the atmosphere - the atmosphere

Question 1

what is in the atmosphere today?

Answer 1

• around 78% is nitrogen
• around 21% is oxygen
• other small proportions of other gases (e.g carbon dioxide, water vapour, and noble gases such as argon)

Question 2

how long have gases in atmosphere stayed pretty constant?

Answer 2

200 million years

Question 3

how old is earth? and what does this mean?

Answer 3

4600 million years old which mean scientists cannot be certain about the early atmosphere

Question 4

what do scientists think happened in the first billion years of earth? what did this release?

Answer 4

intense volcanic activity where the volcanos released the gases that formed the atmosphere. one of these being water vapour

Question 5

what happened to water vapour from billions of years of years ago?

Answer 5

as earth cooled, the water vapour condensed to form the oceans

Question 6

what did volcanoes released the gases huge amounts of? what did earths atmosphere consist of in early stages?

Answer 6

carbon dioxide. in this early stage, atmosphere consisted mainly of carbon dioxide with little or no oxygen

Question 7

what was earth’s atmosphere then similar to?

Answer 7

Mars and Venus today

Question 8

what else did volcanoes released the other than carbon dioxide?

Answer 8

• other noble gases including nitrogen which gradually built up in the atmosphere
• small amounts of methane and ammonia

Question 9

what did early earth atmosphere consist of?

Answer 9

mainly carbon dioxide with a small but increasing amount of nitrogen

Question 10

differences between early atmosphere and the atmosphere today

Answer 10

• early contained large amounts of carbon dioxide where as today it only contains a small amount
• early atmosphere contained very little oxygen where as today 21% of the atmosphere is oxygen

Question 11

what happened to carbon dioxide when water vapour condensed to form oceans?

Answer 11

some carbon dioxide dissolved in the oceans to form a weak acid which reacted with minerals in the sea to form precipitates. over time this formed sediments of carbonate rock on the sea bed

Question 12

what was some of the carbon dioxide in the sea used to make?

Answer 12

corals and shells of organisms such as mussels. when these died, they formed the sedimentary rock limestone. this also removed carbon dioxide from the atmosphere

Question 13

where did oxygen come from?

Answer 13

photosynthetic algae first evolved in the oceans. photosynthesis produced oxygen which entered the atmosphere. over the billion years, plants involved increasing the amount of oxygen in the atmosphere. at some point the levels of oxygen reached a point where animals could evolve

Question 14

how did carbon dioxide levels reduce?

Answer 14

• the carbon can be trapped in fossil fuels and again caused levels of carbon dioxide in atmosphere to fall
• dissolved in the oceans
• used in photosynthesis