Revision: Earthquakes
Earth’s structure
Crust – the cool and solid outer layer of the Earth
Mantle – the hot and semi-molten layer between the Earth’s crust and core
Outer core – the hot and molten layer between the Earth’s mantle and inner core
Inner core – the extremely hot and solid centre of the Earth
Plates and plate boundaries
The Earth’s crust is divided
into a number of large and
small plates that are driven by
convection currents in the
mantle.
Continental crust is old, light
and floats on the mantle.
Oceanic crust is young, heavy
and sinks into the mantle.
Some plates are moving
together
(destructive
and
collision boundaries), drifting
apart (constructive boundaries) or sliding past each other (conservative boundaries).
Earthquakes happen at most plate boundaries. The UK does not experience severe
earthquakes because it is not located on or close to a major fault or plate boundary.
Occasional minor earthquakes are caused by small faults in the crust beneath the British Isles.
Destructive plate boundaries
Earthquakes happen at destructive plate
boundaries when a heavier oceanic plate is
pulled down (subducted) beneath a lighter
continental plate. In Japan, this is happening to
the Pacific (oceanic) and Eurasian (continental)
plates. Friction between the two plates causes
energy to build up until the plates slip and
release vast amounts of energy at the focus in
the crust. This creates an earthquake.
Impacts and management of earthquakes and tsunamis
Primary impacts – violent shaking, damage to buildings, collapsed buildings, broken gas and
water mains, damage to roads / railways, surface cracks, extensive flooding, injuries, deaths.
Secondary impacts – fires, loss of homes, loss of property, illness, trauma, lack of medicine,
loss of jobs, loss of education, lack of clean water / food, lack of communications, looting.
Management – monitoring, prediction, warning system, earthquake / tsunami drills, earthquake
proof buildings, tsunami walls / barriers, evacuation plans, emergency services.