questions 2

Question 1

what 2 elements were made when the universe cooled after the Big Bang?

Answer 1

H and He

Question 2

how are heavier elements than Fe made?

Answer 2

neutron capture and supernova

Question 3

what is accretion?

Answer 3

rocky planet formation

Question 4

what heated up the earth during formation?

Answer 4

radioactive decay

Question 5

what forms most of the mantle?

Answer 5

Si

Question 6

how old is earth?

Answer 6

4.5 Ga

Question 7

how was the moon formed?

Answer 7

collision with the planetary embryo

Question 8

where do oceans and the atmosphere come from?

Answer 8

outgassing of volatiles

Question 9

2 abundant gases in the early atm

Answer 9

CO2 and N2

Question 10

how old is the first proposed evidence for life on earth?

Answer 10

3.8 Ga

Question 11

how old are the oldest fossils fo life?

Answer 11

3.5-3.3 Ga

Question 12

what evidence supports sea floor spreading?

Answer 12

symmetric magnetic reversal either side of the mid Atlantic ridge

Question 13

what is rifting?

Answer 13

the process of continents splitting apart

Question 14

name of the ancient bits of continental crust

Answer 14

cratons

Question 15

what co-existing gases represent disequilibrium in the atm?

Answer 15

O2 and CH4

Question 16

what gas dominates the atmospheres of Mars and Venus?

Answer 16

CO2

Question 17

what does the Gaia hyp propose is being regulated by life?

Answer 17

atm

Question 18

what is the habitable zone?

Answer 18

the distances from a star compatible with liquid water

Question 19

how much less luminous was the sun when earth first formed?

Answer 19

30%

Question 20

what kept the early earth warm and so allowed liquid water on the surface?

Answer 20

higher amounts of CO2, lower albedo and higher amounts of CH4

Question 21

what process removes CO2 from the atm?

Answer 21

silicate weathering

Question 22

what counteracts the steady brightening of the sun?

Answer 22

accelerated silicate weathering

Question 23

when were the first stromatolites?

Answer 23

3.5 Ga