Plate tectonics

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continental drift?
proposed by alfred wegner in 1912, 300 million years ago there was just 1 super continent pangea. supported by climatological, biological and geological evidence.
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climatological evidence?
coal can be found in antarctica- must have once had a hot climate.
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biological evidence?
similar fossils of plants and invertebrates can be found on different continents,
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geological evidence?
continents of africa and south america seem to fit together, glacial deposits can be found in south america, antarctica and india.
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what further evidence was found to support the 'theory of plate tectonics'?
sea floor spreading. reverses in polarity recorded in stripes, mirrored either side of mid atlantic ridge. growth of new crust at constructive margins means tectonic plates elsewhere must be destroyed. ocean trenches show subduction.
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structure of the earths crust?
Lithosphere-outer part of mantle made of rigid material. asthenosphere-lower part of mantle which is molten.
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what causes the movement of tectonic plates?
driven by thermal convection currents in upper mantle using heat from radioactive decay from the core from when the earth formed.
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constructive plate margin (divergent margin)?
plates move away from eachother. magma rises to the surface to fill the gap, creating oceanic crust at ocean ridges or continental crust at rift valleys. shallow focus earthquakes and volcanic activity occurs here. e.g. mid atlantic ridge.
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destructive (convergent) plate margin?
oceanic-oceanic, oceanic-continental, one plate subducts under the other.
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collision plate margin?
continental- continental, plates made of continental crust move towards eachother.
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oceanic-continental boundaries?
dense oceanic crust subducts under light continental crust creating deep ocean trenches, volcanic mountain chains and shallow to intermediate focus earthquakes e.g. Chile feb 2010.
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oceanic-oceanic boundaries?
forms volcanic island arc with adjacent deep ocean trench e.g. pacific ring of fire. also shallow to deep focus earthquakes occur.
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continental-continental boundaries?
crust is forced up forming fold mountains e.g. himalayas. shallow focus earthquakes and no volcanic activity.
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conservative (transform) boundaries?
plates slide past eachother, there is no volcanic activity however shallow focus earthquakes occur at faults running parallel to the margin. e.g. san andreas fault.
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what hazards are associated with tectonic events?
primary hazard- earthquakes and volcanoes. secondary hazard- mudslides, tsunami, short term climate change.
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how can eruptions be classified?
effusive- outpouring magma which is low in viscosity and gas content. explosive eruptions-which are viscous and acidic.
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what two types of volcanoes are there?
shield volcano and stratovolcanoes (composite)
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what is a shield volcano?
flate shape and wide diameter as layers of basaltic lava cool over a wide area. lava produced is hot and less viscous and gas escapes easily. e.g mauna loa, hawaii
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what is a composite volcano?
pyramidal cross section, built up with layers of lava ash and rock. eruptions are explosive due to lava being cooler and less viscous causing gas content to build up. e.g. mayon, philippines
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what is a caldera?
when the cone is blown off causing the crater to collapse.
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why do earthquakes occur?
due to the sudden release of pressure as tectonic plates move past eachother creating seismic waves.
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focus
is the inital point of rupture.
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epicenter
the point at ground level directly above the focus.
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what can the impacts of an earthquake be?
tsunami, landslides,volcanic eruptions.
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Other cards in this set

Card 2

Front

coal can be found in antarctica- must have once had a hot climate.

Back

climatological evidence?

Card 3

Front

similar fossils of plants and invertebrates can be found on different continents,

Back

Preview of the back of card 3

Card 4

Front

continents of africa and south america seem to fit together, glacial deposits can be found in south america, antarctica and india.

Back

Preview of the back of card 4

Card 5

Front

sea floor spreading. reverses in polarity recorded in stripes, mirrored either side of mid atlantic ridge. growth of new crust at constructive margins means tectonic plates elsewhere must be destroyed. ocean trenches show subduction.

Back

Preview of the back of card 5
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