P1 - The Earth in the Universe Flashcards
When it first formed, the Earth was completely _____.
Molten (hot liquid)
How old do scientists estimate the Earth to be?
4500 million years old
Why do scientists estimate the Earth to be 4500 million years old?
Because it has to be older than its oldest rocks, which have been found at about 4000 million years old
What is the age of the oldest rocks found on Earth?
4000 million years old
What can studying rocks tell us?
More about the Earth’s structure and how it has changed
In what ways has the Earth’s structure changed? [4 things]
- Erosion
- Craters
- Mountain formation
- Folding
Explain how erosion has changed the Earth’s structure.
The Earth’s surface is made of rock layers, one on top of another. The oldest is usually at the bottom. The layers are compacted sediment, produced by weathering and erosion. Erosion changes the surface over time.
Explain how craters have changed the Earth’s structure.
The Moon’s surface is covered with impact craters from meteors. Meteors also hit the Earth but craters have been erased by erosion.
Explain how mountain formation has changed the Earth’s structure.
If new mountains weren’t being formed, the Earth’s surface would have eroded down to sea level.
Explain how folding has changed the Earth’s structure.
Some rocks look as if they’ve been folded in half. This required huge force over a long time.
Other than rocks, what else can be studied to give further evidence of the Earth’s age?
- Fossils of plants and animals in sedimentary rock layers, which show how life has changed
- The radioactivity of the rocks
How does studying the fossils of plants and animals in sedimentary rock layers help to give further evidence of the Earth’s age?
They show how life has changed
How does studying the radioactivity of rocks help to give further evidence of the Earth’s age?
A rock’s radioactivity decreases over time and radioactive dating measures radiation levels to find out a rock’s age.
What 3 parts make up the main structure of the Earth?
- Thin rocky crust
- The mantle
- The core
Give 3 points about the thin rocky crust that makes up part of the main structure of the Earth.
- Thickness varies between 10km and 100km
- Oceanic crust lies beneath the oceans
- Continental crust forms continents
Give 3 points about the mantle that makes up part of the main structure of the Earth.
- Extends almost halfway to the centre of the Earth
- Has a higher density, and different composition, than rock in the crust
- Very hot, but under pressure
Give 3 points about the core that makes up part of the main structure of the Earth.
- Accounts for over half of the Earth’s radius
- Made of nickel and iron, and has a liquid outer part and a solid inner part
- The decay of radioactive elements inside the Earth releases energy, keeping the interior hot.
Who proposed the continental drift theory?
Wegener
What did Wegener notice that made him propose the theory of continental drift?
He saw that the continents had a jigsaw fit, with mountain ranges and rock patterns matching up.
What did Wegener notice about fossils of the same animals on different continents?
He said that different continents had separated and drifted apart.
What did Wegener claim happened when two continents collided?
They forced each other upwards to make mountains
For what reasons did geologists struggle to accept Wegener’s theory about Continental Drift?
- He wasn’t a geologist so was seen as an outsider
- The supporting evidence was limited
- It could be explained more simply, e.g. a bridge connecting continents had eroded over time
- The movement of the continents wasn’t detectable
a) What finally convinced geologists that Wegener’s theory about Continental Drift was right?
b) Through this ______ ________ process it became an accepted theory.
a) Evidence from seafloor spreading
b) peer review
The Earth’s crust is cracked into several large pieces called what?
Tectonic plates
How are tectonic plates able to float on the Earth’s mantle?
Because they’re less dense
True or False?
Tectonic plates are incapable of moving apart.
False - Tectonic plates are able to move apart, and also towards or slide past one another
What are the lines where tectonic plates meet called?
Plate boundaries
What normally occurs at plate boundaries (the lines where tectonic plates meet)?
Volcanoes, earthquakes and mountain formations
What can often result from earthquakes near coastlines or at sea?
Tsunamis
What is a geohazard?
A natural hazard
Give 2 examples of a geohazard
- Floods
- Hurricanes
What can be done as a precautionary measure to prepare for a geohazard that could strike without warning?
- Buildings in earthquake zones are designed to withstand tremors
- Authorities will often refuse planning permission in areas prone to flooding
The mantle is fairly ____ just below the Earth’s crust. Further down it’s ________.
- solid
- liquid
What causes magma to rise in the mantle?
Convection currents
What can convection currents cause in the mantle?
Rise of magma
How can convection currents cause magma to rise in the mantle?
The currents move the solid part of the mantle and the tectonic plates.
Explain seafloor spreading.
Where tectonic plates move apart, magma reaches the surface and hardens, forming new areas of oceanic crust (seafloor) and pushing the existing floor outwards.
New crust is continuously forming at the crest of an oceanic ridge and old rock is pushed out. This causes seafloors to spread by a few centimetres a year.
True or False?
The earth has a magnetic field. (HT)
True
How often does the magnetic field of the Earth change polarity? (HT)
Every million years
How are rock stripes of alternating polarity formed? (HT)
Seafloor spreading combined with the change in polarity of the Earth’s magnetic field every million years.
Combined with seafloor spreading, what is produced by the polarity change in the Earth’s magnetic field every million years? (HT)
Rock stripes of alternating polarity
How can geologists see how quickly crust is forming? (HT)
By the width of the rock stripes with alternating polarity on the crust of the earth
Where are rock stripes of alternating polarity formed? (HT)
At constructive plate boundaries where plates are moving apart.
What happens when oceanic and continental plates collide? (HT)
The denser oceanic plate is forced under the continental plate
What is it called when an oceanic and a continental plate collide, and the denser oceanic plate is forced under the continental plate? (HT)
Subduction
Explain what is meant by the term subduction. (HT)
When an oceanic and a continental plate collide, and the denser oceanic plate is forced under the continental plate
a) When a denser oceanic plate is forced under a colliding continental plate (subduction), what happens to the oceanic plate? (HT)
b) Where does this occur? (HT)
a) The oceanic plate melts and molten rock can rise to form volcanoes.
b) destructive plate boundaries
Where do mountain ranges form? (HT)
Along colliding plate boundaries as sedimentary rock is forced up by the pressure created in a collision.
Explain in stages how earthquakes occur most frequently at plate boundaries. (3 stages) (HT)
- The plates slide past each other or collide
- Pressure builds up as plates push on each other
- Eventually, stored energy is released and waves of energy spread from the epicentre.
Explain how plate movement is crucial in the rock cycle. (HT)
- Old rock is destroyed through subduction
- Igneous rock is formed when magma reaches the surface
- Plate collisions can produce high temperatures and pressure, causing the rock to fold
- Sedimentary rock becomes metamorphic rock
Earthquakes produce wave motions where?
On the surface and inside the Earth
What is the device used to detect wave motions on the surface caused by earthquakes?
Seismograph
What are the two types of waves generated by an earthquake?
- Primary waves (P-waves)
- Secondary waves (S-waves)
Give 3 points about P-waves (primary waves).
- Travel faster than s-waves
- Can travel through both liquids and solids
- Can travel through the liquid region of the outer core of the Earth
Give 2 points about s-waves (secondary waves).
- Can only travel thruogh solids
- Can’t travel through the liquid ergion of the outer core of the Earth
What kind of waves are p-waves? (HT)
Longitudinal waves
What kind of waves are s-waves? (HT)
Transverse waves
True or False?
P-waves and S-waves travel at the same speeds no matter the density in the rocks. (HT)
False - P-waves and S-waves travel at different speeds in rocks of different density.
P-waves and S-waves travel at different speeds in rocks of different density. Do the waves travel faster or slower if the rock has a high density? (HT)
Faster
P-waves and S-waves travel at different speeds in rocks of different density. Do the waves travel faster or slower if the rock has a lower density? (HT)
Slower
What effect do the boundaries between different types of rock have on p-waes and s-waves?
Changes in speed
What leads to changes in speed in p-waves and s-waves?
The boundaries between the different types of rock
The boundaries between the different types of rock lead to changes in the speed of p-waves and s-waves. What two things could this cause in waves?
Refraction or reflection
Measurements taken from seismographs at different points on the Earth’s surface can be used to give evidence about what?
The structure of the Earth
What can be used to give evidence about the structure of the earth by using measurements at different points on the Earth’s surface?
Seismographs
What provides the heat in the Earth’s core?
The decay of radioactive elements
What evidence do scientists study to obtain information about the Earth’s age?
Fossils of plants and animals, and radioactivity of rock
What type of wave, generated by an earthquake, travels through the liquid outer core of the Earth?
P-waves
In plate movement, old rock is destroyed by which process? (HT)
Subduction
What two factors produce rock stripes of alternating polarity? (HT)
Deep-floor spreading and the changing polarity of the earth’s magnetic field every million years
What are waves?
Regular patterns of disturbance that transfer energy from one point to another without transferring particles of matter.
What are the two types of waves?
- Longitudinal
- Latitudinal
In what type of wave does sound travel?
Longitudinal waves.
Give an example of something that travels through longitudinal waves.
Sound
Give two points about each particle that travels in longitudinal waves.
- Each particle vibrates backwards and forwards about its normal position
- Each particle moves backwards and forwards in the same plane as the direction of wave movement
Give two points about each particle that travels in transverse waves.
- Each particle vibrates up and down about its normal position
- Each particle moves up and down at right angles (90°) to the direction of wave movement
Give 3 examples of things that travel in transverse waves.
- Light
- Water ripples
- All electromagnetic waves
What 3 important features do all waves contain?
- Amplitude
- Wavelength
- Frequency
Explain what amplitude is in waves.
The maximum disturbance caused by a wave, measured by the distance from a crest (or trough) of the wave to the undisturbed position.
How is amplitude measured?
By the distance from a crest (or trough) of the wave to the undisturbed position
Explain what wavelength is in waves.
The distance between corresponding points on two adjacent disturbances.
Explain what frequency is in waves.
The number of waves produced (or passing a particular point) in one second. Frequency is measured in hertz (Hz).
How is frequency in waves measured?
In hertz (Hz)
a) What does the measurement Hz stand for?
b) What can this be used to measure?
a) Hertz
b) Frequency in waves
How is hertz written in abbreviated form?
Hz
For a wave travelling at a constant speed, what will happen if you increase its frequency?
The wavelength will decrease
For a wave travelling at a constant speed, what will happen if you decrease its frequency?
The wavelength will increase
What happens to a wave travelling at a constant speed when its wavelength increases?
The frequency decreases
What happens to a wave travelling at a constant speed when its wavelength decreases?
The frequency increases
Frequency is _______ _________ to wavelength.
Inversely proportional
__________ is inversely proportional to wavelength.
Frequency
Frequency is inversely proportional to ______.
Wavelength
True or False?
Frequency is inversely proportional to wavelength.
True
For a wave travelling at a constant frequency, what will happen if you increase its wave speed?
The wavelength will increase
For a wave travelling at a constant frequency, what will happen if you decrease its wave speed?
The wavelength will decrease
What happens to a wave travelling at a constant frequency when its wavelength increases?
The wave speed has increased
What happens to a wave travelling at a constant frequency when its wavelength decreases?
The wave speed has decreased
Which between speed, frequency, and amplitude of a wave is independent to the others?
The speed of a wave is usually independent of its frequency and amplitude
What is the formula that related wave speed, frequency and wavelength?
wave speed (m/s) = frequency (Hz) x wavelength (m)
A tuning fork of frequency 480Hz produces sound waves with a wavelength of 70cm when it is tapped. What is the speed of the wave?
Wave speed = frequency x wavelength
Wave speed = 480Hz x 0.7m
Wave speed = 336m/s
What formula is used to calculate the distance a wave travels at a given speed in a certain time?
distance (m) = wave speed (m/s) x time (secs.)
How can you work out the frequency or wavelength of a wave? (HT)
By rearranging the wave speed formula:
wave speed = frequency x wavelength
Radio 5 Live transmits on a frequency of 909,000Hz. If the speed of radio waves is 300,000,000m/s, on what wavelength does it transmit? (HT)
Wavelength = wave speed / frequency Wavelength = 300,000,000m/s / 909,000Hz Wavelength = 330m
A water wave has a frequency of 5Hz and a wavelength of 0.1m. What is the speed of the wave?
0.5m/s
What is a student describing if they tell you the number of waves produced each second?
Frequency
A station broadcasts signals at a frequency of 30MHz. If the speed of light is 3 x 10[8]m/s, what is the wavelength? (HT)
10m
When was the solar system formed?
5000 million years ago.
What happened when the solar system was formed about 5000 million years ago? Explain in 3 stages.
- The solar system started as dust and gas clouds, pulled together by gravity
- This created intense heat. Nuclear fusion began and the Sun (a star) was born.
- The remaining dust and gas formed smaller masses, which were attracted to the Sun
The Sun is massive compared to other plants. What percentage of the mass of the solar system does the Sun contain?
99%
The Sun is massive compared to other plants. Give some examples of some smaller masses in our solar system.
- Planets
- Moons
- Asteroids
- Comets
- Dwarf planets
Explain planets as masses within our solar system.
Eight large masses that orbit the Sun
Explain moons as masses within our solar system.
Small masses that orbit planets
Explain asteroids as masses within our solar system.
Small, rocky masses that orbit the Sun
Explain comets as masses within our solar system.
Small, icy masses that orbit the Sun
Explain dwarf planets as masses within our solar system.
Small masses (e.g. Pluto) orbiting the Sun.
Give an example of a dwarf planet.
Pluto
What 3 types of smaller masses within our solar system move in elliptical orbits?
- Planets
- Moons
- Asteroids
What orbits are planets, moons and asteroids examples of within our solar system?
Elliptical orbits
What are elliptical orbits?
Slightly squashed, circular orbits
What type or orbit do comets move in?
Highly elliptical orbits
Give an example of a small mass within our solar system that moves by highly elliptical orbits.
Comets
How long does it take for the Earth to make a complete orbit of the Sun?
1 year
Which planet takes 1 year to make a complete orbit of the Sun?
The Earth
How much older is the Sun than the Earth?
500 million years
Which is older: the Sun or the Earth?
The Sun
Where does the Sun’s energy come from?
Nuclear fusion
Explain how the Sun obtains its energy from nuclear fusion.
- Hydrogen atoms fuse together to produce an atom with a larger mass, i.e. a new chemical element
- Binding energy stored in hydrogen atoms is released
How were all the chemical elements that are larger than helium formed?
By nuclear fusion in earlier stars
What part of the hydrogen atom fuses together during nuclear fusion?
The nuclei
The nuclei of hydrogen atoms fuse together in which process?
Nuclear fusion
How much older is the Universe than the Sun?
14,000 million years
At what kind of speed does light travel at?
A very high by finite (limited) speed
What can be measured if the distance of light is high enough?
The speed of light
In what conditions can the speed of light be measured?
If the distance is far enough
In what conditions is the speed of light measured at 300,000km/s?
Through space, a vaccum
What is the speed of light measured at through space (a vaccum)?
300,000km/s
Which is faster: light or sound?
Speed of light
How much faster is the speed of light than the speed of sound?
Around a million times faster
How long does it take for light from Earth to reach the moon (approx. 384,400km away)?
Just over 1 second
How far away is the moon from the Earth approximately?
384,400km
How long does sunlight take to reach Earth?
Eight minutes
a) When we look at the Sun, what are we actually looking at?
b) Why is this?
a) The Sun as it was 8 minutes earlier
b) Because it takes 8 minutes for sunlight to reach the Earth
How are vast space distances measured?
In light-years
What can light-years be used to measure?
Vast space distances
Explain what a light-year is.
One light-year is the distance light travels in one year
Approximately how much/far does light travel in one year (i.e. a light- year)?
Approx. 9500 billion km
How far away is the nearest galaxy to the Milky Way?
2.2 million light-years away
In which 2 ways can distances in space be measured?
- Relative brightness
- Parallax
Explain how relative brightness can be used to measure distances in space.
The dimmer a star, the further away it is. However, brightness can vary so a star’s distance is never certain.
Why is a star’s distance never certain when measured using relative brightness?
Brightness indicates how far away a star is, but the brightness can vary meaning the distance is never certain
Explain how a parallax can be used to measure distances in space.
Stars in the near distance appear to move against the background of distant stars. The closer they are, the more they appear to move. The further the star, the less accurate the measurement is.
What human model can be used to explain how a parallax works?
If you hold a finger at arm’s length and close each eye in turn, your finger appears to move. The closer your finger, the more it seems to move.
What can the following model be used to explain?
If you hold a finger at arm’s length and close each eye in turn, your finger appears to move. The closer your finger, the more it seems to move.
It can be used to explain how a parallax works out the distance of a star.
What are the types of radiation that can be produced by stars? (3 things)
- Visible light
- Ultraviolet
- Infrared
What is light pollution?
When electric lights on Earth make it difficult to see stars
At what height does the Hubble Space Telescope orbit the Earth?
600km
True or False?
The Hubble Telescope can be affected by light pollution.
False - The Hubble Telescope orbits at 600km so is not affected by light pollution or other atmospheric conditions.
If a source of light is moving ______ from us, the wavelengths are longer than if the source is stationary.
Away
If a source of light is moving away from us, the wavelengths are ________ than if the source is stationary.
Longer
Wavelengths of light from nearby galaxies are longer than scientists expect. What does this mean?
That galaxies are moving away from us.
Who observed that almost all galaxies are moving away from us? (HT)
Edwin Hubble
What did Edwin Hubble discover? (HT)
That almost all galaxies are moving away from us, and the further away they are, the faster they are moving away.
Edwin Hubble showed that almost all galaxies are moving away from us, and the further away they are, the faster they are moving away. What law was this developed into? (HT)
Hubble’s Law.
What does Hubble’s Law state? (HT)
The speed at which a galaxy is moving away is proportional to its distance from us.
According to Hubble’s Law, what is meant if all the galaxies are moving away from us? (HT)
That the universe is expanding.
If an electromagnetic wave appears to have a longer wavelength than it should have, how would you describe what has happened to it? (HT)
It has been red shifted
If an electromagnetic wave appears to have a longer wavelength than it should have, then it’s been red shifted. What, therefore, must have been happening to the object? (HT)
It must have been moving away
Complete the sentence:
The more the wavelengths are red shifted… (HT)
…the faster the object is moving away.
True or False?
The more the wavelengths are red shifted, the slower the object is moving away. (HT)
False - The more the wavelengths are red shifted, the faster the object is moving away.
True or False?
The waves from a star in a galaxy moving away appear to have a shorter wavelength than those from a stationary source.
False - The waves from a star in a galaxy moving away appear to have a longer wavelength than those from a stationary source.
The waves from a star in a galaxy moving away appear to have a longer wavelength than those from a stationary source. This means they appear to be __ ____. The lines in the spectrum are ______ towards the red end of the spectrum.
- Red shifted
- Displaced
What does the Big Bang theory say?
That the Universe began with a huge explosion 14,000 million years ago
For what 3 reasons 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
- The assumptions made in interpreting observations
What else is required to predict the future of the Universe? (HT)
A knowledge of the quantity of mass in the Universe is also required to predict the future
Why is a knowledge of the quantity of mass in the Universe required to predict the future? (HT)
Because if there isn’t enough mass, the Universe will keep expanding. If there’s too much mass, gravity will pull everything back together and the Universe will collapse.
What will happen if there’s not enough mass in the Universe? (HT)
The Universe will keep expanding
What will happen if there’s too much mass in the Universe? (HT)
Gravity will pull everything back together and the Universe will collapse.
What is the difference between moons and asteroids?
Moons orbit planets; asteroids orbit the Sun
How do spectra give evidence for red shift? (HT)
They’re displaced towards the red end of the spectrum
What is the relationship between the distance of galaxies and the speed at which they’re moving away? (HT)
They’re proportional to one another
Give some ways by which local authority might protect the population from possible earthquakes.
- Set up warning systems
- Not allow multi-storey buildings to be built
- Train emergency services to deal with rescue procedures, casualties and fires
- Identify evacuation procedures
- Ensure buildings have energy-absorbing foundations
A 3m wave has a frequency of 12Hz. At what speed is it travelling?
36m/s
