Volcanos.....

Volcanoes happen when hot magma forces its way to the surface through a channel in the earth’s crust called a vent. These vents are usually found at plate boundaries or where the earth’s crust is very thin. When the hot molten rock reaches the surface it is known as lava . When lava is reaching the earth's surface, it is known as erruption. When these erruptions are reapeted around a vent, it eventually build's up to form a cone-shaped mountain. Volcanoes are classified as being active (erupting regularly), dormant (no eruption for a very long period) and extinct (when they have not erupted in recorded time and probably won't again). The ‘Pacific Ring of Fire' is a region where two thirds of the world's volcanoes are found.