the geologic time scale (chronological order)

GEOLOGIC TIME SCALEJason John V. Tabujara BSEdGS IV

START

WHAT IS A GEOLOGIC TIME SCALE?

System of chronologic measurement relating to stratigraphy to time that is used by geologist and other earth scientists

INTRODUCTION TO CONCEPT:

The period is the basic unit of geological time in which a single

type of rock system is formed. Two or more periods comprise a

geological Era. Two or more Eras form an Eon, the largest division of

geologic time. Some periods are divided into epochs.

The major periods in the geologic history of the Earth are

(mya=million years ago):

INTRODUCTION TO CONCEPT:

EonEra

PeriodEpoch

Period

Era Period

PRECAMBRIAN:Hadean, Archean and Proterozoic Eons

PRECAMBRIANHadean Eon4.6 to 3.9

billion years ago

“Rockless Eon" - The solidifying of

the Earth's continental and oceanic crusts.

Archeozoic Eon(Archean)3.9 to 2.5

billion years ago

"Ancient Life" The first life forms evolve

Proterozoic Eon 

2.5 billion years ago

to 540 mya*multi-celled, animals appear, including sponges.

*Single supercontinent called Rodinia.

*First multicellular life: colonial algae and soft-bodied invertebrates appear.

PHANEROZOIC EON:Paleozoic Era

PHANEROZOIC EONPaleozoic Era:

The Paleozoic is bracketed by two of the most important events in the

history of animal life. 1. Multicellular animals went

dramatic diversity explosion2. Largest Mass extinction of mostly

90% of marine organisms

PALEOZOIC ERACambrian Period

"The Age of Trilobites"540 to 500 mya

PALEOZOIC ERA

Ordovician Period505 to 438 mya

PALEOZOIC ERA

Silurian Period438 to 408 mya

PALEOZOIC ERA

Devonian Period"The Age of Fishes"

408 to 360 mya

PALEOZOIC ERA

Carboniferous Mississippian Period

360 to 325 mya

PALEOZOIC ERA

Carboniferous Pennyslvanian Period

325 to 280 mya

PALEOZOIC ERA

Permian Period"The Age of Amphibians"

280 to 248 mya

PHANEROZOIC EON:Mesozoic Era

PHANEROZOIC EONMesozoic Era:

Many of the Old life forms had just gone extinct in the Permian

Extinction, the world’s largest mass extinction.

Depleted state was followed by an explosion of new life forms such as

dinosaurs, mammals, birds and flowering plants

MESOZOIC ERA

Triassic Period248 to 208 mya

MESOZOIC ERA

Jurassic Period208 to 146 mya

MESOZOIC ERA

Cretaceous Period146 to 65 mya

PHANEROZOIC EON:Cenozoic Era

PHANEROZOIC EONCenozoic Era:

The most recent Era of the three major subdivisions of animal history.Also called as the Age of Mammals65.5 million years ago to present

REFERENCES:

TARBUCK AND LUTGENS