Eons
Eras
Basic Understanding
Extinctions
Fossil Record
100
This is the largest division of time used on the geologic time scale.
What is an eon?
100
This division of time is shorter than an eon, but longer than an epoch.
What is an era?
100
Scientists estimate Earth is about this old.
What is 4.6 Billion years?
100
This is an event where many species die out in a short period of time.
What is a mass extinction?
100
Fossils are the preserved remains or impressions of...
Plants and animals.
200
True or false: There are only four eons total in Earth's history.
True
200
This era is known as the Age of Dinosaurs.
What is the Mesozoic Era?
200
This tool organizes Earth's history and life over time.
What is the Geologic Time Scale?
200
The extinction that killed the dinosaurs was caused by this.
What is an asteroid impact?
200
This law states that lower rock layers are older than layers above them.
What is the Law of Superposition?
300
We currently live in this eon.
What is the Phanerozoic Eon?
300
This era is known as the Age of Mammals.
What is the Cenozoic Era?
300
Put these in order from longest to shortest: era, eon, epoch.
Eon -> Era -> Epoch
300
This extinction was the largest in Earth's history.
What is the Permian-Triassic Extinction?
300
This type of dating gives an exact age using radioactive materials.
What is absolute dating?
400
The first life on Earth appeared during this eon.
What is the Archean Eon?
400
The era in which humans appeared
What is the Cenozoic Era?
400
Scientists divide Earth's history into sections mainly to make it _________________________.
Easier to study and understand.
400
This led to the Permian-Triassic extinction, the largest loss of life Earth has ever seen.
What is a volcanic eruption?
400
This type of dating relies on the Law of Superposition to compare rock layers in order to determine the age of a fossil or artifact.
What is Relative Dating?
500
This eon saw oxygen build up in the atmosphere and multicellular life begin.
What is the Proterozoic Eon?
500
This era includes the Cambrian Explosion and a huge increase in biodiversity.
What is the Paleozoic Era?
500
This division of time on the Geologic Time Scale covers the longest amount of time.
What is an Eon?
500
Mass extinctions are important because they...
Change which species survive and evolve.
500
These fossils lived for a short time but are found in many places, making them useful in relative dating.
What are index fossils?