Geological Time Scale

Question 1

Earth’s history is divided into units of time that make up a ?

Answer 1

geological time scale

Question 2

We live during the ? Eon

Answer 2

Phanerozoic Eon began 541 million years ago 12% of Earth’s history

Question 3

Eons

Answer 3

longest subdivisions; based on abundance of fossils.

Question 4

Hadean, Archean, and Proterozoic are sometimes informally referred to ?

Answer 4

as the “Precambrian”

Question 5

Eras

Answer 5

marked by significant worldwide changes in the types of fossils present in rock.

Question 6

Phanerozoic Eon is broken into three eras:

Answer 6

Paleozoic, Mesozoic, Cenozoic.

Question 7

Periods

Answer 7

Periods – divided eras based on types of existing life globally at a particular time

Question 8

Epochs

Answer 8

divided periods characterized by differences in life forms.

Question 9

Why is the GTS useful?

Answer 9

makes showing Earth’s History easier.

It is a clear visual record of the life forms and geologic events .

Question 10

When does the geological time scale begin?

Answer 10

Geological time begins with a long span of time called Precambrian Time

Question 11

Earth formed roughly ? years ago.

Answer 11

4.6 billion

Question 12

Precambrian Time (4.6 billion-544 million years ago)

Answer 12

first several hundred million years atmosphere, oceans and continents began to form.
very few fossils remain
Precambrian rocks have been buried, causing fossils to be changed by heat and pressure
organisms lacked hard parts

Question 13

Earliest life form to appear

Answer 13

cyanobacteria added oxygen through photosynthesis.

Question 14

Paleozoic era Phanerozoic

Answer 14

oldest era divided into six periods

Question 15

Mesozoic era Phanerozoic

Answer 15

middle era divided into three periods

Question 16

Cenozoic era Phanerozoic

Answer 16

youngest era divided into two periods.

Question 17

Early Paleozoic consists of the Cambrian and Ordovician periods.

Answer 17

Age of Invertebrates
continents covered by large, shallow inland seas
no life on land; Ordovician period ended with mass extinction

Question 18

Cambrian Explosion

Answer 18

A period during early Paleozoic Era, most of the major groups of animals first appear in the fossil record.
sudden increase in oxygen to near-modern levels in ocean created this event.

Question 19

Middle Paleozoic consists of Silurian and Devonian periods

Answer 19

Age of Fish
some invertebrates on land (cockroaches/dragonflies)
continents collided to form mountain ranges

Question 20

Late Paleozoic consists of Carboniferous and Permian periods

Answer 20

Age of Amphibians (reptiles from amphibians)
continental collisions => formation of Pangaea
largest mass extinction occurred, reason under debate

Question 21

Mesozoic Era 245 million to 65 million years ago

Answer 21

Age of the Reptiles
Triassic, Jurassic and Cretaceous periods
dinosaurs dominated, small mammals and birds
flowering plants (angiosperms) appeared
Pangaea separated into continents, oceans form
mass extinction from large meteorite impact

Question 22

Cenozoic Era 65 million to now

Answer 22

Early in Tertiary period, mountains like Himalayans and Alps are formed.
new grasses flowering plants dominated land
mammals evolve
Homo sapiens or humans appeared about 400,000 years ago
We => Quaternary period