Relative Dating

Geologic Time: The science of Geology didn't take shape until the discovery of geologic time (deep time).

Relative Dating: Thus the notion of Geological time was born. Using Steno's and Hutton's priciples of stratigraphy, it began to be possible to say what order the separate rock layers had formed in, provided they could be seen in association. I.e., Rocks could be dated relative to one another.

The rock record tells us more than relative age. It also tells us about the environment i which the rock formed. In fact, we say that:

A rock is a record of the environment in which it formed.

So, rocks tell us about ancient environments and how they have changed. Let's use sedimentary rocks as an example.

Depositional environment: Places where sediments are deposited. The physical characteristics and geographical location determines the type of sediment that will normally be deposited. In broad strokes, we classify depositional environments as:

Sedimentary structures: The keys to the identification of sedimentary environments are small scale physical features they display. Here are a few common or familiar examples.