Plate tectonics Flashcards
(29 cards)
What is slab pull?
Slab pull is a force that results from denser oceanic plates sinking beneath less dense continental plates along DESTRUCTIVE boundaries and SUBDUCTION ZONES. The GRAVITATIONAL force of the sinking oceanic plate drags the rest of the oceanic plate with it.
What is ridge push?
molten magma that rises at mid ocean ridge is very hot and heats rock around it, expanding it and elevating it above the surrounding sea floor . as the rock that forms is more buoyant than rocks further from the ridge. it cools and gets denser and gravity causes it to slide away from the ridge, as it slides, new molten magma UPWELLS forming the new lithosphere.
What is the thickness, temperature, composition and physical state of the lithosphere-continental crust?
Temp: 400*c
Thick: 30-70km
Composition: Mainly granite, silicon, aluminium, oxygen.
State: Solid
What is the thickness, temperature, composition and physical state of the lithosphere-oceanic crust?
Temp: 400*c
Thick: 6-10km
Composition: Mainly basalt, silicon, aluminium, oxygen
State: Solid
What is the thickness, temperature, composition and physical state of the Mantle?
Temp: On average 3000*c
Thick: Upper asthenosphere (upper mantle) = 100-700km
Lower mantle: 700km-2900km
Composition: silicon, oxygen, silicates of iron & magnesium
State: Upper mantle = semi-molten, lower mantle = solid
What is the thickness, temperature, composition and physical state of the Outer core?
Temp: 4000c to 5000c
Thick: 2900km to 5100km deep
Composition: iron and nickel
State:liquid (generates magnetic field)
What is the thickness, temperature, composition and physical state of the Inner core?
Temp: >6000*c
Thick: 5150-6378km
Composition: 20% nickel, 80% iron
State: solid (source of heat = radioactive decay/nuclear activity)
Cheeky photo of the Earth’s structure for yah
What is a constructive plate boundary, hazards and what landforms does it create give examples.
What: tectonic plates move away from each other (where ridge push occurs). When this happens, the magma from the mantle rises up to make (or construct) a new crust. The movement of the plates over the mantle can cause earthquakes.
Hazards: Volcano (shield) e.g. Mt Nyiragongo, small earthquakes not as bad as others tho
Landforms: Rift valley = East African Rift Valley, oceanic ridge = Mid-Atlantic ridge (where the Eurasian plate and the North Atlantic plate are moving apart from each other under the Atlantic Ocean.)
Small scale landforms = geysers and lava tubes
What is a destructive plate boundary, hazards and what landforms does it create give examples.
plates are moving towards one another, as the plates collide, the oceanic plate is forced beneath the continental plate. This is known as
subduction.
Hazards: earthquakes e.g. Haiti, (strato)volcanoes-violent (Pacific ring of fire)
Landforms: Island arcs (Caribbean), deep sea trench (Mariana trench)
What is a conservative plate boundary plus hazards, landforms and examples.
What: where two tectonic plates slide past each other, moving either in opposite directions or at different speeds in the same direction. Pressure builds up because the plates are still trying to move. When the pressure is released it sends out huge amounts of energy, causing an earthquake. The earthquakes at a conservative plate boundary can be very destructive as they occur close to the Earth’s surface. There are no volcanoes at a conservative plate boundary.
Landform: Fault Line-San Andreas Fault, California.
What is a collision boundary plus hazards, landforms and examples.
What: two continental plates collide, neither can sink and so the land buckles upwards to form fold mountains
Hazards: earthquakes (Nepal 2015)
Landforms: fold mountains e.g. Himalayas
what are convection currents?
Tectonic plates ‘float’ on the magma beneath them in the asthenosphere. Convection currents, that occur within the molten rock in the mantle, act like a conveyor belt for the plates. Tectonic plates move in different directions. The direction of movement and type of plate margin is determined by which way the convection currents are flowing. Heat from the Earth’s core causes molten rock (magma) to rise, creating circular currents in the mantle. As the magma cools, it sinks back down, dragging the tectonic plates across the Earth’s surface.
what contributes to tectonic plate movement?
Convection currents
ridge push
slap pull
gravitational sliding
sea floor spreading
what is sea floor spreading?
tectonic plates are split apart as molten lava rises between them making the rock more bouyant. The magma rises to the ocean floor surface, causing the denser sides to travel awayfrom the mid ocean ridge. oncethhe lavacools, new upwlling lava seperates the cooledlava and the process continues.
what is gravitational sliding?
As the crust moves away from a mid-ocean ridge, it cools and becomes denser and thicker. This causes the lithosphere to slope away from the ridge and gravity pulls the lithosphere down this slope, pushing it forwards. This is known as gravitational sliding
Magma plumes and there relationship to plate movement
Magma plumes are areas of hot, upwelling mantle. They are independent to plate movement
A hot spot develops above the plume in the crust. Magma generated by the hot spot rises through the rigid plates of the lithosphere and produces active low viscosity volcanoes at the Earth’s surface. As oceanic volcanoes move away from the hot spot with the migration of their tectonic plate, they cool and subside, producing older island chains.
The Hawaiian Island chain is being constructed in this way. As continental volcanoes move away from the hot spot, they cool, subside, and become extinct.
What type of plate boundaries does slab pull occur at?
Destructive
Who published the theory of continental drift?
Alfred Wegner 1912
Who noticed the jigsaw fit in the 17th century?
Francis Bacon
What is the theory of continental drift?
The theory that continents are moving, and splitting from each other to form new continents
What were the 3 pieces of evidence for the theory of continental drift?
Fossil evidence
Tectonic fit
geological fit
Give an example of fossil remains that provide evidence for continental drift.
Mesosaurus remains found in South America and Southern Africa - freshwater and land reptile
Give an example of how rock patterns (geological fit) provide evidence for continental drift.
geology of eastern south america and west africa have ancient rock outcrops that are continuous from one continent to the other (2 million years old)
