The Atmosphere

Question 1

what was the earths surface and sky like for the first billion years or so (phase 1)

Answer 1

• the ground was originally molten

- there was almost no atmosphere

Question 2

what happened after the earth cooled in phase 1

Answer 2

• the surface cooled, forming a thin crust

- but volcanoes kept erupting, releasing gases from inside the earth

Question 3

what kind of gasses did volcanoes spit out in phase 1

Answer 3

• the degassing released mainly carbon dioxide

- but also steam, methane and ammonia

Question 4

what was the earth’s atmosphere like at the end of phase 1

Answer 4

• the earth’s atmosphere was composed of mainly CO2 and water
• there was very little oxygen

Question 5

how were oceans formed and in what stage did they form

Answer 5

• oceans were formed in stage 1

- and it was from the cooling and condensation of water vapour in the atmosphere

Question 6

what happened to a lot of the early CO2 in the atmosphere in phase 2

Answer 6

it dissolved into the oceans

Question 7

how was nitrogen gas (N2) put into the atmosphere in phase 2

Answer 7

• in two ways
• it was formed by ammonia reacting with oxygen
• and released by bacteria denitrifying

Question 8

why was the amount of N2 in the atmosphere increased through out phase 2

Answer 8

• because N2 isnt very reactive
• so it is produced and stays in the atmosphere without being broken down
• allowing it to accumulate

Question 9

what phase were green plants beginning to evolve over the earth and what did they do

Answer 9

• they were evolving during phase 2
• and they were photosynthesising
• meaning they were absorbing CO2 from the atmosphere and producing O2

Question 10

what is the effect of plants evolving in phase 2 (how did they change the atmosphere)

Answer 10

• the amount of O2 in the air gradually built up

- and a lot of the CO2 was locked up in fossil fuels and sedimentary rocks

Question 11

what did the build up of oxygen in the air do to organisms in phase 3

Answer 11

• it killed off early organisms that couldnt tolerate it

- but it allowed for the evolution of more complex organisms that made use of the oxygen

Question 12

what did the production of oxygen by plants from phase 2 create in phase 3

Answer 12

• the oxygen created the o zone layer (O3)
• which blocked harmful rays from the sun
• and enabled even more complex organisms to evolve

Question 13

how much CO2 is in the air in phase 3

Answer 13

barely any

Question 14

what is the test for oxygen in the atmosphere

Answer 14

checking if the gas in the atmosphere will relight a glowing splint

Question 15

what are the simple descriptions of each phase of the creation of the atmosphere

Answer 15

• phase 1, volcanoes gave out steam and CO2
• phase 2, green plants evolved and produced oxygen
• phase 3, o zone layer allows for the evolution of complex animals

Question 16

when did the phases of the creation of the atmosphere each occur

Answer 16

• phase 1 was the first billion years of earth
• phase 2 was the next two billion years
• phase 3 has been the last billion years or so