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
