PLATE TECTONCIS
THE THEORY….
• … Is a scientific theory for the large scale
movements of the Earths lithosphere. (The
crust and the mantle- 100km thick)
• Earth's outermost layer, is broken into 7 large
rigid pieces called plates: the African, North
American, South American, Eurasian,
Australian, Antarctic, and Pacific plates.
• The movement is caused by heat dissipation
from the Earths Mantle.
THE EVIDENCE
• In 1912 a German Scientist called Alfred Wegener
proposed that these two continents were once
joined together then somehow drifted apart. He
proposed that all the continents were once stuck
together as one big land mass called Pangea. He
believed that Pangea was intact until about 200
million years ago.
• If you look at a map you can see that the coast lines
of many countries would fit snugly together
therefore suggesting that this evidence is true.
CONVERGENT PLATE BOUNDARY
• Is also known as a destructive plate boundary. (due to
subduction. See slide)
• A convergent plate boundary is one where two or more
fragments of lithosphere move toward one another and
collide.
• This causes pressure, friction, earthquakes and volcanoes.
DIVERGENT PLATE BOUNDARY
… Is also known as a constructive plate boundary.
The most active form of constructive plate
boundaries are between oceanic plates.
A constructive plate boundary is one which can lead
to volcanic islands!
The 2 tectonic plates move away from each other
which form oceanic basins.
When a volcanic island occurs…. when the plates
move apart to produce gaps which molten lava rises
to fill. This creates a shield volcano which would
eventually build up to become a volcanic island.
SUBDUCTION ZONE
• ….takes place at convergent boundaries where one
tectonic plate moves under the other. A subduction
zone is an area on Earth where two tectonic plates
move towards one another and subduction occurs.
• Rates of subduction are measured in centimetres per
year.
TYPES OF VOLCANOES
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Types of volcanoes
Volcanic caldera or super volcano
Cinder cone
Complex volcano
Cryovolcano
Fissure vent
Guyot
Lava dome
Monogenetic volcanic field
Mud volcano
Pancake dome
Polygenetic volcanic field
Pyroclastic cone
Pyroclastic shield
Shield volcano
Strato volcano (also known as a Composite volcano)
Subaqueous volcano
Subglacial volcano
Submarine volcano
Somma volcano
Tuya
Volcanic field
Volcanic plug
THEY OCCUR WHEN
• A volcano is an opening, or rupture, in a planet's
surface or crust, which allows hot magma, ash and
gases to escape from below the surface.
• Volcanoes are generally found where tectonic plates
are diverging or converging.
• Volcanoes can also form where there is stretching
and thinning of the Earth's crust.
EARTHQUAKES
• …is the result of a sudden release of energy in the
Earth's crust.
• Earthquakes are recorded with a seismometer, also
known as a seismograph.
• Intensity of shaking is measured on the modified
Mercalli scale.
TYPES OF WAVES
seismic waves
(P-waves S-waves)
Body waves
Surface waves
Rayleigh waves
Love Waves
FINDING AN EPICENTRE.
• http://www.sciencecourseware.com/VirtualEa
rthquake/VQuakeExecute.htm