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The early atmosphere
· Volcanoes on earth today release mainly carbon dioxide and water vapour along with ammonia, methane and nitrogen.
· The atmosphere of Titan is 98% nitrogen which some scientists think was released by volcanoes also.
· They feel Earth's early atmosphere may of been like this (nitrogen)
· there are also volcanoes on Mars and Venus but their atmospheres are mainly carbon dioxide. This has lead other scientist
to believe that Earth's early atmosphere may of been Carbon dioxide.
· Recent results from space probes have revealed that titan's interior is icy rather than earth's rocky one (like Mars, Venus)
which doesn't explain how earth now contains so much nitrogen.
· Scientists cannot be certain which theory is correct.
OXYGEN
· Scientists are more certain there was little or no oxygen in the early atmosphere on Earth.
· Evidence: volcanoes do not release oxygen, iron compounds found in Earth's oldest rocks are compounds which would only
form in the ABSENSE of oxygen
· As the Earth became older, it cooled down.
· Water vapour in hot atmosphere= cooled=
· condensed in to liquid water=oceans…read more

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A changing atmosphere
· After oceans were formed, carbon dioxide in the atmosphere dissolved into the oceans
· Scientists feel half of the carbon dioxide in the atmosphere was lost this way.
· Some marine organisms (coral, molluscs and star fish) use dissolved carbon dioxide to make shells of calcium carbonate.
· As they die, their shells fell and formed sediment. Over millions of years, the layers of sediment became sedimentary rock.
· Limestone is mostly calcium carbonate.
PHOTOSYNTHESIS
· Taking in co2 and releasing o2
· Life started 4 billion years ago, 1billion years ago photosynthesis occurred ( believe)
· Increasing level of photosynthesis= sped up rate of co2 removal= same rate of 02 released.…read more

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The atmosphere today
· Nitrogen and oxygen are the most abundant gases in the atmosphere today (99%)
· Water vapour changes daily so not included in composition of dry air
· Some noble gases, mainly argon are some of the other 1% gas
· Small amount of co2 is also found
· Trace gases: carbon monoxide, sulfur dioxide and methane.
· Can be change in amount found.
· NATURAL: volcanoes- release a lot of sulfur dioxide. Lightening produces nitrogen oxides
· HUMAN ACTIVITIES: deforestation- increase in co2, burning fossil fuels- increase of c02, CO, sulfur dioxide.
· Cattle and rice fields- methane
· Some are harmful to people/environment scientists have to monitor.
NITROGEN
· Nitrogen main gas in atmosphere today
· One theory- released by volcanoes
· Other- gradual addition of nitrogen.…read more

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Rocks and their formation
METAMORPHIC
· The action of heat and/ or pressure can change rock causing
IGNEOUS new crystals to form.
· Rocks deep in the earth may become hot enough to melt. · changed rock=metamorphic
· Molten rock = magma. ·Marble is a metamorphic rock formed from chalk/limestone.
· Erupt- larva ·Grains in chalk are weakly joined with gaps.
· When molten rock cools, it solidifies= solid rock. ·When marble forms, grains become new crystals that interlock
· Contain crystals which interlock tightly.
· Size of crystal depends of rate of magma/larva to cool. ·This makes marble harder than chalk
· Slower it cools, the larger the crystals. E.g. Granite.
SEDIMENTARY
· Rocks are broken into smaller pieces by physical processes such as expansion of water when it freezers.
· Also by chemical reactions with water/air
· Erosion happens when pieces of rock are TRANSPORTED in a river. Rivers carry large amounts of
broken rock towards sea where they are DEPOSITED.
· Most sedimentary rocks are formed this way. Other are formed by hard parts of dead organisms.
· CHALK and limestone (mostly contain CaCo3)can be formed by sea shells
· Layers of sediment build up on sea bed, layers compacted, form rock.
· Sedimentary rock may contain fossil remains or imprints such as footmarks
EROSION
· Sedimentary rocks are more susceptible to erosion than other two.
· This is because: the other two have interlocking crystals, they are harder and less easily eroded. Sedimentary are layered.…read more

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BENIFITS DRAWBACKS
Limestone and its uses Helps locals (jobs) Dusty, noisy
Exported- helps UK' Affect quality of life
s economy
USES
· Limestone is cut into blocks to be used for construction of buildings Valuable natural Damage tourist
· Crushed into smaller lumps to be used to make firm base for railway lines/roads resource-need for attractions
· Raw material for the manufacture of cement, concrete and glass! other materials
Heavy lorries-
QUARRYING pollution, traffic
· Limestone is removed from the ground at a quarry
· Explosives are used to break limestone into pieces. Land cannot be
used again- though
· They are cut or crushed into useful sizes
they are restored.
· Transported by rail/ road to customers
THERMAL DECOMOSITION
· Limestone, chalk and marble are natural sources of calcium carbonate
· Heated strongly, CACO3 breaks down (Decompose) to form calcium oxide and carbon dioxide Cement made in
· Calcium carbonate calcium oxide+ carbon dioxide cement kiln.
· Thermal decomposition of limestone is used in the manufacture of cement and glass
CEMENT AND CONTRETE
· Cement is made by heating limestone with powdered clay
· Cement is used in mortar- mixture used by bricklayers to hold breaks together.
· Concrete is made by mixing cement with SAND, GRAVEL and WATER. Widely used in construction of buildings/bridges
· glass is made by heating limestone with sand and sodium carbonate. Chemical reaction- liquid glass. Cools and hardens to
form hard, solid, transparent windows.…read more

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