Geological Timescales and Dating Techniques

The same processes and natural laws that operated in the past are operating at present - the present is the key to the past.

is the principle of ____.

Who realised the observable geologic processes would require vast amounts of time to produce the mountains and valleys that we see on Earth today.

The order of events or objects from first (oldest) to last (youngest):

What simple principles can be applied to determine relative age?

• Original horizontality and lateral continuity

• Superposition

• Inclusions and unconformities

• Correlation of rock units and fossils

The age of events or objects, expressed as a number or numbers:

How is numerical age determined?

• Using radiometric dating

• Determining how much radioactive decay of a specific element has occurred since a rock unit formed or an event occurred.

• Inclusions and unconformities

• Correlation of rock units

Surfaces separating successive rock layers (beds):

Body of rock of considerable thickness with recognisable characteristics allowing it to be distinguished from adjacent rock layers:

Beds of sediment deposited in water formed as horizontal or nearly horizontal layers:

Within an undisturbed sequence of sedimentary or volcanic rock, layers get younger from bottom to top.