Transcript Geologic Time - Paramus Public Schools

Geologic Time
How is Earth’s geologic history classified?
We find no vestige of a
beginning,–no prospect of an
end.
- James Hutton
Geologic Time Scale
Record of Earth’s history from its origin
to the present
 Based on fossils found in rocks
 Used to correlate geologic events,
environmental changes and development
of life forms that are preserved in rocks

Geologic Time
 Eon
◦ Longest time unit
◦ Measured in billion of years
◦ Archean Eon, Proterozoic Eon, and
Phanerozoic Eon (Current)
Geologic Time
 Eras
◦ Measured in hundreds of millions to
billions of years
 Paleozoic Era – Wide variety of plants and
animals
 Mesozoic Era – Dinosaurs
 Cenozoic Era – Mammals, Humans develop
Geologic Time
 Periods
◦ Defined by the life forms that were abundant
or became extinct during the time in which
specific rocks were deposited
◦ Measured in terms of tens of millions of years
◦ Some are named for the geographic region in
which the rocks of that age were first
observed
Jurassic Period
Geologic Time
 Epoch
◦ Measured in millions of years to tens of
millions of years
◦ Groups of organisms used to distinguish
◦ Ex: Holocene Epoch, Pleistocene Epoch
Why study fossils?
Interpret Earth’s history
 Determine patterns and cycles to help
predict future events such as climatic
changes
 Locate energy resources (Petroleum
geologists locate oil)

Answer in NB:
Why do you think scientists know more
about the Cenozoic Era than they do
about the other eras? (Hint: Look at their
time frames)
 What eon, era, period, and epoch do we
live in?
