2.1 Earthquakes and Volcanoes Flashcards
Oceanic crust
Younger
Heavier (sinks)
Constantly being destroyed and replace
Continental crust
Older
Lighter (cannot sink)
Permanent
What is the general distribution of earthquakes and volcanoes?
Found near plate boundaries
Pacific ring of fire
Mid-Atlantic ridge
Collision boundary
Two continental plates move towards each other.
e.g. Indo Australian and Eurasian plate
Constructive boundary
Two plates moving away from each other.
e.g. North American and Eurasian plate (mid-Atlantic ridge)
Conservative boundary
Two plates slide past each other.
North american plate and Pacific plate
Destructive boundary
Oceanic plate is subducted by a continental plate.
What do constructive boundaries cause?
Gentle earthquakes and volcanoes
No fold mountains
What do destructive boundaries cause?
Violent earthquakes and volcanoes
Fold mountains
What do collision boundaries cause?
Violent earthquakes
Fold mountains
No volcanoes
What do conservative boundaries cause?
Violent earthquakes
No volcanoes
No fold mountains
Earthquake
Series of vibrations or movements in the earth’s crust
How is an earthquake caused?
Two plates get stuck; pressure builds up; one plate jerks forward sending shock waves.
Focus
The point of origin of an earthquake
Epicentre
The point on the earth’s surface vertically above the focus of an earthquake
Seismic waves
Waves of energy that travel through the Earth’s layers
Subduction zone
Where one plate goes under another (destructive margin)
Effects of earthquakes (5)
Deaths Water pipes burst Water contamination - water borne diseases Buildings destroyed Tsunami can follow
Ways of predicting an earthquake (3)
Measure earth tremors
Find patterns in locations
Unusual animal behaviour
Ways of preparing for an earthquake (5)
Build earthquake-proof buildings Training emergency services Setting up warning systems Evacuation plans Practice drills
Ways of making a building earthquake-proof (4)
Weights on roof to reduce movement
Rubber-shock absorbers in foundations
Foundations sunk deep into bedrock
Automatic shutters to protect from broken windows.
Volcano
A vent in the earth’s surface were magma, gas or ash escapes.
Explain how a volcano is created at a constructive margin
Plates move away from each other
Magma rises to fill the gap
Explain how a volcano is created at a destrutcive margin
Subducted oceanic plate melts due to heat from mantle
New, hot magma is less dense and rises to the surface.
Active volcano
Has erupted recently
Dormant volcano
Hasn’t erupted recently but may in future
Extinct
Unlikely to ever erupt (no magma inside)
Shield volcano (4)
Gentle slopes
Slow flowing lava but frequent eruptions
Made from solidified lava
Constructive boundaries
Cone volcano (2)
Steep slopes
Violent eruption
Composite volcano / stratovolcano (5)
Mix of cone and shield volcanoes Eruptions vary in strength Made of layers of ash and lava Destructive boundaries Pyroclastic flow
Advantages a volcano brings (3)
Tourism
Fertile soil
Geothermal energy
Disadvantages a volcano brings (3)
Destruction of land/homes/transport/jobs Poisonous gases (SO2) Pyroclastic flow
How can we predict a volcano (4)
Tremors within the volcano
Ground temperatures rise
Volcano emits gas and steam
Animal behaviour
How can we prepare for a volcano (4)
Warning systems
Evacuation plan
Better trained emergency services
Emergency food supply
Pyroclastic flow
Mixture of hot steam, ash, rock and dust
Crater
Bowl-shaped geological formation at the top of the volcano
Vent
Opening exposed on the earth’s surface where volcanic material is emitted
Magma chamber
Reservoir of magma within the earth’s crust beneath a volcano.
Seismograph
Instrument that measures and records force and duration of earthquake
Tectonic plates
Rigid pieces of the earth’s lithosphere which together make the earth crust
