The Archaen

Question 0

What event/period marked the beginning of the Archean eon?

Answer 0

The Late Heavy Bombardment

Question 1

Time period of the Archean eon:

Answer 1

3.8-2.5 Ga

lasted 1.3 billion years

Question 2

What eon did life originate in?

Answer 2

Archaen

Question 3

3 Important events of the Archaen:

Answer 3

End of Late Heavy Bombardment, origin of life, first accretion of continents.

Question 4

Archean Tectonics were different from current tectonics in what ways?

Answer 4

More volcanism/abundant magma, faster moving plates, more heat in system, smaller cratons

Question 5

Where are Archean rocks typically found?

Answer 5

exposed shield area of cratons

Question 6

How much of exposed Precambrian rock is Archean (instead of Proterozoic)?

Answer 6

22%

Question 7

What geologic features do not appear in Archean rock that normally appears in sedimentary rock?

Answer 7

Epicontinental seas, carbonate rocks, broad continental shelves

Question 8

Archean rock types:

Answer 8

Greenstone 20%, granite-gneiss complexes 80%

Question 9

what is a greenstone association?

Answer 9

Metamorphosed underwater volcanics and sediment derived from weathering of volcanics, usually in a syncline formation with 3 layers

Question 10

What do greenstone belts represent?

Answer 10

• successive phases of cratonic accretion
• Suturing island arcs together to form early cratons
• A stage before Proterozoic craton-craton accretion

Question 11

How old is Canadian continental crust?

Answer 11

4.04 Ga

Question 12

How big are cratons at the end of the Archean relative to their current size?

Answer 12

30-40%

Question 13

What was the atmosphere of the Archean like?

Answer 13

very low oxygen, lots of acidic rain from volcanism

Question 14

What is Abiogenesis?

Answer 14

the formation of life from lifelessness

Question 15

What made abiogenesis possible in the Archean that is now not the case? (why can life not evolve from lifelessness now?)

Answer 15

Very low free oxygen in the atmosphere during the Archean made abiogenesis possible.

Question 16

How long ago is it believed that life first arose?

Answer 16

4 billion years approximately… end of hadean or early Archean.

Question 17

lineages of individuals that evolve through descent with modification describes?

Answer 17

life

Question 18

What were the first super continents?

Answer 18

valbara and ur

Question 19

What was Archean life probably like?

Answer 19

prokaryotic, no cellular respiration/anaerobic, probably chemo autotrophic

Question 20

When did eukaryotes first appear?

Answer 20

2.7 Ga in chemical trace fossils

Question 21

What created the first oxygen-rich atmosphere?

Answer 21

Cyanobacteria evolved a non-cyclic photosynthesis that released oxygen.

Question 22

How old are stromatolites?

Answer 22

3.45 Ga

Question 23

What is the RNA world hypothesis?

Answer 23

life first transmitted genetic information with RNA that later evolved to DNA.

Question 24

Why do living cells need a container?

Answer 24

to protect from outside chemical reactions, keep inside chemistry materials concentrated or dilute as needed

Question 25

The Miller-Urey experiment refers to

Answer 25

the synthesis of amino acids in water using electricity as a catalyst.

Question 26

greenstone accretion occurred before the later process of

Answer 26

Proterozoic craton-craton accretion