W2 - Geological Time Scale

Question 1

What is an eon?

Answer 1

Largest geochronologic time unit
Differentiated by large events (ex: extinction events)
4 of them

Question 2

What is the Precambrian?

Answer 2

Informal unit of time describing the Hadean, Archean, and Phanerozoic eons
Occurred before the Cambrian period (explosion of life)
Most of Earth’s history happened here
Little is known about its history
Some life, but very basic

Question 3

What is the Phanerozoic eon?

Answer 3

From 541 mya to today
Makes up 12% of Earth’s history (smallest chunk)

Question 4

What is the Proterozoic eon?

Answer 4

From 2.5bya-541mya
Makes up 42% of Earth’s history (largest chunk)

Question 5

What is the Archean eon?

Answer 5

From 4-2.5bya
Makes up 33% of Earth’s history

Question 6

What is the Hadean eon?

Answer 6

From 4.54-4bya
Makes up 13% of Earth’s history

Question 7

What is an era?

Answer 7

Second largest geological time unit
10 of them

Question 8

What are the 3 Phanerozoic eras?

Answer 8

1) Paleozoic era = 541-252mya
2) Mesozoic era = 252-66mya
3) Cenozoic era = 66mya-present

Question 9

What is a period?

Answer 9

Third largest geochronic time unit
22 of them

Question 10

What are the 3 periods in the Cenozoic era?

Answer 10

1) Paleogene period = 66-23mya
2) Neogene period = 23-2.6mya
3) Quaternary period = 2.6mya-present