P1

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P1 THE EARTH IN THE UNIVERSE Revision Power
Point GM
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OUR EARTH is about 4.5 billion years old
Rocks provide evidence of changes in the Earth
EROSION by wind, water, ice and chemical reaction.
SEDIMENTATION layers of sediments compressed to
form layered rocks over millions of years
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OUR EARTH
The earth is made up of 4 main parts
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PLATE TECTONICS
Wegener was the first to propose the theory of
CONTINENTAL DRIFT and from that PLATE TECTONICS
theory was developed

• The evidence came from
• Fossil and rock finds,
• The continents fitting together.

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SEAFLOOR SPEADING

• In the 40s and 50s, ridges and trenches were
  detected on the sea floor.

• Older rocks were further away from the ridges.

The drift is about 10cm per year. The Earths
magnetic field changes over millions of years and
this is captured in the rocks
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SEAFLOOR SPEADING
DIVERGENT PLATE BOUNDARY
Heat energy from decaying radioactive rocks
allows the mantle to melt and form magma. The
magma forms new crust.
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SUBDUCTION ZONES
CONVERGENT PLATE BOUNDARY
Parts of the Oceanic plate melt and form magma,
this rises to form volcanoes
Continental plate
Oceanic plate
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GEOHAZARDS (VOLCANOES EARTHQUAKES)
occur at plate boundaries
EARTHQUAKES
These occur when 2 plates collide or slide past
each other.
The San Andreas fault in California is an example
of slide fault
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VOLCANOES
VISCOUS MAGMA DESTRUCTIVE VOLCANO eg
Mount St Helens blowing up Less viscous
magma results in lava flows.
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COMETS ASTEROIDS
ASTEROIDS pieces of rock that orbit the sun
(most between Mars and Jupiter)
COMETS made of ice and dust, they orbit
elliptically and the comets tail can be seen as
it approaches the Sun.
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METEORS METEORITES
Shooting Stars Burn up in
Atmosphere
Meteors
Meteorites
Dont burn up and hit the
ground Large ones can cause
IMPACT CRATERS
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IMPACTS
The Earth has been hit by many large asteroids
and may have lead to mass extinctions
65 million years ago an impact in the YUCATAN in
Mexico may have led to the demise of the
Dinosaurs.
Evidence suggests that Dinosaurs died out at this
time, but there is also evidence that the
Dinosaurs were dying out 20 million years
previously.
Some scientists have produced other theories
based on different evidence.
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OUR STAR THE SUN
The Sun FUSES Hydrogen into Helium
This releases a large amount of energy which
gives us heat and light.
The SUN will give out this energy for the next 4
to 5 billion years.
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OUTSIDE THE SOLAR SYSTEM
Light is an electromagnetic wave and travels at
300,000 km / s
Nearest star
Distance to the stars is measured in LIGHT YEARS
We see stars as they once were (4.3 years ago
for the nearest star)
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VIEWING THE STARS
We use telescopes to see stars because stars give
off light and other energies.
Light pollution can interfere with those
observations. So telescopes are put on high
mountains or in space.
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DISTANCE TO STARS
We can measure the distance of stars by using two
methods
- only nearby stars can be
measured using this technique. The star appears
to move relative to other more distant stars
a) PARALLAX

distances can be worked out by using the relative
and actual brightness of certain stars.
b) RELATIVE BRIGHTNESS.
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OUTSIDE THE SOLAR SYSTEM
Our SUN is only one of at least 100 billion stars
in our GALAXY (the MILKY WAY)
There are billions of galaxies that make up the
UNIVERSE
No EVIDENCE of alien life has been found on Earth
or on other planets.
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Theory of the BIG BANG and the EXPANDING UNIVERSE
Edwin Hubble noticed that distant galaxies were
moving away from us Expanding Universe theory
The further the galaxies are away, the faster
they are moving away from us)
BIG BANG THEORY
The UNIVERSE is about 14 billion years old.
As the Universe expands so SPACE itself is
expanding)
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Will the UNIVERSE go on forever?
There are three theories.
Scientists dont have the data, observations and
evidence yet to develop one theory.
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LIFE CYCLE OF THE SUN

• Gas Nebula collapses

• The Sun switches on as a main sequence star
  (total 10 billion years)

• Fusion of Hydrogen stops and the SUN becomes RED
  GIANT destroying the EARTH

• Gas is expelled and the SUN becomes a WHITE
  DWARF (earth size)

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Radiation Life

• P2

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The electromagnetic spectrum
Electromagnetic radiation delivers energy in
packets called photons.
Highest energy

• Lowest energy

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Energy delivered

• the energy deposited by a beam of electromagnetic
  radiation depends on both the

• the energy that each photon delivers

• number of photons arriving

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Intensity

• the intensity of electromagnetic radiation is
• the energy arriving at a surface each second

• intensity of a beam of electromagnetic radiation
  decreases with distance because the beam spreads
  out (diverges) over a larger area

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Sources Detectors

• Radiation can be

• Reflected

• Transmitted

• Absorbed

• one object (a source) emits radiation

• radiation may be absorbed by another object (a
  detector) some distance away

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Ionising Radiation
Ultra violet, X rays Gamma rays all have enough
energy to break molecules up into charged
particles ( called ions)

• H These ions can then take part in other chemical
  reactions

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Effects of Ultra Violet (UV)

• Most UV is stopped preventing too much skin
  damage from the ionising effect of UV radiation.
• Otherwise maybe Skin cancer
• We can protect ourselves from the risk.
• Wear clothing and apply sun-screens

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Ozone

• UV radiation is absorbed by a layer of ozone in
  the atmosphere.
• The UV breaks down the ozone to form Oxygen. H

H

• Oxygen then recombines
• to form ozone. H

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IONISING RADIATION
Any ionising radiation must be limited as it can
cause cancer by changing the DNA in cells. The
ALARA principle is used to limit this radiation
As Low As Reasonably Achievable
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Damage to living cells

• Low intensity microwave radiation emitted by
  mobile phones and masts may be a danger.

• Metal cases and door screens protect users on
  microwave ovens

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Risk

• Actual risk- the risk that we know is there.
• Percieved risk the risk that someone thinks is
  present

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Electromagnetic (E.M.) Radiation allows life to
exist on Earth
Infra red to warm the earth. Light for
photosynthesis The atmosphere allows this
radiation to pass through
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PHOTOSYNTHESIS Taking Carbon Dioxide from the air
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Respiration

• All living cells respire
• take in Oxygen and Glucose
• give out Carbon Dioxide and Water

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The Carbon Cycle
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Decomposers

• break down complex compounds
• return carbon to the soil
• they also release CO2 into the atmosphere
• through respiration

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GREENHOUSE EFFECT
H

• more greenhouse gases
• more radiated heat trapped from the Earth.

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Correlation
Graph B shows a rise in CO2 since 1960
(Graph A). increase in average temperature
B
A
There is a correlation
This, however, does NOT prove that CO2 causes
global warming
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Computer modelling

• Scientists use computer modelling to predict the
  effects of global warming
• Possible effects

• Growing different crops

• Extreme weather in certain areas

• Rising sea levels from melting ice, flooding low
  lying areas

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Rising carbon dioxide levels
Carbon dioxide levels have been rising steadily
over the last 200 years

• The increase is due to

• burning more Fossil Fuels

• burning Forests to clear land

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Microwaves

• Microwaves heat by making water molecules

Vibrate

• They heat more when they are
• more powerful
• And switched on for longer.

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Transmitting information

• infrared, microwaves and radio waves are used for
  transmitting information.

• Infrared used in remote controls

• Microwaves used in mobile phones

• Radio waves transmit Radio and TV signals

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The structure of the atom
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The structure of the atom
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Isotopes
An isotope is an atom with a different number of
neutrons
A radioisotope is simply an isotope that is
radioactive e.g. carbon 14, which is used in
carbon dating.
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What is Radioactivity?

• The isotopes of many atoms are unstable (have
  extra energy). These are called radioisotopes.

• Radioisotopes emit this extra
• energy (radiation),
• to become more stable,
• by splitting up..

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Types of radiation
1) Alpha (?) an atom decays into a new atom
and emits an alpha particle (2 protons and 2
neutrons the nucleus of a helium atom)
Unstable nucleus
New nucleus
Alpha particle
2) Beta (?) an atom decays into a new atom by
changing a neutron into a proton and electron.
The fast moving, high energy electron is called a
beta particle.
Beta particle
Unstable nucleus
3) Gamma after ? or ? decay surplus energy is
sometimes emitted. This is called gamma
radiation and has a very high frequency with
short wavelength. The atom is not changed.
Unstable nucleus
New nucleus
Gamma radiation
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Penetration Properties
Sheet of paper
Few mm of aluminium
Few cm of lead
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Half life
The HALF-LIFE of an atom is the time taken for
HALF of the radioisotopes in a sample to decay
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Ionisation
When radiation collides with neutral atoms or
molecules it alters their structure by knocking
off electrons. This will leave behind IONS
this is called IONISING RADIATION.
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Uses of ionising radiation
Ionising radiation can be used to treat
cancer sterilise surgical instruments
sterilise food
Radiation dose is measured in sievert . It is a
measure of the possible harm done to your body
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Power stations
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Nuclear power stations
These work in a similar way to normal power
stations
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Nuclear fission
New nuclei (e.g. barium and krypton)
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Chain reactions
Each fission reaction releases neutrons that are
used in further reactions.