Tectonic Hazards Key Words.

Useful key words for learning and understanding plate tectonics and their hazards.

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Tectonic plates- tectonic plates are huge pieces of rock formed from the earth's crust
Destructive plate margin/boundary- a boundary at which the tectonic plates are moving
towards each other, this usually involves an oceanic and continental plate. The oceanic
plate is denser and is forced underneath the continental plate. The point at which this
happens is called the subduction zone. As the oceanic plate is being forced under the
continental plate it melts to form magma and earthquakes are triggered. The magma
collects to form a magma chamber. The magma then rises up through cracks in the
continental crust. As pressure builds up, a volcanic eruption may occur.
Collision zone-the area where the tectonic plates collide
Subduction zone- an area of tectonic plate collision where the heavier plate will sub duct
or follow a path underneath the less dense plate
Mantle-the widest section of the earth, it is made up of semi-molten rock called magma,
in the upper parts of the mantle the rock is hard but lower down the rock is soft and
beginning to melt.
Constructive plate margin/boundary- a boundary at which the tectonic plates are
moving apart due to convection currents inside the earth, as the plates slowly move
apart, magma rises from the mantle. It cools and solidifies into igneous rock; this rock
builds up to form volcanoes. These plate boundaries are usually found under the ocean,
chains of underwater volcanoes have formed along these boundaries. They can erupt out
of the sea to create volcanic islands such as, west man islands near Iceland.
Conservative margin/boundary- a boundary at which the tectonic plates slides past
each other, there are no volcanoes caused but the friction between the plates can cause
earthquakes. An example of this is San Andreas Fault in California (between North
American plate and pacific plate).
Tremor- a shaking or trembling released caused by the sudden release of energy in the
earth's crust that causes seismic waves.
Richter scale- used to measure the magnitude of an earthquake, the amount of energy it
Mercalli scale- a scale used to measure the intensity of an earthquake.
Primary effects- the immediate effects of the disaster e.g. buildings collapsing, roads
cracking, bridges giving way.
Secondary effects- the effects that result from the primary effects e.g. homelessness,
businesses going bankrupt, and fires due to explosion of escaping gas from cracked pipes
(primary effect).

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Lava- Molten rock expelled from a volcano during eruption and the resulting rock after
solidification and cooling.
Magma- hot liquefied rock located deep below the earth's surface.
Hot spot- fixed places within the mantle or oceanic lithosphere where rocks melt to
generate magma. When a hot spot is located in the oceanic lithosphere a class of
volcanoes called shield volcanoes are built.…read more


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