tectonic plates Flashcards
plates are moving because of what
convection currents
destructive
towards - when an oceanic meets a continental the oceanic subducts because it is denser and is destroyed creating gas rich magma. volcanoes and oceanic trenches are made here.
where 2 continental meet the ground is folded upwards creating fold mountains.
constructive
away - magma rises from the mantle to fill the gaps and cools, creating new crust - e.g. Eurasian and north American moving away creating the Atlantic ridge.
conservative
sideways - either same direction at diff speeds or opposite directions. crust is not created or destroyed.
volcanoes occur at which plate boundaries or margins
constructive - magma rises up into the gap created by the plates moving apart, forming a volcano
destructive - oceanic plate subducts under the continental plate and is destroyed, forming gas rich magma. this magma rises through vents and erupts as lava at the surface, forming a volcano
what happens when a volcano erupts
it emits lava and gas, some emit lots of ash, which can cover land and block out the sun and form pyroclastic flows
what plate margins do earthquakes occur at
all three - constructive, destructive and conservative when tension builds up
explain how tension builds up at each of the plate margins
constructive - tension builds along cracks as the plates move away
destructive - tension builds when one plate gets stuck as it moves past the other
conservative - tension is built when plates that are grinding past each other get stuck
explain what happens when the tension built up is released
shock waves are sent out, these vibrations are the earthquake. shock waves spread out from the focus, this is where the earthquake starts. epicentre is the point above the focus on the earths surface. measures in the moment magnitude scale.
moment magnitude scale
measures amount of energy released. it is logarithmic so each number is 10x more. mag 7 is where it gets really damaging
why do people choose to live in areas at risk from teccy hazards
leaving means losing jobs or family
soil near volcanoes are very fertile, attracting farmers
tourism
name the 4 management strategies
monitoring, planning, prediction, protection
explain breifly the 4 management strats
- prediction - scientists can forecast where earthquakes may occur by monitoring the movement of tectonic plates, eruptions can be predicted
- protection - for earthquakes new buildings can be reinforced with concrete to absorb the earthquakes energy an existing bridges and buildings can be reinforced with steel frames so they are less likely to collapse. automatic shut of switches to shut of electricity to prevent fires. for volcanoes trenches can be used to divert lava and buildings can be strengthened so they are less likely to collapse under the weight of ash.
- planning - future developments can avoid high risk areas. people can be educated so they know what to do in the event of a hazard. governments can plan evacuation routes to get people away wuickly and safely.
