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What was Earth like when it first formed?
Earth was completely molten (hot liquid)
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How old do scientists estimate the Earth is and why?
4500 million years old as it has to be older than its oldest rocks.
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What are examples of processes that can support geologists suggestions on how the Earth has changed?
Mountain building, erosion, sedimentation, dissolving, evaporation.
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What are these processes?
Erosion-earth's surface made of layers, oldest usually at bottom. layers=compacted sediments, produced by weathering+erosion. erosion changes surface over time. Craters.Mountain formation. Folding (requires huge force over time).
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What else can be studied to show further evidence of the Earth's age?
Fossils of plants+animals in sedimentary rock layers which show how life has changed. The radioactivity of rocks. A rock's radioactivity decreases over time+radioactive dating measures radiation levels to find out its age.
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What is the thin rocky crust?
Thickness varies between 10km and 100km. Oceanic crust lies beneath the oceans. Continental crust forms continents.
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What is the mantle?
Extends almost halfway to centre of Earth. Has higher density and different composition than rock in crust. Very hot but under pressure.
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What is the core?
Accounts for over half of Earth's radius. Made of nickle and iron and has liquid outer part and solid inner part. The decay of radioactive elements inside the earth releases energy, keeping interoir hot.
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Who was the theory of continental drift proposed by? Why?
By Wegner as he saw continents had a jigsaw fit, with mountain ranges and rock patterns matching up. Were also fossils of same animals on different continents. Said they'd drifted apart but when they collide form moutains.
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Why didn't geologists accept Wegners theory?
Because he wasn't a geologist so seen as outsider. Supporting evidence=limited. Could be explained more simply (e.g. bridge connecting continents eroded over time). Movement of continents not detectable.
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What evidence convinced scientific community that Wegner was correct? How did it become an accepted theory?
Evidence from seafloor spreading. Through peer review process became accpeted theory.
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What do the tectonic plates do?
Float on Earth's mantle as less dense. Can move apart, move toards or slide past each other.
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What are plate boundaries and what normally occurs there?
The lines where plates meet. Volcanoes, earthquakes and mountain formations normally occur there.
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What can earthquakes near coastlines or at sea often result in?
A tsunami
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What is a geohazard?
A natural hazard e.g. floods and hurricanes. Some have warning signs that give authorities time to evacuate are, use sandbags, etc.
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Why do precautionary measures need to be taken?
Because geohazards can strike at any time.
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What are some examples of precautionary measures?
Buildings in earthquake zones are designed to withstand tremors. Authorities will often refuse planning permission in areas prone to flooding.
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What is the consistency of the mantles like the further you go from the crust?
It becomes more liquid like.
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What do convection currents in the mantle cause?
Magma to rise. The currents move the solid part of the mantle and the tectonic plates
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What does the magma do when the plates are moving apart?
Magma reaches surface and hardens, forming new areas of oceanic crust (seafloor) and pushing the existing floor outwards.
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What causes seafloors to spread by a few centimetres a year?
New crust is continuously forming at the crest of an oceanic ridge and old rock is pushed out.
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What produces rock stripes of alternating polarity?
Earth has a magnetic field which changes polarity every million years. This combined with seafloor spreading produces rock stripes of alternating polarity.
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How can geologists see how quickly crust is forming?
By the width of the stripes
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Where do the rock stripes occur?
At constructive plate boundries where plates are moving apart.
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What is subduction?
When oceanic and continental plates collide, the denser oceanic plate is forced under the continental plate.
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What occurs at destructive plate boundaries?
The oceanic plate melts and molten rock can rise to form volcanoes.
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Where and why do mountain ranges form?
Along colliding plate boundaries as sedimentary rock is forced up by the pressure created in a collision.
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Where do earthquakes mostly occur?
At plate boundaries
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How do earthquakes occur at plate boundaries?
Plates slide past each other or collide. Pressure builds up as plates push on eachother. Eventually, stored energy is released and waves of energy spread from the epicentre.
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Why is plate movement crucial in the rock cycle?
Old rock destroye through subduction.Igneous rock formed when magma reaches the surface.Plate collisions can produce high temp+pressure, causing rock to fold. Sedimentary rock becomes metamorphic rock.
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What do earthquakes produce?
Wave motions on the surface and inside the Earth.
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How can the waves be detected?
By onstruments located on the Earth's surface, such as a seismograph.
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What are the two types of wave generated by earthquakes?
Primary waves (P waves) and secondary waves (S waves)
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How do P waves travel?
Travel faster than S wave. Can travel through liquids and solids and can travel through liquid region of outer core of Earth.
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How do S waves travel?
Only travel through solids, can't travel through liquid region of outer core of Earth.
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What type of waves are P waves+ S waves?
p waves = longitudinal waves. s waves = transverse waves.
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What speed do P and S waves travel at in rocks of different densities?
Different speed in rocks of different density.
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At what speed will the waves travel at if the rock has a high density?
Waves will travel faster.
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What causes refraction or reflections of waves?
the boundaries between the different types of rock lead to changes in the speed of P or S waves - hence causing refraction/reflection
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What can measurements taken from seismographs at different points on the Earth's surface be used as evidence for?
To give evidence about the structure of the Earth.
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What are waves?
Regular patterns of disturbance that transfer energy from one point to another without transferring particles of matter.
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What happens to each particle in a longitudinal wave?
Each one vibrates backwards+forwards about its normal position. Moves backwards+forwards in the same plane as the direction of wave movement.
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What is an example of a longitudinal wave?
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What happens to each particle in a transverse wave?
Vibrates up+down about its normal position. Moves up and down at right angles (90 degrees) to the direction of wave movement.
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What are examples of transverse waves?
light, water, all electromagnetic waves.
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What is the amplitude of a wave?
The maximum disturbance caused by a wave, measured by the distance from a crest (or trough) of the wave to the undisturbed position.
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What is the wavelength of a wave?
The distane between corresponding points on two adjacent disturbances.
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What is the frequency of a wave?
The number of waves produced (or passing a particular point) in one second. Measured in hertz (hz).
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What happens to the wavelength of a wave travelling at a constant speed if its frequency is increased or decreased?
Increased freq = decreased wavelength Decreased freq = increased wavelength
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How is frequency proportional to wavelength?
It is inversely proportional.
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What will happen to the wavelength of a wave that has a constant frequency if its wave speed is increased/decreased?
Increased wave speed = increased wavelength. Decreased wave speed = decreased wavelength.
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What is the formula for calculating wave speed (metres per second - m/s)
Wave speed (m/s) = frequency (hertz, hz) x Wavelength (metres, m)
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What is the formula used for calculating the distance a wave travels at a given speed in a certain time?
Distance (m) = wave speed (m/s) x time (s)
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When was the solar system formed and how?
about 5000 million years ago. Solar system started as dust+gas clouds, pulled together by gravity, which created intense heat. Nuclear fusion began+a star(the Sun) was born. Remaining dust+gas formed smaller masses, which were attracted to Sun.
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How big is the Sun?
Massive when compared with planets and contains over 99% of the mass of the solar system.
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What are smaller masses in our solar system?
planets(8 large masses that orbit Sun), moons(small masses that orbit planets), asteroids(small, rocky masses that orbt Sun), comets(small, icy masses that orbit Sun), dwarf planets (small masses, e.g. Pluto, that orbit Sun).
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What masses in our solar system move in elliptical (slightly sqaushed, circular) orbits?
planets, moons and asteroids.
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What moves in a highly elliptical orbit?
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How long does it take Earth to make a complete orbit?
One year.
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how much older is the Sun than the Earth?
only 500 million years older.
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Where does the Sun's energy come from? What is this?
Nuclear fusion. Hydrogen atoms fuse together to produce an atoms with a larger mass, i.e. a new chemical element. Binding energy stored in hydrogen atoms is released.
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How were all chemical elements larger than helium formed?
By nuclear fusion in earlier stars.
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What fuses together during nuclear fusion?
The nuclei of hydrogen atoms.
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How old is the Universe approx?
14,000 million years old.
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How many galaxies are in the Universe and what is inbetween them?
Billions of galaxies, with vast distances between them.
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At what speed does light travel?
At very hgih but finite (limited) speeds.
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When can the speed of light be measured?
If the distances are great enough.
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What is the speed of light through space (a vacuum)?
300,000km/s (one million times faster than sound)
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How long does light from Earth take to reach the Moon?
just over a second
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How long does sunlight take to reach Earth?
8 minutes
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What are vast space distance measured in? What is this?
Light years. One light year is distance light travels in one year (approx 9500 billion km)
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How far is the nearest galaxy to the Milky Way?
2.2 million light years away.
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What is relative brightness?
The dimmer a star, the further away it is. however brightness can vary so a stars distance is never certain.
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What is parallax?
hold finger at arms length+close each eye in turn,finger appears to move,closer the finger-more it moves.Stars in near distance appear to move against background of distant stars.Closer they are,more appear to move.Further star=less accurate reading.
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how is distance measured?
using parallx or relative brightness.
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What do stars give us that tell us about what we know about them? What types are there?
Radiation. Visible light, ultraviolet and infared.
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What is light pollution?
When electric lights on Earth make it difficult to see stars.
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Why isn't the Hubble Space Telescope affected by light pollution?
Because it orbits at a height of 600km.
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What happens to the wavelengths of light from a light source is the source is moving away?
They become longer than if the source was stationary.
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What suggests that galaxies are moving away from us?
Wavelengths of light from nearby galaxies are longer than scientists expect.
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Whose observations showed that all galaies are moving away from us and the further they are, the faster they are moving?
Edwin Hubble
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What is Hubble's Law?
States that the speed at which a galaxy is moving away is proportional to its distance from us.
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What must it mean if all the galaxies are moving away from us?
Must mean universe is expanding.
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How can you tell if an EM wave has been redshifted?
If it appears to have a longer wavelength than it should have.
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If an object has been red shifted, then what must it mean? What will it mean if even more wavelengths are redshifted?
Must mean object is moving away. more red shifted wavelengths = the faster the object is moving away.
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how can you see if the lines in a spectrum have been redshifted?
They will have been displaced towards the red end of the spectrum
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What is the diameter of the earth and Sun?
Earth=12,742 km Sun=110 times diameter of Earth
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What is the size of the Earth's orbit, the solar system and the Milky Way?
earths orbit=107times diameter of Sun. Solar system=several thousand light years. Milky Way=100,000 light years.
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What is the distance of the Sun to the nearest star?
4 light years.
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What does the Big Bang theory say?
That the Universe began with a huge explosion 14,000 million years ago
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Why is the future of the Universe hard to predict?
Because of the difficulties in measuring the very large distances involved, the motion of very distant objects and the assumptions made in interpreting observations.
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What else is required to predict the future of the Universe?
A knowledge of the quantity of mass in the Universe.
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What will happen is there isn't enough mass?
The Universe will keep expanding.
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What will happen if there is too much mass?
gravity will pull everything back together and the Universe will collapse.
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Card 2


How old do scientists estimate the Earth is and why?


4500 million years old as it has to be older than its oldest rocks.

Card 3


What are examples of processes that can support geologists suggestions on how the Earth has changed?


Preview of the front of card 3

Card 4


What are these processes?


Preview of the front of card 4

Card 5


What else can be studied to show further evidence of the Earth's age?


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