Evolution of the Earths atmosphere

• released gases like nitrogen, CO2, methane and ammonia • released water vapour which, when the earth cooled, condensed to form oceans

• nitrogen • carbon dioxide • water vapour • methane • ammonia

• 78% nitrogen • 21% oxygen • 1% argon • 0.04% carbon dioxide and

• when water vapour condensed, it formed the oceans • lots of carbon dioxide was removed from the early atmosphere as some dissolved in the oceans to form a weak acid, and this reacted with minerals in the sea, to form precipitates, • Over time, this formed sediments of carbonate rock on the sea bed • some of the carbon dioxide in the sea was used to make corals and shells of organisms such as mussels • when these died, they formed the sedimentary rock limestone, which also removed co2 from the air

• some of the carbon that algae and green plants took in from the atmosphere and oceans became locked in rocks and fossil fuels after the organisms died

limestone coal

• algae producing oxygen by carrying out photosynthesis • billions of years later, plants evolved and also started carrying out photosynthesis • at some point, the level of oxygen reached a point where animals could evolve

2.7 billion years ago

more complex life like animals could evolve

• when plants,plankton and marine animals die, they fall to the seabed and get buried in layers of sedimentary rock, oil and gas, which trap the carbon and help keep co2 levels in the atmosphere reduced

• early atmosphere contained large amounts of CO2, atmosphere today only contains a small amount • early atmosphere contained very little oxygen, atmosphere today contains a lot

• around 2.7 bil years ago, algae evolved in oceans, they then carried out photosynthesis, which produces oxygen, and entered the atmosphere • over the following billion years, plants evolved, this increased the amount of oxygen in the atmosphere, and at some point the level of oxygen reached the point where animals could evolve

• form over millions of years • non renewable, will eventually run out

• from the remains of ferns and trees • if these die in marshy wetlands, they do not decompose, and this can be due to lack of oxygen or acidic conditions -(These both prevent bacteria from carrying out decomposition) • over time the plant remains are covered with sediment and compressed • high temperature and pressure create coal

• from plankton which are tiny plants and animals found in the sea • when these die, they settle in mud on the sea bed • if oxygen is not present, they don’t decompose • over time these are compressed by sediment • heat and pressure then convert them into crude oul

the hydrocarbon methane

• formed from plankton • found near deposits of oil

• all contain trapped carbon, and the carbon was part of the co2 taken in by photosynthesis

because the earth is around 4600 million years old

venus