A volcano is (typically) formed when tectonic plates come together and the oceanic plate passes below (subducts) the thicker, continental plate. Once the subducting plate travels down around 160 kilometres into the mantle, it begins to melt. The magma starts to slowly travel to the surface. As they travel, they create chambers of magma. If the chamber does not become solid before reaching the surface, a volcano is formed and the magma is ejected as lava.Download this ActiveWorksheet
As well as watching the volcano erupt, you can see the magma chamber and other elements that make a volcano. Also, observe a pyroclastic flow (a mix of very hot gasses, rocks and debris that can travel at up to from 100 to 450 km/h) as a part of the volcano side is blown away through the force of the eruption.