Tectonic hazards

• what are the three layers of the Earth

  • core
  • mantle
  • crust
• explain the core

  • in the centre and split into two layers: inner metallic core (solid) and outer core (liquid
  • it is the hottest part of the Earth
• explain the mantle

  • surrounds the core
  • consists of semi-molten rock
• explain the crust

  • a very thin outer shell of the Earth
  • the layer we live on
  • floating on the semi-molten rock mantle
  • broken into large pieces called tectonic plates
• what are the two types of tectonic plates

  • continental
  • oceanic
• what is a continental plate

  continental plates are thicker, older and lighter, so they do not sink (subduct)
• what is an oceanic plate

  oceanic plates are thinner, younger, and denser so they can sink (subduct) under another plate
• what is a plate margin or plate boundary

  they describe the location on Earth where 2 tectonic plates meet or sit next to each other
• tectonic plates move according to the movements below in the mantle
• where do convection currents happen

  in the upper mantle
• convection currents

  • the core is hot and heats molten (melted) rock
  • this heated rock rises and hits the underside of the plate
  • when heated molten rock rises, the molten rock drags the tectonic plate that is on top of the mantle with it
  • this means some plates are being pushed apart and some are being dragged together
• what are the three main types of plate margins

  • destructive
  • constructive
  • conservative
• explain what happens at constructive plate margins

  • the plates move apart (diverge)
  • the convection currents diverge (push apart) and cause a gap to form between the plates
  • magma rises up to fill the gap that is created between the 2 plates
• what happens at destructive plate margins

  • the oceanic plate slips beneath the continental plate. The point at which this happens is called a subduction zone.
  • the rocks catch one another as the plates are not smooth surfaces.
  • the pressure between the plates builds until the plates can't take the stress.
  • they slip past each other, which can cause both plates to move and , as a result, the ground may shake (earthquake)
• what happens at conservative plate margins

  • plates are sliding past each other
  • the plates are made of rock that has jagged edges so they catch and snag against one another
  • friction and pressure between the plates builds until the plates can't take the stress
  • they slip past each other, which causes both plates to move and, as a result, the ground may shake (earthquake)
• what types of volcanoes are formed at constructive plate margins

  shield volcanoes
• what type of volcanoes are formed at destructive plate margins

  composite volcanoes
• What is a volcano

  An opening in the Earths crust that is formed when magma rises from inside the Earth and erupts through the Earth’s crust
• at what plate margins can volanoes be formed

  • constructive
  • Destructive
• destructive plate margins - volcanoes

  • the denser oceanic plate is forced under the continental plate at destructive margins
  • the friction and pressure cause cracks (vents) to form in the continental plate. The magma rises to the surface of the Earth through the cracks in the continental plate
  • this usually creates a composite volcano that produces a lot of gas and lava (magma above the surface)
• hotspots

  • do not happen at plate boundaries but still count as volcanic activity
  • happen on parts of the Earth's crust over hotter parts of the Earth's mantle
  • the rising hot air weakens the Earth's crust and magma can reach the surface, bubbling upon through the weakness in the crust
• constructive plate margins - volcanoes

  • tectonic plates move apart (diverge) because the convection currents in the mantle diverge, creating outward pressure.
  • magma bubbles up to fill the gap between the plates, creating a shield volcano
• what does a volcanic eruption produce

  • lava
  • gases
  • ash
  • pyroclastic flows
• define lava

  magma above the surface of the Earth
• volcanoes emit lots of gases
• define ash in terms of volcanoes

  • tiny pieces of burnt rock fragments that are blown into the atmosphere, usually at some force.
  • these pieces fall on land and can float in the air, causing a volcanic winter (by blocking out the sun)
  • a volcanic winter describes when a volcano erupts, producing lots of ash, which then blocks the sun.
• define pyroclastic flows - volcanoes

  • currents of hot ash, lava and gas that can move downhill very quickly during an eruption and are impossible to outrun
  • they are very hot (up to 1000 C) and can cover far distances (uo to 30km) from the volcano
• what are primary effects

  effects that happen during the natural disaster
• what are secondary effects

  effects that happen later on because of the primary effects
• define 'earthquake'

  a sudden or violent movement within the Earth's crust followed by a series of shocks. An earthquake happens when the Earth's tectonic plates move and cause the ground to shake
• plates forcing their way past each other

  • as plates move past each other, pressure builds up from the friction between them
  • when the pressure is sufficient, the plates give way. The tectonic plates will surge past each other and the ground will shake from this violent movement
• where can earthquakes happen

  at all 3 plate margins (destructive, constructive and conservative)
• what happens at constructive plate margins

  pressure can build up from cracks in the plates when they move apart
• what happens at destructive plate margins

  the oceanic plate can get stuck as it is forced under the continental plate. This can cause tension to build
• what happens at conservative plate margins

  • when plates move past each other, there can be friction between them because the plates are not smooth.
  • when the pressure is enough, the plates give way. This causes th plates to move past each other and the ground to shake
• what are the different aspects of an earthquake

  • focus
  • shock (seismic) waves
  • epicentre
• explain the focus of an earthquake

  • where the pressure is released underground and where the energy radiates out from.
  • this is the place with the strongest waves that cause the most destruction
• explain shock (seismic) waves

  • energy is released from the focus in shock waves (called seismic waves)
  • the most damage will occur at the places where the shock waves are the strongest (closest to the epicentre)
• explain the epicentre of an earthquake

  the point on the Earth's crust that is directly above the centre of the earthquake
• what do we use to measure earthquakes

  the moment magnitude scale (measures the magnitude of an earthquake by measuring how much energy it releases)