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Volcanoes
Factfile |
 Volcanoes |
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How Volcanoes Are Formed |
Most people when asked to describe a volcano will describe a cone shaped mountain, with lots of fire and smoke spurting out of. But volcanoes aren't that simple as they come in different shapes, with the ability to explode with clouds of gas, steam and ash.
Our planet is made up of 3 layers - the Core, the Mantle and the Crust. (If you imagine our Earth as a hard-boiled egg, with a shell that has been cracked in places, this is a good comparison. The yolk represents the core, the egg white represents the mantle and the shell represents the Earth's crust).
The Earth's outer layer, the crust is broken into a number of sections called tectonic plates. These plates are enormous, the size of continents and they are constantly moving, floating on the magma in the mantle below. This movement is very slow (a few mm per year) and currents in the mantle, which keeps the magma moving, create the movement. The way these plates move is called Continental Drift and for most of the time, this movement happens without any negative consequence.
Plate Boundaries
| 1 - Indo-Australian Plate |
8 - African Plate |
| 2 - Antarctica Plate |
9 - Europe/Asia Plate |
| 3 - Nazca Plate |
10 - Iranian Plate |
| 4 - South American Plate |
11 - Arabian Plate |
| 5 - Cocos Plate |
12 - Philippine Plate |
| 6 - Caribbean Plate |
13 - Pacific Plate |
| 7 - North American Plate |
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However, these plates meet at plate boundaries or margins and any one of the following actions can provide the start for volcanic activity:
Other volcanoes are found in places
known as `hot spots'. This is where a hole is made in
the middle of a plate, where it is very thin and magma
can force its way through from the mantle. Over millions
and millions of years, the plate above the hot spot
slowly moves over it, causing the volcano to die. But
then a new volcano is created when another hole is made
in the covering plate. This results in a chain of
volcanoes very slowly being built up.
Example: the volcanic islands of Hawaii
Hot spots - Kahoolawe - Jack Lockwood
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