AQA A2 Geography Plate tectonics

This is a summary of all the plate tectonic stuff which is good to listen to.

HideShow resource information
  • Created by: Rhys
  • Created on: 30-05-12 22:15
Preview of AQA A2 Geography Plate tectonics

First 356 words of the document:

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 the other layers the crust is much thinner. It floats upon
the softer, denser mantle. The crust is made up of solid material but this material is not the
same everywhere, this layer has the least dense and coolest. There are two types of crust,
the oceanic and continental, these have a range of thickness with up to 70 kilometres on
the continental crust and only 10 kilometres on the oceanic crust. It is separated from the
Mantle by the Mohorovijic (Moho) boundary.
The mantle: The layer above the core is the mantle. It begins about 6 miles (10 kilometres)
below the oceanic crust and roughly 19 miles (30 km) below the continental crust. The
function of the mantle is to separate the inner mantle and the outer mantle. It is about
1,800 miles (2,900 kilometres) thick and makes up nearly 80 percent of the Earth's total
volume. It is a semi-moltern layer at about 5000°c, at these high temperature there are
convection currents in the mantle.
The outer core: The outer core is about 1,800 miles below the earth's surface and is roughly
the size of Mars. The core is a dense ball of the elements iron and nickel which are liquid at
about 6000°c.
The inner core: This is also at 6000°c but due to the high pressure the nickel and iron which it
is made up of remains solid it is at the centre of the earth.
This is the layer of the earth which consists the ridged top part of the Mantle and the crust
The asthenosphere is the ductile part of the earth just below the lithosphere, including the
lower mantle. The asthenosphere is about 180 km thick.

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

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
oceanic crust is formed as the magma rises and solidifies e.g. Eurasian and North American
In other parts of the world the plates are moving together e.g.…read more

Page 3

Preview of page 3

Here's a taster:

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 in Antarctica (showing it used to be more
equatorial). Also glacial deposits in India, South America, Africa and Australia which are too
hot for glaciers today.…read more

Page 4

Preview of page 4

Here's a taster:

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 activity, low magnitude and not dangerous
Volcanic activity at conservative plate margins is often associated with fissure type eruptions.…read more

Page 5

Preview of page 5

Here's a taster:

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 outcome is that two continental masses become crumpled and
compressed together to form Fold Mountains e.g. The Himalayas.
Geosynclines: This is a vast down warping of
the crust which occurs when two continental
plates collide.…read more

Page 6

Preview of page 6

Here's a taster:

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
Waves travel at 800km/h (500mph), but due to enormous wavelength the wave
oscillation can take 20-30mins to complete a cycle and has amplitude of 1metre.…read more

Page 7

Preview of page 7

Here's a taster:

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 enriched with water vapour - high explosive
Stratovolcanoes are constructed from feeder conduits extending to the surface
Granitic (rhyolitic) intrusions are also formed, becoming trapped within the volcanic pile
overlying the region of subduction…read more

Page 8

Preview of page 8

Here's a taster:

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 systems, hospitals, transport and electrical networks hindered aid
and response
This is a point on the crust immediately above a hot plume within the mantle
Heat from the mantle (and some magma) rises to…read more

Page 9

Preview of page 9

Here's a taster:

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 visible as are small
scale intrusive features. Sometimes a swarm of dykes will form.
Sill: e.g. Great Whin Sill, Northumberland - cooled and solidified magma between two strata
(layers of rock) along the bedding plain.…read more

Page 10

Preview of page 10

Here's a taster:

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 processes
The likely effects of a process of a given magnitude if it were to occur now
Making all of this information available in a form useful to planners and public officials
responsible for making…read more


No comments have yet been made

Similar Geography resources:

See all Geography resources »See all resources »