Introduction to Earthquakes & Tsunamis
Turn on the TV or read the newspapers and almost always there is something devastating happening somewhere as a result of sheer nature's power. Examples of such natural occurrences are hurricanes, tornados, wildfires, volcanic eruptions, flooding, earthquakes and tsunamis. These are usually not caused directly by humans, but their effects live with us for a long time. In this lesson we shall look at one of such natural occurrences...earthquakes!
What is an Earthquake?
Simply, earthquakes are the rumblings, shaking or rolling of the earth's surface. It is usually what happens when two blocks of the earth suddenly slip past one another, or break apart from each other as a result of tension caused by prolonged energy build up.
Earthquakes come in many forms. It can be felt as a shock under your feet, or may be very powerful and destructive enough to flatten an entire city. They can happen anywhere, land or sea.
Foreshocks, Mainshocks and Aftershocks:
Sometimes, there are smaller shocks that occur before (foreshock) and after (aftershock) a main earthquake (mainshock). Sometimes foreshocks are so big and scientists are unsure if it is the main shock. Foreshocks and aftershocks can occur for days, weeks and months of a main earthquake.
Earthquakes are also called temblors.
It is important to understand
the earth’s makeup to help understand earthquakes better.
In this diagram, you will notice that the inner and outer core of the earth (middle part) are liquid in nature, containing iron and nickel of extreme temperatures (5,500°C).
The Mantle is semi-molten rock, also called magma. The outer is the crust, which is the hard part of the earth that forms the surface. This outer crust includes the land on which we live, the oceans and ocean deeps and anything within 40km (approx) down the earth's surface.
Earthquakes are developed in the outer crust of the earth.