Pricesses Operating At Plate Margins

Question 1

What does slab pull cause at divergens plate margins

Answer 1

Driven by slab Pull diverging plates bring magma to the surface to form a ridge

And example of this is the mid Atlantic Ridge separating the South American and African plates rising up to 3 km above the ocean for the plates are spreading at an average of 2.5 cm per year

Volcanoes form along the ridge and may rise above sea level creating islands for example Surtsey 32 km from Iceland was formed between 1963 and 1967 from volcanic eruptions at the mid-Atlantic Ridge

Question 2

What happens where continental plates diverge ?

Answer 2

Mountain ridges are found at the plate margins as hot magma forces the crust to bulge

As plates move apart the brittle crust fractures forming parallel faults

Areas of crossed slowly subside between the faults to form a Rift Valley

The East African rift Valley is an example stretching 3000 km as a result of the African plate splitting into two and moving apart at 7 cm per year

Volcanic activity can occur along the plate margin for example Mount Kilimanjaro in Tunisia which lies on the eastern edge of the east African Rift Valley

Question 3

What happens where to oceanic plates converge

Answer 3

The colder than simply will subducting of the other forming an ocean trench

Question 4

What happens where an oceanic and continental crust converge

Answer 4

The denser oceanic crust is subducted by slab pull

The less dense continental crust gets buckled and folded to form mountain chains

Magma rises up through weaknesses in the Continental crust to form volcanoes

Question 5

What happens at conservative plate margins

Answer 5

Plates slide past each other and there is no subduction so no volcanic activity however earthquakes will occur and these can be powerful if the buildup of pressure is suddenly released

And example of this is the San Andreas fault in California where the Pacific plate is moving 5 cm a year faster anything direction as the North American plate

Question 6

What are hotspots

Answer 6

Small areas away from plate margins with unusually high heat flow linked to volcanic activity

Question 7

How do you hotspots form volcanoes

Answer 7

Magma rises as a plume from the asthenosphere the magma pushes through the crust volcanoes the surface

As the point moves over the hotspot it creates an alarm for volcanoes which move with the plate

As oceanic volcanoes move away from the hotspot they call and subside remaining as islands or if on the water seamounts

And example of this is the Hawaiian islands extending 2400 km