Plate Boundary Flashcards
What is a conservative plate boundary?
Where 2 plates do not directly collide but slide past each other along a fault (weakness), no volcanoes are found along these plate boundaries but earthquakes do occur, eg. San Andreas fault
What is a collision boundary?
When 2 plates of similar densities move together (such as 2 continental plates), causes material between them to buckle and rise up, forming fold mountains, eg. Himalayas are an example of fold mountains, formed by the Indian plate colliding into the Eurasian plate
What is a constructive plate boundary?
2 plates are moving away leaving a gap in the middle for magma to rise up through, volcanoes form but don’t erupt with power as the magma can escape easily, earthquakes occur, eg. Mid Atlantic ridge, rift valleys can also form as land falls into space left as plates move apart (Iceland)
What is a destructive plate boundary?
Dense oceanic plate descend below less dense continental plate, as the plate descends it is melted due to friction (in the subduction) with the continental plate, farming hot, liquid magma, magma can rise through cracks in the continental plate and form volcanoes if it reaches
What is a rift valley?
A deep valley that forms where two plates move apart (constructive plate boundary)
How are rift valleys formed?
Where plates diverge beneath land rising magma causes the continental crust to bulge and fracture forming fault lines. As the plates keep moving the crust between the parallel fault lines drop down to form a rift valleys. Volcanoes are found around rift valleys.
What is a continental plate?
Thicker, average 40-75km, less dense, older (1500 million years), granite silica and aluminium
What are oceanic plates?
Shallow, average 5-12km deep, younger (less than 200 million years old), more dense, mainly basalt, silica and magnesium
How are fold mountains formed?
When tectonic plates collide A the sedimentary rocks that have built up between them are folded and forced upwards to form mountains.
Explain destructive margin: continental and oceanic:
Denser oceanic plate subducts below continental plate, the plate subducting leaves a deep ocean trench, built up pressure from the melting plate causes explosive volcanoes bursting through the continental plate
Explain destructive margin: oceanic and oceanic:
Heavier plate subducts leaving an ocean trench, built up pressure causes underwater volcanoes bursting through oceanic plate, lava cools and creates new land called island arcs
Explain destructive margin: continental and continental:
Both plates are not as dense as oceanic so lots of pressure builds, ancient oceanic crust is subducted slightly but there is no subduction of continental crust, pile up of continental crust on top of lithosphere due to pressure between plates, fold mountains formed from piles of continental crust
Explain constructive margin: oceanic and oceanic:
Magma rises in between the gap left by the two plates separating, forming new land when it cools, less explosive underwater volcanoes formed as magma rises, New land forming on the ocean floor by lava filling the gap is known as sea floor spreading (as the floor spreads and gets wider)
Explain constructive margin: continental to continental
Any land in the middle of the separation is forced apart, causing a rift valley, volcanoes form where the magma rises, eventually the gap will most likely fill with water and separate completely from the main island
What is ridge push?
The slope created when plates move apart has gravity acting upon it as it is at a higher elevation, gravity pushes the plates further away, widening the gap (as this movement is influenced by gravity, it is known as gravitational sliding)
What is slap pull?
When a plate subducts, the p,ate sinking into the mantle pulls the rest of the plate (slab) with it causing further subduction
