraphy is the study of strata (sedimentary layers) in the Earth's crust.Correlation with them has helped geologists date many New Zealand rocks, including those containing dinosaurs.
From the beginning of this course, we have stated that the Earth is about 4.6 billion years old.Principle of Original Horizontality Sedimentary strata are deposited in layers that are horizontal or nearly horizontal, parallel to or nearly parallel to the Earth's surface.