earthquakes & volcanoes

    Cards (49)

    • what are the four layers of the earth?
      crust, mantle, outercore, innercore
    • the crust
      thickness-100km
      temperature-600c
      made of- solid rock
    • mantle
      thickness- 2900km
      temperature- 1000-3700c
      made of- molten rock
    • outercore
      thickness- 2300km
      temperature- 4400c
      made of- molten metals
    • inner core
      thickness-1220km
      temperature-6000c
      made of- heave metals like Fe
    • patterns of tectonic activity
      • volcanoes and earthquakes tend to occur in similar places, along narrow belts, which follow the lines of the plate boundaries
      • there is a concentration of tectonic activity around the pacific ocean. due to high numbers it is known as the 'ring of fire'
      • some volanoes do not follow this pattern and occur in the middle of plates and these arease are known as hot spots
    • convection currents
      transfer heat from the core to the mantle - as magma rises plates push apart. then it cools, condenses and sinks back down
    • ridge push
      when gravity causes the mid-ocean ridge to sink down and spread out
    • slab pull
      when the weight of the descending oceanic plate pulls the whole plate along and down
    • constructive
      • plates move apart
      • magma rises up through the gap between the two plates
      • the magma cools down and turns into solid rock, creating new land
      • gentle volcanic eruptions
      • gentle earthquakes
      • Eg. iceland, mid-atlantic ridge
    • destructive
      • plates move towards eachother (one oceanic and one continental)
      • oceanic crust subducts (goes under) the continental crust
      • oceanic crust melts into a magma, due to friction and intense heat in the subduction zone
      • violent volcanic eruptions
      • violent earthquakes
      • Eg. pacific ring of fire
    • collision
      • plates move towards each other (both continental)
      • continental plates collide into each other
      • layers of rock are crumpled, buckled and folded up into mountains
      • no volcanic activity
      • violent earthquakes
      • Eg. Himalaya Mountains
    • conservative
      • plates slide past eachother
      • pressure and stress build up along the boundary between the two plates
      • the pressure is suddenly released as an earthquake and the two plates 'spring' past each other
      • no volcanic empire
      • violent earthquakes
      • Eg. san andreas fault, west coast of North America
    • magma
      molten rock
    • magma chamber
      underground store for magma
    • main vent
      main channel for magma to travel the surface to travel to the surface
    • crater
      opening at the top of the volcano
    • lava flow
      molten rock flowing down the side of the volcano
    • volcanic bombs
      lumps of molten rock thrown out of the volcano
    • steam, gas and dust
      hot clouds of small particles
    • secondary vent
      channels which form when the main vent is blocked
    • what is the volcanic explositivity index
      ranges from zero-eight showing how often a volcano erupts
    • shield volcano
      • gentle sides
      • cover a wide area
      • thin, runny lava, low viscosity
      • basaltic lava flows
      • e.g mauna loa
    • stratovolanoes (composite cone)
      • steep sides
      • cone shaped
      • viscous, sticky lava
      • explosive eruptions due to gas building up
      • rhyolite + andesite
      • e.g mt pelee
    • why do people live near volcanoes?
      • fertile soil that is good for agriculture
      • the presence of minerals
      • geothermal energy to produce electricity
      • tourism: volcanoes attract millions of visitors every year
    • prediction
      volcanologists monitor volcanoes all over the world taking readings to determine change so they can predict wether a volcano is likely to erupt
    • planning
      helps communities to respond and recover from a natural disaster, such as volcanic eruption. it includes drawing up evacuation plans and using hazard maps to prevent building in high risk areas where lava may flow
    • preparation
      involves educating people on what to do if a nearby volcano erupts
    • satellites
      used to monitor volcanoes by detecting changed in the earths surface, such as ground deformation
    • tiltmeters
      measures small changes in the slope of the ground and shape at volcano
    • seismographs
      measures + records vibrations from the ground
    • gas trapping bottles
      captures volcanic gases to be analysed
    • where are earthquakes found?
      • most earthquakes occur in lines/bands along plate margins
      • they can happen along all types of plate margins
      • examples include along the mid atlantic ridge and around the pacific ring of fire
      • there are some exceptions of earthquakes that dont occur near a plate margin, such as those along intraplate fault lines in the uk
    • what is an earthquake?
      an earthquake is a sudden jolt or movement within the earths crust causing vibrations which are felt on ground surface
    • how do earthquakes occur
      the fault line is where two pieces of crust have split. the point within the earths crust where they have split is called the focus. the sudden jolted movement at the focus causes seismic waves to radiate outwards. the point directly above the focus at the ground surface is called the epicentre. once the seismic waves reach the ground surface, shaking is felt with the most shaking occuring at the epicentre. further away from the epicentre the shaking is less violent.
    • richter scale
      • measures how much energy is released during the earthquake using seisometers
      • quantative
    • mercalli scale
      • measures the intensity of shaking created by and earthquake
      • records observations
      • subjective + qualitative
    • landslides
      • fractured rocks can be shaken loose
      • buildings/transport destroyed
      • trigged by earthquakes in areas where material on a slope is unstable
    • tsunamis
      • when an earthquake occurs underwater the sudden shift in the seafloor causes a displacement of water
      • series of extremley long waves is generated
      • waves continue to travel across the ocean
      • when a tsunami enters shallow waters the height increases
      • tsunami can travel inland for up to 10 miles
    • liquefication
      • occurs when soil which is waterlogged is shaken violently during an earthquake
      • buildings are moved/ collapse
      • once shaking stops it returns to solid