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Destructive plate margins - Coggle Diagram
Destructive plate margins
Continental and oceanic plates
Denser oceanic plate subducts
below the continental.
The plate subducting leaves a deep
ocean trench.
The oceanic crust is melted as it
subducts into the asthenosphere.
Continental plate made up of granite. Oceanic plate made up of heavier basalt (denser)
Explosive (moderate to high VEI scale 5-6)
Oceanic trench; fold mountains with volcano peaks
Trench gas low heat flow and negative gravity anomaly; range of rock age
Seismic actvity: Range of focal depths from shallow to 700 km along Wadati-Benioff zone.
Often high magnitude (8-9)
Explosive, high pressure volcanoes erupt through the continental plate, known as composite volcanoes.
Heat rising and falling inside the mantle creates convection currents generated by radioactive decay in the core.
Composite volcanoes are the most common type of volcano and are common at destructive plate boundaries.
The lava is viscous (thick) and has a higher silica level than with shield volcanoes.
In a composite volcano the magma is too stiff to allow easy escape of volcanic gases.
Friction causes melting of the oceanic plate and may trigger earthquakes.
Destructive plate margins occur where an oceanic and continental plate move towards each other.
Examples below include the Pacific Plate and Eurasian Plate and the Nazca Plate and the South American Plate.
As it sinks below the continental plate the oceanic plate melts due to friction in the subduction zone. The crust becomes molten called magma.