C13-The Earth's Atmosphere Flashcards
What three gases is the Earth’s atmosphere made of ?
- 78% itrogen
- 21% oxygen
- Small proprotions of other gases (CO2 and noble gas Argon).
- These have gases have stayed pretty constant for about 200 million years .
Why can’t scientists be certain of the early atmosphere ?
-As the earth is around 4600 billion years old .
Stage one of the Earth’s early atmosphere formation .
-There were volcanic eruptions , these volcanic eruptions releases gases that formed the atmospehre one of these being large amounts water vapour and co2 and small amounts of nitrate and ammonium .
Stage two of the Earth’s early atmosphere formation .
-As the water vapour condensed to form oceans .
Stage three of the Earth’s early atmosphere formation ..
- Some of this Co2 dissolved int he oceans to form a weak acid .
- This reacted with minerals to form preciptates .
Stage four of the Earth’s early atmosphere formation . .
Overtime this formed sediments of carbonate rock on the sea bed .
What was some of the Co2 in the ocean used to make ?
- To make corals and shels of orrganisms such as mussels .
- When these died they formed limestone . This also removed Co2 from the atmosphere .
Where did the oxyegn come from ? fourth stage of the Earth’s early atmosphere formation .
-Around 2.7 billion yers ago , photsynthetic alage first evolved in the oceans increasign mount of oxyegn in the atmosphere .
Lasts tage of the Earth’s early atmosphere formation ..
-At some point , oxygen levels reached where animals could evolve . Nitrogen levels were also steadily increasing
What is the formula for photosynthesis , give balanced equation .
Carbiondioxide +water —-> glucose + oxyegn
check sheet for balanced equation
How else did Co2 in the atmosphere decrease ?
- As well as producing oxygen , photosyntheisis takes in Co2 .
- The carbon can be then trapped in fossil fuels causing the level of Co2 to fall .
Key differences between early atmospehre and now .
- Early atmosphere large amounts of Carbon dioxide and little oxyegn .
- Now , small amounts og carbnodioxoide and 21% oxygen .
nitrogen in early atmosphere
-Mainly Co2 but with small but increasing amounts of nitrogen .
How long does it take to form fossil fuels ?
-Millions of years .
Fossil fuels are non-renewable , what does this mean ?
-If we keep using them , they will run out .
How does coal form ?
- Coal is formed from the remains of ferns and trees .
- If these die in marshy wetlands , they do not decompose .
What could cause the ferns and trees to not decompsoe ?
- Due to the lack of oxyegn or acidic conditions .
- These both prevent bacteria from carrying out decomposoition .
- Overtime the plant remains are covered in sediment nd are compressed .
- High temperature and pressure creates coal .
How does oil form ?
- Crude oil is made from plankton which are tiny plants and animas found in the sea .
- When they die , they settle in mud on the sea-bed .
- Overtime they are compressed by sediment , heat and pressure converts them into crude oi .
How does natural gas form ?
- Natrua gas is mainly the hydrocarbon of methane .
- We often find natrual gas near deposits of oil .
- As natural gas if ormed from plankton - a similr way to crude oil .
What are the three fossil fuels
- Coal
- Oil
- Natural gas
What is the key fact about all three fossil fuels ?
-All fossil fuels contian trapped carbon . That carbon was part of the carbodndioxide taken in byb photosynthesis .
What are the other gases in the atmosphere
-MOstly oxygen and nitroge
BUT - Water Vapour , Carbondioxide , methane .
How is thw amount of water vapour in the atmosphere variable ?
-It changees depending on the temperature .
What is the first stage of the green house effect ?
- Energy from the sun travels to the Earth as short wavelength radiation - e.g UV and Visible light .
What is the second stage of the green house effect ?
- Some of the short wavelength radiation simpl reflects back into space , but most of it passes easiy throguh the atmopshere .
Why does most short wavelength radiation pass easily through the atmosphere ?
This is because hsort wave length radiation does not ineract strongly with the gas molecules in the atmosphere .
What is the third stage of the green house effect ?
The energy of the radiation is absorbed when it reaches the surface of the Earth .
What is the fourth stage of the green house effect ?
The surface of the Earth now radiates the energy as long wavelength radiation such as infrared .