GEOLOGIC TIME
A giant calendar for Earth's 4.54 billion-year history
Geologic Time Scale
What is the largest formal division of geologic time?
Eon
How many periods are in the Paleozoic Era?
Six
Approximately how old is Earth according to modern scientific estimates?
About 4.54 billion years old.
If the Paleozoic is an era and the Permian is a period, what smaller division can be used to further divide the Permian?
Epoch
What process gradually built Earth from smaller materials?
Accretion
A fault cuts through several layers of sedimentary rock. Based on the principle of relative dating, which formed first: the rock layers or the fault?
The rock layers formed first; the fault is younger because it cuts through them.
In the geologic time scale, what sequence represents the hierarchy of time divisions from the broadest span of Earth's history to the most specific?
Eons → Eras → Periods → Epochs → Ages
What are the two ancient supercontinents that formed during the Proterozoic Eon?
Nuna/Columbia and Rodinia