The earth's crust
The earth's crust is not just one huge rock 'skin'. It actually consists of 20 pieces called 'plates'. Earth's hills and mountains were formed as the plates bumped into each other.

Faults
The plates are always moving. They usually slide past each other very very slowly, and the movement is not noticeable. If the edges of the plates get stuck, rocks bend and split, causing a fault, or a weakness, in the earth's crust.
.........Railway lines and overhead wires after an earthquake

Earthquakes
Earthquakes happen where Earth's plates meet. Most earthquakes occur under the sea. Where the plates are stuck, pressure builds up and eventually the earth shakes. There are about 3000 earthquakes every day, so small that they are not noticed.

Earthquake damage, Los Angeles 1994

Large earthquakes shake the ground and destroy buildings. People get killed or injured, and gas and water pipes underground are twisted and burst. Railway lines get buckled by the earthquake.

Measuring earthquake strength

Scientists use instruments called seismographs (say size-mu-graphs) to measure the strength of tremors and earthquakes.

The Richter Scale, named after Dr. Charles F. Richter of the California Institute of Technology, is the best known scale for measuring the magnitude of earthquakes.The Richter Scale is the measure of the tremors.
The Modified Mercalli Scale measures the damage caused by an earthquake.

Go here to find out about the Richter Scale and the Modified Mercalli Scale. http://www.geo.mtu.edu/UPSeis/intensity.html

Go to this address to read about an earthquake that struck Newcastle, Australia in 1989, includes pictures.
http://allshookup.org/images/ncquake/ncquake.htm

If you use any of this information in your own work acknowledge this source in your bibliography like this:
Sydenham, S & Thomas, R. Earthquakes [Online] www.kidcyber.com.au (2008)

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updated  September 2008 © kidcyber