Geologic History Vocabulary

The branch of science involving the physical composition and history of the planet. 

• Geology 
• Biology 
• Math 
• Chemistry 

The system of time measurement involving the formation of and changes of the Earth. 

• Index Fossil 
• Geologic Time Scale 
• Law of Superposition 
• Preserved Fossil 

Very large division of geologic time; usually referred to as the longest division of time. 

• Era
• Epoch 
• Eon 
• Period

Subdivision of an eon (Paleozoic, Mesozoic, Cenozoic)

• Era 
• Period
• Epoch 
• Eon 

Subdivision of an Era

• Era 
• Eon 
• Period 
• Epock

Subdivision of a period; shortest division of geologic time. 

• Eon 
• Era 
• Period 
• Epoch 

Occurs when a species( organism) dies out and no longer lives on the planet. 

• Extinction 
• Fossil 
• Epoch 
• Relative Age

Method of determining the age based on measuring radioactive elements (radiometric) 

• Radioactive Dating 
• Relative Age 
• Index Fossil 
• Law of Superposition 

Determination of the age of a rock based on the surrounding evidence 

• Radioactive Dating 
• Relative Age 
• Trace Fossil 
• Carbonized Fossil 

A common fossil found in many areas from a specific time; used to help identify the age of other formations. 

• Trace Fossil 
• Mold Fossil 
• Cast Fossil 
• Index Fossil