Of the about 500,000 detectable earthquakes every year,
approximately 100,000 caused enough of a stir to rumble through
the ground and be felt on the Earth's surface.
The most common type of earthquake is caused by continuously
moving tectonic plates.
When rocks press against each other,
they initially bend to accommodate the opposing forces.
As they grind together, they get stuck and pressure builds.
When they reach a point at which they cannot bend
any further,
they break and shock waves vibrate up through the earth.
This energy is released in the form of seismic waves.
Scientists record these waves on a seismograph and grade earthquakes
on the moment magnitude scale.
The biggest earthquake ever recorded was the Valdivia earthquake in
1960,
also known as the Great Chilean Earthquake,
which registered a whopping 9.5 magnitude.
Not all earthquakes caused this much damage,
but they can happen anywhere and at any time.
Many buildings and bridges and earthquake zones are designed to
sway and move with the trembling earth,
creating safer spaces for the public the next time the
ground begins to rumble.