Earthquake Causes

Earthquakes are a naturally occurring shock or movement that occurs on or just below the earth crust. This can cause massive devastation in the area of the earthquake and in areas spreading out from the center of the quake.

All true earthquakes are natural and are not linked to any man made activities such as shocks from nuclear testing or landslides that result from extensive building work. There are two main causes of earthquakes - Tectonic activity which is caused by the earth plates moving or faults or volcanic activity which is caused by volcanic eruptions.

Earthquake & Tsunami In Japan

Out of the two earthquake causes tectonic activity is the most common, although volcanic activity can cause earthquakes in certain areas of the world. Tectonic earthquake causes begin when there is movement in the earth Tectonic plates. These plates are made up of sections of the earth crust and they float on the earth mantle. Most of the time these plates are slowly in moving; they might slide towards or away from each other or even slip past each other. However, it is when these Tectonic plates collide or move too closely to each other that an earthquake is caused.

Scientists have devised the Elastic Rebound Theory to describe what happens during these times of movement. To explain this, think about bending a green twig. You will know that you can bend the twig and it will hold up until a certain point, until the energy on the twig becomes too much and it snaps. The point of snapping is known as the Elastic Limit. When this happens the energy created during the bending process is released which makes the twig vibrate.

When Tectonic plates collide or rub against each other the same process occurs and this will cause an earthquake. One example of constantly moving plates is the San Andreas Fault in the US. Here the North American Plate and the Pacific Plate both move in the same direction, but one is faster than the other. This leads to small shocks and occasionally large quakes in the San Francisco area of America.

Volcanic earthquakes are created when a volcano erupts, which can be quite a violent explosion. Usually these earthquakes will affect an area of up to 20 miles around the volcano and the earthquake is not likely to be felt anywhere else in the world.

A volcano is more likely to explode if it contains acidic lava. This is lava that will quickly cool and set when in contact with the air. When this happens the vent of the volcano will become blocked and pressure will build up inside it. Over time this pressure will increase until the volcano erupts. Volcanoes that do not contain acidic lava or which have free flowing lava tend not to erupt in this way and are considered to be much safer.

As you can see there are two main earthquake causes - Tectonic plate activity and volcanic eruptions. Tectonic earthquakes are much more common although there are still instances of volcanic earthquakes in various countries around the globe.

Earthquake Causes