The earth and the atmosphere Flashcards
Name the four layers of the earth from the center out…
Inner core
Outer core
Mantle
Crust
What is the inner core?
A solid ball of nickel and iron reaching temperatures of 5500 degrees C
What is the outer core?
A liquid layer made of nickel and iron reaching similar temperatures to the inner core
What is the mantle?
The widest section of earth which is approximately 2900km thick- made up of semi-molten rock called magma with a harder top and a softer lower part
What is the crust?
The thinnest layer of earth at up to 75km deep (30-40km under land mass)- made up of tectonic plates
How do we know the earth’s structure is like how it is?
Scientists use evidence from earthquakes-the way seismic waves travel is affected by the earth’s structure and density and mass
What are the current percentages of gases in our atmosphere?
Nitrogen= 78% Oxygen= 21% Argon= 0.9% Carbon dioxide= 0.04% Other gases= 0.06%
What is the surface of the earth split into?
Tectonic plates
How do tectonic plates move across the earth’s surface?
Convection currents in the mantle
What happens where plates meet and when they rub against each other?
- Volcanoes form
- Earthquakes occur
- Tsunamis may happen
How do convection currents work?
- Radioactive decay in the centre of the earth produces a lot of energy
- The energy heats up molten materials in the mantle
- The heated part of the mantle expands, becoming less dense and rising towards the surface to be replaced with cooler material
- This causes movement
Why are earthquakes and volcanic eruptions difficult to predict?
The plates move suddenly/unexpectedly quickly past each other
Name briefly the 3 phases of the evolution of the atmosphere
1) Volcanoes gave out gases
2) Green plants evolved and produced oxygen
3) Ozone layer allows evolution of complex animals
What was the earth’s early atmosphere made up of?
Mostly carbon dioxide with small amounts of methane, ammonia and water vapour
What happened in the early stage of the evolution of the atmosphere? (Volcanoes gave out gases)
- The earth’s surface was molten so no atmosphere could be formed (as it just boiled away into space)
- Eventually the surface cooled slightly but volcanoes kept erupting
- The volcanoes gave out lots of gases (forming the atmosphere and oceans)
- The oceans formed when water vapour condensed and the atmosphere was mainly carbon dioxide with no oxygen
What happened during the middle stage of the evolution of the earth’s atmosphere? (Green plants evolved and produced oxygen)
- Green plants and algae formed over most of the earth
- A lot of early carbon dioxide was dissolved in the oceans and green plants also absorbed it, producing oxygen by photosynthesis
- Carbon and hydrocarbons were locked up in sediment from early marine shellfish and dead plants (becoming fossil fuels today)
What happened during the later stage of the evolution of the atmosphere? (Ozone layer allows evolution of complex animals)
- The build up of oxygen in the atmosphere killed off some early organisms but allowed other, more complex ones to evolve
- The oxygen also created the ozone layer which blocked harmful rays of sun allowing even more complex organisms to form
- There is virtually no carbon dioxide left now
What are the 3 main theories for how life started on earth?
- The Miller-Urey experiment (the earth’s early gases and state allowed life to begin)
- Meteors crashed from space bringing life in the form of organic molecules (extra-terrestrial seeding)
- Biological molecules could have been sourced from deep ocean near volcanic vents (with the chemicals and conditions required to make the building blocks of life)
Explain the Miller Urey experiment and the evidence surrounding it
- Used a mixture of water, ammonia, methane and hydrogen with a high voltage spark to stimulate a reaction like that of early earth creating amino acids
- E. Possible to make molecules of life from gases that may have been in our early atmosphere
- E. Amino acids are essential for making proteins and therefore life-with these conditions they found that amino acids had formed
- Could have formed a primordial soup
Explain the theory of extra terrestrial seeding and the evidence surrounding it
- Meteors crashed from space to earth bringing life in the form of organic molecules which evolved elsewhere
- E. In 1969 a meteorite fell from the sky above Australia (known as the Murchison meteorite) with a mass of over 100kg containing a range of organic molecules and amino acids
Explain the theory of biological molecules being sourced from deep under the oceans and the evidence surrounding it (primordial soup links to the Miller Urey experiment theory)
- Building blocks of earth- organic molecules could have formed a primordial soup and all molecules could have been in the sea
- E. Near volcanic vents we get both the chemicals and conditions we need (MU)
- E. Protein molecules are capable of replicating
How can noble gases be useful?
They are unreactive and so can be used in situations to be safer than more reactive materials
What are uses of helium?
- Airships and party balloons: low density, floats in air, safer, does not react with oxygen to catch fire
- Breathing mixture for divers (with oxygen): reduces chances of “bends”
What are uses of argon?
Everyday lightbulb (filament): inert atmosphere inside bulb, no chemical reaction takes place between the metal filament and argon gas, stops filament burning away and makes light bulb last longer
What are uses of neon?
Electrical discharge tubes/neon lights
What is the continental drift theory?
In 1945 Alfred Wegener suggested that the continents had once been joined together but then slowly drifted apart
What was Wegener’s evidence for the continental drift theory?
- The shapes of the continents fit together like a jigsaw
- The types of fossils and rocks matched together when the continents were lined up
Why were Wegener’s ideas not accepted at the time? (Continental drift theory)
- No evidence for suggesting how the continents could move
- Other scientists had different views and ideas
- Wegener was not an expert geologist
How do you separate gases in air?
Fractional distillation
Used to separate a mixture of liquids with different boiling points
Explain the process of fractional distillation?
- Gaseous air is cooled below -200 degrees C so it condenses to a liquid- achieved using high pressure
- Pressure is released so air expands rapidly- this causes the temperature to decrease further so that carbon dioxide and water solidify so they can be removed
- Liquid air is allowed to warm up, lower boiling point gases boil off at first and are separated
What are some of the ways that earthquake and volcanic activity can be predicted?
- Plates normally move slowly but a sudden release of strain energy causes earthquakes
Why can’t scientists predict when earthquakes and volcanic activity will occur?
Can’t be certain …
- about what is happening under the crust
- where the forces/pressure are building up
- about the size of the forces
- when the forces will reach their limit
Why has carbon dioxide decreased in our atmospheres?
- plants/microorganisms
- absorbed carbon dioxide in photosynthesis
- dissolves in oceans
- used to form the shell/skeletons of marine organisms
- locked up as limestone carbonates
- locked up as fossil fuels
Why has oxygen increased in our atmosphere?
- plants/bacteria
- releasing oxygen in photosynthesis
Why has nitrogen increased our atmosphere?
- ammonia reacted with oxygen
- bacteria/microorganisms release nitrogen
Why has water vapour decreased in our atmosphere?
- as earth’s temperature cooled, water vapour condensed to form oceans
