science unit 4: plate tectonics

7th grade

plates are made of…

rigid pieces of the lithosphere

plates are moved by

the convention currents of the mantle

oceanic plates

3-5 miles thick, very dense (which means it sinks!), made of basalt

continental plates

20-30 miles thick, less dense, made of granite

subduction

downward movement of the crust going into the mantle, below another plate (↘⬅)

subduction zone

the area where subduction happens

boundary

the region where two tectonic plates meet, leading to interactions such as earthquakes, volcanic activity, or plate movement.

divergent

boundary between 2 tectonic plates that are separating, as plates move apart, magma fills the gap (➡⬅)

continental-continental diver

•  creates rift/rift valley 

• ex: iceland has a divergent boundary, and grows 5cm every year

• ex: the red sea between arabian plate and african plate creates rift/rift valley 

oceanic-oceanic divergent

• creates sea floor spreading, called a mid ocean ridge or an ocean basin

• ex: mid atlantic ridge 

• ex: east pacific rise

• the crust close to the rift is newer/younger than the crust far away from the rift

convergent

boundary between two tectonic plates that are colliding/moving towards each other (➡⬅)

oceanic-oceanic continental

• creates trenches, volcanoes, and island arcs

• ex: mariana trench

continental-continental convergent

• ground buckles as it is pushed together

• creates folded mountains

• ex: mariana trench

oceanic-continental convergent

• oceanic subduction because it is denser

• creates volcanoes, island arcs, and trenches

• ex: aleskian and caribbean islands

transform (def)

when two plates slide past each other in opposite directions (⬆⬇)

transform

• creates earthquakes and faults

• ex: san andreas fault

• ex: gulf of cali rift zone

alfred wegener