Geological DatingGeological Dating

Relative DatingRelative Dating

Relative dating is used to determine the Relative dating is used to determine the age of something based on it’s position age of something based on it’s position according to other things. according to other things.

It tells if an object is older or younger It tells if an object is older or younger than another object by using the Principle than another object by using the Principle of Superposition.of Superposition.

Principle of SuperpositionPrinciple of Superposition

This principle states that younger rock This principle states that younger rock layers will be on top of older rock layers.layers will be on top of older rock layers.

Absolute DatingAbsolute Dating

Absolute dating is used by geologists to Absolute dating is used by geologists to determine the actual age of a material. It determine the actual age of a material. It can be achieved through the use of can be achieved through the use of historical records and through the historical records and through the analysis of biological and geological analysis of biological and geological patterns. patterns.

Radioactive DecayRadioactive Decay

Naturally-occurring radioactive materials Naturally-occurring radioactive materials break down into other materials at known break down into other materials at known rates. rates.

Each radioactive isotope has its own Each radioactive isotope has its own unique unique half-lifehalf-life. A half-life is the . A half-life is the time it time it takes for half of the parent radioactive takes for half of the parent radioactive element to decayelement to decay to a daughter product. to a daughter product.

Geologic ColumnGeologic Column

The geologic column is an ideal The geologic column is an ideal sequence of rock layers that contains all sequence of rock layers that contains all the known fossils and rock formations on the known fossils and rock formations on Earth.Earth.

This is done by combining the This is done by combining the information from all the known information from all the known undisturbed rock sequences around the undisturbed rock sequences around the world.world.

Index FossilIndex Fossil

Index Fossils lived during a relatively Index Fossils lived during a relatively short but well-defined time span. This short but well-defined time span. This allows scientist to determine the age of allows scientist to determine the age of the rocks these fossils are found in.the rocks these fossils are found in.

An example is a Phacops from the An example is a Phacops from the Trilobite genus. They lived 400 million Trilobite genus. They lived 400 million years ago. So the rock layers they are years ago. So the rock layers they are found in can be dated at about 400 found in can be dated at about 400 million years.million years.

TrilobiteTrilobite

Types of FossilsTypes of Fossils

True Form Fossils – Fossils of the actual True Form Fossils – Fossils of the actual animal or body part.animal or body part.

Mold Fossils – Fossils made of the imprint of Mold Fossils – Fossils made of the imprint of the animal or body part.the animal or body part.

Cast Fossils – Fossils from a mold that has Cast Fossils – Fossils from a mold that has been filled in.been filled in.

Trace Fossils – Nests or gastroliths that were Trace Fossils – Nests or gastroliths that were used by animals but not the animal itself.used by animals but not the animal itself.