The Earth is a 4.5 billion-year-old ball of molten rock with an iron core
and a cool crust.
The crust is made up of plates, moving at the rate of about 10cm a year.
They are propelled by convection currents in the molten mantle.
Most earthquakes occur along the edges of the Earth's plates.
Earthquakes occur when parts of two tectonic plates move suddenly against
each other.
The rocks usually break deep underground at the focus or hypocentre. This
causes the earth or sea above to shake violently.
Earthquakes can be detected by the different types of waves they generate.
The Primary wave travels fastest through the centre of the earth while the
Secondary wave moves more slowly.
Waves also spread from the epicentre, the point on the surface above the
hypocentre. If an earthquake occurs under the sea, it can cause a TSUNAMI
or a Tidal Wave tgat spreads for thousands of miles
Click here for graphics of how earthquake occurs:
http://news.bbc.co.uk/1/hi/world/4126809.stm
and a cool crust.
The crust is made up of plates, moving at the rate of about 10cm a year.
They are propelled by convection currents in the molten mantle.
Most earthquakes occur along the edges of the Earth's plates.
Earthquakes occur when parts of two tectonic plates move suddenly against
each other.
The rocks usually break deep underground at the focus or hypocentre. This
causes the earth or sea above to shake violently.
Earthquakes can be detected by the different types of waves they generate.
The Primary wave travels fastest through the centre of the earth while the
Secondary wave moves more slowly.
Waves also spread from the epicentre, the point on the surface above the
hypocentre. If an earthquake occurs under the sea, it can cause a TSUNAMI
or a Tidal Wave tgat spreads for thousands of miles
Click here for graphics of how earthquake occurs:
http://news.bbc.co.uk/1/hi/world/4126809.stm
