📍
The Composition and Evolution of the Earth’s
Atmosphere
Date: @July 2, 2023
Topic: The Composition and Evolution of the Earth’s Atmosphere
Recall Notes
How much nitrogen is present in For 200 million years the proportions of different gases in the atmosphere have been very similar to
todays atmosphere? what they were.
How much oxygen is present in Nitrogen - 4/5 or 80%
todays atmosphere?
Oxygen - 1/5 or 20%
Which gases are trace in todays
Carbon dioxide, water vapour, noble gases - trace
atmosphere?
The Earth was formed around 4.6 billions years ago and evidence for the early atmosphere is limited
Why is evidence for the early
due to the time scale of 4.6 billion years. One theory suggests that during the first billion years of the
atmosphere limited?
Earth’s atmosphere, volcanoes released carbon dioxide, water vapour and nitrogen and that these
Which gases did volcanoes gases formed in the early atmosphere. Water vapour condensed as the Earth cooled down and fell as
release? rain and oceans were formed. At this point the atmopshere may have been like that of Mars and Venus
as it consisted of CO2 and little/no oxygen. Volcanoes produced nitrogen which gradually built up and
What is the equation for
may have been small amounts of methane and ammonia. When the oceans formed CO2 could have
photosynthesis?
dissolved in the water and carbonates precipitated making sediments (and reducing the amount of
When did algae first produce
CO2).
oxygen?
Algae and plants produced the oxygen now present in the atmosphere via photosynthesis which can be
What decreased the amount of
represented by the equation:
CO2 and how?
How are limstone deposits
formed?
How is coal formed?
How is crude oil and natural gas
formed?
Algae first produced oxygen about 2.7 billion years ago and soon after O2 appeared in the atmosphere.
Over the next billion years plants evolved and the percentage gradually increase to a level so animals
could evolve.
Algae and plants decreased the percentage of CO2 via photosyntheis. It was also decreased by the
formation of sedimantary rocks and fossil fuels containing carbon.
Coal is classed as a sedimentary rock and was formed from thick deposits of plant material e.g. ancient
trees and ferns. When plants died in swamps they were buried, in the abscene of O2, and compressed
over millions of years.
Crude oil and natural gas were formed from plankton remains in mud and on the seabed. These
remains were covered by sediments and were compessed over millions of years. They are now found,
trapped under layers of rock.
Limestone deposits are formed when tiny shells and skeletons from marine organisms settle on the
ocean floor, get compacted, and undergo a process called lithification to become solid rock over a very
long time.
📌 SUMMARY: The modern atmosphere is made up of nitrogen, oxygen, CO2, water vapour and noble gases. The Earth was formed
4.6 billion years ago and evidence for the early atmosphere is difficult to find due to the long timescale. Volcanoes released CO2,
H2O and nitrogen. Water vapour condensed and formed rain and then oceans. Algae and plants produced the now present oxygen
via photosynthesis and also reduced the amount of CO2. Coal, crude oil, natural gas and limestone are all formed from
compressing plants and small organisms.
The Composition and Evolution of the Earth’s Atmosphere 1
The Composition and Evolution of the Earth’s
Atmosphere
Date: @July 2, 2023
Topic: The Composition and Evolution of the Earth’s Atmosphere
Recall Notes
How much nitrogen is present in For 200 million years the proportions of different gases in the atmosphere have been very similar to
todays atmosphere? what they were.
How much oxygen is present in Nitrogen - 4/5 or 80%
todays atmosphere?
Oxygen - 1/5 or 20%
Which gases are trace in todays
Carbon dioxide, water vapour, noble gases - trace
atmosphere?
The Earth was formed around 4.6 billions years ago and evidence for the early atmosphere is limited
Why is evidence for the early
due to the time scale of 4.6 billion years. One theory suggests that during the first billion years of the
atmosphere limited?
Earth’s atmosphere, volcanoes released carbon dioxide, water vapour and nitrogen and that these
Which gases did volcanoes gases formed in the early atmosphere. Water vapour condensed as the Earth cooled down and fell as
release? rain and oceans were formed. At this point the atmopshere may have been like that of Mars and Venus
as it consisted of CO2 and little/no oxygen. Volcanoes produced nitrogen which gradually built up and
What is the equation for
may have been small amounts of methane and ammonia. When the oceans formed CO2 could have
photosynthesis?
dissolved in the water and carbonates precipitated making sediments (and reducing the amount of
When did algae first produce
CO2).
oxygen?
Algae and plants produced the oxygen now present in the atmosphere via photosynthesis which can be
What decreased the amount of
represented by the equation:
CO2 and how?
How are limstone deposits
formed?
How is coal formed?
How is crude oil and natural gas
formed?
Algae first produced oxygen about 2.7 billion years ago and soon after O2 appeared in the atmosphere.
Over the next billion years plants evolved and the percentage gradually increase to a level so animals
could evolve.
Algae and plants decreased the percentage of CO2 via photosyntheis. It was also decreased by the
formation of sedimantary rocks and fossil fuels containing carbon.
Coal is classed as a sedimentary rock and was formed from thick deposits of plant material e.g. ancient
trees and ferns. When plants died in swamps they were buried, in the abscene of O2, and compressed
over millions of years.
Crude oil and natural gas were formed from plankton remains in mud and on the seabed. These
remains were covered by sediments and were compessed over millions of years. They are now found,
trapped under layers of rock.
Limestone deposits are formed when tiny shells and skeletons from marine organisms settle on the
ocean floor, get compacted, and undergo a process called lithification to become solid rock over a very
long time.
📌 SUMMARY: The modern atmosphere is made up of nitrogen, oxygen, CO2, water vapour and noble gases. The Earth was formed
4.6 billion years ago and evidence for the early atmosphere is difficult to find due to the long timescale. Volcanoes released CO2,
H2O and nitrogen. Water vapour condensed and formed rain and then oceans. Algae and plants produced the now present oxygen
via photosynthesis and also reduced the amount of CO2. Coal, crude oil, natural gas and limestone are all formed from
compressing plants and small organisms.
The Composition and Evolution of the Earth’s Atmosphere 1
