Geological Time
This is the largest unit of geologic time.
The remains or traces of ancient life.
What is a Fossil?
This law states older layers are on bottom.
What is the law of superposition?
This type of dating gives a numerical age.
What is absolute dating?
Life first appeared as this type of organism.
What are single-celled organisms?
These are grouped together to form an era.
What are Periods?
These fossils show movement like footprints or burrows.
What are trace fossils?
Rocks are originally laid down in this position.
What is horizontal (original horizontality)?
This method uses radioactive isotopes.
What is radiometric dating?
This era included dinosaurs.
What is the Mesozoic?
This era is known as “age of mammals.”
What is the Cenozoic?
Fossils used to determine the relative age of rock layers.
What are index fossils?
A feature that cuts through rock is this relative age.
What is younger?
Time it takes for half of a substance to decay.
What is half-life?
This event wiped out many species at once.
What is a mass extinction?
Earth formed approximately this many years ago.
What is 4.6 billion years ago?
This process fills pores with minerals to form fossils.
What is mineral replacement?
Gaps in the rock record caused by erosion are called this.
What are unconformities?
This method uses tree rings.
What is dendrochronology?
Plants appeared on land during this era.
What is the Paleozoic?
These divide periods into smaller units.
What are epochs?
This process changes the mineral structure due to heat/pressure.
What is recrystallization?
Matching rock layers across regions is called this.
What is correlation?
This dating method is used for organic material.
What is carbon-14 (radiocarbon dating)?
This principle says the present explains the past.
What is uniformitarianism?