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Plate Tectonics
The structure of the earth

The earth structure is split up into four layers, these are the crust , mantle, outer core and
inner core.

The crust: The crust covers the mantle and is the earth's hard outer shell, the surface on
which we are living. Compared to…

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Both parts are in a series of interlocked pieces called plates
The point between 2 plates is called a plate boundary
The plates are constantly moving (very slowly). In parts of the world where the plates are
moving apart, a constructive (or divergent or tensional) plate boundary is formed. New…

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began to split and 50 million years ago they had started to spread out into the world map we know
today.

Evidence to support this includes:

Fossil evidence - same species of land animals found on opposite sides of the Atlantic Ocean
Climate evidence - coal deposits and fern fossils…

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Typical slopes of 15°
Lava flows down slope, away from the central vent
Many shield volcanoes have a central caldera
Examples: Hekla and Katla

Ocean Ridge Volcanoes

Volcanic activity under water, for example at the Mid Atlantic Ridge
Submarine oceanic ridge volcanoes e.g. Surtsey 1964, form new islands
Passive volcanic…

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Destructive Plate Boundaries
These types of boundaries are:

Continental-Continental Boundaries
Oceanic-Oceanic Boundaries
Oceanic-Continental Boundaries

Continental-continental Boundaries

When two continents meet in a collision zone, there is very little/no subduction (no volcanic
activity as neither are absorbed into the mantle) as both are relatively light and buoyant, resisting
downward movement. The…

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The water is vertically displaced and waves
move outwards as the sea floor is deformed as the
earthquake strikes.
Tsunami waves travel very fast on the open
ocean but their destructive power comes from their
towering heights which they attain as they approach the
coast
Waves travel at 800km/h (500mph),…

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Tsunamis, generated close to the shoreline can also occur at this type of plate margin

Volcanic Activity

Volcanoes result from magma rising of the melting subducted plate
The composition of the magma is andesitic (melted basaltic crust plus sediment carried on
the crust)
The magma is very gaseous, particularly when…

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No subduction so no volcanic activity at transform boundaries

Case Study: Haiti 2010

Date: 12th January 2010
Magnitude: 7
Depth: 13km
316000 deaths
300000 injured
1 000 000 homeless
caused major damage to capital Port-au-Prince
No building regulations so everything destroyed
Starvation and diseases were secondary impacts
Damage to communication…

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Form as magma cools and solidifies within the crust, particularly along faults and bedding plains.

Battholith: e.g. Dartmoor, Devon - massive magma intrusions into the crust which cools and
solidifies. Tors are the uppermost part of the exposed battholith.
Dyke: magma intrusion into a vertical fault which solidifies. Not usually…

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Management of Natural Hazards


Assessing Hazards and Risks

Hazard and risk assessment are not synonymous

Hazard Assessment consists of the following:

When and where hazardous processes have occurred in the past and the severity of the
physical effects of the past hazardous processes (magnitude)
The frequency of occurrence of hazardous…

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