Unit 1A - Tectonic hazards Flashcards
What are the contents of the earth’s core?
a ball of solid and liquid (iron & nickel)
What are the contents of the earth’s mantle?
semi-molten rock that moves very slowly
What are the contents of the crust?
two crusts, continental and oceanic
What is the continental crust?
thicker (30km-50km) less dense
What is the oceanic crust?
is thinner (5-10km) and more dense
Why are the plates moving?
because of convection currents in the mantle underneath the crust
What is the oceanic crust?
thinner(5-10km) more dense
Why are the plates moving?
because of the convection currents in the mantle underneath the crust
What is it called when plates meet?
plate margins or plate boundaries
What is a destructive margin?
is where two plates are moving towards each other
Describe how destructive margins occur?
oceanic and continental plates meet, the most dense plate is forced down in the mantle and destroyed, creating volcanoes and oceanic trenches
What is a constructive margin?
where two plates are moving away from each other
Describe how constructive margins work?
magma rises from the mantle to fill the gap and cools, creating new crust
What is a conservative margin?
two plates are moving sideways past each other/ same direction but at different speeds
Why do oceanic plates go under continental plates?
because it’s more dense
How are volcanoes formed?
- oceanic plate moves down into mantle, melted and destroyed
- a pool of magma forms
- magma rises through cracks in the crust called vents
- magma erupts onto the surface forming a volcano
What happens constructive margins in the formation of volcanoes?
magma rises up into the gap created by the plates moving apart
Where do volcanos sometimes form?
over parts of the mantle that are really hot = hot spots
What happens when a volcano erupts?
emits lava and gases, some emit lot’s of ash
What is a pyroclastic flow?
when ash covers the land and blacks out the sun
What are earthquakes caused by?
tension that builds up all three types of plate margins
What is destructive margins?
tension built up when one plate gets stuck as it’s moving past the other into the mantle
What is constructive margin?
tension builds up along cracks within the plates as they move away from eachother
What is conservative margin?
tension builds up when plates that are grinding past each other get stuck
What are shockwaves caused by?
plates eventually jerking past each other “earthquake”
Where do shockwaves spread out from?
the focus - point of the earth where the earthquake starts
Where is the epicentre?
point on the earth surface straight above the focus
What earthquakes measured by?
moment magnitude scale
How do moment magnitude scales work?
- measures amount of energy released
What does magnitude 6 mean?
earthquakes that only cause slight damage to buildings, worse in built up areas
What does magnitude 7 mean?
earthquakes causing major damage and deaths
What are the primary effects of earthquakes?
- buildings collapse and homes destroyed
- people injured, killed by collapsed debris
- roads, railways, ports & airports damaged
- electricity cables, gas and water pipes and communications networks damaged
What are the secondary effects of earthquakes?
- landslides and tsunamis
- leaking gas
- shortage of clean water
- trade vehicles can’t get through
- business’s damaged
What are the immediate responses to a earthquake?
- rescue trapped people
- recover dead bodies
- set up temporary shelters
- provide energy & supplies
- charity sent aid workers
What are the long-term responses to a earthquake?
- re-house
- repair or rebuild buildings
- reconnect electricity, water and gas
- economic recovery
What are the primary effects of volcanoes?
- buildings and roads destroyed
- people and animals injured
- crops damaged
- people, plants and animals suffocate
What are the secondary effects of volcanoes?
- mudflows
- flooding
- transport networks blocked
- homelessness
- ash makes fields more fertile
What are the immediate responses to a volcanoes?
- evacuation
- provide food, drink and shelter
- rescue anyone cut off by damage
- provide temporary power
- tech companies may set up response mechanisms
What are the long-term responses to a volcanoes?
- repair, rebuild or resettle
- repair and reconnect
- boost the economy
Why do people choose to live near a volcano?
- always lived their
- employed their
- confident of support from the government
- don’t think disasters can happen again
- soil around is fertile
- tourist attraction
What are the 4 management strategies?
monitoring, prediction, protection and planning
How does monitoring reduce the effects of tectonic hazards?
seismometers monitor earth movements, early warning system. Scientists can monitor signs coming from volcanic eruption
How does prediction reduce the effects of tectonic hazards?
scientists can forecast which areas should be prepared, volcanoes can be predicted if well-monitored
How does protection reduce the effects of tectonic hazards?
future developments can be planned to avoid disasters, people can be educated, plan evacuation routes, emergency supplies can be accessible
