Hazards

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What is the core?
It consists of two parts, inner core = solid and made of rocks e.g. iron and nickel. Outer core = semi molten liquid about 3000
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what is the mantle?
made of silicate rocks rich in iron and magnesium. Semi molten and similar temp to the core.
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what is the lithosphere?
The crust - rocks rich in silicon, oxygen e.c.t..
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what is the aesthenosphere
part of the upper mantle on the earth on which the plates move.
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how do plates move?
heat from the core warms the mantle, hot rock rises towards the surface. As it cools it sinks back down, creating a convection current.
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what are characteristics of the oceanic plate?
young, thin, dense and continuously formed and destroyed
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what are the characteristics of the continental plate?
old, thick, light and is permanent
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which 4 pieces of evidence support Wegeners continental drift theory?
1) Continental fit 2) Biological evidence (fossils) 3) Geological evidence (same rock types) 4) Climatological evidence (areas that have had glaciers, left scratches such as in Africa - must have been somewhere colder)
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what is palaeomagnetism?
supports the idea that continents are drifting. The magnetic north reverses itself periodically. Iron alligns to the north if the magnetic north is in the north, and alligns south when the poles reverse. This happens along the mid atlantic ridge.
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how does palaeomagnetism explain sea floor spreading?
Hess discovered that the youngest rock is closest to the mid atlantic ridge and that the oldest rocks are closest to the USA and Europe and the Atlantic ocean is widening by 5cm per year.
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what is ridge push?
gravity acting on the weight of the lithosphere near the ridge, pushes the older part of the plate
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what is slab pull?
following subduction, the lithosphere sinks into the mantle under its own weight, helping to pull the rest of the plate with it.
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what is a constructive plate margin and give an example.
When two plates move apart. An example is the mid atlantic ridge where the Eurasian and North American plates are moving apart. As plates diverge, magma rises.
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What is a transform fault?
large cracks which are produced where there is lateral movement along the mid-ocean ridges. They're produced at right angles to the plate boundary.
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What is pillow lava?
occurs on the mid atlantic ridge when volcanoes errupt under the sea. its basalt lava on land.
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what type of lava occurs on constructive margins and what are the characteristics of it?
Basalt lava. It has low viscosity, low silica content, long time to cool and solidify so creates flat volcanoes.
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What volcano shapes are found at a constructive boundary?
Lava Plateau, Fissures and Shield volcanoes.
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How are fissures, plateaus and shield volcanoes formed?
fissures occur when two plates move apart and lava is ejected. Plateaus are formed from fissures as the basalt may fill in hollows. Shield volcanoes occur due to the low viscosity and silica content of the lava.
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What lava is found at a destructive boundary?
Andesitic lava.
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What are the nature of eruptions at a constructive boundary?
Icelandic = gentle and frequent Hawaiian = crater eruption (shield) Frequent eruptions. Gentle, but more powerful releasing Sulfur.
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What is the hazard management cycle?
Preparedness = education reduces impact Response = speed of response depends on lives saved Recovery = restoring the area Mitigation = actions aimed to reduce severity (after) e.g. earthquake proof buildings.
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which 3 phases are described in the Park model?
Relief= the immediate response in terms of aid, Rehabilitation= infrastructure and services restored to normal and Reconstruction= restoring to the same or better quality of life
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What are rift valleys and how are they formed?
Land forms at constructive boundaries.As sections move apart, crust fractures and areas of crust drop down to form valleys. This is because the area of crust here is much thinner. Magma still forces its way up to form volcanoes.
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Give an example of a rift valley and the two plates involved.
The East African rift. The two african plates (rubian and somali)
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What are hotspots and how are they formed
stationary where the volcano above is always active. Caused by a concentration of radioactive elements below the crust. Plume of magma then rises- when this magma breaks through to the surface, active volcanoes form above the hotspot. Island chains.
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what are the 3 types of destructive plate boundaries?
Oceanic meets continental, continental plate meets continental plate and oceanic plate meets oceanic plate
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How are fold mountains formed?
when oceanic plate meets continental. The oceanic plate subducts and melts. As the two plates collide the bending of the oceanic plate creates deep ocean trench. When the plates converge, continental land mass is uplifted and folded into chains of fo
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what are the characteristics of andesitic lava?
viscous, high silica content, cools and solidifies quickly so produces steep sided features such as composite volcanoes
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What is a conservative plate boundary and give an example of two plates
When two plates slide past eachother or in the same direction but at different speeds. for e.g. north american and pacific plate
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what is the focus/hypocentre
the point within the crust where the pressure release occurs.
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what is the epicentre?
the place on the earths surface which is immediately above the focus.
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what are the 3 types of seismic wave?
P-WAVE, S-WAVE and SURFACE WAVE
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what are P-WAVES?
The fastest waves that shake the earth back and forth and make buildings move up and down. They can travel through the core.
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What are S-WAVES?
slower waves that move side to side. they do more damage than P-WAVES and make buildings move up and down
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What are SURFACE WAVES?
travel near the surface and are the slowest waves but the most destructive. They include long waves and raleigh waves which make buildings roll
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Other cards in this set

Card 2

Front

what is the mantle?

Back

made of silicate rocks rich in iron and magnesium. Semi molten and similar temp to the core.

Card 3

Front

what is the lithosphere?

Back

Preview of the front of card 3

Card 4

Front

what is the aesthenosphere

Back

Preview of the front of card 4

Card 5

Front

how do plates move?

Back

Preview of the front of card 5
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