composition of the earth's atmosphere

Question 1

earth’s current composition

Answer 1

nitrogen - 78%
oxygen - 21%
other gases - 1%

Question 2

what was stage 1

Answer 2

volcanic activity

Question 3

how did volcanic activity shape the earth’s atmosphere

Answer 3

-released CO2, H2O vapour, methane
-little to no oxygen

Question 4

what was stage 2

Answer 4

cooling and oceans form

Question 5

how did cooling and oceans form, form the atmosphere

Answer 5

-water vapour condensed to form oceans
-CO2 dissolved in oceans –> formed carbonates –> reduced CO2 in air

Question 6

what was stage 3

Answer 6

photosynthesis begins

Question 7

how did photosynthesis beginning form the atmosphere

Answer 7

-algae and plants —>photosynthesis —> produced oxygen and removed CO2

Question 8

what was stage 4

Answer 8

formation of the ozone layer

Question 9

how did formation of the ozone layer form the atmosphere

Answer 9

O2 –> O3 (ozone), which blocks Uv radiation —> life on land develops

Question 10

timeline

Answer 10

-atmosphere formed from gases released by volcanoes
-earth cooled, evaporated and seas were formed
-early bacteria carried out photosynthesis