"Deep below the Earth's crust, the temperatures and
pressures are great enough to melt rock. When this molten
rock blasts to the surface, the result is a volcano - and for
the inhabitants of the place, it's as if Hell has been let loose."
(Natural Disasters, Readers Digest,1996)
Volcanoes occur when the Earth's plates pull apart causing magma to rise to the surface. Volcanoes can also occur over hotspots and where one plate dives beneath another, forcing magma to rise to the surface. Plates diving under one another is known as subduction.
Volcanoes usually occur on the edges of plates, similar to where earthquakes occur. A lot of volcanoes occur in the area around the edge of the Pacific ocean called the Pacific Ring of Fire. Volcanoes can also occur in the middle of plates, in hotspots. One such hotspot has formed the Hawaiian islands chain. As the earth rotated, it passed over the hotspot and new islands were formed.
(Readers Digest, Natural Disasters, 1996)
Mt St Helens
The Ring of Fire
Lava, mud and ash
Explosion, then tsunami
La Soufrière, St Vincent
Mont Pelée, Martinique
Mount Merapi, Java
Mount Lamington, PNG
Mount St Helens, USA
Nevado del Ruiz, Columbia