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67 Cards in this Set
- Front
- Back
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What are convection currents? |
The earths mantle is the hottest close to the core- lower parts of the aesthenosphere heat up and rise They move to the top of the aesthenosphere where they cool and sink again They move in circle |
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What is SLAB PULL? |
Denser crust is forced under the less dense crust The sinking of the plate pulls the rest of the plate towards the boundary |
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What is ridge push? |
At CONSTRUCTIVE margins, magma rises to the surface forming a new crust. This heats surround rocks which expand and rise above the surface, forming a slope |
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What then happens? |
The new crust cools and becomes more dense. The gravity causes the denser rock to move downslope from the plate margin . |
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What does this out pressure on? |
The tectonic plates so they move apart |
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What is this also known as? |
GRAVITATIONAL SLIDING |
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Where do EARTHQUAKES and VOLCANOES occur? |
At CONSTRUCTIVE plate margins |
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How do constructive margins occur? |
From to plates moving apart (DIVERGING) |
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How does it creates a volcano? |
By releasing pressure when moving apart, this melts the mantle and produces magma. |
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Why does the magma rise forming a volcano? |
Because it is less dense than the plate above |
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How does it make Earthquakes |
Because some parts move faster than others causing pressure to build up. |
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What happens when the pressure is too high? |
The plate cracks making a full-time and causing an EARTHQUAKE |
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What landforms do CONSTRUCTIVE margins create? |
OCEAN RIDGES RIFT VALLEYS |
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What ocean ridge has already been created? |
The MID ATLANTIC RIDGE |
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How are they formed? |
Underwater volcanoes erupt which build up above sea level |
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How is a rift valley formed? |
Rising Magna create continental drift to bulge and fracture - FAULT LINE |
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What is an example of a rift valley? |
EAST AFRICAN RIFT SYSTEM |
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Where else do volcanoes and earthquakes occur? |
DESTRUCTIVE margins |
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Where do destructive margins occur? |
Where two plates are moving towards eachother (CONVERGING) |
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What does the happening of these margins depend on? |
Whether the plate is continental or oceanic |
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How are DEEP SEA trenches formed? |
When a continental and oceanic crust converge, the density of oceanic crust is forced under the continental crust |
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How do FOLD MOUNTAINS occur |
Where plates meet they are made up of sediments that have accumulated on the continental crust which are folded upward along the edge of the continental crust |
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What do eruptions underwater create? |
Island arcs e.g the Mariana islands |
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When continental plates move towards eachother what happens? |
Nothing, neither are subducted, but when the pressure is released an earthquake happens |
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what is the only thing that happens at conservative plate margins? (going past eachother) |
Earthquakes |
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How are hot spot chains created? |
By magma plumes away from plate margins |
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What happens in the first stage? |
The magma plume, a vertical column of extra hit magma, rises from the mantle |
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What happens in the second stage? |
Volcanoes form above magma plume |
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What happens in the third stage |
The magma plume remains stationary over time but the crust moves it about |
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What happens in the fourth stage |
Volcanic activity in the part of the crust that was above the magma plume decreases as It moves away |
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What happens in the fifth stage |
New volcanoes form of in the part of the crust that is new above the magma plume |
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What happens in the sixth stage |
The new crust continues to move, chain of volcanoes is formed |
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What is an example? |
The Hawaii hot-spot chain |
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What lavas are formed at destructive margins |
ANDEISTIC RHYOLITIC They are cooler and less runny, more vicious |
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What lava do hot-spot chains have |
Basaltic Forming SHEILD VOLCANOS |
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What are the primary hazards? |
Pyroclastic flows Lava flows Volcanic gases Ash fallout |
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What are pyroclastic flows |
Mix of superheated gas, ash and rock the flows down the sides of volcano's They cause widespread destruction end death |
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What is a lava flow |
Melted rock I.e magma Most are slow, giving people time to evacuate |
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What are volcanic gasses |
Carbon in lava, sulfur dioxide into atmosphere Sulfur dioxide causes breathing difficulties |
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What is ash falloht |
Ash falls back to ground Heavier particles, tephra can damage buildings and hinder transport |
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What are the SECONDARY hazards |
Lahars Acid rain |
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What are lahars |
When volcanic material mixes with water e.g snow or rainfall Travel at 80kmph Bury and destroy |
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What is acid rain |
Volcanic gases react with water vapour in the atmosphere, which falls as acid rain I.e sulphur reacts with water to create sulfuric acid |
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How often does a volcano erupt |
Every 100000 years or so Others ever few months |
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SIESMIC hazards |
Earthquakes Tsunamis |
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How are earth quakes caused |
By tensions that build up in all types of plate margins |
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When is the quake strongest |
Near the focus, if it's a shallow focus, there is more destruction |
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What is the epicentre |
The point of the earths surface where the quake is felt first |
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How are they measured |
Richter scale Mercalli scale Moment magnitude scale |
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What is the Richter scale |
It measures the magnitude Major quakes are above 7 |
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What is the mms |
Energy released by the quake. It is logarithmic and has no upper limit. More accurate than Richter scale |
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What is the mercalli scale |
Measures the impact of the quake using observations of the event Scale between 1-12 |
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Are are tsunamis caused |
By the displacement of large volumes of water Truggered by underwater quakes |
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How will the wave lose energy |
When it is formed further away from the coast |
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What is a landslide |
When the ground slides due to shaking and loosening |
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What is liquefaction |
The the soil is made easier to deform |
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Where do seismic hazards occur |
Near destructive and conservative plate margins |
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Which earthquakes have a lower magnitude |
Those near constructive margins |
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What does a deep focus mean |
That there will be less damage because the shock is lower in the earth |
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How often do low magnitude seismic hazards occur |
Hundreds daily |
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How do tropical storms occur |
over 27 degrees water temps Low air pressure Coriolis effect 5 degrees from equator Caribbean sea |
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How do they lose strength |
By hitting land Sea gives them energy |
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Which direction do they spin in the northern hemisphere |
Anti clockwise |
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What direction do they spin in the southern hemisphere |
Clockwise |
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How are stoms magnitude measured |
Using the saffir Simpson scale |
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How does the scale work |
By measuring the wind speed Cat five is strongest with winds over 250 kmh |
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What do the storms cause |
High winds Storm surges Rain Flooding Landslides |
