- A scale that subdivides the 4.5-billion-year history of Earth into many different units and provides a meaningful time frame within which the events of the geologic past are arranged.

EON ERA PERIOD EPOCH

PHANEROZOIC

CENOZOIC

QUATERNARY HOLOCENE

PLEISTOCENE

TERTIARY PLIOCENE

MIOCENE

OLIGOCENE

EOCENE

PALEOCENE

MESOZOIC CRETACEOUS “Age of Reptiles”JURASSIC

TRIASSIC

PALEOZOIC

PERMIAN “Age of Amphibians”CARBONI-

FEROUSPENNSYLVANIAN

MISSISSIPPIAN

DEVONIAN “Age of Fishes”SILURIAN

ORDOVICIAN “Age of Invertebrates”CAMBRIAN

PRECAMBRIAN

EON• Two or more geological eras

form an Eon, which is the largest division of geologic time, lasting many hundreds of millions of years.

PRECAMBRIAN- means: "before the Cambrian

period." - From 4.6 billion years ago to the

beginning of the Cambrian Period (about 570 mya)

- It is actually composed of three Eons: HADEAN, ARCHEAN, AND PROTEROZOIC.

- The Precambrian represents about 88 % of the Geologic Time.

HADEAN EON• Hadean ("Hades-like") Eon. • 4.5 to 3.9 billion years ago• During this era the surface of the Earth was

like popular visions about Hades: oceans of liquid rock, boiling sulfur, and impact craters everywhere.

HADEAN EARTH("Hades-like")

ARCHEAN EON• Archean ("Ancient" or "Primitive") Eon.• 3.9 to 2.5 billion years ago• This eon began about a billion years after the

formation of the earth, and things have changed a lot! Mostly everything has cooled down. Most of the water vapor that was in the air has cooled and condensed to form a global ocean.

ARCHEAN EARTH("Ancient" or "Primitive")

The first life forms evolve - one celled organisms.

The cyanobacteria or "blue-green algae," have left a fossil record that extends far back into the Precambrian - the oldest cyanobacteria-like fossils known are nearly 3.5 billion years old, among the oldest fossils currently

known.

PROTEROZOIC EON

• 2.5 billion years ago to 540 mya• First multicellular life: colonial

algae and soft-bodied invertebrates appear. Oxygen build-up in the Mid-Proterozoic.

PROTEROZOIC EARTH("Early Life")

PHANEROZOIC EON- Is derived from Greek words

meaning visible life.- It is an appropriate description

because the rocks and deposits of the Phanerozoic eon contain abundant fossils that document major evolutionary trends.

- It is composed of three eras: PALEOZOIC, MESOZOIC, and CENOZOIC.

ERA• Two or more geological

periods comprise an era, which is hundreds of millions of years in duration.

PALEOZOIC ERA• Paleo = ancient zoe = life• 540 to 248 mya • At its beginning, multicelled animals

underwent a dramatic "explosion" in diversity, and almost all living animal phyla appeared within a few millions of years.

• At the other end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species.

MESOZOIC ERA

• Meso = Middle zoe = life• "THE AGE OF REPTILES"• from 248 million to 65 million

years ago.

• The continents were jammed together at the beginning of the Mesozoic Era, forming the supercontinent of Pangaea, but would start breaking apart toward the middle of the Mesozoic Era.

CENOZOIC ERA• Ceno = recent zoe = life• 65 Million Years to the Present• sometimes called the “Age of

Mammals”

PERIODThe period is the basic unit of geological time in which a single type of rock system is formed, lasting tens of millions of years.

PALEOZOIC ERAPERMIAN

CARBONIFEROUS PENNSYLVANIAN

MISSISSIPPIAN

DEVONIAN

SILURIAN

ORDOVICIAN

CAMBRIAN

MESOZOIC ERA

CRETACEOUS

JURASSIC

TRIASSIC

CENOZOIC ERA

•QUATERNARY•TERTIARY