Plate Tectonics, Earthquakes and Volcanoes!

This can be a particularly fascinating topic for pupils, nonetheless, it can be difficult to understand and grasp certain concepts. Therefore I will try and break it down into sizeable chunks, as well as making it enjoyable and interesting.

To understand earthquakes and volcanoes, it is vital to look at the Earth's plates. So what exactly are the Earth's plates and what do they do?

*The movement of the Earth's plates causes earthquakes and volcanoes.


*The map above shows the world's main tectonic plates. The point at which two plates meet is called a plate boundary.

*Most of the world's earthquakes and volcano zones are found on or near to plate boundaries.

The Earth's plates move in different directions, and there are three main types of plate boundary. These are listed below:
1) At a constructive plate boundary two plates move apart from each other.
2) At a destructive plate boundary two plates move towards each other.
3) At a conservative plate boundary two plates slide past eachother.

An easier way to remember this is that constructive plate boundaries create new land; destructive plate boundaries destroy land; and conservative plate boundaries neither create nor destroy land.

Plate Tectonics in more detail-

Constructive plate boundaries: At a constructive plate boundary (also known as a divergent plate boundary) two plates move apart from each other. As the plates move apart, magma rises through the gap in the Earth's crust and cools down to form new crust. An example is the Mid-Atlantic Ridge, where a chain of underwater volcanoes have formed along the plate boundary.

Destructive plate boundaries: At a destructive plate boundary (also known as a convergent plate boundary) two plates move towards each other. When an oceanic plate moves towards a continental plate, the denser oceanic plate sinks below the continental plate. As the oceanic plate sinks, it melts and forms magma. Magma sometimes rises through the cracks in the continental crust to form a volcano. In addition, at a destructive plate boundary, the movement of the plates may push the continental crust upward to form fold mountains. This process is called folding.

Conservative plate boundaries: At a conservative plate boundary (also known as a transform plate boundary) the plates move horizontally past each other, without creating or destroying the earth's crust. A famous example is the San Andreas Fault, USA.

Below is a diagram to show all three plate boundaries:

Earthquakes-

Instead of me blabbering on, here is a great video by the National Geographic on earthquake destruction:



We have established that the movement of the Earth's plates can cause earthquakes. So why is this? Plates do not move smoothly. Sometimes a plate gets stuck. Pressure builds up and when this pressure is released an earthquake can occur.

The point below the Earth's surface where the pressure is released is called the focus. The point on the Earth's surface directly above the focus is called the epicentre. When pressure is released from the focus, shock waves are produced. These waves are called seismic waves. The seismic waves are strongest at the epicentre of an earthquake. This is where the most damage is caused during an earthquake. The seismic waves spread out from the focus like ripples on a pond. As they travel outwards they lose energy.

Earthquakes can have a devastating effect on people and the environment. The immediate or primary effects of an earthquake include the collapse of buildings, roads and railways. People may be killed or injured and property is damaged. The long-term or secondary effects of an earthquake include gas explosions and fires. Communications can fail, as telephone lines and computer links are cut. Water can become contaminated as sewage and clean water pipes fracture. A lack of clean water can lead to the spread of disease. Below is a video of the Seattle earthquake of 2001. Have a look at the effects of the earthquake. Could it have been more devastating?



Nonetheless, the damage could have been worse if it wasn't for the fact that Seattle is in a MEDC. Natural disasters such as earthquakes tend to have as greater impact upon LEDCs than MEDCs. Buildings in LEDCs are not always strong enough to withstand the damage caused by earthquakes. LEDCs do not have sufficient healthcare facilities to deal with emergency situations. Access and communications in LEDCs tend to be poor. It is difficult to warn people about possible dangers on bring them emergency supplies. LEDCs also have limited money and resources to rebuild areas that are damaged.

Measuring earthquakes-

The strength of an earthquake is recorded using a machine called a seismometer. This picks up vibrations and tremors recording the strength of an earthquake. This strength, or scientifically known as magnitude, is measured using the Richter Scale.