Hazards - Tectonic plates Flashcards
What are the layers of the earth? (4)
1 - Inner core
2 - Outer core
3 - Mantle - asthenosphere + Lithosphere
4 - Crust - continental + oceanic
Describe the inner core?
A solid ball containing iron and Nickel
Describe the outer core?
Is semi-molten and contains Iron and Nickel
Describe the mantel?
Mostly made of Silicate rocks
Describe the lithosphere? (3)
1 - Is the crust and the uppermost mantle
2 - This constitutes the hard and ridged outer layer of the earth
3 - It is the layer which is split into a number of tectonic plates.
Describe the asthenosphere? (2)
1 - That part of the mantle which lies directly beneath the lithosphere
2 - Is semi - molten
What is happening at a constructive plate margin?
The plates are moving apart/diverging
What occurs at constructive plate margins?
1 - Earthquakes
2 - Volcanoes
What landfroms are created a constructive plate margins? (2)
1 - Ocean ridge
2 - Ridge valley
What is happening at destructive plate margins?
Plates are moving towards each other (converging)
What occurs at destructive plate margins?
1 - Volcanoes
2 - Eathquakes
What are the three types of destructives margins?
1 - Oceanic-Continental
2 - Oceanic-Oceanic
3 - Continental-Continental
What three landforms occur at destructive plate margins?
Oceanic - Continental = Deep sea trench + fold mountains
Oceanic - Oceanic = Deep sea trench + Island arcs
Continental - Continental = Fold mountains
What happens at conservative plate margin?
Plates are sliding past one another
What occur at conservative plate margins?
Earthquakes
What landform is created at conservative plate margins, giving a named example?
1 - Fault lines
2 - e.g San Andreas Fault in California.
Compare the continental and oceanic crust?
Continental crust is thicker
What is the average temperature of the inner core?
60000c
What is the average temperature of the mantel?
1000-35000c
What are the earths sources of internal energy? (3)
1 - Heat from inner core + mantel
2 - Heat energy left over from the earths formation
3 - Radioactive decay of elements
What are plate margins/boundaries?
The places where the plates meet
What is the theory of plate tectonics?
The earths lithosphere is made up of plates that move
What is the theroy of convection currents? (4)
1 - lower parts of the asthenosphere, closer to the core, heat up, becomes less dense and slowly rises
2 - As they move towards the top of the asthenosphere they cool down, become more dense and slowly sink
3 - The circular movement of this semi-molten rock are called convection currents
4 - They create a drag on the base of the tectonic plates - causing them to move
What is the theory of slab pull? (2)
1 - At destructive plate margins, denser crust is subducted under less dense crust
2- The sinking of the denser plates edge pulls the rest of the plate towards the boundary
What is the theory of ridge push/ gravitational sliding?(4)
1 - At constructive plate margins, hot magma rises to the surface and forms new crust
2 - The hot magma heats the surrounding rock which expands and rises above the surface of the surroudning crust forming a slope
3 - The new crust cools and becomes denser. Gravity causes the dense rock to slide downslope, away from the margin
4 - This puts pressure on the tectonic plates, causing them to move apart
What is sea floor spreading? (3)
1 - When tectonic plates diverge, magma rises to fill the gap, cools and forms new crust
2 - Over time the new crust is dragged apart and new crust forms between it
3 - If this occurs under the sea at a plate margin, the sea floor gets wider
How doe volcanoes and earthquakes occur at constructive plate margins? (3)(2)
Volcanoes:
1 - The mantel is under pressure from the above plates
2 - when they diverge the pressure is released, causing the mantel to melt, producing magama
3 - Magma is less dense than the plate above so rises and erupys to form a volcanoe
Earthquakes:
1 - When the plates diverge, some parts move faster than others causing pressure to build up
2 - This causes the plate to crack, making a fault line and causing an earthquake
How are ocean ridges formed at constructive margins, giving a named exmaple? (2)
1 - When plates diverge underwater
E.g Mid-Atlantic ridge formed where Eurasian and North American plate are diverging
2 - Underwater volcanoes can erupt along mid-ocean ridges and can build up to be above sea level
E.g Iceland formed by the build up of underwater volacnoes along the Mid-Atlantic ridge
How are rift valleys formed at constructive plate margins, named examples ? (3)
1 - When plates divereg beneath land, magma rises and causes the continental crust to bulge and fracture, forming fualt lines
2 - As the plates continue to diverge, the crust between parralell fault lines drops down to form a rift valley
E.g East African rift system formed from Nubian and Somalian plates are diverging
3 - Volacnoes are found around rift valleys
E.g Mount Kilimangaro is a volcanoe in the East African rift system
How do deep sea trenches and fold mountains form at Oceanic-Continental plate margins, named examples?
Deep sea trench:
1 - Dense oceanic crust is subducted under the lighter continental crust
E.g Peru-Chile trench In Pacific
Fold mountains:
1 - When sediment accumulates on the continental crust the edge of the crust and the sediment is folded upwards
How are Volacnoes and Eathquakes formed at oceanic-continental plate margins? (2)(2)
Volcanoes:
1 - The oceanic crust is melted by friction into magma
2 - The magma is less dense than the continental crust above so rises to the surface forming volcanoes
Earthquakes:
1 - When plates get stuck this can causes pressure to build up
2 - This can cause plates to jerk past eachother causing an earthquake
How are Island arcs and deep sea trenches formed at Oceanic-Oceanic plate margins, named example? (2)
Deep sea trench:
1 - Denser of the two plates will subduct
2 - This triggers earthquakes and volacnic eruptions
Island arcs
1 - Formed by volacanic eruptions underwater
E.g Mariana Islands
How are fold mountains and earthquakes formed at Continental - Continetal margins, named example?
1 - When continental crust converges
E.g Himalayas
2 - Pressure that builds up between contiental crust can cause earthquakes
How are earthquakes formed at Conservative plate margins, names example? (3)
1 - Plates get locked together in places and pressure build up
2 - This causes the plates to jerk past eachother and crack to from fault line
3 - The energy is released as an earthquake
E.g Many earthquakes occur along Sand Andreas fault line
How do magma plumes form a chain of volacnoes, named example? (6)
1 - A magma plume is a column of very hot magma that rises from the mantel
2 - Volacanoes form above magma plumes
3 - The crust above the magma plume moves
4 - Volacanic activity in the part of the crust that was above the plume decreases as it moves away from the plume
5 - New volacnoes form in the part of the crust that is now above the magma plume
6 - As the crust continues to move a chain of volacnoes are formed
E.g Hawaii formed by magma plumes
