Earthquakes and volcanoes Details Flashcards
Features of strato-volcanoes
-Erupt with great violence
-Usually occur in mountain regions where great pressure can build up beneath the ground
-Lava is more acidic and viscous
Features of shield volcanoes
-Much less violent, damaging and explosive
-Created where there was no great build-up of pressure
-Erupt more often
-Lava is more basic and runny
How strato-volcanoes are created
-Magma builds up below the Earth’s crust in magma chambers
-Pressure from the rocks causes an explosive eruption through a vent
-Magma(now called lava) flows out
How shield volcanoes are created
Magma leaks through where there is a weakness in the Earth’s crust
Location of convection currents
The mantle
Features of continental plates
-Mostly above the ocean, forming land
-Between 25km and 100km thick
-Mostly made of granite
Features of oceanic plates
-Mostly below the ocean
-Between 5km and 10km thick
-Mostly made of basalt
Why do oceanic plates sink below continental plates?
Basalt(what oceanic plates are mostly made of) is heavier and denser than granite(what continental plates are mostly made of)
Types of plate boundaries
-Convergent boundary
-Divergent boundary
-Conservative boundary
How plates move at convergent boundaries
By subduction
How plates move at divergent boundaries
By spreading apart
How plates move at conservative boundaries
They slide sideways by each other
Effect of movement at convergent boundaries
-Destructive
-Old crust destroyed
Effect of movement at divergent boundaries
-Constructive
-New crust created
Effect of movement at conservative boundaries
Crust neither created nor destroyed
Relief formed at convergent boundaries
Trenches
Relief formed at divergent boundaries
Ridges
Relief formed at conservative boundaries
No major effect
Activity at convergent boundaries
Earthquakes and strato-volcanoes
Activity at divergent boundaries
Earthquakes and shield volcanoes
Activity at conservative boundaries
Earthquakes
Major earthquakes/volcanoes may still occur near you even if you don’t live near plate boundaries as…
-The plates move(albeit extremely slowly), carrying volcanoes away from the original boundary
-Hotspots can burn a whole to form a weakness/exploit an existing one, allowing magma to rise to the surface and form shield volcanoes
Positives of earthquakes
Underground minerals may be brought closer to the surface
Negatives of earthquakes
-Kills people and wildlife
-Destroys buildings
-Destroys roads, railways and infrastructure
-Can create tsunamis
Positives of volcanoes
-Attractive for tourists
-Brings in income for locals and countries
-Minerals
-Light ash falls can add nutrients to soil
-Potential for geothermal power
Negatives of volcanoes
-Kills people and wildlife
-Can destroy farms and woodland
-Ash can cause problems for aircraft
-Heavy ash can cover area in thick layers and cause roof collapse
Measures to reduce the impacts of earthquakes
Constructing buildings that are more resistant to earthquakes
Measures to reduce the impacts of volcanoes
NOTHING.
But volcanoes can be predicted, giving time for people to evacuate
