What have scientists used to build a chronology of earths past

Hi,

Scientists have used rock samples to date the Earth's past. They also might use Steno's principles. 

Relative dating is the determination of the age of a rock or geological event by comparing with other rock/ geologic events. Absolute dating is a form of geologic dating that gives an actual date or age in history that the item was formed or died in years. 

Steno's principles are: 

Law of superposition - Bottom layer is the oldest, top layer of the youngest In undisturbed layers of sedimentary rock or magma.

Original horizontally - When sedimentary rock layers form, they are "created in a horizontal form.

The Principle of Lateral Continuity - States that layers of sediment initially extend laterally in all directions.

Faith xoxo

Cultural convergence is the theory that two cultures will be more and more like each other a very notable example of this is around the u.s.-mexico border, where