3.1.1.2 Tectonic hazards Flashcards
(40 cards)
Name and describe the 4 layers that make up the Earth
- Core of Earth is a ball of solid (inner) and liquid (outer) iron and nickel
- Around core is mantle → semi-molten rock that moves very slowly
- Outer layer of Earth is crust
Name and describe the 2 types of crust
Oceanic crust - Thinner (5-10km) and more dense
Continental crust - Thicker (30-50km) and less dense
Why do tectonic plates move?
Plates are moving because of convection currents in mantle underneath crust
What are plate margins/plate boundaries?
Places where plates met
Name the 3 types of plate margins
Destructive Margins
Constructive Margins
Conservative Margins
What are destructive margins and give an example where they can be found?
Where two plates are moving towards each other e.g along west coast of South America
Where and how are ocean trenches formed?
Formed at a destructive margin, where an oceanic plate meets a continental plate, denser oceanic plate is formed down into mantle and destroyed = often creates ocean trenches
What are ocean trenches?
Very deep sections of ocean floor where oceanic plate goes down
Where and how are mountain ranges formed?
Formed at a destructive margin, where two continental plates meet, plates collide and ground is folded and forced upwards to create mountain ranges
What are constructive margins and give an example where they can be found
Where two plates move away from each other e.g. At mid-Atlantic ridge
Where and how is new crust formed?
At constructive margin, where two plates move away from each = magma (molten rock) rises from mantle to fill gap and cools, creating new crust
What are conservative margins and give an example where they can be found?
Where two plates are moving sideways past each other, or are moving in same direction but at different speeds e.g. Along west coasts of USA
Is crust destroyed or created at conservative margins?
No
Where are volcanoes formed?
Volcanoes are found at destructive and constructive plate margins
How does a volcano form at a destructive margin?
At destructive plate margins, oceanic plate goes under continental plate because it’s more dense.
Oceanic plate moves down into mantle where it’s melted and destroyed
A pool of magma forms.
Magma rises through cracks in crust called vents.
Magma erupts onto surface (called lava) forming volcano.
How does a volcano form at a constructive margin?
At constructive margins magma rises up into gap created by plates moving apart = forming a volcano
Where else can a volcano form and give an example?
Volcanoes also form over parts of mantle that are really hot called hotspots e.g. Hawaii
What does a volcano emit when it erupts?
Lava and gases
What happens when a volcano emits a lot of ash? (name 3 things)
The ash can cover land, block out the sun and form pyroclastic flows
What are pyroclastic flows?
Super-heated currents of gas, ash and rock
Where do earthquakes occur?
At all three plate margins
How are earthquakes caused?
Earthquakes are caused by tension that builds up at all 3 types of plate margin
Plates eventually jerk past each other, sending out shock
waves (vibrations - earthquakes)
Shock waves spread out from focus (point in earth
where earthquake starts)
Describe how tension is built up at each plate margin
Destructive - Tension builds up when one plate gets stuck as it’s moving down past other into mantle
Constructive - Tension builds along cracks within plates as they move away from each other
Conservative - Tension builds up when plates that are
grinding past each other get stuck
Where are the shock waves the strongest and most damaging?
Near focus, waves are stronger and cause more damage
