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A volcano is a major natural hazard that occurs on the Earth’s surface. It exists when harmful gases, magma, ash and large rocks exit out of a mountain, from the mantel, with an immense force causing an explosion. Volcanoes regularly form near tectonic plate boundaries. The reason for this is that tectonic plates can collide or move apart from another plate. These plate boundaries are known as convergent boundaries and divergent boundaries (Refer to figure 2). Volcanoes can also form in the middle of tectonic plates when hotspots are present (Refer to figure 3). Hot spots are when magma builds up until it breaks through the Earth’s crust, forming a volcano. They are active for many years as the tectonic plate continues to move over it. There are approximately over 1,500 around the world and 75% of these volcanoes are consisted in 'the Ring of Fire', as shown in the image below (figure 1).

Figure 1:

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(This image clearly shows the active volcanoes around the world. It was found at http://geopix.org/volcanoes/volcano_images/VL80_world_map.jpg)

Figure 2:

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CONVERGENT BOUNDARY
(This image shows the process of a convergent boundary, where the oceanic plate has subducted under the continental plate. It can be found at http://tasaclips.com/illustrations.html )

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(This image demonstrates the process of a divergent boundary. Divergent boundary occurs when two plates are pulled apart.This image can be found on the MSM 2010 intranet.)


Figure 3:

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(This image displays how a volcanic hotspot continues to build volcanoes as the plate continues to move. It can be found at www.dkimages.com/.../ Hot-Spot/Hot-Spot-1.html.)

Structure of a Volcano:
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A volcano is generally triggered by an earthquake, causing movement of the tectonic plates. This movement instigates hot magma to heat up and rise inside the conduit. The speed, pressure and heat of the intensifying magma forces it to explode, with immense force, out of the crater at the summit of the volcano. When doing so, it carries the rocks, ash, lava and gases with it, which also exits the volcano alongside the magma. Volcanoes are gradually formed when the ash and lava flows down the outside of the mountain and dries into a solid, as shown in this image.






(This diagram shows the basic layout of inside a volcano. More information on this image can be found at sites4school.com/ volcano.html)