The plates interact at the surface in a variety of ways Flashcards
What is the summary of a divergent oceanic oceanic plate margin?
The rising convection current below lifts the lithosphere, producing a mid-ocean ridge
What forms along the oceanic oceanic divergent plate margin?
3000m high ridge
What is the summary of a divergent continental continental plate margin?
As the plates are torn apart, the plate arch due to convection. It is torn thin by extensional forces, fracturing the plate so that the central area sinks down to form a Rift Valley.
What forms along the bottom of divergent continental continental plate margins?
Large lakes - if it drops below sea water then ocean water will seep in
What is the summary of convergent oceanic continental plate margin?
The denser oceanic plate plunges beneath the lighter, less dense continental plate. The sub-ducting plate is forced into higher temperatures and begins to melt. Following the theory of convection, some of the magma rises forming batholiths (large pockets of magma) which explains the bulging of the land, other magma forces through building a magma chamber.
What is the summary of convergent oceanic oceanic plate margin?
The older, denser oceanic plate is sub-ducted occurs so the plates are depressed into the asthenosphere below
What is the summary of conservative plate movement?
The two plates slide past each other, so the relative moment is horizontal. In the San Andreas fault the pacific plate pushes causing the NAP the buckle up, mountains then begin to form.
What earthquake activity takes place on a divergent oceanic oceanic plate margin?
Frequent low magnitude earthquakes occur as rock is ripped and stretched.
What earthquake activity takes place on a divergent continental continental plate margin?
As the plates are stretched and magma forces into the gaps frequent low magnitude earthquakes occur.
What earthquake activity takes place on a convergent oceanic oceanic plate margin?
The pressure created by the friction is released causing the occurrence of high magnitude and frequent earthquakes.
What earthquake activity takes place on a convergent continental continental plate margin?
Earthquake activity is frequent and can be high magnitude. Earthquakes occur throughout collision zone where folding occurs.
What earthquake activity takes place on a conservative faults?
Earthquakes tend to be the strongest centrally and weaker towards the edge of the fault zone.
What volcanic activity takes place on a divergent oceanic oceanic plate margin?
As volcanoes are eventually pulled off ridge they become extinct. In some places the magma may escape/erupt at the surface creating shield volcanoes
What volcanic activity takes place on a divergent continental continental plate margin?
As the plate is torn and stretched some magma escapes at surface resulting in volcanoes
What volcanic activity takes place on a convergent oceanic continental plate margin?
The magma rises creating magma chambers, eventually it will erupt in the form of an explosive volcano.
What volcanic activity takes place on convergent oceanic oceanic plate margins?
The plate melts to form magma, which rises to the top of the overriding oceanic plate and erupts on the ocean floor
What volcanic activity takes place on convergent continental continental plate margins?
As theres no subduction or friction in the Benoiff zone, there’s no volcanic activity
How might there be a Tsunami threat on an oceanic oceanic convergent plate margin?
As the toe of the plate is down-warped it may result in pressure being released by the toe flicking back towards the oceanic plate resulting in a huge displacement of the water column above creating a Tsunami.
What landforms are associated with oceanic oceanic divergent plate margins?
Occasionally volcanoes may portrude the ocean surface creating islands
Mid-atlantic ridge
What landforms are associated with continental continental divergent plate margins?
Steep sided valleys
Large lakes
What landforms are associated with oceanic continental convergent plate margins?
Fold mountains
Ocean trenches
What landforms are associated with oceanic oceanic convergent plate margins?
Volcanic island arcs
What landforms are associated with continental continental convergent plate margins?
Large young fold mountains
What is an example of volcanoes protruding the surface?
Ascension Islands
What is an example of a large lake?
Tanganyika Maldive Kirie Lake
What is an example of a steep sided valley?
East African Rift Valley
What is an example of young fold mountains?
Himalayas
How do hotspots develop?
Concentration of radioactive elements below the crust causes a plume of magma to rise and eat into the plate above
Lava breaks through the surface and active volcanoes form above the spot.
The basaltic lava flows slowly and forms huge but flattish volcanoes, sometimes referred to as ‘shield’ volcanoes
What is an examine of a hot spot?
The Hawaiian Islands in the Pacific Ocean
Why has the Hawaiian hot spot got a chain volcanoes?
The hot spot is stationary, so as the Pacific plate moves over it, a line of volcanoes is created
What are the main landforms associated with plate movements?
Ocean ridges, Rift Valleys, Deep sea trenches, Island arcs, Young fold mountains
What is an ocean ridge?
Formed when plates move apart in oceanic areas. The space between the plates is filled with basaltic lava upwelling form below to form a ridge.
What is a Rift Valley?
Form when plates move apart in continental areas. Brittle crust drops down between parallel faults to form the valley. An area between two parallel rift valleys forms an upstanding block, known as a Horst.
What is a deep sea trench?
Where oceanic and continental plates meet, the denser oceanic plate is forced underneath the lighter continental one. The downwarping of the oceanic plate forms a very deep part of the ocean known as a trench.
What are Island arcs?
During subduction, the descending plate melts. Being less dense than the surrounding asthenosphere, it rises to the surface as plutons of magma. Eventually forming volcanoes.
What are young fold mountains?
As there is no subduction, the plates move towards each other, giving a buckling effect, forming young fold mountains.
What earthquake activity takes place on convergent oceanic continental plate margins?
As the more dense, thinner oceanic plate sub-ducts beneath the lighter, less dense continental plate, the area for which the plates remain in contact creates an extremely high pressure zone (Benioff zone) where earthquakes can take place.
Whats so important about the benoiff zone?
The deeper/steeper the Benioff zone, the deeper the focus, the deeper the focus the less energy the earthquake will have as there is greater area to dissipate the waves.
The more shallow/gentle gradient the Benioff zone, the more shallow the focus, the more shallow the focus, the greater energy of the earthquake
