advanced info C13 Flashcards
earth formed about
4.6 billion years ago
why is it hard to know the history of the earths atmosphere
little direct evidence from billions of years ago
earth’s early atmosphere
probably manly carbon dioxide
could’ve been some water vapour, nitrogen and traces of methane and ammonia
little or no oxygen
like todays Mars and Venus
volcanic activity
Earths surface covered in volcanoes
in 1st billion years, intense volcanic activity released the gases that formed the early atmosphere
volcanoes also produced nitrogen that gradually built up in the atmosphere
How did oceans form?
As the earth cooled down, water vapour in the atmosphere condensed to form oceans.
when did life begin
about 3.4 billion years ago
algae evolved about 2.7 billion years ago, used energy from sunlight to photosynthesise.
How did oxygen levels in the atmosphere increase?
Algae evolved 2.7 billion years ago, using sunlight during photosynthesis to make energy.
More and more plants evolved, photosynthesising and removing CO2 from and releasing oxygen into the atmosphere.
Over the next billion years, levels of oxygen steadily rose, making it possible for animals to evolve.
earth’s atmosphere today
about 0.04% carbon dioxide
about 80% nitrogen
about 20% oxygen
small proportions of other gases eg. water vapour and noble gases.
How did the levels of CO2 in the atmosphere decrease?
-algae and plants decreased % of CO2 in early atmosphere by photosynthesis
-CO2 removed from early atmosphere by dissolving in oceans. Produced insoluble carbon compounds which precipitated on the seabed as sediments
Over millions of years, animal remains became covered in layers of sediment at the bottom of oceans. Under pressure of sediment, deposits formed sedimentary carbonate rocks, eg. limestone formed from the shells and skeletons of marine organisms
fossil fuels coal, crude oil and natural gas formed from plant and animal remains.
forming coal
sedimentary rock
formed from thick deposits of plant material
plant material buried in the absence of oxygen and compressed over millions of years
forming crude oil and natural gas
Formed from the remains of plankton deposited in mud on the seabed
remains covered by sediments that became layers of rock when compressed over millions of years. The crude oil and natural gas were trapped in the layers of rocks.
How were methane and ammonia removed from the atmosphere
reacted with the oxygen produced during photosynthesis, these reactions produced carbon dioxide and nitrogen.
