theory of plate tectonics 1.1

what is the subduction zone

where 2 plates meet

convergent plate boundary

plates moving towards each other

oceanic plate subducts under continental plate as its denser forming deep ocean trenches in the subduction zone

Earthquake and volcanoes occur

Divergent plate boundary

Plates move apart

Convection current diverge causing gap between plates where magma rises up to fill gap causing new crust to form

collision plate boundary

plates move towards each other, plates are same density so they’re forced upwards. no volcanic activity as no subduction zone. earthquakes occur

conservative boundary

Plates move past each other

They become stuck and pressure builds causing plates to snap past each other

Fiction causes earthquakes but not volcanoes

the crust

continental- thicker, less dense layer

oceanic- thinner, denser layer

upper mantle

asthenosphere- semi molten layer which moves under high pressure

Lithosphere- rigid layer above astehnosphere

lower mantle

hotter and denser,

core

inner core- solid centre, composed of iron

outer core- semi molten, liquid iron and nickel

what are the 2 types of tectonic plates

Oceanic- makes up ocean floor, high density, subducts under plates

Continental- makes up Earths land, less dense, dosen’t subduct

What are hotspots

At hotspots there’s hot mass of rising heat under weakness in a plate.

Magma rises to surface through this weakness

Hawaiian islands formed

Intra Plate volcanoes

Volcanoes can happen at hotspots

Mantle plumes rise towards surface generating basaltic volcanoes.

Plume is stationary but tectonic plate above moves slowly over it

Continuing plate movement over time creates chain of volcanoes

Intra plate earthquakes

Don’t happen at plate boundaries- linked to hot spots or fault lines

Formed by tectonic stresses causing ancient fault lines to reactivate.

Zones of weaknesses are created as plates move and stress increases