Eons
What are eons divided into?
Eras
How many eras are there in Earth's history?
Three
How many periods are in Earth's history?
Twelve
What is the smallest division of time in a geologic timescale?
Epoch
How old is the Earth?
4.6 billion years old
What are the 2 major eons?
What are eras divided into?
Periods
What are periods divided into?
Epochs
What epoch do we live in today?
Holocene
Why do we have only a little information about Earth's oldest rocks?
They have been eroded, buried, or melted.
What is the time period of the Precambrian Eon?
4.5 billion years to 500 million years
What are the eras of Earth's history in order from oldest to youngest?
Paleozoic, Mesozoic, Cenozoic
What are the three most popular periods in order from oldest to youngest?
Triassic, Jurassic, Cretaceous
If the geologic timeline was a chapter book what would epochs represent?
The lines or sentences.
What do rock and fossil records provide?
Evidence of change over time.
What is the time period of the Phanerozoic Eon?
500 million years to present
What is the most popular era?
Mesozoic Era
What periods do humans live in today?
Quaternary
About how many epochs are in the Phanerozoic Eon?
17
Why are divisions of the geologic time scale not equal?
The divisions are based on major events and changes in Earth's history.
In what eon did photosynthesis first occur in?
Archean Eon
Why does the Precambrian eon not have any eras?
We have very limited information about it so we leave it as one big eon.
In what period does the Age of Mammals exist?
Paleogene
How many years ago did the Holocene begin?
If all of Earth's history was squeezed into a 12 hour period how many hours would the Precambrian time take up?
10 hours and 30 minutes