distribution of tectonic hazards Flashcards
(21 cards)
What do they include?
Tectonic hazards include earthquakes and volcanic activity.
Where do they occur?
Hazards occur at plate boundaries - divergent, convergent and conservative.
What are tectonic hazards?
A hazard is a natural or geophysical event that has the potential to be a significant risk to life, livelihoods or the economy.
What’s the distribution like?
The distribution of hazards is uneven - some areas are at high risk, others are at a low risk.
Earthquakes - hazards
Earthquakes are a common hazard which can develop into a major disaster -> high magnitude, shallow focus, densely populated area.
Divergent plate boundaries.
Plates move apart from each other. <— —>
What do they form?
Magma rises from the mantle forming new crust and rift volcanoes -> generally less explosive but more effusive, basaltic lava.
How frequent are they?
Earthquakes tend to be frequent, small and low hazard risk as most occur in the ocean.
Examples of rift valleys.
Great African rift valley and mid ocean ridges e.g. mid Atlantic ridge.
Convergent plate boundaries. ( collision )
Two continental plates collide into each other.
What happens with them?
They are the same density so neither subduction, forcing the two plates upwards which buckle and form fold mountains e.g. the Himalayas.
Consequences of convergent plate boundaries?
Earthquakes occurs due to the build up of pressure that is released when the plates get ‘unstuck’
Properties of convergent plate boundaries.
No volcanic activity.
Infrequent shallow, high magnitude earthquakes.
Conservative plate boundaries.
Plates slide over each other along transformer faults e.g. San Andreas fault.
Properties of conservative plate boundaries
No volcanic activity
Earthquakes tend to be shallow focus and considerable magnitude
Convergent plate boundaries. ( destructive )
Oceanic plate subducts under the continental plate as it is more dense and melts which generates magma that erupts explosively.
What do the destructive convergent plate boundaries create?
Creates andesitic / composite volcanoes e.g. mt Fuji
Creates some of the largest earthquakes in the world.
Island and arcs are formed here.
Oceanic trenches are created by the sea floor and the lithosphere bending due to subduction of the subduction of the oceanic plate
What do they cause?
Tsunamis can be caused here
Earthquakes can be caused.
Volcanic hotspots.
An area in the mantle from which heat rises as magma plumes from the core.
Hugh heat and low pressure at the base of the lithosphere melts rocks which rises through cracks in the crust to form volcanoes.
Volcanic hotspots 2
As the tectonic plate moves over the stationary hotspot, the volcanoes move away and new ones are formed.
Oceanic volcanoes cool and produce new island called atolls and seamounts - over this time this creates chains of volcanoes e.g. the Hawaiian islands.
