origin of earth

Question 1

eons

Answer 1

largest time division

Question 2

Eons determined by

Answer 2

major changes in the Earth

Question 3

Most recent Eon started with

Answer 3

started with the proliferation of multicellular animals = Phanerozoic Eon

Question 4

what Three Eons make up what was previously know as the Precambrian Period

Answer 4

1) Proterozoic (most recent)
2) Archean
3) Hadean

Question 5

hadean eon started

Answer 5

4.5 billion years ago

Question 6

during the hadean eon

Answer 6

Earth & planets formed from dust and gasses surrounding the sun
Electromagnetic forces & Gravity gathers dust into large lumps, called planetisimals
collisions between lumps made lots of heat, made earth molten
Steam atmosphere formed
temperature of earth cooled and first rocks formed

Question 7

Heavy elements in planets suggest

Answer 7

dust/gas from supernova

Question 8

how do other solar systems form

Answer 8

They form in diffuse nebulae

Question 9

planetisimals

Answer 9

Electromagnetic forces & Gravity gathers dust into large lumps

Question 10

how did the steam atmosphere form from hadean eon

Answer 10

from light elements & water vapor from comet

Question 11

oldest earth rock

Answer 11

3.8 billion years old

Question 12

oldest meteorites and lunar rocks

Answer 12

4.5 billion years old

Question 13

what destroyed all Earth rocks older than 3.8 by

Answer 13

erosion and plate tectonics

Question 14

the Archean eon start and end

Answer 14

3.8 (oldest rocks) - 2.5 bya first life

Question 15

Archean eon

Answer 15

Began with formation of solid rock
Volcanoes added heavier gasses to atmosphere (CO2, N2)
Water condensed
oceans formed
First life appeared on Earth (most primitive, most archaic)

Question 16

Archean atmosphere

Answer 16

(CO2, H2O, N2- still in modern atmo)
(CO, H2S, HCl- rare in modern)
no free oxygen or ozone

Question 17

oldest fossil

Answer 17

3.5 byo

Question 18

life must have evolved before there was

Answer 18

free oxygen because oxygen breaks down macromolecules, and if they couldn’t form, neither could living cells

Question 19

BIFS

Answer 19

banded iron formation

Question 20

BIFS time line (start, peak, end)

Answer 20

began forming about 3.5 bya = 1st free O2
reached peak about 2.5 bya
deposition ended about 1.8 bya

Question 21

early Archean sediment

Answer 21

dark colored, unoxidized, deposited before free oxygen

Question 22

oxidized (rusted) sediment appears in the

Answer 22

Proterozoic Eon

Question 23

what was Indirect (non-fossil) evidence for the presence of

Cyanobacteria – 3.5 bya

Answer 23

Banded iron formation

Question 24

BIFS created

Answer 24

iron dissolves in anaerobic water
when iron bonds to O2 it becomes solid
the solid sinks to the ocean floor is deposited in layers
Layers of oxidized iron are red

Question 25

what likely happened to form BIFS

Answer 25

O2 made by cyanobacteria at ocean surface
Toxic O2 removed by iron until iron runs out
Then O2 builds up & kills off most cyanobacteria
O2 levels drop
Unoxidized dark sediments deposited

Question 26

Why are BIFs Banded?

Answer 26

When runoff added more Fe to the water the entire process stared over again. Iron has to move back in and cyanobacteria have to grow back

Question 27

Proterozoic eon time

Answer 27

2.5-.54 billion years ago

Question 28

what happened in Proterozoic

Answer 28

end of BIFS (consistent free oxygen)
Cyanobacteria resistant to oxygen poisoning by 1.8 billion years ago (early proterozoic)
Spontaneous formation of new cells no longer possible (because of free oxygen)
Diversification of bacteria
First Eukaryotes appear ( protists)
Ediacaran fauna appear (soft invertebrates)

Question 29

Phanerozoic eon time

Answer 29

.54 bya- present

Question 30

Phanerozoic eon

Answer 30

Began with the Cambrian explosion of multicellular animal species and complex land plants