Transcript Intro Geologic Time

GEOLOGIC TIME
“HISTORY OF THE EARTH”
LEARNING TARGETS
2a) I can distinguish between eons, eras,
periods, and epochs (DOK 1).
2b) I can identify the order of the eras and the
relative length of the eras (DOK 1).
2c) I can identify key geological and biological
features of the 4 different eras (DOK 1).
ESSENTIAL QUESTION
How is Earth’s history organized?
HOW OLD IS THE EARTH?
About 4.6 billion years old
HOW WAS EARTH FORMED?
13.7 bya-BIG Bang
 Explosion of atomic particles
 Cooling to form clouds of H and He
 Star formation Galaxies Clusters
4.5 bya-Solar System Forms
(Nebular Hypothesis)
 Solar nebula (rotating cloud dust/gas)
 Planetesimals (clumps formed in spinning disk of matter)
 8 Protoplanets & moons
 Early Earth impact moon
HOW IS EARTH’S HISTORY ORGANIZED?
Scientist use fossils and other clues to organize the events in
Earth’s history into a timeline.
Geologic time is organized into lengths of time based on life
forms present and events such as extinctions.
There are 5 mass extinctions that scientist know about
throughout history.
-Cretaceous-Tertiary (KT) extinction, 65 myaKilled the dinosaurs.
- Permian-Triassic (PT) extinction, 251 mya–
Killed about 95 % of all species.
WHEN WERE THE MASS EXTINCTION EVENTS?
Mass Extinction Event
Time Frame
(mya)
Types of Life Effected
Late/End Ordovician
443 mya
Many species of Trilobites, Brachiopods,
Graptolites, Echinoderms and Corals
Late/End Devonian
354 mya
Many marine families on tropical reefs,
Corals, Brachiopods, Bivalves, Sponges
Late/End Permian
248 mya
57% of all marine families, Trilobites,
Eurypterids, Mollusca devastated along
with Brachiopods. Many vertebrates
Late/End Triassic
206 mya
Mollusca phyla, Sponges, marine
vertebrates, large amphibians, many
mammal-like reptiles
Late/End Cretaceous
65 mya
Ammonites, Marine reptiles, dinosaurs,
pterosaurs, microscopic marine plankton,
Brachiopods, bivalves, and echinoderms
WHAT ARE THE DIVISIONS OF GEOLOGIC TIME?
Geologic time is divided into:
Eons
Eras
Periods
Epochs
WHAT ARE THE FOUR ERAS?
1. Precambrian Era (4600-544 mya) Longest
era, bacteria-like life forms present.
WHAT ARE THE FOUR ERAS?
2. Paleozoic Era (544-248 mya) Broken down
into 7 periods. 1st plants, fish, reptiles,
amphibians, and insects.
WHAT ARE THE FOUR ERAS?
3. Mesozoic Era (248-65 mya) Broken down into 3
periods. Era of the dinosaurs and first mammals
and birds.
WHAT ARE THE FOUR ERAS?
4. Cenozoic Era (65 mya – present) 2 periods,
mammals are abundant. Homo sapiens
evolve.
CHECK FOR UNDERSTANDING
Write a paragraph that covers the following:
How Earth was formed
How Earth’s history is organized
The divisions of time that is used for Earth’s
history
A summary of the four eras