PLATE TECTONICS: A2

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Earth split into three layers
Core, Mantle, Crust
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Which is part of the crust, Asthenosphere or Lithosphere?
Lithosphere - rigid mantle and crust
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Plates meet plates and form
Plate Boundaries (Plate Margins)
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Plates move by
Convection Currents in the mantle
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When plates move apart in the ocean, what is this process?
Sea Floor Spreading - new sea floor is made
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Sea Floor Spreading creates
Mid Ocean Ridges
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First person to suggest theory for Continental Drift
Alfred Wegener - 1912
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1950's brought further evidence with
Palaeomagnetism
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1960's what was discovered to help evidence Continental Drift
Sea Floor Spreading
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Name the 4 sources of evidence for the theory
Geology, Fossil Records, Living Species (earthworms), Palaeomagnetism
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3 types of plate margins
Constructive, Destructive, Conservative
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Do earthquakes and volcanoes occur at Constructive margins?
Yes
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2 Landforms created from constructive margins
Mid-Ocean Ridges and Rift Valleys
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Earthquakes and Volcanoes occur at destructive margins?
Yes
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Oceanic - Continental margin creates
Deep sea trenches and fold mountains (w/ volcanoes and earthquakes)
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Oceanic - Oceanic margin creates
Deep Sea Trenches (no fold mountains) And Island Arcs (underwater volcanoes)
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Continental - Continental margin creates
No Volcanoes due to no subduction. Earthquakes and fold mountains occur
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Conservative plate margins occur when 2 plates
are moving past each other
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What happens here
Earthquakes (fault lines)
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Volcanic eruptions (2 types)
Intrusive and Extrusive
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Intrusive have 4 features
Batholiths, Sills, Dykes, Cooling Cracks
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Lava eruptions a form of extrusive activity, name the 3 types of lava
Basaltic, Andesitic, Rhyolitic
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Name the plate margins in which these lava forms are created
Constructive (Basaltic) Destructive (Andesitic+Rhyolitic)
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What eruptions does Basaltic lava form
Frequent, long periods, non-violent
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What eruptions do A + R lava form
Violent, short lived and intermittent
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4 Types of Volcanoes
Caldera, Dome, Shield, Fissure
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Describe Dome
Steep sides, found at destructive margins, Andesitic and Rhyolitic lava
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Describe Shield
Gentle sloping sides, found at destructive margins, Basaltic lava
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Describe Caldera
Collapsed centre part due to eruption below, found at destructive margins, produces a + r lava, several km wide
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Fissure
Couple metres wide but many km long, found at constructive margins, basaltic lava
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Groundwater source of a spring flows close to an area of intrusive volcanic activity, creating
Hot Springs - water is heated by the mantle
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What 2 other types of hot springs are there?
Geysers and Boiling Mud Pools
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Geysers eject what from the earths surface? and what from?
Hot water and steam, from vents in the surface
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What do Geysers need in order to eject these?
Pressure!!
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Boiling Mud Pools are formed when 2 things mix
Hot spring water and soil
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The bright coloured mud is caused by what from the water?
Minerals
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Volcanoes formed away from plater margins are called
Hot Spots
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Hot Spots are formed by a magma..
plume
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What remains stationary and what moves?
Crust moves, hot spot remains stationary
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What is formed after time
Chain of volcanoes
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Example of these in the world?
Hawaii (USA)
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Earthquakes caused by what that built up at all the plate margins?
Tension
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How is this tension released?
When the plates jerk past each other
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Name of the 3 plate margins
Constructive, Destructive, Conservative
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What does this release cause?
Seismic Waves (vibrations)
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What is the focus?
Point in the lithosphere where the earthquake begins
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What is the epicentre?
Point on the earths surface when the earthquake beings, directly above the focus
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Subsidence can also cause earthquakes, what causes subsidence?
Deep Mining (i.e. shale mining)
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3 main types of seismic waves
P (primary) S (secondary) S (surface: love + Rayleigh)
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P waves move the earth in what direction to the wave
Same direction
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S waves move the earth in what direction to the wave
90 degrees to the direction of the wave
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Can both P and S waves travel through water and solids?
No, P can, S can only travel through solids
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Which is more damaging? and which is faster?
S - more damaging, P - faster
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Love waves move in what way
Side to Side
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Rayleigh waves move in what motion
Rolling motion - like a wave
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Earthquakes measure using what?
Seismometers
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What do they measure?
Magnitude of the wave, and direction and duration of vibrations
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2 different scales to measure earthquakes?
Richter Scale, Mercalli Scale
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Richter Scale measures?
Magnitude of the quake
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What does logarithmic mean in this context?
Each value to 10x greater amplitude (size of wave) and 30x more energy released
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After what value is it deemed a major earthquake?
7+
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Mercalli scale measures what?
Impact
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How does it do this?
Uses observations from the event, i.e. photos and reports
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What is the scale?
1 to 12 - 12 being highest
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What does the 1 represent?
Quake only detected by instruments
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12?
Total destruction!
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Tsunami's caused by..
the displacement of large volumes of water
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Can be triggered by what underwater?
Underwater Earthquakes
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What happens to the seabed?
Moves - displacing the water
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Can also be caused by?
Volcanic eruptions and landslides
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If they start closer to the coast they will be
More powerful
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In open ocean (deep water) how fast do they travel?
500-950km/h
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What wavelengths? and Amplitude (wave height)?
200km and 1m (small amplitude)
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Wavelengths? and Amplitude?
20km and many metres (larger amplitude)
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What is drawback?
When water retreats back from the coast down the shore
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How far do they usually travel inland, large or short distance?
Short - they lose a lot of energy quickly
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Tectonic hazards are caused by
movement of tectonic plates
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3 types of management
Prediction, Building Techniques, Planning and Education
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Can you predict earthquakes?
NO - but there are clues, i.e. strange animal behaviour
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Earthquake Warning Systems can detect what type of wave?
P wave - but only after the earthquake has begun
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Is it possible to predict future earthquakes?
Yes - using previous quake data
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What can indicate a volcanic eruption in the near future?
Bulges in the volcanoes shape, tiny earthquakes
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Can it be difficult to evacuate everyone?
Yes - some people refuse to leave and/or dont believe the eruption will occur
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What do Tsunami warning systems rely on?
Earthquake Detection Systems
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What do the warning systems rely on in order to evacuate people?
Good communication systems
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What materials are used to make buildings 'earthquake-proof'
Strong Materials - reinforced concrete
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Construction Laws in Japan and USA mean what for new buildings?
Have to be built to withstand earthquakes - safer
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Can buildings be 'volcano-proof'
They cant prevent lava flow, but can be strengthened to withstand ash fall
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What happened in the 1983 Mt Etna eruption?
Lava Flow diverted by rubble barrier
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How are buildings designed for tsunamis?
Raised, open foundations with strong materials
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Planning and Education can be more?
Cost effective method
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Future developments are..
designed away from high risk areas
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Who are being trained to deal with disasters?
Emergency Services (FEMA)
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What happened in Oregon concerning tsunami's?
leaflets provided containing evacuation routes
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What regularly occurs in Japan to prepare for disasters?
Earthquake and Tsunami drills (education)
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Name the 3 main factors making the impacts more severe
Development level of the country, population, timing
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Lower the development of a country the...
higher impact a hazard will bring
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Less money means
Less money on planning and responses for disasters
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Highest economic impact found in higher or lower developed country?
Often higher because buildings and infrastructure worth a lot of money
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More people in an area =
More people affected by the hazard
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Densely populated areas pose what sort of risk and why?
Big risk, lots of big buildings collapsing
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Why would an earthquake at night pose more a risk?
Less people awake, dont get out of buildings quick enough etc.
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Other cards in this set

Card 2

Front

Which is part of the crust, Asthenosphere or Lithosphere?

Back

Lithosphere - rigid mantle and crust

Card 3

Front

Plates meet plates and form

Back

Preview of the front of card 3

Card 4

Front

Plates move by

Back

Preview of the front of card 4

Card 5

Front

When plates move apart in the ocean, what is this process?

Back

Preview of the front of card 5
View more cards

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